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OpenCloudOS-Kernel/tools/objtool/check.c

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
*/
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
#include <sys/mman.h>
#include <objtool/builtin.h>
#include <objtool/cfi.h>
#include <objtool/arch.h>
#include <objtool/check.h>
#include <objtool/special.h>
#include <objtool/warn.h>
#include <objtool/endianness.h>
#include <linux/objtool_types.h>
#include <linux/hashtable.h>
#include <linux/kernel.h>
#include <linux/static_call_types.h>
struct alternative {
struct alternative *next;
struct instruction *insn;
bool skip_orig;
};
static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
static struct cfi_init_state initial_func_cfi;
static struct cfi_state init_cfi;
static struct cfi_state func_cfi;
static struct cfi_state force_undefined_cfi;
struct instruction *find_insn(struct objtool_file *file,
struct section *sec, unsigned long offset)
{
struct instruction *insn;
hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
if (insn->sec == sec && insn->offset == offset)
return insn;
}
return NULL;
}
struct instruction *next_insn_same_sec(struct objtool_file *file,
struct instruction *insn)
{
if (insn->idx == INSN_CHUNK_MAX)
return find_insn(file, insn->sec, insn->offset + insn->len);
insn++;
if (!insn->len)
return NULL;
return insn;
}
static struct instruction *next_insn_same_func(struct objtool_file *file,
struct instruction *insn)
{
struct instruction *next = next_insn_same_sec(file, insn);
struct symbol *func = insn_func(insn);
if (!func)
return NULL;
if (next && insn_func(next) == func)
return next;
/* Check if we're already in the subfunction: */
if (func == func->cfunc)
return NULL;
/* Move to the subfunction: */
return find_insn(file, func->cfunc->sec, func->cfunc->offset);
}
static struct instruction *prev_insn_same_sec(struct objtool_file *file,
struct instruction *insn)
{
if (insn->idx == 0) {
if (insn->prev_len)
return find_insn(file, insn->sec, insn->offset - insn->prev_len);
return NULL;
}
return insn - 1;
}
static struct instruction *prev_insn_same_sym(struct objtool_file *file,
struct instruction *insn)
{
struct instruction *prev = prev_insn_same_sec(file, insn);
if (prev && insn_func(prev) == insn_func(insn))
return prev;
return NULL;
}
#define for_each_insn(file, insn) \
for (struct section *__sec, *__fake = (struct section *)1; \
__fake; __fake = NULL) \
for_each_sec(file, __sec) \
sec_for_each_insn(file, __sec, insn)
#define func_for_each_insn(file, func, insn) \
for (insn = find_insn(file, func->sec, func->offset); \
insn; \
insn = next_insn_same_func(file, insn))
#define sym_for_each_insn(file, sym, insn) \
for (insn = find_insn(file, sym->sec, sym->offset); \
insn && insn->offset < sym->offset + sym->len; \
insn = next_insn_same_sec(file, insn))
#define sym_for_each_insn_continue_reverse(file, sym, insn) \
for (insn = prev_insn_same_sec(file, insn); \
insn && insn->offset >= sym->offset; \
insn = prev_insn_same_sec(file, insn))
#define sec_for_each_insn_from(file, insn) \
for (; insn; insn = next_insn_same_sec(file, insn))
#define sec_for_each_insn_continue(file, insn) \
for (insn = next_insn_same_sec(file, insn); insn; \
insn = next_insn_same_sec(file, insn))
static inline struct symbol *insn_call_dest(struct instruction *insn)
{
if (insn->type == INSN_JUMP_DYNAMIC ||
insn->type == INSN_CALL_DYNAMIC)
return NULL;
return insn->_call_dest;
}
static inline struct reloc *insn_jump_table(struct instruction *insn)
{
if (insn->type == INSN_JUMP_DYNAMIC ||
insn->type == INSN_CALL_DYNAMIC)
return insn->_jump_table;
return NULL;
}
static bool is_jump_table_jump(struct instruction *insn)
{
struct alt_group *alt_group = insn->alt_group;
if (insn_jump_table(insn))
return true;
/* Retpoline alternative for a jump table? */
return alt_group && alt_group->orig_group &&
insn_jump_table(alt_group->orig_group->first_insn);
}
static bool is_sibling_call(struct instruction *insn)
{
/*
* Assume only STT_FUNC calls have jump-tables.
*/
if (insn_func(insn)) {
/* An indirect jump is either a sibling call or a jump to a table. */
if (insn->type == INSN_JUMP_DYNAMIC)
return !is_jump_table_jump(insn);
}
/* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */
return (is_static_jump(insn) && insn_call_dest(insn));
}
/*
* This checks to see if the given function is a "noreturn" function.
*
* For global functions which are outside the scope of this object file, we
* have to keep a manual list of them.
*
* For local functions, we have to detect them manually by simply looking for
* the lack of a return instruction.
*/
static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
int recursion)
{
int i;
struct instruction *insn;
bool empty = true;
#define NORETURN(func) __stringify(func),
static const char * const global_noreturns[] = {
#include "noreturns.h"
};
#undef NORETURN
if (!func)
return false;
if (func->bind == STB_GLOBAL || func->bind == STB_WEAK)
for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
if (!strcmp(func->name, global_noreturns[i]))
return true;
if (func->bind == STB_WEAK)
return false;
if (!func->len)
return false;
insn = find_insn(file, func->sec, func->offset);
if (!insn || !insn_func(insn))
return false;
func_for_each_insn(file, func, insn) {
empty = false;
if (insn->type == INSN_RETURN)
return false;
}
if (empty)
return false;
/*
* A function can have a sibling call instead of a return. In that
* case, the function's dead-end status depends on whether the target
* of the sibling call returns.
*/
func_for_each_insn(file, func, insn) {
if (is_sibling_call(insn)) {
struct instruction *dest = insn->jump_dest;
if (!dest)
/* sibling call to another file */
return false;
/* local sibling call */
if (recursion == 5) {
/*
* Infinite recursion: two functions have
* sibling calls to each other. This is a very
* rare case. It means they aren't dead ends.
*/
return false;
}
return __dead_end_function(file, insn_func(dest), recursion+1);
}
}
return true;
}
static bool dead_end_function(struct objtool_file *file, struct symbol *func)
{
return __dead_end_function(file, func, 0);
}
static void init_cfi_state(struct cfi_state *cfi)
{
int i;
for (i = 0; i < CFI_NUM_REGS; i++) {
cfi->regs[i].base = CFI_UNDEFINED;
cfi->vals[i].base = CFI_UNDEFINED;
}
cfi->cfa.base = CFI_UNDEFINED;
cfi->drap_reg = CFI_UNDEFINED;
cfi->drap_offset = -1;
}
static void init_insn_state(struct objtool_file *file, struct insn_state *state,
struct section *sec)
{
memset(state, 0, sizeof(*state));
init_cfi_state(&state->cfi);
/*
* We need the full vmlinux for noinstr validation, otherwise we can
* not correctly determine insn_call_dest(insn)->sec (external symbols
* do not have a section).
*/
if (opts.link && opts.noinstr && sec)
state->noinstr = sec->noinstr;
}
static struct cfi_state *cfi_alloc(void)
{
struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
if (!cfi) {
WARN("calloc failed");
exit(1);
}
nr_cfi++;
return cfi;
}
static int cfi_bits;
static struct hlist_head *cfi_hash;
static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
{
return memcmp((void *)cfi1 + sizeof(cfi1->hash),
(void *)cfi2 + sizeof(cfi2->hash),
sizeof(struct cfi_state) - sizeof(struct hlist_node));
}
static inline u32 cfi_key(struct cfi_state *cfi)
{
return jhash((void *)cfi + sizeof(cfi->hash),
sizeof(*cfi) - sizeof(cfi->hash), 0);
}
static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
{
struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
struct cfi_state *obj;
hlist_for_each_entry(obj, head, hash) {
if (!cficmp(cfi, obj)) {
nr_cfi_cache++;
return obj;
}
}
obj = cfi_alloc();
*obj = *cfi;
hlist_add_head(&obj->hash, head);
return obj;
}
static void cfi_hash_add(struct cfi_state *cfi)
{
struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
hlist_add_head(&cfi->hash, head);
}
static void *cfi_hash_alloc(unsigned long size)
{
cfi_bits = max(10, ilog2(size));
cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANON, -1, 0);
if (cfi_hash == (void *)-1L) {
WARN("mmap fail cfi_hash");
cfi_hash = NULL;
} else if (opts.stats) {
printf("cfi_bits: %d\n", cfi_bits);
}
return cfi_hash;
}
static unsigned long nr_insns;
static unsigned long nr_insns_visited;
/*
* Call the arch-specific instruction decoder for all the instructions and add
* them to the global instruction list.
*/
static int decode_instructions(struct objtool_file *file)
{
struct section *sec;
struct symbol *func;
unsigned long offset;
struct instruction *insn;
int ret;
for_each_sec(file, sec) {
struct instruction *insns = NULL;
u8 prev_len = 0;
u8 idx = 0;
if (!(sec->sh.sh_flags & SHF_EXECINSTR))
continue;
if (strcmp(sec->name, ".altinstr_replacement") &&
strcmp(sec->name, ".altinstr_aux") &&
strncmp(sec->name, ".discard.", 9))
sec->text = true;
if (!strcmp(sec->name, ".noinstr.text") ||
!strcmp(sec->name, ".entry.text") ||
!strcmp(sec->name, ".cpuidle.text") ||
!strncmp(sec->name, ".text.__x86.", 12))
sec->noinstr = true;
/*
* .init.text code is ran before userspace and thus doesn't
* strictly need retpolines, except for modules which are
* loaded late, they very much do need retpoline in their
* .init.text
*/
if (!strcmp(sec->name, ".init.text") && !opts.module)
sec->init = true;
for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
if (!insns || idx == INSN_CHUNK_MAX) {
insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
if (!insns) {
WARN("malloc failed");
return -1;
}
idx = 0;
} else {
idx++;
}
insn = &insns[idx];
insn->idx = idx;
INIT_LIST_HEAD(&insn->call_node);
insn->sec = sec;
insn->offset = offset;
insn->prev_len = prev_len;
ret = arch_decode_instruction(file, sec, offset,
sec->sh.sh_size - offset,
insn);
if (ret)
return ret;
prev_len = insn->len;
/*
* By default, "ud2" is a dead end unless otherwise
* annotated, because GCC 7 inserts it for certain
* divide-by-zero cases.
*/
if (insn->type == INSN_BUG)
insn->dead_end = true;
hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
nr_insns++;
}
// printf("%s: last chunk used: %d\n", sec->name, (int)idx);
sec_for_each_sym(sec, func) {
if (func->type != STT_NOTYPE && func->type != STT_FUNC)
continue;
if (func->offset == sec->sh.sh_size) {
/* Heuristic: likely an "end" symbol */
if (func->type == STT_NOTYPE)
continue;
WARN("%s(): STT_FUNC at end of section",
func->name);
return -1;
}
if (func->return_thunk || func->alias != func)
continue;
if (!find_insn(file, sec, func->offset)) {
WARN("%s(): can't find starting instruction",
func->name);
return -1;
}
sym_for_each_insn(file, func, insn) {
insn->sym = func;
if (func->type == STT_FUNC &&
insn->type == INSN_ENDBR &&
list_empty(&insn->call_node)) {
if (insn->offset == func->offset) {
list_add_tail(&insn->call_node, &file->endbr_list);
file->nr_endbr++;
} else {
file->nr_endbr_int++;
}
}
}
}
}
if (opts.stats)
printf("nr_insns: %lu\n", nr_insns);
return 0;
}
/*
* Read the pv_ops[] .data table to find the static initialized values.
*/
static int add_pv_ops(struct objtool_file *file, const char *symname)
{
struct symbol *sym, *func;
unsigned long off, end;
struct reloc *reloc;
int idx;
sym = find_symbol_by_name(file->elf, symname);
if (!sym)
return 0;
off = sym->offset;
end = off + sym->len;
for (;;) {
reloc = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
if (!reloc)
break;
func = reloc->sym;
if (func->type == STT_SECTION)
func = find_symbol_by_offset(reloc->sym->sec,
reloc_addend(reloc));
idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long);
objtool_pv_add(file, idx, func);
off = reloc_offset(reloc) + 1;
if (off > end)
break;
}
return 0;
}
/*
* Allocate and initialize file->pv_ops[].
*/
static int init_pv_ops(struct objtool_file *file)
{
static const char *pv_ops_tables[] = {
"pv_ops",
"xen_cpu_ops",
"xen_irq_ops",
"xen_mmu_ops",
NULL,
};
const char *pv_ops;
struct symbol *sym;
int idx, nr;
if (!opts.noinstr)
return 0;
file->pv_ops = NULL;
sym = find_symbol_by_name(file->elf, "pv_ops");
if (!sym)
return 0;
nr = sym->len / sizeof(unsigned long);
file->pv_ops = calloc(sizeof(struct pv_state), nr);
if (!file->pv_ops)
return -1;
for (idx = 0; idx < nr; idx++)
INIT_LIST_HEAD(&file->pv_ops[idx].targets);
for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
add_pv_ops(file, pv_ops);
return 0;
}
static struct instruction *find_last_insn(struct objtool_file *file,
struct section *sec)
{
struct instruction *insn = NULL;
unsigned int offset;
unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
insn = find_insn(file, sec, offset);
return insn;
}
/*
* Mark "ud2" instructions and manually annotated dead ends.
*/
static int add_dead_ends(struct objtool_file *file)
{
struct section *rsec;
struct reloc *reloc;
struct instruction *insn;
s64 addend;
/*
* Check for manually annotated dead ends.
*/
rsec = find_section_by_name(file->elf, ".rela.discard.unreachable");
if (!rsec)
goto reachable;
for_each_reloc(rsec, reloc) {
if (reloc->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in %s", rsec->name);
return -1;
}
addend = reloc_addend(reloc);
insn = find_insn(file, reloc->sym->sec, addend);
if (insn)
insn = prev_insn_same_sec(file, insn);
else if (addend == reloc->sym->sec->sh.sh_size) {
insn = find_last_insn(file, reloc->sym->sec);
if (!insn) {
WARN("can't find unreachable insn at %s+0x%" PRIx64,
reloc->sym->sec->name, addend);
return -1;
}
} else {
WARN("can't find unreachable insn at %s+0x%" PRIx64,
reloc->sym->sec->name, addend);
return -1;
}
insn->dead_end = true;
}
reachable:
/*
* These manually annotated reachable checks are needed for GCC 4.4,
* where the Linux unreachable() macro isn't supported. In that case
* GCC doesn't know the "ud2" is fatal, so it generates code as if it's
* not a dead end.
*/
rsec = find_section_by_name(file->elf, ".rela.discard.reachable");
if (!rsec)
return 0;
for_each_reloc(rsec, reloc) {
if (reloc->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in %s", rsec->name);
return -1;
}
addend = reloc_addend(reloc);
insn = find_insn(file, reloc->sym->sec, addend);
if (insn)
insn = prev_insn_same_sec(file, insn);
else if (addend == reloc->sym->sec->sh.sh_size) {
insn = find_last_insn(file, reloc->sym->sec);
if (!insn) {
WARN("can't find reachable insn at %s+0x%" PRIx64,
reloc->sym->sec->name, addend);
return -1;
}
} else {
WARN("can't find reachable insn at %s+0x%" PRIx64,
reloc->sym->sec->name, addend);
return -1;
}
insn->dead_end = false;
}
return 0;
}
static int create_static_call_sections(struct objtool_file *file)
{
struct static_call_site *site;
struct section *sec;
struct instruction *insn;
struct symbol *key_sym;
char *key_name, *tmp;
int idx;
sec = find_section_by_name(file->elf, ".static_call_sites");
if (sec) {
INIT_LIST_HEAD(&file->static_call_list);
WARN("file already has .static_call_sites section, skipping");
return 0;
}
if (list_empty(&file->static_call_list))
return 0;
idx = 0;
list_for_each_entry(insn, &file->static_call_list, call_node)
idx++;
sec = elf_create_section_pair(file->elf, ".static_call_sites",
sizeof(*site), idx, idx * 2);
if (!sec)
return -1;
/* Allow modules to modify the low bits of static_call_site::key */
sec->sh.sh_flags |= SHF_WRITE;
idx = 0;
list_for_each_entry(insn, &file->static_call_list, call_node) {
/* populate reloc for 'addr' */
if (!elf_init_reloc_text_sym(file->elf, sec,
idx * sizeof(*site), idx * 2,
insn->sec, insn->offset))
return -1;
/* find key symbol */
key_name = strdup(insn_call_dest(insn)->name);
if (!key_name) {
perror("strdup");
return -1;
}
if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
STATIC_CALL_TRAMP_PREFIX_LEN)) {
WARN("static_call: trampoline name malformed: %s", key_name);
free(key_name);
return -1;
}
tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
key_sym = find_symbol_by_name(file->elf, tmp);
if (!key_sym) {
if (!opts.module) {
WARN("static_call: can't find static_call_key symbol: %s", tmp);
free(key_name);
return -1;
}
/*
* For modules(), the key might not be exported, which
* means the module can make static calls but isn't
* allowed to change them.
*
* In that case we temporarily set the key to be the
* trampoline address. This is fixed up in
* static_call_add_module().
*/
key_sym = insn_call_dest(insn);
}
free(key_name);
/* populate reloc for 'key' */
if (!elf_init_reloc_data_sym(file->elf, sec,
idx * sizeof(*site) + 4,
(idx * 2) + 1, key_sym,
is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
return -1;
idx++;
}
return 0;
}
static int create_retpoline_sites_sections(struct objtool_file *file)
{
struct instruction *insn;
struct section *sec;
int idx;
sec = find_section_by_name(file->elf, ".retpoline_sites");
if (sec) {
WARN("file already has .retpoline_sites, skipping");
return 0;
}
idx = 0;
list_for_each_entry(insn, &file->retpoline_call_list, call_node)
idx++;
if (!idx)
return 0;
sec = elf_create_section_pair(file->elf, ".retpoline_sites",
sizeof(int), idx, idx);
if (!sec)
return -1;
idx = 0;
list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
if (!elf_init_reloc_text_sym(file->elf, sec,
idx * sizeof(int), idx,
insn->sec, insn->offset))
return -1;
idx++;
}
return 0;
}
static int create_return_sites_sections(struct objtool_file *file)
{
struct instruction *insn;
struct section *sec;
int idx;
sec = find_section_by_name(file->elf, ".return_sites");
if (sec) {
WARN("file already has .return_sites, skipping");
return 0;
}
idx = 0;
list_for_each_entry(insn, &file->return_thunk_list, call_node)
idx++;
if (!idx)
return 0;
sec = elf_create_section_pair(file->elf, ".return_sites",
sizeof(int), idx, idx);
if (!sec)
return -1;
idx = 0;
list_for_each_entry(insn, &file->return_thunk_list, call_node) {
if (!elf_init_reloc_text_sym(file->elf, sec,
idx * sizeof(int), idx,
insn->sec, insn->offset))
return -1;
idx++;
}
return 0;
}
static int create_ibt_endbr_seal_sections(struct objtool_file *file)
{
struct instruction *insn;
struct section *sec;
int idx;
sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
if (sec) {
WARN("file already has .ibt_endbr_seal, skipping");
return 0;
}
idx = 0;
list_for_each_entry(insn, &file->endbr_list, call_node)
idx++;
if (opts.stats) {
printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int);
printf("ibt: superfluous ENDBR: %d\n", idx);
}
if (!idx)
return 0;
sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal",
sizeof(int), idx, idx);
if (!sec)
return -1;
idx = 0;
list_for_each_entry(insn, &file->endbr_list, call_node) {
int *site = (int *)sec->data->d_buf + idx;
struct symbol *sym = insn->sym;
*site = 0;
if (opts.module && sym && sym->type == STT_FUNC &&
insn->offset == sym->offset &&
(!strcmp(sym->name, "init_module") ||
!strcmp(sym->name, "cleanup_module")))
WARN("%s(): not an indirect call target", sym->name);
if (!elf_init_reloc_text_sym(file->elf, sec,
idx * sizeof(int), idx,
insn->sec, insn->offset))
return -1;
idx++;
}
return 0;
}
static int create_cfi_sections(struct objtool_file *file)
{
struct section *sec;
struct symbol *sym;
int idx;
sec = find_section_by_name(file->elf, ".cfi_sites");
if (sec) {
INIT_LIST_HEAD(&file->call_list);
WARN("file already has .cfi_sites section, skipping");
return 0;
}
idx = 0;
for_each_sym(file, sym) {
if (sym->type != STT_FUNC)
continue;
if (strncmp(sym->name, "__cfi_", 6))
continue;
idx++;
}
sec = elf_create_section_pair(file->elf, ".cfi_sites",
sizeof(unsigned int), idx, idx);
if (!sec)
return -1;
idx = 0;
for_each_sym(file, sym) {
if (sym->type != STT_FUNC)
continue;
if (strncmp(sym->name, "__cfi_", 6))
continue;
if (!elf_init_reloc_text_sym(file->elf, sec,
idx * sizeof(unsigned int), idx,
sym->sec, sym->offset))
return -1;
idx++;
}
return 0;
}
static int create_mcount_loc_sections(struct objtool_file *file)
{
size_t addr_size = elf_addr_size(file->elf);
struct instruction *insn;
struct section *sec;
int idx;
sec = find_section_by_name(file->elf, "__mcount_loc");
if (sec) {
INIT_LIST_HEAD(&file->mcount_loc_list);
WARN("file already has __mcount_loc section, skipping");
return 0;
}
if (list_empty(&file->mcount_loc_list))
return 0;
idx = 0;
list_for_each_entry(insn, &file->mcount_loc_list, call_node)
idx++;
sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size,
idx, idx);
if (!sec)
return -1;
sec->sh.sh_addralign = addr_size;
idx = 0;
list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
struct reloc *reloc;
reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx,
insn->sec, insn->offset);
if (!reloc)
return -1;
set_reloc_type(file->elf, reloc, addr_size == 8 ? R_ABS64 : R_ABS32);
idx++;
}
return 0;
}
static int create_direct_call_sections(struct objtool_file *file)
{
struct instruction *insn;
struct section *sec;
int idx;
sec = find_section_by_name(file->elf, ".call_sites");
if (sec) {
INIT_LIST_HEAD(&file->call_list);
WARN("file already has .call_sites section, skipping");
return 0;
}
if (list_empty(&file->call_list))
return 0;
idx = 0;
list_for_each_entry(insn, &file->call_list, call_node)
idx++;
sec = elf_create_section_pair(file->elf, ".call_sites",
sizeof(unsigned int), idx, idx);
if (!sec)
return -1;
idx = 0;
list_for_each_entry(insn, &file->call_list, call_node) {
if (!elf_init_reloc_text_sym(file->elf, sec,
idx * sizeof(unsigned int), idx,
insn->sec, insn->offset))
return -1;
idx++;
}
return 0;
}
/*
* Warnings shouldn't be reported for ignored functions.
*/
static void add_ignores(struct objtool_file *file)
{
struct instruction *insn;
struct section *rsec;
struct symbol *func;
struct reloc *reloc;
rsec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
if (!rsec)
return;
for_each_reloc(rsec, reloc) {
switch (reloc->sym->type) {
case STT_FUNC:
func = reloc->sym;
break;
case STT_SECTION:
func = find_func_by_offset(reloc->sym->sec, reloc_addend(reloc));
if (!func)
continue;
break;
default:
WARN("unexpected relocation symbol type in %s: %d",
rsec->name, reloc->sym->type);
continue;
}
func_for_each_insn(file, func, insn)
insn->ignore = true;
}
}
/*
* This is a whitelist of functions that is allowed to be called with AC set.
* The list is meant to be minimal and only contains compiler instrumentation
* ABI and a few functions used to implement *_{to,from}_user() functions.
*
* These functions must not directly change AC, but may PUSHF/POPF.
*/
static const char *uaccess_safe_builtin[] = {
/* KASAN */
"kasan_report",
"kasan_check_range",
/* KASAN out-of-line */
"__asan_loadN_noabort",
"__asan_load1_noabort",
"__asan_load2_noabort",
"__asan_load4_noabort",
"__asan_load8_noabort",
"__asan_load16_noabort",
"__asan_storeN_noabort",
"__asan_store1_noabort",
"__asan_store2_noabort",
"__asan_store4_noabort",
"__asan_store8_noabort",
"__asan_store16_noabort",
"__kasan_check_read",
"__kasan_check_write",
/* KASAN in-line */
"__asan_report_load_n_noabort",
"__asan_report_load1_noabort",
"__asan_report_load2_noabort",
"__asan_report_load4_noabort",
"__asan_report_load8_noabort",
"__asan_report_load16_noabort",
"__asan_report_store_n_noabort",
"__asan_report_store1_noabort",
"__asan_report_store2_noabort",
"__asan_report_store4_noabort",
"__asan_report_store8_noabort",
"__asan_report_store16_noabort",
/* KCSAN */
"__kcsan_check_access",
"__kcsan_mb",
"__kcsan_wmb",
"__kcsan_rmb",
"__kcsan_release",
"kcsan_found_watchpoint",
"kcsan_setup_watchpoint",
"kcsan_check_scoped_accesses",
"kcsan_disable_current",
"kcsan_enable_current_nowarn",
/* KCSAN/TSAN */
"__tsan_func_entry",
"__tsan_func_exit",
"__tsan_read_range",
"__tsan_write_range",
"__tsan_read1",
"__tsan_read2",
"__tsan_read4",
"__tsan_read8",
"__tsan_read16",
"__tsan_write1",
"__tsan_write2",
"__tsan_write4",
"__tsan_write8",
"__tsan_write16",
"__tsan_read_write1",
"__tsan_read_write2",
"__tsan_read_write4",
"__tsan_read_write8",
"__tsan_read_write16",
"__tsan_volatile_read1",
"__tsan_volatile_read2",
"__tsan_volatile_read4",
"__tsan_volatile_read8",
"__tsan_volatile_read16",
"__tsan_volatile_write1",
"__tsan_volatile_write2",
"__tsan_volatile_write4",
"__tsan_volatile_write8",
"__tsan_volatile_write16",
"__tsan_atomic8_load",
"__tsan_atomic16_load",
"__tsan_atomic32_load",
"__tsan_atomic64_load",
"__tsan_atomic8_store",
"__tsan_atomic16_store",
"__tsan_atomic32_store",
"__tsan_atomic64_store",
"__tsan_atomic8_exchange",
"__tsan_atomic16_exchange",
"__tsan_atomic32_exchange",
"__tsan_atomic64_exchange",
"__tsan_atomic8_fetch_add",
"__tsan_atomic16_fetch_add",
"__tsan_atomic32_fetch_add",
"__tsan_atomic64_fetch_add",
"__tsan_atomic8_fetch_sub",
"__tsan_atomic16_fetch_sub",
"__tsan_atomic32_fetch_sub",
"__tsan_atomic64_fetch_sub",
"__tsan_atomic8_fetch_and",
"__tsan_atomic16_fetch_and",
"__tsan_atomic32_fetch_and",
"__tsan_atomic64_fetch_and",
"__tsan_atomic8_fetch_or",
"__tsan_atomic16_fetch_or",
"__tsan_atomic32_fetch_or",
"__tsan_atomic64_fetch_or",
"__tsan_atomic8_fetch_xor",
"__tsan_atomic16_fetch_xor",
"__tsan_atomic32_fetch_xor",
"__tsan_atomic64_fetch_xor",
"__tsan_atomic8_fetch_nand",
"__tsan_atomic16_fetch_nand",
"__tsan_atomic32_fetch_nand",
"__tsan_atomic64_fetch_nand",
"__tsan_atomic8_compare_exchange_strong",
"__tsan_atomic16_compare_exchange_strong",
"__tsan_atomic32_compare_exchange_strong",
"__tsan_atomic64_compare_exchange_strong",
"__tsan_atomic8_compare_exchange_weak",
"__tsan_atomic16_compare_exchange_weak",
"__tsan_atomic32_compare_exchange_weak",
"__tsan_atomic64_compare_exchange_weak",
"__tsan_atomic8_compare_exchange_val",
"__tsan_atomic16_compare_exchange_val",
"__tsan_atomic32_compare_exchange_val",
"__tsan_atomic64_compare_exchange_val",
"__tsan_atomic_thread_fence",
"__tsan_atomic_signal_fence",
"__tsan_unaligned_read16",
"__tsan_unaligned_write16",
/* KCOV */
"write_comp_data",
"check_kcov_mode",
"__sanitizer_cov_trace_pc",
"__sanitizer_cov_trace_const_cmp1",
"__sanitizer_cov_trace_const_cmp2",
"__sanitizer_cov_trace_const_cmp4",
"__sanitizer_cov_trace_const_cmp8",
"__sanitizer_cov_trace_cmp1",
"__sanitizer_cov_trace_cmp2",
"__sanitizer_cov_trace_cmp4",
"__sanitizer_cov_trace_cmp8",
"__sanitizer_cov_trace_switch",
/* KMSAN */
"kmsan_copy_to_user",
"kmsan_report",
"kmsan_unpoison_entry_regs",
"kmsan_unpoison_memory",
"__msan_chain_origin",
"__msan_get_context_state",
"__msan_instrument_asm_store",
"__msan_metadata_ptr_for_load_1",
"__msan_metadata_ptr_for_load_2",
"__msan_metadata_ptr_for_load_4",
"__msan_metadata_ptr_for_load_8",
"__msan_metadata_ptr_for_load_n",
"__msan_metadata_ptr_for_store_1",
"__msan_metadata_ptr_for_store_2",
"__msan_metadata_ptr_for_store_4",
"__msan_metadata_ptr_for_store_8",
"__msan_metadata_ptr_for_store_n",
"__msan_poison_alloca",
"__msan_warning",
/* UBSAN */
"ubsan_type_mismatch_common",
"__ubsan_handle_type_mismatch",
"__ubsan_handle_type_mismatch_v1",
"__ubsan_handle_shift_out_of_bounds",
"__ubsan_handle_load_invalid_value",
/* STACKLEAK */
"stackleak_track_stack",
/* misc */
"csum_partial_copy_generic",
"copy_mc_fragile",
"copy_mc_fragile_handle_tail",
"copy_mc_enhanced_fast_string",
"ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
"rep_stos_alternative",
"rep_movs_alternative",
"__copy_user_nocache",
NULL
};
static void add_uaccess_safe(struct objtool_file *file)
{
struct symbol *func;
const char **name;
if (!opts.uaccess)
return;
for (name = uaccess_safe_builtin; *name; name++) {
func = find_symbol_by_name(file->elf, *name);
if (!func)
continue;
func->uaccess_safe = true;
}
}
/*
* FIXME: For now, just ignore any alternatives which add retpolines. This is
* a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
* But it at least allows objtool to understand the control flow *around* the
* retpoline.
*/
static int add_ignore_alternatives(struct objtool_file *file)
{
struct section *rsec;
struct reloc *reloc;
struct instruction *insn;
rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
if (!rsec)
return 0;
for_each_reloc(rsec, reloc) {
if (reloc->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in %s", rsec->name);
return -1;
}
insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
if (!insn) {
WARN("bad .discard.ignore_alts entry");
return -1;
}
insn->ignore_alts = true;
}
return 0;
}
__weak bool arch_is_retpoline(struct symbol *sym)
{
return false;
}
__weak bool arch_is_rethunk(struct symbol *sym)
{
return false;
}
static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
{
struct reloc *reloc;
if (insn->no_reloc)
return NULL;
if (!file)
return NULL;
reloc = find_reloc_by_dest_range(file->elf, insn->sec,
insn->offset, insn->len);
if (!reloc) {
insn->no_reloc = 1;
return NULL;
}
return reloc;
}
static void remove_insn_ops(struct instruction *insn)
{
struct stack_op *op, *next;
for (op = insn->stack_ops; op; op = next) {
next = op->next;
free(op);
}
insn->stack_ops = NULL;
}
static void annotate_call_site(struct objtool_file *file,
struct instruction *insn, bool sibling)
{
struct reloc *reloc = insn_reloc(file, insn);
struct symbol *sym = insn_call_dest(insn);
if (!sym)
sym = reloc->sym;
/*
* Alternative replacement code is just template code which is
* sometimes copied to the original instruction. For now, don't
* annotate it. (In the future we might consider annotating the
* original instruction if/when it ever makes sense to do so.)
*/
if (!strcmp(insn->sec->name, ".altinstr_replacement"))
return;
if (sym->static_call_tramp) {
list_add_tail(&insn->call_node, &file->static_call_list);
return;
}
if (sym->retpoline_thunk) {
list_add_tail(&insn->call_node, &file->retpoline_call_list);
return;
}
/*
* Many compilers cannot disable KCOV or sanitizer calls with a function
* attribute so they need a little help, NOP out any such calls from
* noinstr text.
*/
if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
if (reloc)
set_reloc_type(file->elf, reloc, R_NONE);
elf_write_insn(file->elf, insn->sec,
insn->offset, insn->len,
sibling ? arch_ret_insn(insn->len)
: arch_nop_insn(insn->len));
insn->type = sibling ? INSN_RETURN : INSN_NOP;
if (sibling) {
/*
* We've replaced the tail-call JMP insn by two new
* insn: RET; INT3, except we only have a single struct
* insn here. Mark it retpoline_safe to avoid the SLS
* warning, instead of adding another insn.
*/
insn->retpoline_safe = true;
}
return;
}
if (opts.mcount && sym->fentry) {
if (sibling)
WARN_INSN(insn, "tail call to __fentry__ !?!?");
if (opts.mnop) {
if (reloc)
set_reloc_type(file->elf, reloc, R_NONE);
elf_write_insn(file->elf, insn->sec,
insn->offset, insn->len,
arch_nop_insn(insn->len));
insn->type = INSN_NOP;
}
list_add_tail(&insn->call_node, &file->mcount_loc_list);
return;
}
if (insn->type == INSN_CALL && !insn->sec->init)
list_add_tail(&insn->call_node, &file->call_list);
if (!sibling && dead_end_function(file, sym))
insn->dead_end = true;
}
static void add_call_dest(struct objtool_file *file, struct instruction *insn,
struct symbol *dest, bool sibling)
{
insn->_call_dest = dest;
if (!dest)
return;
/*
* Whatever stack impact regular CALLs have, should be undone
* by the RETURN of the called function.
*
* Annotated intra-function calls retain the stack_ops but
* are converted to JUMP, see read_intra_function_calls().
*/
remove_insn_ops(insn);
annotate_call_site(file, insn, sibling);
}
static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
{
/*
* Retpoline calls/jumps are really dynamic calls/jumps in disguise,
* so convert them accordingly.
*/
switch (insn->type) {
case INSN_CALL:
insn->type = INSN_CALL_DYNAMIC;
break;
case INSN_JUMP_UNCONDITIONAL:
insn->type = INSN_JUMP_DYNAMIC;
break;
case INSN_JUMP_CONDITIONAL:
insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
break;
default:
return;
}
insn->retpoline_safe = true;
/*
* Whatever stack impact regular CALLs have, should be undone
* by the RETURN of the called function.
*
* Annotated intra-function calls retain the stack_ops but
* are converted to JUMP, see read_intra_function_calls().
*/
remove_insn_ops(insn);
annotate_call_site(file, insn, false);
}
static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
{
/*
* Return thunk tail calls are really just returns in disguise,
* so convert them accordingly.
*/
insn->type = INSN_RETURN;
insn->retpoline_safe = true;
if (add)
list_add_tail(&insn->call_node, &file->return_thunk_list);
}
static bool is_first_func_insn(struct objtool_file *file,
struct instruction *insn, struct symbol *sym)
{
if (insn->offset == sym->offset)
return true;
/* Allow direct CALL/JMP past ENDBR */
if (opts.ibt) {
struct instruction *prev = prev_insn_same_sym(file, insn);
if (prev && prev->type == INSN_ENDBR &&
insn->offset == sym->offset + prev->len)
return true;
}
return false;
}
/*
* A sibling call is a tail-call to another symbol -- to differentiate from a
* recursive tail-call which is to the same symbol.
*/
static bool jump_is_sibling_call(struct objtool_file *file,
struct instruction *from, struct instruction *to)
{
struct symbol *fs = from->sym;
struct symbol *ts = to->sym;
/* Not a sibling call if from/to a symbol hole */
if (!fs || !ts)
return false;
/* Not a sibling call if not targeting the start of a symbol. */
if (!is_first_func_insn(file, to, ts))
return false;
/* Disallow sibling calls into STT_NOTYPE */
if (ts->type == STT_NOTYPE)
return false;
/* Must not be self to be a sibling */
return fs->pfunc != ts->pfunc;
}
/*
* Find the destination instructions for all jumps.
*/
static int add_jump_destinations(struct objtool_file *file)
{
struct instruction *insn, *jump_dest;
struct reloc *reloc;
struct section *dest_sec;
unsigned long dest_off;
for_each_insn(file, insn) {
if (insn->jump_dest) {
/*
* handle_group_alt() may have previously set
* 'jump_dest' for some alternatives.
*/
continue;
}
if (!is_static_jump(insn))
continue;
reloc = insn_reloc(file, insn);
if (!reloc) {
dest_sec = insn->sec;
dest_off = arch_jump_destination(insn);
} else if (reloc->sym->type == STT_SECTION) {
dest_sec = reloc->sym->sec;
dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
} else if (reloc->sym->retpoline_thunk) {
add_retpoline_call(file, insn);
continue;
} else if (reloc->sym->return_thunk) {
add_return_call(file, insn, true);
continue;
} else if (insn_func(insn)) {
/*
* External sibling call or internal sibling call with
* STT_FUNC reloc.
*/
add_call_dest(file, insn, reloc->sym, true);
continue;
} else if (reloc->sym->sec->idx) {
dest_sec = reloc->sym->sec;
dest_off = reloc->sym->sym.st_value +
arch_dest_reloc_offset(reloc_addend(reloc));
} else {
/* non-func asm code jumping to another file */
continue;
}
jump_dest = find_insn(file, dest_sec, dest_off);
if (!jump_dest) {
struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
/*
* This is a special case for zen_untrain_ret().
* It jumps to __x86_return_thunk(), but objtool
* can't find the thunk's starting RET
* instruction, because the RET is also in the
* middle of another instruction. Objtool only
* knows about the outer instruction.
*/
if (sym && sym->return_thunk) {
add_return_call(file, insn, false);
continue;
}
WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
dest_sec->name, dest_off);
return -1;
}
/*
* Cross-function jump.
*/
if (insn_func(insn) && insn_func(jump_dest) &&
insn_func(insn) != insn_func(jump_dest)) {
/*
* For GCC 8+, create parent/child links for any cold
* subfunctions. This is _mostly_ redundant with a
* similar initialization in read_symbols().
*
* If a function has aliases, we want the *first* such
* function in the symbol table to be the subfunction's
* parent. In that case we overwrite the
* initialization done in read_symbols().
*
* However this code can't completely replace the
* read_symbols() code because this doesn't detect the
* case where the parent function's only reference to a
* subfunction is through a jump table.
*/
if (!strstr(insn_func(insn)->name, ".cold") &&
strstr(insn_func(jump_dest)->name, ".cold")) {
insn_func(insn)->cfunc = insn_func(jump_dest);
insn_func(jump_dest)->pfunc = insn_func(insn);
}
}
if (jump_is_sibling_call(file, insn, jump_dest)) {
/*
* Internal sibling call without reloc or with
* STT_SECTION reloc.
*/
add_call_dest(file, insn, insn_func(jump_dest), true);
continue;
}
insn->jump_dest = jump_dest;
}
return 0;
}
static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
{
struct symbol *call_dest;
call_dest = find_func_by_offset(sec, offset);
if (!call_dest)
call_dest = find_symbol_by_offset(sec, offset);
return call_dest;
}
/*
* Find the destination instructions for all calls.
*/
static int add_call_destinations(struct objtool_file *file)
{
struct instruction *insn;
unsigned long dest_off;
struct symbol *dest;
struct reloc *reloc;
for_each_insn(file, insn) {
if (insn->type != INSN_CALL)
continue;
reloc = insn_reloc(file, insn);
if (!reloc) {
dest_off = arch_jump_destination(insn);
dest = find_call_destination(insn->sec, dest_off);
add_call_dest(file, insn, dest, false);
if (insn->ignore)
continue;
if (!insn_call_dest(insn)) {
WARN_INSN(insn, "unannotated intra-function call");
return -1;
}
if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
WARN_INSN(insn, "unsupported call to non-function");
return -1;
}
} else if (reloc->sym->type == STT_SECTION) {
dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
dest = find_call_destination(reloc->sym->sec, dest_off);
if (!dest) {
WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
reloc->sym->sec->name, dest_off);
return -1;
}
add_call_dest(file, insn, dest, false);
} else if (reloc->sym->retpoline_thunk) {
add_retpoline_call(file, insn);
} else
add_call_dest(file, insn, reloc->sym, false);
}
return 0;
}
/*
* The .alternatives section requires some extra special care over and above
* other special sections because alternatives are patched in place.
*/
static int handle_group_alt(struct objtool_file *file,
struct special_alt *special_alt,
struct instruction *orig_insn,
struct instruction **new_insn)
{
struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
struct alt_group *orig_alt_group, *new_alt_group;
unsigned long dest_off;
orig_alt_group = orig_insn->alt_group;
if (!orig_alt_group) {
struct instruction *last_orig_insn = NULL;
orig_alt_group = malloc(sizeof(*orig_alt_group));
if (!orig_alt_group) {
WARN("malloc failed");
return -1;
}
orig_alt_group->cfi = calloc(special_alt->orig_len,
sizeof(struct cfi_state *));
if (!orig_alt_group->cfi) {
WARN("calloc failed");
return -1;
}
insn = orig_insn;
sec_for_each_insn_from(file, insn) {
if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
break;
insn->alt_group = orig_alt_group;
last_orig_insn = insn;
}
orig_alt_group->orig_group = NULL;
orig_alt_group->first_insn = orig_insn;
orig_alt_group->last_insn = last_orig_insn;
orig_alt_group->nop = NULL;
} else {
if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
orig_alt_group->first_insn->offset != special_alt->orig_len) {
WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
orig_alt_group->last_insn->offset +
orig_alt_group->last_insn->len -
orig_alt_group->first_insn->offset,
special_alt->orig_len);
return -1;
}
}
new_alt_group = malloc(sizeof(*new_alt_group));
if (!new_alt_group) {
WARN("malloc failed");
return -1;
}
if (special_alt->new_len < special_alt->orig_len) {
/*
* Insert a fake nop at the end to make the replacement
* alt_group the same size as the original. This is needed to
* allow propagate_alt_cfi() to do its magic. When the last
* instruction affects the stack, the instruction after it (the
* nop) will propagate the new state to the shared CFI array.
*/
nop = malloc(sizeof(*nop));
if (!nop) {
WARN("malloc failed");
return -1;
}
memset(nop, 0, sizeof(*nop));
nop->sec = special_alt->new_sec;
nop->offset = special_alt->new_off + special_alt->new_len;
nop->len = special_alt->orig_len - special_alt->new_len;
nop->type = INSN_NOP;
nop->sym = orig_insn->sym;
nop->alt_group = new_alt_group;
nop->ignore = orig_insn->ignore_alts;
}
if (!special_alt->new_len) {
*new_insn = nop;
goto end;
}
insn = *new_insn;
sec_for_each_insn_from(file, insn) {
struct reloc *alt_reloc;
if (insn->offset >= special_alt->new_off + special_alt->new_len)
break;
last_new_insn = insn;
insn->ignore = orig_insn->ignore_alts;
insn->sym = orig_insn->sym;
insn->alt_group = new_alt_group;
/*
* Since alternative replacement code is copy/pasted by the
* kernel after applying relocations, generally such code can't
* have relative-address relocation references to outside the
* .altinstr_replacement section, unless the arch's
* alternatives code can adjust the relative offsets
* accordingly.
*/
alt_reloc = insn_reloc(file, insn);
if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
!arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
WARN_INSN(insn, "unsupported relocation in alternatives section");
return -1;
}
if (!is_static_jump(insn))
continue;
if (!insn->immediate)
continue;
dest_off = arch_jump_destination(insn);
if (dest_off == special_alt->new_off + special_alt->new_len) {
insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
if (!insn->jump_dest) {
WARN_INSN(insn, "can't find alternative jump destination");
return -1;
}
}
}
if (!last_new_insn) {
WARN_FUNC("can't find last new alternative instruction",
special_alt->new_sec, special_alt->new_off);
return -1;
}
end:
new_alt_group->orig_group = orig_alt_group;
new_alt_group->first_insn = *new_insn;
new_alt_group->last_insn = last_new_insn;
new_alt_group->nop = nop;
new_alt_group->cfi = orig_alt_group->cfi;
return 0;
}
/*
* A jump table entry can either convert a nop to a jump or a jump to a nop.
* If the original instruction is a jump, make the alt entry an effective nop
* by just skipping the original instruction.
*/
static int handle_jump_alt(struct objtool_file *file,
struct special_alt *special_alt,
struct instruction *orig_insn,
struct instruction **new_insn)
{
if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
orig_insn->type != INSN_NOP) {
WARN_INSN(orig_insn, "unsupported instruction at jump label");
return -1;
}
if (opts.hack_jump_label && special_alt->key_addend & 2) {
struct reloc *reloc = insn_reloc(file, orig_insn);
if (reloc)
set_reloc_type(file->elf, reloc, R_NONE);
elf_write_insn(file->elf, orig_insn->sec,
orig_insn->offset, orig_insn->len,
arch_nop_insn(orig_insn->len));
orig_insn->type = INSN_NOP;
}
if (orig_insn->type == INSN_NOP) {
if (orig_insn->len == 2)
file->jl_nop_short++;
else
file->jl_nop_long++;
return 0;
}
if (orig_insn->len == 2)
file->jl_short++;
else
file->jl_long++;
*new_insn = next_insn_same_sec(file, orig_insn);
return 0;
}
/*
* Read all the special sections which have alternate instructions which can be
* patched in or redirected to at runtime. Each instruction having alternate
* instruction(s) has them added to its insn->alts list, which will be
* traversed in validate_branch().
*/
static int add_special_section_alts(struct objtool_file *file)
{
struct list_head special_alts;
struct instruction *orig_insn, *new_insn;
struct special_alt *special_alt, *tmp;
struct alternative *alt;
int ret;
ret = special_get_alts(file->elf, &special_alts);
if (ret)
return ret;
list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
orig_insn = find_insn(file, special_alt->orig_sec,
special_alt->orig_off);
if (!orig_insn) {
WARN_FUNC("special: can't find orig instruction",
special_alt->orig_sec, special_alt->orig_off);
ret = -1;
goto out;
}
new_insn = NULL;
if (!special_alt->group || special_alt->new_len) {
new_insn = find_insn(file, special_alt->new_sec,
special_alt->new_off);
if (!new_insn) {
WARN_FUNC("special: can't find new instruction",
special_alt->new_sec,
special_alt->new_off);
ret = -1;
goto out;
}
}
if (special_alt->group) {
if (!special_alt->orig_len) {
WARN_INSN(orig_insn, "empty alternative entry");
continue;
}
ret = handle_group_alt(file, special_alt, orig_insn,
&new_insn);
if (ret)
goto out;
} else if (special_alt->jump_or_nop) {
ret = handle_jump_alt(file, special_alt, orig_insn,
&new_insn);
if (ret)
goto out;
}
alt = malloc(sizeof(*alt));
if (!alt) {
WARN("malloc failed");
ret = -1;
goto out;
}
alt->insn = new_insn;
alt->skip_orig = special_alt->skip_orig;
orig_insn->ignore_alts |= special_alt->skip_alt;
alt->next = orig_insn->alts;
orig_insn->alts = alt;
list_del(&special_alt->list);
free(special_alt);
}
if (opts.stats) {
printf("jl\\\tNOP\tJMP\n");
printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
}
out:
return ret;
}
static int add_jump_table(struct objtool_file *file, struct instruction *insn,
struct reloc *next_table)
{
struct symbol *pfunc = insn_func(insn)->pfunc;
struct reloc *table = insn_jump_table(insn);
struct instruction *dest_insn;
unsigned int prev_offset = 0;
struct reloc *reloc = table;
struct alternative *alt;
/*
* Each @reloc is a switch table relocation which points to the target
* instruction.
*/
for_each_reloc_from(table->sec, reloc) {
/* Check for the end of the table: */
if (reloc != table && reloc == next_table)
break;
/* Make sure the table entries are consecutive: */
if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
break;
/* Detect function pointers from contiguous objects: */
if (reloc->sym->sec == pfunc->sec &&
reloc_addend(reloc) == pfunc->offset)
break;
dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
if (!dest_insn)
break;
/* Make sure the destination is in the same function: */
if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
break;
alt = malloc(sizeof(*alt));
if (!alt) {
WARN("malloc failed");
return -1;
}
alt->insn = dest_insn;
alt->next = insn->alts;
insn->alts = alt;
prev_offset = reloc_offset(reloc);
}
if (!prev_offset) {
WARN_INSN(insn, "can't find switch jump table");
return -1;
}
return 0;
}
/*
* find_jump_table() - Given a dynamic jump, find the switch jump table
* associated with it.
*/
static struct reloc *find_jump_table(struct objtool_file *file,
struct symbol *func,
struct instruction *insn)
{
struct reloc *table_reloc;
struct instruction *dest_insn, *orig_insn = insn;
/*
* Backward search using the @first_jump_src links, these help avoid
* much of the 'in between' code. Which avoids us getting confused by
* it.
*/
for (;
insn && insn_func(insn) && insn_func(insn)->pfunc == func;
insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
break;
/* allow small jumps within the range */
if (insn->type == INSN_JUMP_UNCONDITIONAL &&
insn->jump_dest &&
(insn->jump_dest->offset <= insn->offset ||
insn->jump_dest->offset > orig_insn->offset))
break;
table_reloc = arch_find_switch_table(file, insn);
if (!table_reloc)
continue;
dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
continue;
return table_reloc;
}
return NULL;
}
/*
* First pass: Mark the head of each jump table so that in the next pass,
* we know when a given jump table ends and the next one starts.
*/
static void mark_func_jump_tables(struct objtool_file *file,
struct symbol *func)
{
struct instruction *insn, *last = NULL;
struct reloc *reloc;
func_for_each_insn(file, func, insn) {
if (!last)
last = insn;
/*
* Store back-pointers for unconditional forward jumps such
* that find_jump_table() can back-track using those and
* avoid some potentially confusing code.
*/
if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
insn->offset > last->offset &&
insn->jump_dest->offset > insn->offset &&
!insn->jump_dest->first_jump_src) {
insn->jump_dest->first_jump_src = insn;
last = insn->jump_dest;
}
if (insn->type != INSN_JUMP_DYNAMIC)
continue;
reloc = find_jump_table(file, func, insn);
if (reloc)
insn->_jump_table = reloc;
}
}
static int add_func_jump_tables(struct objtool_file *file,
struct symbol *func)
{
struct instruction *insn, *insn_t1 = NULL, *insn_t2;
int ret = 0;
func_for_each_insn(file, func, insn) {
if (!insn_jump_table(insn))
continue;
if (!insn_t1) {
insn_t1 = insn;
continue;
}
insn_t2 = insn;
ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
if (ret)
return ret;
insn_t1 = insn_t2;
}
if (insn_t1)
ret = add_jump_table(file, insn_t1, NULL);
return ret;
}
/*
* For some switch statements, gcc generates a jump table in the .rodata
* section which contains a list of addresses within the function to jump to.
* This finds these jump tables and adds them to the insn->alts lists.
*/
static int add_jump_table_alts(struct objtool_file *file)
{
struct symbol *func;
int ret;
if (!file->rodata)
return 0;
for_each_sym(file, func) {
if (func->type != STT_FUNC)
continue;
mark_func_jump_tables(file, func);
ret = add_func_jump_tables(file, func);
if (ret)
return ret;
}
return 0;
}
static void set_func_state(struct cfi_state *state)
{
state->cfa = initial_func_cfi.cfa;
memcpy(&state->regs, &initial_func_cfi.regs,
CFI_NUM_REGS * sizeof(struct cfi_reg));
state->stack_size = initial_func_cfi.cfa.offset;
state->type = UNWIND_HINT_TYPE_CALL;
}
static int read_unwind_hints(struct objtool_file *file)
{
struct cfi_state cfi = init_cfi;
struct section *sec;
struct unwind_hint *hint;
struct instruction *insn;
struct reloc *reloc;
int i;
sec = find_section_by_name(file->elf, ".discard.unwind_hints");
if (!sec)
return 0;
if (!sec->rsec) {
WARN("missing .rela.discard.unwind_hints section");
return -1;
}
if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
WARN("struct unwind_hint size mismatch");
return -1;
}
file->hints = true;
for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
hint = (struct unwind_hint *)sec->data->d_buf + i;
reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
if (!reloc) {
WARN("can't find reloc for unwind_hints[%d]", i);
return -1;
}
insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
if (!insn) {
WARN("can't find insn for unwind_hints[%d]", i);
return -1;
}
insn->hint = true;
if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
insn->cfi = &force_undefined_cfi;
continue;
}
if (hint->type == UNWIND_HINT_TYPE_SAVE) {
insn->hint = false;
insn->save = true;
continue;
}
if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
insn->restore = true;
continue;
}
if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
if (sym && sym->bind == STB_GLOBAL) {
if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
}
}
}
if (hint->type == UNWIND_HINT_TYPE_FUNC) {
insn->cfi = &func_cfi;
continue;
}
if (insn->cfi)
cfi = *(insn->cfi);
if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
return -1;
}
cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
cfi.type = hint->type;
cfi.signal = hint->signal;
insn->cfi = cfi_hash_find_or_add(&cfi);
}
return 0;
}
static int read_noendbr_hints(struct objtool_file *file)
{
struct instruction *insn;
struct section *rsec;
struct reloc *reloc;
rsec = find_section_by_name(file->elf, ".rela.discard.noendbr");
if (!rsec)
return 0;
for_each_reloc(rsec, reloc) {
insn = find_insn(file, reloc->sym->sec,
reloc->sym->offset + reloc_addend(reloc));
if (!insn) {
WARN("bad .discard.noendbr entry");
return -1;
}
insn->noendbr = 1;
}
return 0;
}
static int read_retpoline_hints(struct objtool_file *file)
{
struct section *rsec;
struct instruction *insn;
struct reloc *reloc;
rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
if (!rsec)
return 0;
for_each_reloc(rsec, reloc) {
if (reloc->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in %s", rsec->name);
return -1;
}
insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
if (!insn) {
WARN("bad .discard.retpoline_safe entry");
return -1;
}
if (insn->type != INSN_JUMP_DYNAMIC &&
insn->type != INSN_CALL_DYNAMIC &&
insn->type != INSN_RETURN &&
insn->type != INSN_NOP) {
WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
return -1;
}
insn->retpoline_safe = true;
}
return 0;
}
static int read_instr_hints(struct objtool_file *file)
{
struct section *rsec;
struct instruction *insn;
struct reloc *reloc;
rsec = find_section_by_name(file->elf, ".rela.discard.instr_end");
if (!rsec)
return 0;
for_each_reloc(rsec, reloc) {
if (reloc->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in %s", rsec->name);
return -1;
}
insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
if (!insn) {
WARN("bad .discard.instr_end entry");
return -1;
}
insn->instr--;
}
rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
if (!rsec)
return 0;
for_each_reloc(rsec, reloc) {
if (reloc->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in %s", rsec->name);
return -1;
}
insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
if (!insn) {
WARN("bad .discard.instr_begin entry");
return -1;
}
insn->instr++;
}
return 0;
}
static int read_validate_unret_hints(struct objtool_file *file)
{
struct section *rsec;
struct instruction *insn;
struct reloc *reloc;
rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
if (!rsec)
return 0;
for_each_reloc(rsec, reloc) {
if (reloc->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in %s", rsec->name);
return -1;
}
insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
if (!insn) {
WARN("bad .discard.instr_end entry");
return -1;
}
insn->unret = 1;
}
return 0;
}
static int read_intra_function_calls(struct objtool_file *file)
{
struct instruction *insn;
struct section *rsec;
struct reloc *reloc;
rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
if (!rsec)
return 0;
for_each_reloc(rsec, reloc) {
unsigned long dest_off;
if (reloc->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in %s",
rsec->name);
return -1;
}
insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
if (!insn) {
WARN("bad .discard.intra_function_call entry");
return -1;
}
if (insn->type != INSN_CALL) {
WARN_INSN(insn, "intra_function_call not a direct call");
return -1;
}
/*
* Treat intra-function CALLs as JMPs, but with a stack_op.
* See add_call_destinations(), which strips stack_ops from
* normal CALLs.
*/
insn->type = INSN_JUMP_UNCONDITIONAL;
dest_off = arch_jump_destination(insn);
insn->jump_dest = find_insn(file, insn->sec, dest_off);
if (!insn->jump_dest) {
WARN_INSN(insn, "can't find call dest at %s+0x%lx",
insn->sec->name, dest_off);
return -1;
}
}
return 0;
}
/*
* Return true if name matches an instrumentation function, where calls to that
* function from noinstr code can safely be removed, but compilers won't do so.
*/
static bool is_profiling_func(const char *name)
{
/*
* Many compilers cannot disable KCOV with a function attribute.
*/
if (!strncmp(name, "__sanitizer_cov_", 16))
return true;
/*
* Some compilers currently do not remove __tsan_func_entry/exit nor
* __tsan_atomic_signal_fence (used for barrier instrumentation) with
* the __no_sanitize_thread attribute, remove them. Once the kernel's
* minimum Clang version is 14.0, this can be removed.
*/
if (!strncmp(name, "__tsan_func_", 12) ||
!strcmp(name, "__tsan_atomic_signal_fence"))
return true;
return false;
}
static int classify_symbols(struct objtool_file *file)
{
struct symbol *func;
for_each_sym(file, func) {
if (func->bind != STB_GLOBAL)
continue;
if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
func->static_call_tramp = true;
if (arch_is_retpoline(func))
func->retpoline_thunk = true;
if (arch_is_rethunk(func))
func->return_thunk = true;
if (arch_ftrace_match(func->name))
func->fentry = true;
if (is_profiling_func(func->name))
func->profiling_func = true;
}
return 0;
}
static void mark_rodata(struct objtool_file *file)
{
struct section *sec;
bool found = false;
/*
* Search for the following rodata sections, each of which can
* potentially contain jump tables:
*
* - .rodata: can contain GCC switch tables
* - .rodata.<func>: same, if -fdata-sections is being used
* - .rodata..c_jump_table: contains C annotated jump tables
*
* .rodata.str1.* sections are ignored; they don't contain jump tables.
*/
for_each_sec(file, sec) {
if (!strncmp(sec->name, ".rodata", 7) &&
!strstr(sec->name, ".str1.")) {
sec->rodata = true;
found = true;
}
}
file->rodata = found;
}
static int decode_sections(struct objtool_file *file)
{
int ret;
mark_rodata(file);
ret = init_pv_ops(file);
if (ret)
return ret;
/*
* Must be before add_{jump_call}_destination.
*/
ret = classify_symbols(file);
if (ret)
return ret;
ret = decode_instructions(file);
if (ret)
return ret;
add_ignores(file);
add_uaccess_safe(file);
ret = add_ignore_alternatives(file);
if (ret)
return ret;
/*
* Must be before read_unwind_hints() since that needs insn->noendbr.
*/
ret = read_noendbr_hints(file);
if (ret)
return ret;
/*
* Must be before add_jump_destinations(), which depends on 'func'
* being set for alternatives, to enable proper sibling call detection.
*/
if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
ret = add_special_section_alts(file);
if (ret)
return ret;
}
ret = add_jump_destinations(file);
if (ret)
return ret;
/*
* Must be before add_call_destination(); it changes INSN_CALL to
* INSN_JUMP.
*/
ret = read_intra_function_calls(file);
if (ret)
return ret;
ret = add_call_destinations(file);
if (ret)
return ret;
/*
* Must be after add_call_destinations() such that it can override
* dead_end_function() marks.
*/
ret = add_dead_ends(file);
if (ret)
return ret;
ret = add_jump_table_alts(file);
if (ret)
return ret;
ret = read_unwind_hints(file);
if (ret)
return ret;
ret = read_retpoline_hints(file);
if (ret)
return ret;
ret = read_instr_hints(file);
if (ret)
return ret;
ret = read_validate_unret_hints(file);
if (ret)
return ret;
return 0;
}
static bool is_fentry_call(struct instruction *insn)
{
if (insn->type == INSN_CALL &&
insn_call_dest(insn) &&
insn_call_dest(insn)->fentry)
return true;
return false;
}
static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
{
struct cfi_state *cfi = &state->cfi;
int i;
if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
return true;
if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
return true;
if (cfi->stack_size != initial_func_cfi.cfa.offset)
return true;
for (i = 0; i < CFI_NUM_REGS; i++) {
if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
return true;
}
return false;
}
static bool check_reg_frame_pos(const struct cfi_reg *reg,
int expected_offset)
{
return reg->base == CFI_CFA &&
reg->offset == expected_offset;
}
static bool has_valid_stack_frame(struct insn_state *state)
{
struct cfi_state *cfi = &state->cfi;
if (cfi->cfa.base == CFI_BP &&
check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
return true;
if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
return true;
return false;
}
static int update_cfi_state_regs(struct instruction *insn,
struct cfi_state *cfi,
struct stack_op *op)
{
struct cfi_reg *cfa = &cfi->cfa;
if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
return 0;
/* push */
if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
cfa->offset += 8;
/* pop */
if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
cfa->offset -= 8;
/* add immediate to sp */
if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
cfa->offset -= op->src.offset;
return 0;
}
static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
{
if (arch_callee_saved_reg(reg) &&
cfi->regs[reg].base == CFI_UNDEFINED) {
cfi->regs[reg].base = base;
cfi->regs[reg].offset = offset;
}
}
static void restore_reg(struct cfi_state *cfi, unsigned char reg)
{
cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
}
/*
* A note about DRAP stack alignment:
*
* GCC has the concept of a DRAP register, which is used to help keep track of
* the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
* register. The typical DRAP pattern is:
*
* 4c 8d 54 24 08 lea 0x8(%rsp),%r10
* 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
* 41 ff 72 f8 pushq -0x8(%r10)
* 55 push %rbp
* 48 89 e5 mov %rsp,%rbp
* (more pushes)
* 41 52 push %r10
* ...
* 41 5a pop %r10
* (more pops)
* 5d pop %rbp
* 49 8d 62 f8 lea -0x8(%r10),%rsp
* c3 retq
*
* There are some variations in the epilogues, like:
*
* 5b pop %rbx
* 41 5a pop %r10
* 41 5c pop %r12
* 41 5d pop %r13
* 41 5e pop %r14
* c9 leaveq
* 49 8d 62 f8 lea -0x8(%r10),%rsp
* c3 retq
*
* and:
*
* 4c 8b 55 e8 mov -0x18(%rbp),%r10
* 48 8b 5d e0 mov -0x20(%rbp),%rbx
* 4c 8b 65 f0 mov -0x10(%rbp),%r12
* 4c 8b 6d f8 mov -0x8(%rbp),%r13
* c9 leaveq
* 49 8d 62 f8 lea -0x8(%r10),%rsp
* c3 retq
*
* Sometimes r13 is used as the DRAP register, in which case it's saved and
* restored beforehand:
*
* 41 55 push %r13
* 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
* 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
* ...
* 49 8d 65 f0 lea -0x10(%r13),%rsp
* 41 5d pop %r13
* c3 retq
*/
static int update_cfi_state(struct instruction *insn,
struct instruction *next_insn,
struct cfi_state *cfi, struct stack_op *op)
{
struct cfi_reg *cfa = &cfi->cfa;
struct cfi_reg *regs = cfi->regs;
/* ignore UNWIND_HINT_UNDEFINED regions */
if (cfi->force_undefined)
return 0;
/* stack operations don't make sense with an undefined CFA */
if (cfa->base == CFI_UNDEFINED) {
if (insn_func(insn)) {
WARN_INSN(insn, "undefined stack state");
return -1;
}
return 0;
}
if (cfi->type == UNWIND_HINT_TYPE_REGS ||
cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
return update_cfi_state_regs(insn, cfi, op);
switch (op->dest.type) {
case OP_DEST_REG:
switch (op->src.type) {
case OP_SRC_REG:
if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
cfa->base == CFI_SP &&
check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
/* mov %rsp, %rbp */
cfa->base = op->dest.reg;
cfi->bp_scratch = false;
}
else if (op->src.reg == CFI_SP &&
op->dest.reg == CFI_BP && cfi->drap) {
/* drap: mov %rsp, %rbp */
regs[CFI_BP].base = CFI_BP;
regs[CFI_BP].offset = -cfi->stack_size;
cfi->bp_scratch = false;
}
else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
/*
* mov %rsp, %reg
*
* This is needed for the rare case where GCC
* does:
*
* mov %rsp, %rax
* ...
* mov %rax, %rsp
*/
cfi->vals[op->dest.reg].base = CFI_CFA;
cfi->vals[op->dest.reg].offset = -cfi->stack_size;
}
else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
(cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
/*
* mov %rbp, %rsp
*
* Restore the original stack pointer (Clang).
*/
cfi->stack_size = -cfi->regs[CFI_BP].offset;
}
else if (op->dest.reg == cfa->base) {
/* mov %reg, %rsp */
if (cfa->base == CFI_SP &&
cfi->vals[op->src.reg].base == CFI_CFA) {
/*
* This is needed for the rare case
* where GCC does something dumb like:
*
* lea 0x8(%rsp), %rcx
* ...
* mov %rcx, %rsp
*/
cfa->offset = -cfi->vals[op->src.reg].offset;
cfi->stack_size = cfa->offset;
} else if (cfa->base == CFI_SP &&
cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
cfi->vals[op->src.reg].offset == cfa->offset) {
/*
* Stack swizzle:
*
* 1: mov %rsp, (%[tos])
* 2: mov %[tos], %rsp
* ...
* 3: pop %rsp
*
* Where:
*
* 1 - places a pointer to the previous
* stack at the Top-of-Stack of the
* new stack.
*
* 2 - switches to the new stack.
*
* 3 - pops the Top-of-Stack to restore
* the original stack.
*
* Note: we set base to SP_INDIRECT
* here and preserve offset. Therefore
* when the unwinder reaches ToS it
* will dereference SP and then add the
* offset to find the next frame, IOW:
* (%rsp) + offset.
*/
cfa->base = CFI_SP_INDIRECT;
} else {
cfa->base = CFI_UNDEFINED;
cfa->offset = 0;
}
}
else if (op->dest.reg == CFI_SP &&
cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
cfi->vals[op->src.reg].offset == cfa->offset) {
/*
* The same stack swizzle case 2) as above. But
* because we can't change cfa->base, case 3)
* will become a regular POP. Pretend we're a
* PUSH so things don't go unbalanced.
*/
cfi->stack_size += 8;
}
break;
case OP_SRC_ADD:
if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
/* add imm, %rsp */
cfi->stack_size -= op->src.offset;
if (cfa->base == CFI_SP)
cfa->offset -= op->src.offset;
break;
}
if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
/* lea disp(%rbp), %rsp */
cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
break;
}
if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
/* drap: lea disp(%rsp), %drap */
cfi->drap_reg = op->dest.reg;
/*
* lea disp(%rsp), %reg
*
* This is needed for the rare case where GCC
* does something dumb like:
*
* lea 0x8(%rsp), %rcx
* ...
* mov %rcx, %rsp
*/
cfi->vals[op->dest.reg].base = CFI_CFA;
cfi->vals[op->dest.reg].offset = \
-cfi->stack_size + op->src.offset;
break;
}
if (cfi->drap && op->dest.reg == CFI_SP &&
op->src.reg == cfi->drap_reg) {
/* drap: lea disp(%drap), %rsp */
cfa->base = CFI_SP;
cfa->offset = cfi->stack_size = -op->src.offset;
cfi->drap_reg = CFI_UNDEFINED;
cfi->drap = false;
break;
}
if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
WARN_INSN(insn, "unsupported stack register modification");
return -1;
}
break;
case OP_SRC_AND:
if (op->dest.reg != CFI_SP ||
(cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
(cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
WARN_INSN(insn, "unsupported stack pointer realignment");
return -1;
}
if (cfi->drap_reg != CFI_UNDEFINED) {
/* drap: and imm, %rsp */
cfa->base = cfi->drap_reg;
cfa->offset = cfi->stack_size = 0;
cfi->drap = true;
}
/*
* Older versions of GCC (4.8ish) realign the stack
* without DRAP, with a frame pointer.
*/
break;
case OP_SRC_POP:
case OP_SRC_POPF:
if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
/* pop %rsp; # restore from a stack swizzle */
cfa->base = CFI_SP;
break;
}
if (!cfi->drap && op->dest.reg == cfa->base) {
/* pop %rbp */
cfa->base = CFI_SP;
}
if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
op->dest.reg == cfi->drap_reg &&
cfi->drap_offset == -cfi->stack_size) {
/* drap: pop %drap */
cfa->base = cfi->drap_reg;
cfa->offset = 0;
cfi->drap_offset = -1;
} else if (cfi->stack_size == -regs[op->dest.reg].offset) {
/* pop %reg */
restore_reg(cfi, op->dest.reg);
}
cfi->stack_size -= 8;
if (cfa->base == CFI_SP)
cfa->offset -= 8;
break;
case OP_SRC_REG_INDIRECT:
if (!cfi->drap && op->dest.reg == cfa->base &&
op->dest.reg == CFI_BP) {
/* mov disp(%rsp), %rbp */
cfa->base = CFI_SP;
cfa->offset = cfi->stack_size;
}
if (cfi->drap && op->src.reg == CFI_BP &&
op->src.offset == cfi->drap_offset) {
/* drap: mov disp(%rbp), %drap */
cfa->base = cfi->drap_reg;
cfa->offset = 0;
cfi->drap_offset = -1;
}
if (cfi->drap && op->src.reg == CFI_BP &&
op->src.offset == regs[op->dest.reg].offset) {
/* drap: mov disp(%rbp), %reg */
restore_reg(cfi, op->dest.reg);
} else if (op->src.reg == cfa->base &&
op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
/* mov disp(%rbp), %reg */
/* mov disp(%rsp), %reg */
restore_reg(cfi, op->dest.reg);
} else if (op->src.reg == CFI_SP &&
op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
/* mov disp(%rsp), %reg */
restore_reg(cfi, op->dest.reg);
}
break;
default:
WARN_INSN(insn, "unknown stack-related instruction");
return -1;
}
break;
case OP_DEST_PUSH:
case OP_DEST_PUSHF:
cfi->stack_size += 8;
if (cfa->base == CFI_SP)
cfa->offset += 8;
if (op->src.type != OP_SRC_REG)
break;
if (cfi->drap) {
if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
/* drap: push %drap */
cfa->base = CFI_BP_INDIRECT;
cfa->offset = -cfi->stack_size;
/* save drap so we know when to restore it */
cfi->drap_offset = -cfi->stack_size;
} else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
/* drap: push %rbp */
cfi->stack_size = 0;
} else {
/* drap: push %reg */
save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
}
} else {
/* push %reg */
save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
}
/* detect when asm code uses rbp as a scratch register */
if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
cfa->base != CFI_BP)
cfi->bp_scratch = true;
break;
case OP_DEST_REG_INDIRECT:
if (cfi->drap) {
if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
/* drap: mov %drap, disp(%rbp) */
cfa->base = CFI_BP_INDIRECT;
cfa->offset = op->dest.offset;
/* save drap offset so we know when to restore it */
cfi->drap_offset = op->dest.offset;
} else {
/* drap: mov reg, disp(%rbp) */
save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
}
} else if (op->dest.reg == cfa->base) {
/* mov reg, disp(%rbp) */
/* mov reg, disp(%rsp) */
save_reg(cfi, op->src.reg, CFI_CFA,
op->dest.offset - cfi->cfa.offset);
} else if (op->dest.reg == CFI_SP) {
/* mov reg, disp(%rsp) */
save_reg(cfi, op->src.reg, CFI_CFA,
op->dest.offset - cfi->stack_size);
} else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
/* mov %rsp, (%reg); # setup a stack swizzle. */
cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
cfi->vals[op->dest.reg].offset = cfa->offset;
}
break;
case OP_DEST_MEM:
if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
WARN_INSN(insn, "unknown stack-related memory operation");
return -1;
}
/* pop mem */
cfi->stack_size -= 8;
if (cfa->base == CFI_SP)
cfa->offset -= 8;
break;
default:
WARN_INSN(insn, "unknown stack-related instruction");
return -1;
}
return 0;
}
/*
* The stack layouts of alternatives instructions can sometimes diverge when
* they have stack modifications. That's fine as long as the potential stack
* layouts don't conflict at any given potential instruction boundary.
*
* Flatten the CFIs of the different alternative code streams (both original
* and replacement) into a single shared CFI array which can be used to detect
* conflicts and nicely feed a linear array of ORC entries to the unwinder.
*/
static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
{
struct cfi_state **alt_cfi;
int group_off;
if (!insn->alt_group)
return 0;
if (!insn->cfi) {
WARN("CFI missing");
return -1;
}
alt_cfi = insn->alt_group->cfi;
group_off = insn->offset - insn->alt_group->first_insn->offset;
if (!alt_cfi[group_off]) {
alt_cfi[group_off] = insn->cfi;
} else {
if (cficmp(alt_cfi[group_off], insn->cfi)) {
struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
struct instruction *orig = orig_group->first_insn;
char *where = offstr(insn->sec, insn->offset);
WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
free(where);
return -1;
}
}
return 0;
}
static int handle_insn_ops(struct instruction *insn,
struct instruction *next_insn,
struct insn_state *state)
{
struct stack_op *op;
for (op = insn->stack_ops; op; op = op->next) {
if (update_cfi_state(insn, next_insn, &state->cfi, op))
return 1;
if (!insn->alt_group)
continue;
if (op->dest.type == OP_DEST_PUSHF) {
if (!state->uaccess_stack) {
state->uaccess_stack = 1;
} else if (state->uaccess_stack >> 31) {
WARN_INSN(insn, "PUSHF stack exhausted");
return 1;
}
state->uaccess_stack <<= 1;
state->uaccess_stack |= state->uaccess;
}
if (op->src.type == OP_SRC_POPF) {
if (state->uaccess_stack) {
state->uaccess = state->uaccess_stack & 1;
state->uaccess_stack >>= 1;
if (state->uaccess_stack == 1)
state->uaccess_stack = 0;
}
}
}
return 0;
}
static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
{
struct cfi_state *cfi1 = insn->cfi;
int i;
if (!cfi1) {
WARN("CFI missing");
return false;
}
if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
cfi1->cfa.base, cfi1->cfa.offset,
cfi2->cfa.base, cfi2->cfa.offset);
} else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
for (i = 0; i < CFI_NUM_REGS; i++) {
if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
sizeof(struct cfi_reg)))
continue;
WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
i, cfi1->regs[i].base, cfi1->regs[i].offset,
i, cfi2->regs[i].base, cfi2->regs[i].offset);
break;
}
} else if (cfi1->type != cfi2->type) {
WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
cfi1->type, cfi2->type);
} else if (cfi1->drap != cfi2->drap ||
(cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
(cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
} else
return true;
return false;
}
static inline bool func_uaccess_safe(struct symbol *func)
{
if (func)
return func->uaccess_safe;
return false;
}
static inline const char *call_dest_name(struct instruction *insn)
{
static char pvname[19];
struct reloc *reloc;
int idx;
if (insn_call_dest(insn))
return insn_call_dest(insn)->name;
reloc = insn_reloc(NULL, insn);
if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
idx = (reloc_addend(reloc) / sizeof(void *));
snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
return pvname;
}
return "{dynamic}";
}
static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
{
struct symbol *target;
struct reloc *reloc;
int idx;
reloc = insn_reloc(file, insn);
if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
return false;
idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
if (file->pv_ops[idx].clean)
return true;
file->pv_ops[idx].clean = true;
list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
if (!target->sec->noinstr) {
WARN("pv_ops[%d]: %s", idx, target->name);
file->pv_ops[idx].clean = false;
}
}
return file->pv_ops[idx].clean;
}
static inline bool noinstr_call_dest(struct objtool_file *file,
struct instruction *insn,
struct symbol *func)
{
/*
* We can't deal with indirect function calls at present;
* assume they're instrumented.
*/
if (!func) {
if (file->pv_ops)
return pv_call_dest(file, insn);
return false;
}
/*
* If the symbol is from a noinstr section; we good.
*/
if (func->sec->noinstr)
return true;
/*
* If the symbol is a static_call trampoline, we can't tell.
*/
if (func->static_call_tramp)
return true;
/*
* The __ubsan_handle_*() calls are like WARN(), they only happen when
* something 'BAD' happened. At the risk of taking the machine down,
* let them proceed to get the message out.
*/
if (!strncmp(func->name, "__ubsan_handle_", 15))
return true;
return false;
}
static int validate_call(struct objtool_file *file,
struct instruction *insn,
struct insn_state *state)
{
if (state->noinstr && state->instr <= 0 &&
!noinstr_call_dest(file, insn, insn_call_dest(insn))) {
WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
return 1;
}
if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
return 1;
}
if (state->df) {
WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
return 1;
}
return 0;
}
static int validate_sibling_call(struct objtool_file *file,
struct instruction *insn,
struct insn_state *state)
{
if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
return 1;
}
return validate_call(file, insn, state);
}
static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
{
if (state->noinstr && state->instr > 0) {
WARN_INSN(insn, "return with instrumentation enabled");
return 1;
}
if (state->uaccess && !func_uaccess_safe(func)) {
WARN_INSN(insn, "return with UACCESS enabled");
return 1;
}
if (!state->uaccess && func_uaccess_safe(func)) {
WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
return 1;
}
if (state->df) {
WARN_INSN(insn, "return with DF set");
return 1;
}
if (func && has_modified_stack_frame(insn, state)) {
WARN_INSN(insn, "return with modified stack frame");
return 1;
}
if (state->cfi.bp_scratch) {
WARN_INSN(insn, "BP used as a scratch register");
return 1;
}
return 0;
}
static struct instruction *next_insn_to_validate(struct objtool_file *file,
struct instruction *insn)
{
struct alt_group *alt_group = insn->alt_group;
/*
* Simulate the fact that alternatives are patched in-place. When the
* end of a replacement alt_group is reached, redirect objtool flow to
* the end of the original alt_group.
*
* insn->alts->insn -> alt_group->first_insn
* ...
* alt_group->last_insn
* [alt_group->nop] -> next(orig_group->last_insn)
*/
if (alt_group) {
if (alt_group->nop) {
/* ->nop implies ->orig_group */
if (insn == alt_group->last_insn)
return alt_group->nop;
if (insn == alt_group->nop)
goto next_orig;
}
if (insn == alt_group->last_insn && alt_group->orig_group)
goto next_orig;
}
return next_insn_same_sec(file, insn);
next_orig:
return next_insn_same_sec(file, alt_group->orig_group->last_insn);
}
/*
* Follow the branch starting at the given instruction, and recursively follow
* any other branches (jumps). Meanwhile, track the frame pointer state at
* each instruction and validate all the rules described in
* tools/objtool/Documentation/objtool.txt.
*/
static int validate_branch(struct objtool_file *file, struct symbol *func,
struct instruction *insn, struct insn_state state)
{
struct alternative *alt;
struct instruction *next_insn, *prev_insn = NULL;
struct section *sec;
u8 visited;
int ret;
sec = insn->sec;
while (1) {
next_insn = next_insn_to_validate(file, insn);
if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
/* Ignore KCFI type preambles, which always fall through */
if (!strncmp(func->name, "__cfi_", 6) ||
!strncmp(func->name, "__pfx_", 6))
return 0;
WARN("%s() falls through to next function %s()",
func->name, insn_func(insn)->name);
return 1;
}
if (func && insn->ignore) {
WARN_INSN(insn, "BUG: why am I validating an ignored function?");
return 1;
}
visited = VISITED_BRANCH << state.uaccess;
if (insn->visited & VISITED_BRANCH_MASK) {
if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
return 1;
if (insn->visited & visited)
return 0;
} else {
nr_insns_visited++;
}
if (state.noinstr)
state.instr += insn->instr;
if (insn->hint) {
if (insn->restore) {
struct instruction *save_insn, *i;
i = insn;
save_insn = NULL;
sym_for_each_insn_continue_reverse(file, func, i) {
if (i->save) {
save_insn = i;
break;
}
}
if (!save_insn) {
WARN_INSN(insn, "no corresponding CFI save for CFI restore");
return 1;
}
if (!save_insn->visited) {
WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
return 1;
}
insn->cfi = save_insn->cfi;
nr_cfi_reused++;
}
state.cfi = *insn->cfi;
} else {
/* XXX track if we actually changed state.cfi */
if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
insn->cfi = prev_insn->cfi;
nr_cfi_reused++;
} else {
insn->cfi = cfi_hash_find_or_add(&state.cfi);
}
}
insn->visited |= visited;
if (propagate_alt_cfi(file, insn))
return 1;
if (!insn->ignore_alts && insn->alts) {
bool skip_orig = false;
for (alt = insn->alts; alt; alt = alt->next) {
if (alt->skip_orig)
skip_orig = true;
ret = validate_branch(file, func, alt->insn, state);
if (ret) {
BT_INSN(insn, "(alt)");
return ret;
}
}
if (skip_orig)
return 0;
}
if (handle_insn_ops(insn, next_insn, &state))
return 1;
switch (insn->type) {
case INSN_RETURN:
return validate_return(func, insn, &state);
case INSN_CALL:
case INSN_CALL_DYNAMIC:
ret = validate_call(file, insn, &state);
if (ret)
return ret;
if (opts.stackval && func && !is_fentry_call(insn) &&
!has_valid_stack_frame(&state)) {
WARN_INSN(insn, "call without frame pointer save/setup");
return 1;
}
if (insn->dead_end)
return 0;
break;
case INSN_JUMP_CONDITIONAL:
case INSN_JUMP_UNCONDITIONAL:
if (is_sibling_call(insn)) {
ret = validate_sibling_call(file, insn, &state);
if (ret)
return ret;
} else if (insn->jump_dest) {
ret = validate_branch(file, func,
insn->jump_dest, state);
if (ret) {
BT_INSN(insn, "(branch)");
return ret;
}
}
if (insn->type == INSN_JUMP_UNCONDITIONAL)
return 0;
break;
case INSN_JUMP_DYNAMIC:
case INSN_JUMP_DYNAMIC_CONDITIONAL:
if (is_sibling_call(insn)) {
ret = validate_sibling_call(file, insn, &state);
if (ret)
return ret;
}
if (insn->type == INSN_JUMP_DYNAMIC)
return 0;
break;
case INSN_CONTEXT_SWITCH:
if (func && (!next_insn || !next_insn->hint)) {
WARN_INSN(insn, "unsupported instruction in callable function");
return 1;
}
return 0;
case INSN_STAC:
if (state.uaccess) {
WARN_INSN(insn, "recursive UACCESS enable");
return 1;
}
state.uaccess = true;
break;
case INSN_CLAC:
if (!state.uaccess && func) {
WARN_INSN(insn, "redundant UACCESS disable");
return 1;
}
if (func_uaccess_safe(func) && !state.uaccess_stack) {
WARN_INSN(insn, "UACCESS-safe disables UACCESS");
return 1;
}
state.uaccess = false;
break;
case INSN_STD:
if (state.df) {
WARN_INSN(insn, "recursive STD");
return 1;
}
state.df = true;
break;
case INSN_CLD:
if (!state.df && func) {
WARN_INSN(insn, "redundant CLD");
return 1;
}
state.df = false;
break;
default:
break;
}
if (insn->dead_end)
return 0;
if (!next_insn) {
if (state.cfi.cfa.base == CFI_UNDEFINED)
return 0;
WARN("%s: unexpected end of section", sec->name);
return 1;
}
prev_insn = insn;
insn = next_insn;
}
return 0;
}
static int validate_unwind_hint(struct objtool_file *file,
struct instruction *insn,
struct insn_state *state)
{
if (insn->hint && !insn->visited && !insn->ignore) {
int ret = validate_branch(file, insn_func(insn), insn, *state);
if (ret)
BT_INSN(insn, "<=== (hint)");
return ret;
}
return 0;
}
static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
{
struct instruction *insn;
struct insn_state state;
int warnings = 0;
if (!file->hints)
return 0;
init_insn_state(file, &state, sec);
if (sec) {
sec_for_each_insn(file, sec, insn)
warnings += validate_unwind_hint(file, insn, &state);
} else {
for_each_insn(file, insn)
warnings += validate_unwind_hint(file, insn, &state);
}
return warnings;
}
/*
* Validate rethunk entry constraint: must untrain RET before the first RET.
*
* Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
* before an actual RET instruction.
*/
static int validate_unret(struct objtool_file *file, struct instruction *insn)
{
struct instruction *next, *dest;
int ret;
for (;;) {
next = next_insn_to_validate(file, insn);
if (insn->visited & VISITED_UNRET)
return 0;
insn->visited |= VISITED_UNRET;
if (!insn->ignore_alts && insn->alts) {
struct alternative *alt;
bool skip_orig = false;
for (alt = insn->alts; alt; alt = alt->next) {
if (alt->skip_orig)
skip_orig = true;
ret = validate_unret(file, alt->insn);
if (ret) {
BT_INSN(insn, "(alt)");
return ret;
}
}
if (skip_orig)
return 0;
}
switch (insn->type) {
case INSN_CALL_DYNAMIC:
case INSN_JUMP_DYNAMIC:
case INSN_JUMP_DYNAMIC_CONDITIONAL:
WARN_INSN(insn, "early indirect call");
return 1;
case INSN_JUMP_UNCONDITIONAL:
case INSN_JUMP_CONDITIONAL:
if (!is_sibling_call(insn)) {
if (!insn->jump_dest) {
WARN_INSN(insn, "unresolved jump target after linking?!?");
return -1;
}
ret = validate_unret(file, insn->jump_dest);
if (ret) {
BT_INSN(insn, "(branch%s)",
insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
return ret;
}
if (insn->type == INSN_JUMP_UNCONDITIONAL)
return 0;
break;
}
/* fallthrough */
case INSN_CALL:
dest = find_insn(file, insn_call_dest(insn)->sec,
insn_call_dest(insn)->offset);
if (!dest) {
WARN("Unresolved function after linking!?: %s",
insn_call_dest(insn)->name);
return -1;
}
ret = validate_unret(file, dest);
if (ret) {
BT_INSN(insn, "(call)");
return ret;
}
/*
* If a call returns without error, it must have seen UNTRAIN_RET.
* Therefore any non-error return is a success.
*/
return 0;
case INSN_RETURN:
WARN_INSN(insn, "RET before UNTRAIN");
return 1;
case INSN_NOP:
if (insn->retpoline_safe)
return 0;
break;
default:
break;
}
if (!next) {
WARN_INSN(insn, "teh end!");
return -1;
}
insn = next;
}
return 0;
}
/*
* Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
* VALIDATE_UNRET_END before RET.
*/
static int validate_unrets(struct objtool_file *file)
{
struct instruction *insn;
int ret, warnings = 0;
for_each_insn(file, insn) {
if (!insn->unret)
continue;
ret = validate_unret(file, insn);
if (ret < 0) {
WARN_INSN(insn, "Failed UNRET validation");
return ret;
}
warnings += ret;
}
return warnings;
}
static int validate_retpoline(struct objtool_file *file)
{
struct instruction *insn;
int warnings = 0;
for_each_insn(file, insn) {
if (insn->type != INSN_JUMP_DYNAMIC &&
insn->type != INSN_CALL_DYNAMIC &&
insn->type != INSN_RETURN)
continue;
if (insn->retpoline_safe)
continue;
if (insn->sec->init)
continue;
if (insn->type == INSN_RETURN) {
if (opts.rethunk) {
WARN_INSN(insn, "'naked' return found in RETHUNK build");
} else
continue;
} else {
WARN_INSN(insn, "indirect %s found in RETPOLINE build",
insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
}
warnings++;
}
return warnings;
}
static bool is_kasan_insn(struct instruction *insn)
{
return (insn->type == INSN_CALL &&
!strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
}
static bool is_ubsan_insn(struct instruction *insn)
{
return (insn->type == INSN_CALL &&
!strcmp(insn_call_dest(insn)->name,
"__ubsan_handle_builtin_unreachable"));
}
static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
{
int i;
struct instruction *prev_insn;
if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
return true;
/*
* Ignore alternative replacement instructions. This can happen
* when a whitelisted function uses one of the ALTERNATIVE macros.
*/
if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
!strcmp(insn->sec->name, ".altinstr_aux"))
return true;
/*
* Whole archive runs might encounter dead code from weak symbols.
* This is where the linker will have dropped the weak symbol in
* favour of a regular symbol, but leaves the code in place.
*
* In this case we'll find a piece of code (whole function) that is not
* covered by a !section symbol. Ignore them.
*/
if (opts.link && !insn_func(insn)) {
int size = find_symbol_hole_containing(insn->sec, insn->offset);
unsigned long end = insn->offset + size;
if (!size) /* not a hole */
return false;
if (size < 0) /* hole until the end */
return true;
sec_for_each_insn_continue(file, insn) {
/*
* If we reach a visited instruction at or before the
* end of the hole, ignore the unreachable.
*/
if (insn->visited)
return true;
if (insn->offset >= end)
break;
/*
* If this hole jumps to a .cold function, mark it ignore too.
*/
if (insn->jump_dest && insn_func(insn->jump_dest) &&
strstr(insn_func(insn->jump_dest)->name, ".cold")) {
struct instruction *dest = insn->jump_dest;
func_for_each_insn(file, insn_func(dest), dest)
dest->ignore = true;
}
}
return false;
}
if (!insn_func(insn))
return false;
if (insn_func(insn)->static_call_tramp)
return true;
/*
* CONFIG_UBSAN_TRAP inserts a UD2 when it sees
* __builtin_unreachable(). The BUG() macro has an unreachable() after
* the UD2, which causes GCC's undefined trap logic to emit another UD2
* (or occasionally a JMP to UD2).
*
* It may also insert a UD2 after calling a __noreturn function.
*/
prev_insn = prev_insn_same_sec(file, insn);
if (prev_insn->dead_end &&
(insn->type == INSN_BUG ||
(insn->type == INSN_JUMP_UNCONDITIONAL &&
insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
return true;
/*
* Check if this (or a subsequent) instruction is related to
* CONFIG_UBSAN or CONFIG_KASAN.
*
* End the search at 5 instructions to avoid going into the weeds.
*/
for (i = 0; i < 5; i++) {
if (is_kasan_insn(insn) || is_ubsan_insn(insn))
return true;
if (insn->type == INSN_JUMP_UNCONDITIONAL) {
if (insn->jump_dest &&
insn_func(insn->jump_dest) == insn_func(insn)) {
insn = insn->jump_dest;
continue;
}
break;
}
if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
break;
insn = next_insn_same_sec(file, insn);
}
return false;
}
static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
{
struct instruction *insn, *prev;
struct cfi_state *cfi;
insn = find_insn(file, func->sec, func->offset);
if (!insn)
return -1;
for (prev = prev_insn_same_sec(file, insn);
prev;
prev = prev_insn_same_sec(file, prev)) {
u64 offset;
if (prev->type != INSN_NOP)
return -1;
offset = func->offset - prev->offset;
if (offset > opts.prefix)
return -1;
if (offset < opts.prefix)
continue;
elf_create_prefix_symbol(file->elf, func, opts.prefix);
break;
}
if (!prev)
return -1;
if (!insn->cfi) {
/*
* This can happen if stack validation isn't enabled or the
* function is annotated with STACK_FRAME_NON_STANDARD.
*/
return 0;
}
/* Propagate insn->cfi to the prefix code */
cfi = cfi_hash_find_or_add(insn->cfi);
for (; prev != insn; prev = next_insn_same_sec(file, prev))
prev->cfi = cfi;
return 0;
}
static int add_prefix_symbols(struct objtool_file *file)
{
struct section *sec;
struct symbol *func;
for_each_sec(file, sec) {
if (!(sec->sh.sh_flags & SHF_EXECINSTR))
continue;
sec_for_each_sym(sec, func) {
if (func->type != STT_FUNC)
continue;
add_prefix_symbol(file, func);
}
}
return 0;
}
static int validate_symbol(struct objtool_file *file, struct section *sec,
struct symbol *sym, struct insn_state *state)
{
struct instruction *insn;
int ret;
if (!sym->len) {
WARN("%s() is missing an ELF size annotation", sym->name);
return 1;
}
if (sym->pfunc != sym || sym->alias != sym)
return 0;
insn = find_insn(file, sec, sym->offset);
if (!insn || insn->ignore || insn->visited)
return 0;
state->uaccess = sym->uaccess_safe;
ret = validate_branch(file, insn_func(insn), insn, *state);
if (ret)
BT_INSN(insn, "<=== (sym)");
return ret;
}
static int validate_section(struct objtool_file *file, struct section *sec)
{
struct insn_state state;
struct symbol *func;
int warnings = 0;
sec_for_each_sym(sec, func) {
if (func->type != STT_FUNC)
continue;
init_insn_state(file, &state, sec);
set_func_state(&state.cfi);
warnings += validate_symbol(file, sec, func, &state);
}
return warnings;
}
static int validate_noinstr_sections(struct objtool_file *file)
{
struct section *sec;
int warnings = 0;
sec = find_section_by_name(file->elf, ".noinstr.text");
if (sec) {
warnings += validate_section(file, sec);
warnings += validate_unwind_hints(file, sec);
}
sec = find_section_by_name(file->elf, ".entry.text");
if (sec) {
warnings += validate_section(file, sec);
warnings += validate_unwind_hints(file, sec);
}
sec = find_section_by_name(file->elf, ".cpuidle.text");
if (sec) {
warnings += validate_section(file, sec);
warnings += validate_unwind_hints(file, sec);
}
return warnings;
}
static int validate_functions(struct objtool_file *file)
{
struct section *sec;
int warnings = 0;
for_each_sec(file, sec) {
if (!(sec->sh.sh_flags & SHF_EXECINSTR))
continue;
warnings += validate_section(file, sec);
}
return warnings;
}
static void mark_endbr_used(struct instruction *insn)
{
if (!list_empty(&insn->call_node))
list_del_init(&insn->call_node);
}
static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
{
struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
struct instruction *first;
if (!sym)
return false;
first = find_insn(file, sym->sec, sym->offset);
if (!first)
return false;
if (first->type != INSN_ENDBR && !first->noendbr)
return false;
return insn->offset == sym->offset + sym->len;
}
static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
{
struct instruction *dest;
struct reloc *reloc;
unsigned long off;
int warnings = 0;
/*
* Looking for function pointer load relocations. Ignore
* direct/indirect branches:
*/
switch (insn->type) {
case INSN_CALL:
case INSN_CALL_DYNAMIC:
case INSN_JUMP_CONDITIONAL:
case INSN_JUMP_UNCONDITIONAL:
case INSN_JUMP_DYNAMIC:
case INSN_JUMP_DYNAMIC_CONDITIONAL:
case INSN_RETURN:
case INSN_NOP:
return 0;
default:
break;
}
for (reloc = insn_reloc(file, insn);
reloc;
reloc = find_reloc_by_dest_range(file->elf, insn->sec,
reloc_offset(reloc) + 1,
(insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
/*
* static_call_update() references the trampoline, which
* doesn't have (or need) ENDBR. Skip warning in that case.
*/
if (reloc->sym->static_call_tramp)
continue;
off = reloc->sym->offset;
if (reloc_type(reloc) == R_X86_64_PC32 ||
reloc_type(reloc) == R_X86_64_PLT32)
off += arch_dest_reloc_offset(reloc_addend(reloc));
else
off += reloc_addend(reloc);
dest = find_insn(file, reloc->sym->sec, off);
if (!dest)
continue;
if (dest->type == INSN_ENDBR) {
mark_endbr_used(dest);
continue;
}
if (insn_func(dest) && insn_func(dest) == insn_func(insn)) {
/*
* Anything from->to self is either _THIS_IP_ or
* IRET-to-self.
*
* There is no sane way to annotate _THIS_IP_ since the
* compiler treats the relocation as a constant and is
* happy to fold in offsets, skewing any annotation we
* do, leading to vast amounts of false-positives.
*
* There's also compiler generated _THIS_IP_ through
* KCOV and such which we have no hope of annotating.
*
* As such, blanket accept self-references without
* issue.
*/
continue;
}
/*
* Accept anything ANNOTATE_NOENDBR.
*/
if (dest->noendbr)
continue;
/*
* Accept if this is the instruction after a symbol
* that is (no)endbr -- typical code-range usage.
*/
if (noendbr_range(file, dest))
continue;
WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
warnings++;
}
return warnings;
}
static int validate_ibt_data_reloc(struct objtool_file *file,
struct reloc *reloc)
{
struct instruction *dest;
dest = find_insn(file, reloc->sym->sec,
reloc->sym->offset + reloc_addend(reloc));
if (!dest)
return 0;
if (dest->type == INSN_ENDBR) {
mark_endbr_used(dest);
return 0;
}
if (dest->noendbr)
return 0;
WARN_FUNC("data relocation to !ENDBR: %s",
reloc->sec->base, reloc_offset(reloc),
offstr(dest->sec, dest->offset));
return 1;
}
/*
* Validate IBT rules and remove used ENDBR instructions from the seal list.
* Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
* NOPs) later, in create_ibt_endbr_seal_sections().
*/
static int validate_ibt(struct objtool_file *file)
{
struct section *sec;
struct reloc *reloc;
struct instruction *insn;
int warnings = 0;
for_each_insn(file, insn)
warnings += validate_ibt_insn(file, insn);
for_each_sec(file, sec) {
/* Already done by validate_ibt_insn() */
if (sec->sh.sh_flags & SHF_EXECINSTR)
continue;
if (!sec->rsec)
continue;
/*
* These sections can reference text addresses, but not with
* the intent to indirect branch to them.
*/
if ((!strncmp(sec->name, ".discard", 8) &&
strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
!strncmp(sec->name, ".debug", 6) ||
!strcmp(sec->name, ".altinstructions") ||
!strcmp(sec->name, ".ibt_endbr_seal") ||
!strcmp(sec->name, ".orc_unwind_ip") ||
!strcmp(sec->name, ".parainstructions") ||
!strcmp(sec->name, ".retpoline_sites") ||
!strcmp(sec->name, ".smp_locks") ||
!strcmp(sec->name, ".static_call_sites") ||
!strcmp(sec->name, "_error_injection_whitelist") ||
!strcmp(sec->name, "_kprobe_blacklist") ||
!strcmp(sec->name, "__bug_table") ||
!strcmp(sec->name, "__ex_table") ||
!strcmp(sec->name, "__jump_table") ||
!strcmp(sec->name, "__mcount_loc") ||
!strcmp(sec->name, ".kcfi_traps") ||
strstr(sec->name, "__patchable_function_entries"))
continue;
for_each_reloc(sec->rsec, reloc)
warnings += validate_ibt_data_reloc(file, reloc);
}
return warnings;
}
static int validate_sls(struct objtool_file *file)
{
struct instruction *insn, *next_insn;
int warnings = 0;
for_each_insn(file, insn) {
next_insn = next_insn_same_sec(file, insn);
if (insn->retpoline_safe)
continue;
switch (insn->type) {
case INSN_RETURN:
if (!next_insn || next_insn->type != INSN_TRAP) {
WARN_INSN(insn, "missing int3 after ret");
warnings++;
}
break;
case INSN_JUMP_DYNAMIC:
if (!next_insn || next_insn->type != INSN_TRAP) {
WARN_INSN(insn, "missing int3 after indirect jump");
warnings++;
}
break;
default:
break;
}
}
return warnings;
}
static bool ignore_noreturn_call(struct instruction *insn)
{
struct symbol *call_dest = insn_call_dest(insn);
/*
* FIXME: hack, we need a real noreturn solution
*
* Problem is, exc_double_fault() may or may not return, depending on
* whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility
* to the kernel config.
*
* Other potential ways to fix it:
*
* - have compiler communicate __noreturn functions somehow
* - remove CONFIG_X86_ESPFIX64
* - read the .config file
* - add a cmdline option
* - create a generic objtool annotation format (vs a bunch of custom
* formats) and annotate it
*/
if (!strcmp(call_dest->name, "exc_double_fault")) {
/* prevent further unreachable warnings for the caller */
insn->sym->warned = 1;
return true;
}
return false;
}
static int validate_reachable_instructions(struct objtool_file *file)
{
struct instruction *insn, *prev_insn;
struct symbol *call_dest;
int warnings = 0;
if (file->ignore_unreachables)
return 0;
for_each_insn(file, insn) {
if (insn->visited || ignore_unreachable_insn(file, insn))
continue;
prev_insn = prev_insn_same_sec(file, insn);
if (prev_insn && prev_insn->dead_end) {
call_dest = insn_call_dest(prev_insn);
if (call_dest && !ignore_noreturn_call(prev_insn)) {
WARN_INSN(insn, "%s() is missing a __noreturn annotation",
call_dest->name);
warnings++;
continue;
}
}
WARN_INSN(insn, "unreachable instruction");
warnings++;
}
return warnings;
}
/* 'funcs' is a space-separated list of function names */
static int disas_funcs(const char *funcs)
{
const char *objdump_str, *cross_compile;
int size, ret;
char *cmd;
cross_compile = getenv("CROSS_COMPILE");
objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
"BEGIN { split(_funcs, funcs); }"
"/^$/ { func_match = 0; }"
"/<.*>:/ { "
"f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
"for (i in funcs) {"
"if (funcs[i] == f) {"
"func_match = 1;"
"base = strtonum(\"0x\" $1);"
"break;"
"}"
"}"
"}"
"{"
"if (func_match) {"
"addr = strtonum(\"0x\" $1);"
"printf(\"%%04x \", addr - base);"
"print;"
"}"
"}' 1>&2";
/* fake snprintf() to calculate the size */
size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
if (size <= 0) {
WARN("objdump string size calculation failed");
return -1;
}
cmd = malloc(size);
/* real snprintf() */
snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
ret = system(cmd);
if (ret) {
WARN("disassembly failed: %d", ret);
return -1;
}
return 0;
}
static int disas_warned_funcs(struct objtool_file *file)
{
struct symbol *sym;
char *funcs = NULL, *tmp;
for_each_sym(file, sym) {
if (sym->warned) {
if (!funcs) {
funcs = malloc(strlen(sym->name) + 1);
strcpy(funcs, sym->name);
} else {
tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
sprintf(tmp, "%s %s", funcs, sym->name);
free(funcs);
funcs = tmp;
}
}
}
if (funcs)
disas_funcs(funcs);
return 0;
}
struct insn_chunk {
void *addr;
struct insn_chunk *next;
};
/*
* Reduce peak RSS usage by freeing insns memory before writing the ELF file,
* which can trigger more allocations for .debug_* sections whose data hasn't
* been read yet.
*/
static void free_insns(struct objtool_file *file)
{
struct instruction *insn;
struct insn_chunk *chunks = NULL, *chunk;
for_each_insn(file, insn) {
if (!insn->idx) {
chunk = malloc(sizeof(*chunk));
chunk->addr = insn;
chunk->next = chunks;
chunks = chunk;
}
}
for (chunk = chunks; chunk; chunk = chunk->next)
free(chunk->addr);
}
int check(struct objtool_file *file)
{
int ret, warnings = 0;
arch_initial_func_cfi_state(&initial_func_cfi);
init_cfi_state(&init_cfi);
init_cfi_state(&func_cfi);
set_func_state(&func_cfi);
init_cfi_state(&force_undefined_cfi);
force_undefined_cfi.force_undefined = true;
if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
goto out;
cfi_hash_add(&init_cfi);
cfi_hash_add(&func_cfi);
ret = decode_sections(file);
if (ret < 0)
goto out;
warnings += ret;
if (!nr_insns)
goto out;
if (opts.retpoline) {
ret = validate_retpoline(file);
if (ret < 0)
return ret;
warnings += ret;
}
if (opts.stackval || opts.orc || opts.uaccess) {
ret = validate_functions(file);
if (ret < 0)
goto out;
warnings += ret;
ret = validate_unwind_hints(file, NULL);
if (ret < 0)
goto out;
warnings += ret;
if (!warnings) {
ret = validate_reachable_instructions(file);
if (ret < 0)
goto out;
warnings += ret;
}
} else if (opts.noinstr) {
ret = validate_noinstr_sections(file);
if (ret < 0)
goto out;
warnings += ret;
}
if (opts.unret) {
/*
* Must be after validate_branch() and friends, it plays
* further games with insn->visited.
*/
ret = validate_unrets(file);
if (ret < 0)
return ret;
warnings += ret;
}
if (opts.ibt) {
ret = validate_ibt(file);
if (ret < 0)
goto out;
warnings += ret;
}
if (opts.sls) {
ret = validate_sls(file);
if (ret < 0)
goto out;
warnings += ret;
}
if (opts.static_call) {
ret = create_static_call_sections(file);
if (ret < 0)
goto out;
warnings += ret;
}
if (opts.retpoline) {
ret = create_retpoline_sites_sections(file);
if (ret < 0)
goto out;
warnings += ret;
}
if (opts.cfi) {
ret = create_cfi_sections(file);
if (ret < 0)
goto out;
warnings += ret;
}
if (opts.rethunk) {
ret = create_return_sites_sections(file);
if (ret < 0)
goto out;
warnings += ret;
if (opts.hack_skylake) {
ret = create_direct_call_sections(file);
if (ret < 0)
goto out;
warnings += ret;
}
}
if (opts.mcount) {
ret = create_mcount_loc_sections(file);
if (ret < 0)
goto out;
warnings += ret;
}
if (opts.prefix) {
ret = add_prefix_symbols(file);
if (ret < 0)
return ret;
warnings += ret;
}
if (opts.ibt) {
ret = create_ibt_endbr_seal_sections(file);
if (ret < 0)
goto out;
warnings += ret;
}
if (opts.orc && nr_insns) {
ret = orc_create(file);
if (ret < 0)
goto out;
warnings += ret;
}
free_insns(file);
if (opts.verbose)
disas_warned_funcs(file);
if (opts.stats) {
printf("nr_insns_visited: %ld\n", nr_insns_visited);
printf("nr_cfi: %ld\n", nr_cfi);
printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
}
out:
/*
* For now, don't fail the kernel build on fatal warnings. These
* errors are still fairly common due to the growing matrix of
* supported toolchains and their recent pace of change.
*/
return 0;
}
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