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powerpc64/ftrace: Implement support for ftrace_regs_caller() 

With -mprofile-kernel, we always save the full register state in
ftrace_caller(). While this works, this is inefficient if we're not
interested in the register state, such as when we're using the function
tracer.

Rename the existing ftrace_caller() as ftrace_regs_caller() and provide
a simpler implementation for ftrace_caller() that is used when registers
are not required to be saved.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Naveen N. Rao 2018-04-19 12:34:09 +05:30 committed by Michael Ellerman
parent 9ef4042364
commit ae30cc05be
5 changed files with 262 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/powerpc/include/asm/ftrace.h
View File

@ -49,8 +49,6 @@
extern void _mcount(void);
#ifdef CONFIG_DYNAMIC_FTRACE
# define FTRACE_ADDR ((unsigned long)ftrace_caller)
# define FTRACE_REGS_ADDR FTRACE_ADDR
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
/* reloction of mcount call site is the same as the address */

3
arch/powerpc/include/asm/module.h
View File

@ -53,6 +53,9 @@ struct mod_arch_specific {
#ifdef CONFIG_DYNAMIC_FTRACE
unsigned long toc;
unsigned long tramp;
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
unsigned long tramp_regs;
#endif
#endif
/* For module function descriptor dereference */

28
arch/powerpc/kernel/module_64.c
View File

@ -280,6 +280,10 @@ static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
#ifdef CONFIG_DYNAMIC_FTRACE
/* make the trampoline to the ftrace_caller */
relocs++;
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
/* an additional one for ftrace_regs_caller */
relocs++;
#endif
#endif
pr_debug("Looks like a total of %lu stubs, max\n", relocs);
@ -765,7 +769,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
* via the paca (in r13). The target (ftrace_caller()) is responsible for
* saving and restoring the toc before returning.
*/
static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module *me)
static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs,
struct module *me, unsigned long addr)
{
struct ppc64_stub_entry *entry;
unsigned int i, num_stubs;
@ -792,9 +797,10 @@ static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module
memcpy(entry->jump, stub_insns, sizeof(stub_insns));
/* Stub uses address relative to kernel toc (from the paca) */
reladdr = (unsigned long)ftrace_caller - kernel_toc_addr();
reladdr = addr - kernel_toc_addr();
if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
pr_err("%s: Address of ftrace_caller out of range of kernel_toc.\n", me->name);
pr_err("%s: Address of %ps out of range of kernel_toc.\n",
me->name, (void *)addr);
return 0;
}
@ -802,22 +808,30 @@ static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module
entry->jump[2] |= PPC_LO(reladdr);
/* Eventhough we don't use funcdata in the stub, it's needed elsewhere. */
entry->funcdata = func_desc((unsigned long)ftrace_caller);
entry->funcdata = func_desc(addr);
entry->magic = STUB_MAGIC;
return (unsigned long)entry;
}
#else
static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module *me)
static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs,
struct module *me, unsigned long addr)
{
return stub_for_addr(sechdrs, (unsigned long)ftrace_caller, me);
return stub_for_addr(sechdrs, addr, me);
}
#endif
int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
{
mod->arch.toc = my_r2(sechdrs, mod);
mod->arch.tramp = create_ftrace_stub(sechdrs, mod);
mod->arch.tramp = create_ftrace_stub(sechdrs, mod,
(unsigned long)ftrace_caller);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
mod->arch.tramp_regs = create_ftrace_stub(sechdrs, mod,
(unsigned long)ftrace_regs_caller);
if (!mod->arch.tramp_regs)
return -ENOENT;
#endif
if (!mod->arch.tramp)
return -ENOENT;

184
arch/powerpc/kernel/trace/ftrace.c
View File

@ -357,6 +357,8 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int op[2];
void *ip = (void *)rec->ip;
unsigned long entry, ptr, tramp;
struct module *mod = rec->arch.mod;
/* read where this goes */
if (probe_kernel_read(op, ip, sizeof(op)))
@ -368,19 +370,44 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
return -EINVAL;
}
/* If we never set up a trampoline to ftrace_caller, then bail */
if (!rec->arch.mod->arch.tramp) {
/* If we never set up ftrace trampoline(s), then bail */
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
if (!mod->arch.tramp || !mod->arch.tramp_regs) {
#else
if (!mod->arch.tramp) {
#endif
pr_err("No ftrace trampoline\n");
return -EINVAL;
}
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
if (rec->flags & FTRACE_FL_REGS)
tramp = mod->arch.tramp_regs;
else
#endif
tramp = mod->arch.tramp;
if (module_trampoline_target(mod, tramp, &ptr)) {
pr_err("Failed to get trampoline target\n");
return -EFAULT;
}
pr_devel("trampoline target %lx", ptr);
entry = ppc_global_function_entry((void *)addr);
/* This should match what was called */
if (ptr != entry) {
pr_err("addr %lx does not match expected %lx\n", ptr, entry);
return -EINVAL;
}
/* Ensure branch is within 24 bits */
if (!create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
if (!create_branch(ip, tramp, BRANCH_SET_LINK)) {
pr_err("Branch out of range\n");
return -EINVAL;
}
if (patch_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
pr_err("REL24 out of range!\n");
return -EINVAL;
}
@ -388,14 +415,6 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
return 0;
}
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
return ftrace_make_call(rec, addr);
}
#endif
#else /* !CONFIG_PPC64: */
static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
@ -472,6 +491,137 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
#endif /* CONFIG_MODULES */
}
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
#ifdef CONFIG_MODULES
static int
__ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
unsigned int op;
unsigned long ip = rec->ip;
unsigned long entry, ptr, tramp;
struct module *mod = rec->arch.mod;
/* If we never set up ftrace trampolines, then bail */
if (!mod->arch.tramp || !mod->arch.tramp_regs) {
pr_err("No ftrace trampoline\n");
return -EINVAL;
}
/* read where this goes */
if (probe_kernel_read(&op, (void *)ip, sizeof(int))) {
pr_err("Fetching opcode failed.\n");
return -EFAULT;
}
/* Make sure that that this is still a 24bit jump */
if (!is_bl_op(op)) {
pr_err("Not expected bl: opcode is %x\n", op);
return -EINVAL;
}
/* lets find where the pointer goes */
tramp = find_bl_target(ip, op);
entry = ppc_global_function_entry((void *)old_addr);
pr_devel("ip:%lx jumps to %lx", ip, tramp);
if (tramp != entry) {
/* old_addr is not within range, so we must have used a trampoline */
if (module_trampoline_target(mod, tramp, &ptr)) {
pr_err("Failed to get trampoline target\n");
return -EFAULT;
}
pr_devel("trampoline target %lx", ptr);
/* This should match what was called */
if (ptr != entry) {
pr_err("addr %lx does not match expected %lx\n", ptr, entry);
return -EINVAL;
}
}
/* The new target may be within range */
if (test_24bit_addr(ip, addr)) {
/* within range */
if (patch_branch((unsigned int *)ip, addr, BRANCH_SET_LINK)) {
pr_err("REL24 out of range!\n");
return -EINVAL;
}
return 0;
}
if (rec->flags & FTRACE_FL_REGS)
tramp = mod->arch.tramp_regs;
else
tramp = mod->arch.tramp;
if (module_trampoline_target(mod, tramp, &ptr)) {
pr_err("Failed to get trampoline target\n");
return -EFAULT;
}
pr_devel("trampoline target %lx", ptr);
entry = ppc_global_function_entry((void *)addr);
/* This should match what was called */
if (ptr != entry) {
pr_err("addr %lx does not match expected %lx\n", ptr, entry);
return -EINVAL;
}
/* Ensure branch is within 24 bits */
if (!create_branch((unsigned int *)ip, tramp, BRANCH_SET_LINK)) {
pr_err("Branch out of range\n");
return -EINVAL;
}
if (patch_branch((unsigned int *)ip, tramp, BRANCH_SET_LINK)) {
pr_err("REL24 out of range!\n");
return -EINVAL;
}
return 0;
}
#endif
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
unsigned long ip = rec->ip;
unsigned int old, new;
/*
* If the calling address is more that 24 bits away,
* then we had to use a trampoline to make the call.
* Otherwise just update the call site.
*/
if (test_24bit_addr(ip, addr) && test_24bit_addr(ip, old_addr)) {
/* within range */
old = ftrace_call_replace(ip, old_addr, 1);
new = ftrace_call_replace(ip, addr, 1);
return ftrace_modify_code(ip, old, new);
}
#ifdef CONFIG_MODULES
/*
* Out of range jumps are called from modules.
*/
if (!rec->arch.mod) {
pr_err("No module loaded\n");
return -EINVAL;
}
return __ftrace_modify_call(rec, old_addr, addr);
#else
/* We should not get here without modules */
return -EINVAL;
#endif /* CONFIG_MODULES */
}
#endif
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long ip = (unsigned long)(&ftrace_call);
@ -482,6 +632,16 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
new = ftrace_call_replace(ip, (unsigned long)func, 1);
ret = ftrace_modify_code(ip, old, new);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
/* Also update the regs callback function */
if (!ret) {
ip = (unsigned long)(&ftrace_regs_call);
old = *(unsigned int *)&ftrace_regs_call;
new = ftrace_call_replace(ip, (unsigned long)func, 1);
ret = ftrace_modify_code(ip, old, new);
}
#endif
return ret;
}

71
arch/powerpc/kernel/trace/ftrace_64_mprofile.S
View File

@ -20,8 +20,8 @@
#ifdef CONFIG_DYNAMIC_FTRACE
/*
*
* ftrace_caller() is the function that replaces _mcount() when ftrace is
* active.
* ftrace_caller()/ftrace_regs_caller() is the function that replaces _mcount()
* when ftrace is active.
*
* We arrive here after a function A calls function B, and we are the trace
* function for B. When we enter r1 points to A's stack frame, B has not yet
@ -37,7 +37,7 @@
* Our job is to save the register state into a struct pt_regs (on the stack)
* and then arrange for the ftrace function to be called.
*/
_GLOBAL(ftrace_caller)
_GLOBAL(ftrace_regs_caller)
/* Save the original return address in A's stack frame */
std r0,LRSAVE(r1)
@ -100,8 +100,8 @@ _GLOBAL(ftrace_caller)
addi r6, r1 ,STACK_FRAME_OVERHEAD
/* ftrace_call(r3, r4, r5, r6) */
.globl ftrace_call
ftrace_call:
.globl ftrace_regs_call
ftrace_regs_call:
bl ftrace_stub
nop
@ -162,6 +162,7 @@ ftrace_call:
bne- livepatch_handler
#endif
ftrace_caller_common:
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.globl ftrace_graph_call
ftrace_graph_call:
@ -182,6 +183,66 @@ ftrace_no_trace:
mtlr r0
bctr
_GLOBAL(ftrace_caller)
/* Save the original return address in A's stack frame */
std r0, LRSAVE(r1)
/* Create our stack frame + pt_regs */
stdu r1, -SWITCH_FRAME_SIZE(r1)
/* Save all gprs to pt_regs */
SAVE_8GPRS(3, r1)
lbz r3, PACA_FTRACE_ENABLED(r13)
cmpdi r3, 0
beq ftrace_no_trace
/* Get the _mcount() call site out of LR */
mflr r7
std r7, _NIP(r1)
/* Save callee's TOC in the ABI compliant location */
std r2, 24(r1)
ld r2, PACATOC(r13) /* get kernel TOC in r2 */
addis r3, r2, function_trace_op@toc@ha
addi r3, r3, function_trace_op@toc@l
ld r5, 0(r3)
/* Calculate ip from nip-4 into r3 for call below */
subi r3, r7, MCOUNT_INSN_SIZE
/* Put the original return address in r4 as parent_ip */
mr r4, r0
/* Set pt_regs to NULL */
li r6, 0
/* ftrace_call(r3, r4, r5, r6) */
.globl ftrace_call
ftrace_call:
bl ftrace_stub
nop
ld r3, _NIP(r1)
mtctr r3
/* Restore gprs */
REST_8GPRS(3,r1)
/* Restore callee's TOC */
ld r2, 24(r1)
/* Pop our stack frame */
addi r1, r1, SWITCH_FRAME_SIZE
/* Reload original LR */
ld r0, LRSAVE(r1)
mtlr r0
/* Handle function_graph or go back */
b ftrace_caller_common
#ifdef CONFIG_LIVEPATCH
/*
* This function runs in the mcount context, between two functions. As