x86: Regex support and known-movable symbols for relocs, fix _end
This adds a new category of symbols to the relocs program: symbols which are known to be relative, even though the linker emits them as absolute; this is the case for symbols that live in the linker script, which currently applies to _end. Unfortunately the previous workaround of putting _end in its own empty section was defeated by newer binutils, which remove empty sections completely. This patch also changes the symbol matching to use regular expressions instead of hardcoded C for specific patterns. This is a decidedly non-minimal patch: a modified version of the relocs program is used as part of the Syslinux build, and this is basically a backport to Linux of some of those changes; they have thus been well tested. Signed-off-by: H. Peter Anvin <hpa@zytor.com> LKML-Reference: <4AF86211.3070103@zytor.com> Acked-by: Michal Marek <mmarek@suse.cz> Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
This commit is contained in:
H. Peter Anvin
parent
494c2ebfb2
commit
873b5271f8
|
|
@ -9,6 +9,9 @@
|
|||
#include <byteswap.h>
|
||||
#define USE_BSD
|
||||
#include <endian.h>
|
||||
#include <regex.h>
|
||||
|
||||
static void die(char *fmt, ...);
|
||||
|
||||
#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
|
||||
static Elf32_Ehdr ehdr;
|
||||
|
|
@ -30,25 +33,47 @@ static struct section *secs;
|
|||
* the address for which it has been compiled. Don't warn user about
|
||||
* absolute relocations present w.r.t these symbols.
|
||||
*/
|
||||
static const char* safe_abs_relocs[] = {
|
||||
"xen_irq_disable_direct_reloc",
|
||||
"xen_save_fl_direct_reloc",
|
||||
};
|
||||
|
||||
static int is_safe_abs_reloc(const char* sym_name)
|
||||
static const char abs_sym_regex[] =
|
||||
"^(xen_irq_disable_direct_reloc$|"
|
||||
"xen_save_fl_direct_reloc$|"
|
||||
"VDSO|"
|
||||
"__crc_)";
|
||||
static regex_t abs_sym_regex_c;
|
||||
static int is_abs_reloc(const char *sym_name)
|
||||
{
|
||||
int i;
|
||||
|
||||
for (i = 0; i < ARRAY_SIZE(safe_abs_relocs); i++) {
|
||||
if (!strcmp(sym_name, safe_abs_relocs[i]))
|
||||
/* Match found */
|
||||
return 1;
|
||||
return !regexec(&abs_sym_regex_c, sym_name, 0, NULL, 0);
|
||||
}
|
||||
|
||||
/*
|
||||
* These symbols are known to be relative, even if the linker marks them
|
||||
* as absolute (typically defined outside any section in the linker script.)
|
||||
*/
|
||||
static const char rel_sym_regex[] =
|
||||
"^_end$";
|
||||
static regex_t rel_sym_regex_c;
|
||||
static int is_rel_reloc(const char *sym_name)
|
||||
{
|
||||
return !regexec(&rel_sym_regex_c, sym_name, 0, NULL, 0);
|
||||
}
|
||||
|
||||
static void regex_init(void)
|
||||
{
|
||||
char errbuf[128];
|
||||
int err;
|
||||
|
||||
err = regcomp(&abs_sym_regex_c, abs_sym_regex,
|
||||
REG_EXTENDED|REG_NOSUB);
|
||||
if (err) {
|
||||
regerror(err, &abs_sym_regex_c, errbuf, sizeof errbuf);
|
||||
die("%s", errbuf);
|
||||
}
|
||||
|
||||
err = regcomp(&rel_sym_regex_c, rel_sym_regex,
|
||||
REG_EXTENDED|REG_NOSUB);
|
||||
if (err) {
|
||||
regerror(err, &rel_sym_regex_c, errbuf, sizeof errbuf);
|
||||
die("%s", errbuf);
|
||||
}
|
||||
if (strncmp(sym_name, "VDSO", 4) == 0)
|
||||
return 1;
|
||||
if (strncmp(sym_name, "__crc_", 6) == 0)
|
||||
return 1;
|
||||
return 0;
|
||||
}
|
||||
|
||||
static void die(char *fmt, ...)
|
||||
|
|
@ -131,7 +156,7 @@ static const char *rel_type(unsigned type)
|
|||
#undef REL_TYPE
|
||||
};
|
||||
const char *name = "unknown type rel type name";
|
||||
if (type < ARRAY_SIZE(type_name)) {
|
||||
if (type < ARRAY_SIZE(type_name) && type_name[type]) {
|
||||
name = type_name[type];
|
||||
}
|
||||
return name;
|
||||
|
|
@ -448,7 +473,7 @@ static void print_absolute_relocs(void)
|
|||
* Before warning check if this absolute symbol
|
||||
* relocation is harmless.
|
||||
*/
|
||||
if (is_safe_abs_reloc(name))
|
||||
if (is_abs_reloc(name) || is_rel_reloc(name))
|
||||
continue;
|
||||
|
||||
if (!printed) {
|
||||
|
|
@ -501,21 +526,26 @@ static void walk_relocs(void (*visit)(Elf32_Rel *rel, Elf32_Sym *sym))
|
|||
sym = &sh_symtab[ELF32_R_SYM(rel->r_info)];
|
||||
r_type = ELF32_R_TYPE(rel->r_info);
|
||||
/* Don't visit relocations to absolute symbols */
|
||||
if (sym->st_shndx == SHN_ABS) {
|
||||
if (sym->st_shndx == SHN_ABS &&
|
||||
!is_rel_reloc(sym_name(sym_strtab, sym))) {
|
||||
continue;
|
||||
}
|
||||
if (r_type == R_386_NONE || r_type == R_386_PC32) {
|
||||
switch (r_type) {
|
||||
case R_386_NONE:
|
||||
case R_386_PC32:
|
||||
/*
|
||||
* NONE can be ignored and and PC relative
|
||||
* relocations don't need to be adjusted.
|
||||
*/
|
||||
}
|
||||
else if (r_type == R_386_32) {
|
||||
break;
|
||||
case R_386_32:
|
||||
/* Visit relocations that need to be adjusted */
|
||||
visit(rel, sym);
|
||||
}
|
||||
else {
|
||||
die("Unsupported relocation type: %d\n", r_type);
|
||||
break;
|
||||
default:
|
||||
die("Unsupported relocation type: %s (%d)\n",
|
||||
rel_type(r_type), r_type);
|
||||
break;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
|
@ -571,16 +601,15 @@ static void emit_relocs(int as_text)
|
|||
}
|
||||
else {
|
||||
unsigned char buf[4];
|
||||
buf[0] = buf[1] = buf[2] = buf[3] = 0;
|
||||
/* Print a stop */
|
||||
printf("%c%c%c%c", buf[0], buf[1], buf[2], buf[3]);
|
||||
fwrite("\0\0\0\0", 4, 1, stdout);
|
||||
/* Now print each relocation */
|
||||
for (i = 0; i < reloc_count; i++) {
|
||||
buf[0] = (relocs[i] >> 0) & 0xff;
|
||||
buf[1] = (relocs[i] >> 8) & 0xff;
|
||||
buf[2] = (relocs[i] >> 16) & 0xff;
|
||||
buf[3] = (relocs[i] >> 24) & 0xff;
|
||||
printf("%c%c%c%c", buf[0], buf[1], buf[2], buf[3]);
|
||||
fwrite(buf, 4, 1, stdout);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
|
@ -598,6 +627,8 @@ int main(int argc, char **argv)
|
|||
FILE *fp;
|
||||
int i;
|
||||
|
||||
regex_init();
|
||||
|
||||
show_absolute_syms = 0;
|
||||
show_absolute_relocs = 0;
|
||||
as_text = 0;
|
||||
|
|
|
|||
|
|
@ -319,9 +319,7 @@ SECTIONS
|
|||
__brk_limit = .;
|
||||
}
|
||||
|
||||
.end : AT(ADDR(.end) - LOAD_OFFSET) {
|
||||
_end = .;
|
||||
}
|
||||
|
||||
STABS_DEBUG
|
||||
DWARF_DEBUG
|
||||
|
|
|
|||
Loading…
Reference in New Issue