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Merge pull request #525 from euspectre/no-reloc-fix 

kpatch-build: revisit checking for fentry calls
This commit is contained in:
Seth Jennings 2015-10-28 20:49:56 -05:00
parent 0523597ae5 393be6f8fc
commit 2e4dea5236
1 changed files with 50 additions and 5 deletions
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55
kpatch-build/create-diff-object.c
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@ -127,6 +127,7 @@ struct symbol {
int include; /* used in the patched elf */
int strip; /* used in the output elf */
};
int has_fentry_call;
};
struct rela {
@ -472,6 +473,24 @@ void kpatch_create_symbol_list(struct kpatch_elf *kelf)
}
/* Check which functions have fentry calls; save this info for later use. */
static void kpatch_find_fentry_calls(struct kpatch_elf *kelf)
{
struct symbol *sym;
struct rela *rela;
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->type != STT_FUNC || !sym->sec->rela)
continue;
rela = list_first_entry(&sym->sec->rela->relas, struct rela,
list);
if (rela->type != R_X86_64_NONE ||
strcmp(rela->sym->name, "__fentry__"))
continue;
sym->has_fentry_call = 1;
}
}
struct kpatch_elf *kpatch_elf_open(const char *name)
{
@ -510,6 +529,7 @@ struct kpatch_elf *kpatch_elf_open(const char *name)
kpatch_create_rela_list(kelf, sec);
}
kpatch_find_fentry_calls(kelf);
return kelf;
}
@ -1373,6 +1393,25 @@ next:
}
}
static void kpatch_check_fentry_calls(struct kpatch_elf *kelf)
{
struct symbol *sym;
int errs = 0;
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->type != STT_FUNC || sym->status != CHANGED)
continue;
if (!sym->twin->has_fentry_call) {
log_normal("function %s has no fentry call, unable to patch\n",
sym->name);
errs++;
}
}
if (errs)
DIFF_FATAL("%d function(s) can not be patched", errs);
}
void kpatch_verify_patchability(struct kpatch_elf *kelf)
{
struct section *sec;
@ -2658,7 +2697,8 @@ void kpatch_create_mcount_sections(struct kpatch_elf *kelf)
nr = 0;
list_for_each_entry(sym, &kelf->symbols, list)
if (sym->type == STT_FUNC && sym->status != SAME)
if (sym->type == STT_FUNC && sym->status != SAME &&
sym->has_fentry_call)
nr++;
/* create text/rela section pair */
@ -2672,6 +2712,12 @@ void kpatch_create_mcount_sections(struct kpatch_elf *kelf)
if (sym->type != STT_FUNC || sym->status == SAME)
continue;
if (!sym->has_fentry_call) {
log_debug("function %s has no fentry call, no mcount record is needed\n",
sym->name);
continue;
}
/* add rela in .rela__mcount_loc to fill in function pointer */
ALLOC_LINK(rela, &relasec->relas);
rela->sym = sym;
@ -2688,7 +2734,8 @@ void kpatch_create_mcount_sections(struct kpatch_elf *kelf)
sym->sec->data->d_buf = newdata;
insn = newdata;
if (insn[0] != 0xf)
ERROR("function '%s' has no fentry call; unable to patch", sym->name);
ERROR("%s: unexpected instruction at the start of the function",
sym->name);
insn[0] = 0xe8;
insn[1] = 0;
insn[2] = 0;
@ -2697,9 +2744,6 @@ void kpatch_create_mcount_sections(struct kpatch_elf *kelf)
rela = list_first_entry(&sym->sec->rela->relas, struct rela,
list);
if (rela->type != R_X86_64_NONE ||
strcmp(rela->sym->name, "__fentry__"))
ERROR("function '%s' has no fentry call; unable to patch", sym->name);
rela->type = R_X86_64_PC32;
index++;
@ -3019,6 +3063,7 @@ int main(int argc, char *argv[])
*/
kpatch_mark_ignored_sections(kelf_patched);
kpatch_compare_correlated_elements(kelf_patched);
kpatch_check_fentry_calls(kelf_patched);
kpatch_elf_teardown(kelf_base);
kpatch_elf_free(kelf_base);