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create-diff-object: create intermediate .kpatch.arch section

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In addition to .kpatch.relocations and .kpatch.symbols, have
create-diff-object create an .kpatch.arch section. This section can be used
to create .klp.arch. sections that are required for klp modules built for
versions >= 4.9. Each entry in the .kpatch.arch section represents an
arch-specific section (.altinstructions or .parainstructions) and contains
a pointer to the arch-specific section itself (see kpatch_arch struct
member 'sec') and a pointer to the objname string (see kpatch_arch struct
member 'objname'). This is enough information to be able to build
.klp.arch. sections in a later phase of kpatch-build.
This commit is contained in:
Jessica Yu 2017-01-23 12:43:24 -08:00
parent 87643703a7
commit 42902d0fcc
2 changed files with 58 additions and 0 deletions
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53
kpatch-build/create-diff-object.c
View File

@ -1584,6 +1584,8 @@ static void kpatch_regenerate_special_section(struct kpatch_elf *kelf,
/* include both rela and base sections */
sec->include = 1;
sec->base->include = 1;
/* include secsym so .kpatch.arch relas can point to section symbols */
sec->base->secsym->include = 1;
/*
* Update text section data buf and size.
@ -1707,6 +1709,56 @@ static void kpatch_mark_ignored_functions_same(struct kpatch_elf *kelf)
}
}
static void kpatch_create_kpatch_arch_section(struct kpatch_elf *kelf, char *objname)
{
struct special_section *special;
struct kpatch_arch *entries;
struct symbol *strsym;
struct section *sec, *karch_sec;
struct rela *rela;
int nr, index = 0;
nr = sizeof(special_sections) / sizeof(special_sections[0]);
karch_sec = create_section_pair(kelf, ".kpatch.arch", sizeof(*entries), nr);
entries = karch_sec->data->d_buf;
/* lookup strings symbol */
strsym = find_symbol_by_name(&kelf->symbols, ".kpatch.strings");
if (!strsym)
ERROR("can't find .kpatch.strings symbol");
for (special = special_sections; special->name; special++) {
if (strcmp(special->name, ".parainstructions") &&
strcmp(special->name, ".altinstructions"))
continue;
sec = find_section_by_name(&kelf->sections, special->name);
if (!sec)
continue;
/* entries[index].sec */
ALLOC_LINK(rela, &karch_sec->rela->relas);
rela->sym = sec->secsym;
rela->type = R_X86_64_64;
rela->addend = 0;
rela->offset = index * sizeof(*entries) + \
offsetof(struct kpatch_arch, sec);
/* entries[index].objname */
ALLOC_LINK(rela, &karch_sec->rela->relas);
rela->sym = strsym;
rela->type = R_X86_64_64;
rela->addend = offset_of_string(&kelf->strings, objname);
rela->offset = index * sizeof(*entries) + \
offsetof(struct kpatch_arch, objname);
index++;
}
karch_sec->data->d_size = index * sizeof(struct kpatch_arch);
karch_sec->sh.sh_size = karch_sec->data->d_size;
}
static void kpatch_process_special_sections(struct kpatch_elf *kelf)
{
struct special_section *special;
@ -2462,6 +2514,7 @@ int main(int argc, char *argv[])
kpatch_create_strings_elements(kelf_out);
kpatch_create_patches_sections(kelf_out, lookup, hint, objname);
kpatch_create_intermediate_sections(kelf_out, lookup, hint, objname, pmod_name);
kpatch_create_kpatch_arch_section(kelf_out, objname);
kpatch_create_hooks_objname_rela(kelf_out, objname);
kpatch_build_strings_section_data(kelf_out);

5
kpatch-build/kpatch-intermediate.h
View File

@ -40,4 +40,9 @@ struct kpatch_relocation {
char *objname; /* object to which this rela applies to */
struct kpatch_symbol *ksym;
};
struct kpatch_arch {
unsigned long sec;
char *objname;
};
#endif /* _KPATCH_ELF_H_ */