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create-diff-object: Fix ordering of __patchable_function_entries #1451

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Merged
merged 1 commit into from
May 14, 2025
Merged

create-diff-object: Fix ordering of __patchable_function_entries #1451

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26 changes: 13 additions & 13 deletions kpatch-build/create-diff-object.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1992,6 +1992,8 @@ static void kpatch_migrate_included_elements(struct kpatch_elf *kelf, struct kpa
ERROR("malloc");
memset(out, 0, sizeof(*out));
out->arch = kelf->arch;
out->has_pfe = kelf->has_pfe;
out->pfe_ordered = kelf->pfe_ordered;
INIT_LIST_HEAD(&out->sections);
INIT_LIST_HEAD(&out->symbols);
INIT_LIST_HEAD(&out->strings);
Expand Down Expand Up @@ -3729,7 +3731,7 @@ static void kpatch_set_pfe_link(struct kpatch_elf *kelf)
* TODO: Eventually we can modify recordmount so that it recognizes our bundled
* sections as valid and does this work for us.
*/
static void kpatch_create_ftrace_callsite_sections(struct kpatch_elf *kelf, bool has_pfe)
static void kpatch_create_ftrace_callsite_sections(struct kpatch_elf *kelf)
{
int nr, index;
struct section *sec = NULL;
Expand All @@ -3745,13 +3747,7 @@ static void kpatch_create_ftrace_callsite_sections(struct kpatch_elf *kelf, bool
sym->has_func_profiling)
nr++;

if (has_pfe)
/*
* Create separate __patchable_function_entries sections
* for each function in the following loop.
*/
kelf->has_pfe = true;
else
if (!kelf->has_pfe)
/*
* Create a single __mcount_loc section pair for all
* functions.
Expand Down Expand Up @@ -3858,7 +3854,14 @@ static void kpatch_create_ftrace_callsite_sections(struct kpatch_elf *kelf, bool
* - its lone rela is based on the section symbol
*/
sec = create_section_pair(kelf, "__patchable_function_entries", sizeof(void *), 1);
sec->sh.sh_flags |= SHF_WRITE | SHF_ALLOC | SHF_LINK_ORDER;
sec->sh.sh_flags |= SHF_WRITE | SHF_ALLOC;
/*
* Old linkers don't support mixing ordered and unordered sections, so set
* the SHF_LINK_ORDER flag only if it is set in the pfe section generated by
* the compiler.
*/
if (kelf->pfe_ordered)
sec->sh.sh_flags |= SHF_LINK_ORDER;
rela_sym = sym->sec->secsym;
rela_offset = 0;
rela_sym->pfe = sec;
Expand Down Expand Up @@ -4158,7 +4161,6 @@ int main(int argc, char *argv[])
struct section *relasec, *symtab;
char *orig_obj, *patched_obj, *parent_name;
char *parent_symtab, *mod_symvers, *patch_name, *output_obj;
bool has_pfe = false;

memset(&arguments, 0, sizeof(arguments));
argp_parse (&argp, argc, argv, 0, NULL, &arguments);
Expand All @@ -4184,8 +4186,6 @@ int main(int argc, char *argv[])

kpatch_set_pfe_link(kelf_orig);
kpatch_set_pfe_link(kelf_patched);
if (kelf_patched->has_pfe)
has_pfe = true;

kpatch_find_func_profiling_calls(kelf_orig);
kpatch_find_func_profiling_calls(kelf_patched);
Expand Down Expand Up @@ -4266,7 +4266,7 @@ int main(int argc, char *argv[])
kpatch_create_callbacks_objname_rela(kelf_out, parent_name);
kpatch_build_strings_section_data(kelf_out);

kpatch_create_ftrace_callsite_sections(kelf_out, has_pfe);
kpatch_create_ftrace_callsite_sections(kelf_out);

/*
* At this point, the set of output sections and symbols is
Expand Down
13 changes: 11 additions & 2 deletions kpatch-build/kpatch-elf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -559,6 +559,7 @@ struct kpatch_elf *kpatch_elf_open(const char *name)
int fd;
struct kpatch_elf *kelf;
struct section *relasec;
struct section *pfesec;
GElf_Ehdr ehdr;

fd = open(name, O_RDONLY);
Expand Down Expand Up @@ -614,9 +615,17 @@ struct kpatch_elf *kpatch_elf_open(const char *name)
* These sections aren't used by ftrace on this arch, so do not
* bother reading/writing them for x86_64.
*/
if (kelf->arch != X86_64)
if (find_section_by_name(&kelf->sections, "__patchable_function_entries"))
if (kelf->arch != X86_64) {
pfesec = find_section_by_name(&kelf->sections, "__patchable_function_entries");
if (pfesec) {
kelf->has_pfe = true;
/*
* Check if the pfe section generated by the toolchain has the SHF_LINK_ORDER
* flag set. This info is used while generating pfe sections in the diff object.
*/
kelf->pfe_ordered = !!(pfesec->sh.sh_flags & SHF_LINK_ORDER);
}
}

return kelf;
}
Expand Down
1 change: 1 addition & 0 deletions kpatch-build/kpatch-elf.h
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Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,7 @@ struct kpatch_elf {
Elf_Data *symtab_shndx;
int fd;
bool has_pfe;
bool pfe_ordered;
};

/*******************
Expand Down