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create-diff-object: Remove undefined function symbols #1494

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create-diff-object: Remove undefined function symbols #1494

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76 changes: 72 additions & 4 deletions kpatch-build/create-diff-object.c
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Original file line number Diff line number Diff line change
Expand Up @@ -80,7 +80,8 @@ struct special_section {
char *name;
enum architecture arch;
int (*group_size)(struct kpatch_elf *kelf, int offset);
bool (*group_filter)(struct lookup_table *lookup,
bool (*group_filter)(struct kpatch_elf *kelf,
struct lookup_table *lookup,
struct section *relasec, unsigned int offset,
unsigned int size);
};
Expand Down Expand Up @@ -2462,7 +2463,72 @@ static int fixup_group_size(struct kpatch_elf *kelf, int offset)
return (int)(rela->addend - offset);
}

static bool jump_table_group_filter(struct lookup_table *lookup,
/*
* Exclude function symbols absent from any rela sections (except
* .rela__bug_table) to eliminate undefined symbols modpost errors.
*/
static bool bug_table_group_filter(struct kpatch_elf *kelf,
struct lookup_table *lookup,
struct section *relasec,
unsigned int group_offset,
unsigned int group_size)
{
unsigned int i = 0, count = 0;
unsigned int *symindex;
struct section *sec;
struct symbol *sym;
struct rela *rela;
bool found;

list_for_each_entry(rela, &relasec->relas, list) {
if (rela->sym->type == STT_FUNC && rela->sym->sec &&
!rela->sym->sec->include)
count++;
}
symindex = (unsigned int *)malloc(sizeof(unsigned int) * count);
if (!symindex)
ERROR("malloc");
list_for_each_entry(rela, &relasec->relas, list) {
if (rela->sym->type == STT_FUNC && rela->sym->sec &&
!rela->sym->sec->include)
symindex[i++] = rela->sym->index;
}
for (i = 0; i < count; i++) {
found = false;
list_for_each_entry(sec, &kelf->sections, list) {
if (!is_rela_section(sec) ||
is_debug_section(sec))
continue;
if (!strcmp(sec->name, relasec->name) ||
!strcmp(sec->name, ".rela__mcount_loc") ||
!sec->include)
continue;
list_for_each_entry(rela, &sec->relas, list) {
if (symindex[i] == rela->sym->index) {
found = true;
break;
}
}
}
if (!found) {
/*
* Function symbol is present in only __bug_table.
* i.e. function symbol was included earlier, but its
* associated section is not included and not
* referenced in any relas. Exclude the function symbol
* to eliminate UND symbols modpost errors.
*/
sym = find_symbol_by_index(&kelf->symbols, symindex[i]);
if (!sym)
ERROR("could not find function symbol\n");
sym->include = 0;
}
}
return true;
}

static bool jump_table_group_filter(struct kpatch_elf *kelf,
struct lookup_table *lookup,
struct section *relasec,
unsigned int group_offset,
unsigned int group_size)
Expand Down Expand Up @@ -2563,7 +2629,8 @@ static bool jump_table_group_filter(struct lookup_table *lookup,
return true;
}

static bool static_call_sites_group_filter(struct lookup_table *lookup,
static bool static_call_sites_group_filter(struct kpatch_elf *kelf,
struct lookup_table *lookup,
struct section *relasec,
unsigned int group_offset,
unsigned int group_size)
Expand Down Expand Up @@ -2630,6 +2697,7 @@ static struct special_section special_sections[] = {
.name = "__bug_table",
.arch = AARCH64 | X86_64 | PPC64 | S390 | LOONGARCH64,
.group_size = bug_table_group_size,
.group_filter = bug_table_group_filter,
},
{
.name = ".fixup",
Expand Down Expand Up @@ -2837,7 +2905,7 @@ static void kpatch_regenerate_special_section(struct kpatch_elf *kelf,
continue;

if (special->group_filter &&
!special->group_filter(lookup, relasec, src_offset, group_size))
!special->group_filter(kelf, lookup, relasec, src_offset, group_size))
continue;

/*
Expand Down
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