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kpatch-elf: symtab_shndx support 

Symbol indexes over 64k don't fit into st_shndx and are stored in
extended symbol table. Make sure we properly handle these cases. It is
not normally useful during kpatch builds but will come up if we start
diffing linked objects.

Signed-off-by: Artem Savkov <asavkov@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
This commit is contained in:
Artem Savkov 2021-01-12 17:15:45 +01:00
parent 110e196bac
commit 8d81cc8517
2 changed files with 16 additions and 4 deletions
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19
kpatch-build/kpatch-elf.c
View File

@ -263,6 +263,10 @@ void kpatch_create_section_list(struct kpatch_elf *kelf)
sec->index = (unsigned int)elf_ndxscn(scn);
if (sec->sh.sh_type == SHT_SYMTAB_SHNDX)
kelf->symtab_shndx = sec->data;
log_debug("ndx %02d, data %p, size %zu, name %s\n",
sec->index, sec->data->d_buf, sec->data->d_size,
sec->name);
@ -278,6 +282,7 @@ void kpatch_create_symbol_list(struct kpatch_elf *kelf)
struct section *symtab;
struct symbol *sym;
unsigned int symbols_nr, index = 0;
Elf32_Word shndx;
symtab = find_section_by_name(&kelf->sections, ".symtab");
if (!symtab)
@ -305,10 +310,16 @@ void kpatch_create_symbol_list(struct kpatch_elf *kelf)
sym->type = GELF_ST_TYPE(sym->sym.st_info);
sym->bind = GELF_ST_BIND(sym->sym.st_info);
if (sym->sym.st_shndx > SHN_UNDEF &&
sym->sym.st_shndx < SHN_LORESERVE) {
sym->sec = find_section_by_index(&kelf->sections,
sym->sym.st_shndx);
shndx = sym->sym.st_shndx;
if (shndx == SHN_XINDEX &&
!gelf_getsymshndx(symtab->data, kelf->symtab_shndx, sym->index, &sym->sym, &shndx))
ERROR("couldn't find extended section index for symbol %s; idx=%d",
sym->name, sym->index);
if ((sym->sym.st_shndx > SHN_UNDEF &&
sym->sym.st_shndx < SHN_LORESERVE) ||
sym->sym.st_shndx == SHN_XINDEX) {
sym->sec = find_section_by_index(&kelf->sections, shndx);
if (!sym->sec)
ERROR("couldn't find section for symbol %s\n",
sym->name);

1
kpatch-build/kpatch-elf.h
View File

@ -120,6 +120,7 @@ struct kpatch_elf {
struct list_head sections;
struct list_head symbols;
struct list_head strings;
Elf_Data *symtab_shndx;
int fd;
};