The following commit has been merged into the objtool/urgent branch of tip: Commit-ID: 584fd3b31889852d0d6f3dd1e3d8e9619b660d2c Gitweb: https://git.kernel.org/tip/584fd3b31889852d0d6f3dd1e3d8e9619b660d2c Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Mon, 07 Jun 2021 11:45:58 +02:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Thu, 10 Jun 2021 10:08:24 +02:00 objtool: Fix .symtab_shndx handling for elf_create_undef_symbol() When an ELF object uses extended symbol section indexes (IOW it has a .symtab_shndx section), these must be kept in sync with the regular symbol table (.symtab). So for every new symbol we emit, make sure to also emit a .symtab_shndx value to keep the arrays of equal size. Note: since we're writing an UNDEF symbol, most GElf_Sym fields will be 0 and we can repurpose one (st_size) to host the 0 for the xshndx value. Fixes: 2f2f7e47f052 ("objtool: Add elf_create_undef_symbol()") Reported-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Suggested-by: Fangrui Song <maskray@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Link: https://lkml.kernel.org/r/YL3q1qFO9QIRL/BA@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx --- tools/objtool/elf.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 743c2e9..41bca1d 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -717,7 +717,7 @@ static int elf_add_string(struct elf *elf, struct section *strtab, char *str) struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) { - struct section *symtab; + struct section *symtab, *symtab_shndx; struct symbol *sym; Elf_Data *data; Elf_Scn *s; @@ -769,6 +769,29 @@ struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) symtab->len += data->d_size; symtab->changed = true; + symtab_shndx = find_section_by_name(elf, ".symtab_shndx"); + if (symtab_shndx) { + s = elf_getscn(elf->elf, symtab_shndx->idx); + if (!s) { + WARN_ELF("elf_getscn"); + return NULL; + } + + data = elf_newdata(s); + if (!data) { + WARN_ELF("elf_newdata"); + return NULL; + } + + data->d_buf = &sym->sym.st_size; /* conveniently 0 */ + data->d_size = sizeof(Elf32_Word); + data->d_align = 4; + data->d_type = ELF_T_WORD; + + symtab_shndx->len += 4; + symtab_shndx->changed = true; + } + sym->sec = find_section_by_index(elf, 0); elf_add_symbol(elf, sym);
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