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authorPeter Zijlstra <peterz@infradead.org>2021-06-07 12:45:58 +0300
committerPeter Zijlstra <peterz@infradead.org>2021-06-10 11:08:24 +0300
commit584fd3b31889852d0d6f3dd1e3d8e9619b660d2c (patch)
tree6343458bd05d3a2021ca0cdb3f62a13650dc01b2 /tools
parent614124bea77e452aa6df7a8714e8bc820b489922 (diff)
downloadlinux-584fd3b31889852d0d6f3dd1e3d8e9619b660d2c.tar.xz
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@google.com> Suggested-by: Fangrui Song <maskray@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Link: https://lkml.kernel.org/r/YL3q1qFO9QIRL/BA@hirez.programming.kicks-ass.net
Diffstat (limited to 'tools')
-rw-r--r--tools/objtool/elf.c25
1 files changed, 24 insertions, 1 deletions
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 743c2e9d0f56..41bca1d13d8e 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);