For duplicate strings, elf_add_string() just blindly adds duplicates.
That can be a problem for arm64 which often uses two consecutive
instructions (and corresponding relocations) to put an address into a
register, like:
d8: 90000001 adrp x1, 0 <meminfo_proc_show> d8: R_AARCH64_ADR_PREL_PG_HI21 .rodata.meminfo_proc_show.str1.8
dc: 91000021 add x1, x1, #0x0 dc: R_AARCH64_ADD_ABS_LO12_NC .rodata.meminfo_proc_show.str1.8
Referencing two different string addresses in the adrp+add pair can
result in a corrupt string addresses. Detect such consecutive reuses
and force them to use the same string.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
tools/objtool/elf.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 3da90686350d..52ef991115fc 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -1321,6 +1321,8 @@ struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name)
unsigned int elf_add_string(struct elf *elf, struct section *strtab, const char *str)
{
+ static unsigned int last_off;
+ static const char *last_str;
unsigned int offset;
if (!strtab)
@@ -1329,17 +1331,22 @@ unsigned int elf_add_string(struct elf *elf, struct section *strtab, const char
ERROR("can't find .strtab section");
return -1;
}
-
if (!strtab->sh.sh_addralign) {
ERROR("'%s': invalid sh_addralign", strtab->name);
return -1;
}
+ if (last_str && !strcmp(last_str, str))
+ return last_off;
+
offset = ALIGN(strtab->sh.sh_size, strtab->sh.sh_addralign);
if (!elf_add_data(elf, strtab, str, strlen(str) + 1))
return -1;
+ last_str = str;
+ last_off = offset;
+
return offset;
}
--
2.53.0