Re: [PATCH v4 14/22] objtool: Reuse string references
From: Song Liu <song@kernel.org>
Date: 2026-08-11 23:53:13
Also in:
live-patching, lkml
On Sat, Aug 8, 2026 at 4:18 PM Josh Poimboeuf [off-list ref] wrote:
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 addresses in the ADRP+ADD pair would corrupt the memory access. Avoid that by detecting and reusing duplicates when cloning string relocs. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Acked-by: Song Liu <song@kernel.org> With one nitpick below:
quoted hunk ↗ jump to hunk
--- tools/objtool/elf.c | 29 +++++++++++++++++++++++------ tools/objtool/include/objtool/elf.h | 3 ++- tools/objtool/klp-diff.c | 4 +++- 3 files changed, 28 insertions(+), 8 deletions(-)diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 8bf225d70d918..3bb04d6155a8b 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c@@ -1379,9 +1379,27 @@ struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name) return elf; } -unsigned int elf_add_string(struct elf *elf, struct section *strtab, const char *str) +int elf_find_string(struct elf *elf, struct section *strtab, const char *str) {
elf_find_string() returns -1 for error and positive number for addend. It is a good idea to add some comments for this behavior. Thanks, Song [...]