diff options
| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2026-08-02 20:24:27 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2026-08-03 07:12:39 +0200 |
| commit | 029223d301620bc4e1086696047b0d5d6eba5edd (patch) | |
| tree | d31f07a1a1ad20afbf2d64c40a715959d3f61217 /include | |
| parent | f5f762fc93d0b81d30b815a2f96320909ad10eb3 (diff) | |
objtool/klp: Add .klp.symid for sympos disambiguation
Livepatch identifies a duplicate-named symbol by its position (sympos)
among same-named kallsyms entries, which for vmlinux are counted in
ascending address order in the final linked kernel. That order can't be
reliably derived from vmlinux.o: the final link reorders sub-sections
(.text.unlikely*, .data..*, etc).
Bridge the gap with a new .klp.symid section which can be used to
correlate symbols between vmlinux.o and vmlinux so that klp-diff can
reliably determine the sympos.
The table can't survive --gc-sections: keeping it alive would keep every
duplicate-named symbol's section alive, so the reference kernel would
stop matching the one which ships. klp-build rejects
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION instead. Nothing is lost today:
x86_64 is the only HAVE_KLP_BUILD arch and doesn't select
HAVE_LD_DEAD_CODE_DATA_ELIMINATION, arm64 and s390 have never selected
it either, and on powerpc, it's still EXPERIMENTAL and disabled by every
distro kernel.
This is the build-time half of reliable vmlinux sympos computation;
"objtool klp diff" will consume the table in a subsequent commit.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: live-patching@vger.kernel.org
Link: https://patch.msgid.link/64d50f077b569f47883c015cdb7079edb068efe8.1785727106.git.jpoimboe@kernel.org
Diffstat (limited to 'include')
| -rw-r--r-- | include/asm-generic/vmlinux.lds.h | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 5659f4b5a125..ee9c5d354a85 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -839,12 +839,20 @@ .stab.index 0 : { *(.stab.index) } \ .stab.indexstr 0 : { *(.stab.indexstr) } +#ifdef CONFIG_KLP_BUILD +#define KLP_SYMID \ + .klp.symid 0 : { *(.klp.symid) } +#else +#define KLP_SYMID +#endif + /* Required sections not related to debugging. */ #define ELF_DETAILS \ .comment 0 : { *(.comment) } \ .symtab 0 : { *(.symtab) } \ .strtab 0 : { *(.strtab) } \ - .shstrtab 0 : { *(.shstrtab) } + .shstrtab 0 : { *(.shstrtab) } \ + KLP_SYMID #define MODINFO \ .modinfo : { *(.modinfo) . = ALIGN(8); } |