From: George Guo <[email protected]> GCC/GAS on LoongArch references special section entries (__ex_table, __bug_table, __jump_table, .altinstructions) through local text labels (.L*) instead of a section symbol plus offset. The assembler keeps the label because of linker relaxation: a "section + constant offset" reference would go stale when the linker deletes or shrinks instructions, while a symbol reference can be recomputed after relaxation.
convert_reloc_secsym_to_sym() only handles the section symbol form and returns early for such label references. The label is never cloned into the livepatch object, so should_keep_special_sym() cannot correlate the entry with an included function and silently drops it: a GCC-built livepatch module ends up missing the patched function's __ex_table / __bug_table / __jump_table entries, with no error at build or load time. Redirect label references in text sections to the containing function symbol, mirroring the section symbol case. A label with no containing function symbol (e.g. hand-written asm in a plain .text section) can't be correlated; skip it rather than failing, since such entries belong to unchanged code and are dropped anyway. Reported-by: Joe Lawrence <[email protected]> Suggested-by: Joe Lawrence <[email protected]> Signed-off-by: George Guo <[email protected]> --- tools/objtool/klp-diff.c | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c index b9624bd9439b..05fd70e24326 100644 --- a/tools/objtool/klp-diff.c +++ b/tools/objtool/klp-diff.c @@ -1423,8 +1423,41 @@ static int convert_reloc_secsym_to_sym(struct elf *elf, struct reloc *reloc) if (!strcmp(reloc->sec->name, ".rela__patchable_function_entries")) return convert_pfe_reloc(elf, reloc); - if (!is_sec_sym(sym)) + if (!is_sec_sym(sym)) { + /* + * Most toolchains reference special-section entries via the + * section symbol plus an offset. GCC/GAS on LoongArch instead + * references a local text label (.L*): LoongArch linker + * relaxation is the reason GAS keeps the label rather than + * reducing it to a section symbol reference. Such a label is + * never cloned into the livepatch object, so the entry would be + * silently dropped. Redirect the relocation to the containing + * function, mirroring the section-symbol case below. + */ + if (is_local_label(sym) && is_text_sec(sec)) { + unsigned long offset = sym->offset + reloc_addend(reloc); + + sym = find_symbol_containing_inclusive(sec, offset); + if (!sym) { + /* + * A local label with no containing function + * symbol (e.g. hand-written asm in a plain .text + * section). It can't be correlated to a function, + * so skip it rather than failing the build; such + * entries belong to unchanged code and are dropped + * anyway. + */ + return 1; + } + + reloc->sym = sym; + set_reloc_sym(elf, reloc, sym->idx); + set_reloc_addend(elf, reloc, offset - sym->offset); + return 0; + } + return 0; + } sym = find_symbol_containing_inclusive(sec, arch_adjusted_addend(reloc)); if (!sym) { -- 2.25.1
