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objtool/klp: Fix handling of zero-length .altinstr_replacement sections

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When a section is empty (e.g. only zero-length alternative
replacements), there are no symbols to convert a section symbol
reference to.  Skip the reloc instead of erroring out.

Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
This commit is contained in:
Josh Poimboeuf 2026-04-09 18:34:50 -07:00
parent def5b60dcd
commit c4c02d4450
1 changed files with 12 additions and 1 deletions
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13
tools/objtool/klp-diff.c
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@ -1005,6 +1005,13 @@ static int convert_reloc_secsym_to_sym(struct elf *elf, struct reloc *reloc)
/* No dedicated section; find the symbol manually */
sym = find_symbol_containing(sec, arch_adjusted_addend(reloc));
if (!sym) {
/*
* This is presumably an .altinstr_replacement section which is
* empty due to it only having zero-length replacement(s).
*/
if (!sec_size(sec))
return 1;
/*
* This can happen for special section references to weak code
* whose symbol has been stripped by the linker.
@ -1265,6 +1272,7 @@ static int clone_sym_relocs(struct elfs *e, struct symbol *patched_sym)
for_each_reloc(patched_rsec, patched_reloc) {
unsigned long offset;
int ret;
if (reloc_offset(patched_reloc) < start ||
reloc_offset(patched_reloc) >= end)
@ -1278,12 +1286,15 @@ static int clone_sym_relocs(struct elfs *e, struct symbol *patched_sym)
!strcmp(patched_reloc->sym->sec->name, ".altinstr_aux"))
continue;
if (convert_reloc_sym(e->patched, patched_reloc)) {
ret = convert_reloc_sym(e->patched, patched_reloc);
if (ret < 0) {
ERROR_FUNC(patched_rsec->base, reloc_offset(patched_reloc),
"failed to convert reloc sym '%s' to its proper format",
patched_reloc->sym->name);
return -1;
}
if (ret > 0)
continue;
offset = out_sym->offset + (reloc_offset(patched_reloc) - patched_sym->offset);