Commit f2dba603 authored Jan 25, 2026 by Josh Poimboeuf

objtool/klp: Fix bug table handling for __WARN_printf()



Running objtool klp-diff on a changed function which uses WARN() can
fail with:

  vmlinux.o: error: objtool: md_run+0x866: failed to convert reloc sym '__bug_table' to its proper format

The problem is that since commit 5b472b6e ("x86_64/bug: Implement
__WARN_printf()"), each __WARN_printf() call site now directly
references its bug table entry.  klp-diff errors out when it can't
convert such section-based references to object symbols (because bug
table entries don't have symbols).

Luckily, klp-diff already has code to create symbols for bug table
entries.  Move that code earlier, before function diffing.

Fixes: dd590d4d ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Fixes: 5b472b6e ("x86_64/bug: Implement __WARN_printf()")
Reported-by: Song Liu <song@kernel.org>
Tested-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/a8e0a714b9da962858842b9aecd63b4900927c88.1769406850.git.jpoimboe@kernel.org


Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

parent d107b326

tools/objtool/klp-diff.c

+11 −3

Original line number	Diff line number	Diff line
		@@ -1425,9 +1425,6 @@ static int clone_special_sections(struct elfs *e)
		{
		struct section *patched_sec;

		if (create_fake_symbols(e->patched))
		return -1;

		for_each_sec(e->patched, patched_sec) {
		if (is_special_section(patched_sec)) {
		if (clone_special_section(e, patched_sec))
		@@ -1704,6 +1701,17 @@ int cmd_klp_diff(int argc, const char **argv)
		if (!e.out)
		return -1;

		/*
		* Special section fake symbols are needed so that individual special
		* section entries can be extracted by clone_special_sections().
		*
		* Note the fake symbols are also needed by clone_included_functions()
		* because __WARN_printf() call sites add references to bug table
		* entries in the calling functions.
		*/
		if (create_fake_symbols(e.patched))
		return -1;

		if (clone_included_functions(&e))
		return -1;