linux-kernel - [tip: objtool/urgent] objtool/klp: Fix bug table handling for __WARN

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Message-ID: <176958996941.510.4641148219429711553.tip-bot2@tip-bot2>
Date: Wed, 28 Jan 2026 08:46:09 -0000
From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Song Liu <song@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject:
 [tip: objtool/urgent] objtool/klp: Fix bug table handling for __WARN_printf()

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     f2dba60339a6299e181671e95293efe312237e2d
Gitweb:        https://git.kernel.org/tip/f2dba60339a6299e181671e95293efe312237e2d
Author:        Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate:    Sun, 25 Jan 2026 21:56:39 -08:00
Committer:     Josh Poimboeuf <jpoimboe@...nel.org>
CommitterDate: Tue, 27 Jan 2026 08:20:47 -08:00

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 5b472b6e5bd9 ("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: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Fixes: 5b472b6e5bd9 ("x86_64/bug: Implement __WARN_printf()")
Reported-by: Song Liu <song@...nel.org>
Tested-by: Song Liu <song@...nel.org>
Link: https://patch.msgid.link/a8e0a714b9da962858842b9aecd63b4900927c88.1769406850.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 tools/objtool/klp-diff.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index 4d1f9e9..d94531e 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -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;