[PATCH 6.19 067/342] objtool/klp: Disable unsupported pr_debug() usage

Greg Kroah-Hartman
2026-03-31T16:34:05Z

From: Josh Poimboeuf <jpoimboe@kernel.org>

[ Upstream commit e476bb277cf91b7ac3ea803ec78a4f0791bddec3 ]

Instead of erroring out on unsupported pr_debug() (e.g., when patching a
module), issue a warning and make it inert, similar to how unsupported
tracepoints are currently handled.

Reviewed-and-tested-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/3a7db3a5b7d4abf9b2534803a74e2e7231322738.1770759954.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/objtool/klp-diff.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index b1847828217ba..b9340ef8d370c 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -1335,18 +1335,18 @@ static bool should_keep_special_sym(struct elf *elf, struct symbol *sym)
* be applied after static branch/call init, resulting in code corruption.
*
* Validate a special section entry to avoid that. Note that an inert
- * tracepoint is harmless enough, in that case just skip the entry and print a
- * warning. Otherwise, return an error.
+ * tracepoint or pr_debug() is harmless enough, in that case just skip the
+ * entry and print a warning. Otherwise, return an error.
*
- * This is only a temporary limitation which will be fixed when livepatch adds
- * support for submodules: fully self-contained modules which are embedded in
- * the top-level livepatch module's data and which can be loaded on demand when
- * their corresponding to-be-patched module gets loaded. Then klp relocs can
- * be retired.
+ * TODO: This is only a temporary limitation which will be fixed when livepatch
+ * adds support for submodules: fully self-contained modules which are embedded
+ * in the top-level livepatch module's data and which can be loaded on demand
+ * when their corresponding to-be-patched module gets loaded. Then klp relocs
+ * can be retired.
*
* Return:
* -1: error: validation failed
- * 1: warning: tracepoint skipped
+ * 1: warning: disabled tracepoint or pr_debug()
* 0: success
*/
static int validate_special_section_klp_reloc(struct elfs *e, struct symbol *sym)
@@ -1404,6 +1404,13 @@ static int validate_special_section_klp_reloc(struct elfs *e, struct symbol *sym
continue;
}

+ if (strstr(reloc->sym->name, "__UNIQUE_ID_ddebug_")) {
+ WARN("%s: disabling unsupported pr_debug()",
+ code_sym->name);
+ ret = 1;
+ continue;
+ }
+
ERROR("%s+0x%lx: unsupported static branch key %s. Use static_key_enabled() instead",
code_sym->name, code_offset, reloc->sym->name);
return -1;
--
2.51.0