Commit e476bb27 authored by Josh Poimboeuf's avatar Josh Poimboeuf
Browse files

objtool/klp: Disable unsupported pr_debug() usage 



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: default avatarSong Liu <song@kernel.org>
Link: https://patch.msgid.link/3a7db3a5b7d4abf9b2534803a74e2e7231322738.1770759954.git.jpoimboe@kernel.org


Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
parent f9fb44b0

tools/objtool/klp-diff.c

+15 −8
Original line number Diff line number Diff line
@@ -1334,18 +1334,18 @@ 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)
@@ -1403,6 +1403,13 @@ 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;