[RFC 1/4] objtool/klp: add --symvers option to klp diff

Add a --symvers (-s) option that accepts a path to Module.symvers.  When
provided, it replaces the default "Module.symvers" filename used by the
auto-detection logic.

This decoupling helps to enable scenarios like out-of-tree module
patching and unit testing of klp-diff, where object files /
Module.symvers live outside the kernel tree.

The existing auto-detection behavior (try cwd, then top_level_dir()
fallback) is preserved regardless of whether --symvers is specified.

Assisted-by: Cursor:claude-4.6-opus
Signed-off-by: Joe Lawrence <[email protected]>
---
 tools/objtool/klp-diff.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index b9624bd9439b..bd8d64f2f3f6 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -34,6 +34,7 @@ struct export {
 	char *mod, *sym;
 };
 
+static const char *symvers_path = "Module.symvers";
 bool debug, debug_correlate, debug_clone;
 int indent;
 
@@ -47,6 +48,7 @@ static const struct option klp_diff_options[] = {
 	OPT_BOOLEAN('d', "debug", &debug, "enable all debug output"),
 	OPT_BOOLEAN(0, "debug-correlate", &debug_correlate, "enable correlation debug output"),
 	OPT_BOOLEAN(0, "debug-clone", &debug_clone, "enable cloning debug output"),
+	OPT_STRING('s', "symvers", &symvers_path, "path", "path to Module.symvers (default: Module.symvers)"),
 	OPT_END(),
 };
 
@@ -86,16 +88,15 @@ static char *escape_str(const char *orig)
 
 static int read_exports(void)
 {
-	const char *symvers = "Module.symvers";
 	char line[1024], *path = NULL;
 	unsigned int line_num = 1;
 	FILE *file;
 
-	file = fopen(symvers, "r");
+	file = fopen(symvers_path, "r");
 	if (!file) {
-		path = top_level_dir(symvers);
+		path = top_level_dir(symvers_path);
 		if (!path) {
-			ERROR("can't open '%s', \"objtool diff\" should be run from the kernel tree", symvers);
+			ERROR("can't open '%s', \"objtool diff\" should be run from the kernel tree", symvers_path);
 			return -1;
 		}
 
-- 
2.53.0