[PATCH v2 3/8] objtool: Add module specific retpoline rules

[Peter Zijlstra]

David wanted to not use retpolines in .init.text but that will trip up
objtool retpoline validation, fix that.

Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Requested-by: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 scripts/Makefile.build        |    2 ++
 tools/objtool/builtin-check.c |    3 ++-
 tools/objtool/builtin.h       |    2 +-
 tools/objtool/check.c         |    9 +++++++++
 4 files changed, 14 insertions(+), 2 deletions(-)

--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -256,6 +256,8 @@ __objtool_obj := $(objtree)/tools/objtoo
 
 objtool_args = $(if $(CONFIG_UNWINDER_ORC),orc generate,check)
 
+objtool_args += $(if $(part-of-module), --module,)
+
 ifndef CONFIG_FRAME_POINTER
 objtool_args += --no-fp
 endif
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -29,7 +29,7 @@
 #include "builtin.h"
 #include "check.h"
 
-bool no_fp, no_unreachable, retpoline;
+bool no_fp, no_unreachable, retpoline, module;
 
 static const char * const check_usage[] = {
 	"objtool check [<options>] file.o",
@@ -40,6 +40,7 @@ const struct option check_options[] = {
 	OPT_BOOLEAN('f', "no-fp", &no_fp, "Skip frame pointer validation"),
 	OPT_BOOLEAN('u', "no-unreachable", &no_unreachable, "Skip 'unreachable instruction' warnings"),
 	OPT_BOOLEAN('r', "retpoline", &retpoline, "Validate retpoline assumptions"),
+	OPT_BOOLEAN('m', "module", &module, "Indicates the object will be part of a kernel module"),
 	OPT_END(),
 };
 
--- a/tools/objtool/builtin.h
+++ b/tools/objtool/builtin.h
@@ -20,7 +20,7 @@
 #include <subcmd/parse-options.h>
 
 extern const struct option check_options[];
-extern bool no_fp, no_unreachable, retpoline;
+extern bool no_fp, no_unreachable, retpoline, module;
 
 extern int cmd_check(int argc, const char **argv);
 extern int cmd_orc(int argc, const char **argv);
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1920,6 +1920,15 @@ static int validate_retpoline(struct obj
 		if (insn->retpoline_safe)
 			continue;
 
+		/*
+		 * .init.text code is ran before userspace and thus doesn't
+		 * strictly need retpolines, except for modules which are
+		 * loaded late, they very much do need retpoline in their
+		 * .init.text
+		 */
+		if (!strcmp(insn->sec->name, ".init.text") && !module)
+			continue;
+
 		WARN_FUNC("indirect %s found in RETPOLINE build",
 			  insn->sec, insn->offset,
 			  insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");