objtool: Add module specific retpoline rules

David allowed retpolines in .init.text, except for modules, which will
trip up objtool retpoline validation, fix that.

Requested-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 12 insertions, 2 deletions

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index dd6bcd6097f5..694abc628e9b 100644
--- 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(),
 };
 
diff --git a/tools/objtool/builtin.h b/tools/objtool/builtin.h
index 7b6addfce045..28ff40e19a14 100644
--- 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);
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5e5db7b4d77b..472e64e95891 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1958,6 +1958,15 @@ static int validate_retpoline(struct objtool_file *file)
                 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");