[PATCH 10/13] objtool: Add --Werror option

[Josh Poimboeuf]

Any objtool warning has the potential of reflecting (or triggering) a
major bug in the kernel or compiler which could result in crashing the
kernel or breaking the livepatch consistency model.

In preparation for failing the build on objtool errors/warnings, add a
new --Werror option.

[ jpoimboe: commit log, comments, error out on fatal errors too ]

Co-developed-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 tools/objtool/builtin-check.c           |  1 +
 tools/objtool/check.c                   | 15 ++++++++++++---
 tools/objtool/include/objtool/builtin.h |  1 +
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 3de3afa0a19c..c201650efe49 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -101,6 +101,7 @@ static const struct option check_options[] = {
 	OPT_BOOLEAN(0,   "sec-address", &opts.sec_address, "print section addresses in warnings"),
 	OPT_BOOLEAN(0,   "stats", &opts.stats, "print statistics"),
 	OPT_BOOLEAN('v', "verbose", &opts.verbose, "verbose warnings"),
+	OPT_BOOLEAN(0,   "Werror", &opts.werror, "return error on warnings"),
 
 	OPT_END(),
 };
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 3ddaefe97f55..b574f2e8b07f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4737,9 +4737,18 @@ int check(struct objtool_file *file)
 
 out:
 	/*
-	 *  For now, don't fail the kernel build on fatal warnings.  These
-	 *  errors are still fairly common due to the growing matrix of
-	 *  supported toolchains and their recent pace of change.
+	 * CONFIG_OBJTOOL_WERROR upgrades all warnings (and errors) to actual
+	 * errors.
+	 *
+	 * Note that even "fatal" type errors don't actually return an error
+	 * without CONFIG_OBJTOOL_WERROR.  That probably needs improved at some
+	 * point.
 	 */
+	if (opts.werror && (ret || warnings)) {
+		if (warnings)
+			WARN("%d warning(s) upgraded to errors", warnings);
+		return 1;
+	}
+
 	return 0;
 }
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index 25cfa01758b9..b18f114cdaa4 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -39,6 +39,7 @@ struct opts {
 	bool sec_address;
 	bool stats;
 	bool verbose;
+	bool werror;
 };
 
 extern struct opts opts;
-- 
2.48.1