linux-kernel - [PATCH v2 2/4] modpost: inform compilers that fatal() never returns

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Message-Id: <20231203094934.1908270-2-masahiroy@kernel.org>
Date:   Sun,  3 Dec 2023 18:49:32 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/4] modpost: inform compilers that fatal() never returns

The function fatal() never returns because modpost_log() calls exit(1)
when LOG_FATAL is passed.

Inform compilers of this fact so that unreachable code flow can be
identified at compile time.

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Reviewed-by: Nathan Chancellor <nathan@...nel.org>
---

Changes in v2:
  - Use noreturn attribute together with alias

 scripts/mod/modpost.c | 3 +++
 scripts/mod/modpost.h | 5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index ca0a90158f85..c13bc9095df3 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -90,6 +90,9 @@ void modpost_log(enum loglevel loglevel, const char *fmt, ...)
 		error_occurred = true;
 }
 
+void __attribute__((alias("modpost_log")))
+modpost_log_noret(enum loglevel loglevel, const char *fmt, ...);
+
 static inline bool strends(const char *str, const char *postfix)
 {
 	if (strlen(str) < strlen(postfix))
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 9fe974dc1a52..835cababf1b0 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -200,6 +200,9 @@ enum loglevel {
 void __attribute__((format(printf, 2, 3)))
 modpost_log(enum loglevel loglevel, const char *fmt, ...);
 
+void __attribute__((format(printf, 2, 3), noreturn))
+modpost_log_noret(enum loglevel loglevel, const char *fmt, ...);
+
 /*
  * warn - show the given message, then let modpost continue running, still
  *        allowing modpost to exit successfully. This should be used when
@@ -215,4 +218,4 @@ modpost_log(enum loglevel loglevel, const char *fmt, ...);
  */
 #define warn(fmt, args...)	modpost_log(LOG_WARN, fmt, ##args)
 #define error(fmt, args...)	modpost_log(LOG_ERROR, fmt, ##args)
-#define fatal(fmt, args...)	modpost_log(LOG_FATAL, fmt, ##args)
+#define fatal(fmt, args...)	modpost_log_noret(LOG_FATAL, fmt, ##args)
-- 
2.40.1