linux-kernel - [PATCH v2] drivers: lkdtm: fix clang -Wformat warning

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Message-Id: <20220721215706.4153027-1-justinstitt@google.com>
Date:   Thu, 21 Jul 2022 14:57:06 -0700
From:   Justin Stitt <justinstitt@...gle.com>
To:     ndesaulniers@...gle.com
Cc:     arnd@...db.de, gregkh@...uxfoundation.org, justinstitt@...gle.com,
        keescook@...omium.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, nathan@...nel.org, trix@...hat.com
Subject: [PATCH v2] drivers: lkdtm: fix clang -Wformat warning

When building with Clang we encounter the following warning
(ARCH=hexagon + CONFIG_FRAME_WARN=0):
| ../drivers/misc/lkdtm/bugs.c:107:3: error: format specifies type
| 'unsigned long' but the argument has type 'int' [-Werror,-Wformat]
|                 REC_STACK_SIZE, recur_count);
|                 ^~~~~~~~~~~~~~

Cast REC_STACK_SIZE to `unsigned long` to match format specifier `%lu`
as well as maintain symmetry with `#define REC_STACK_SIZE
(_AC(CONFIG_FRAME_WARN, UL) / 2)`.

Link: https://github.com/ClangBuiltLinux/linux/issues/378
Reported-by: Nathan Chancellor <nathan@...nel.org>
Suggested-by: Nathan Chancellor <nathan@...nel.org>
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Reported by Nathan here:
https://lore.kernel.org/all/YtmrCJjQrSbv8Aj1@dev-arch.thelio-3990X/

changes from v1 -> v2:
* Use implicit division conversion with `/ nUL` instead of verbose
`(unsigned long)` ~ Thanks Nick

 drivers/misc/lkdtm/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index 009239ad1d8a..48821f4c2b21 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -29,7 +29,7 @@ struct lkdtm_list {
 #if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0)
 #define REC_STACK_SIZE (_AC(CONFIG_FRAME_WARN, UL) / 2)
 #else
-#define REC_STACK_SIZE (THREAD_SIZE / 8)
+#define REC_STACK_SIZE (THREAD_SIZE / 8UL)
 #endif
 #define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2)
 
-- 
2.37.1.359.gd136c6c3e2-goog