linux-kernel - [PATCH 4/9] kcov: avoid clang out-of-range warning

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Date: Thu, 28 Mar 2024 15:30:42 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: linux-kernel@...r.kernel.org,
	Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	kasan-dev@...glegroups.com,
	llvm@...ts.linux.dev
Subject: [PATCH 4/9] kcov: avoid clang out-of-range warning

From: Arnd Bergmann <arnd@...db.de>

The area_size is never larger than the maximum on 64-bit architectutes:

kernel/kcov.c:634:29: error: result of comparison of constant 1152921504606846975 with expression of type '__u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
                if (remote_arg->area_size > LONG_MAX / sizeof(unsigned long))
                    ~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The compiler can correctly optimize the check away and the code appears
correct to me, so just add a cast to avoid the warning.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 kernel/kcov.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/kcov.c b/kernel/kcov.c
index f9ac2e9e460f..c3124f6d5536 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -627,7 +627,8 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
 		mode = kcov_get_mode(remote_arg->trace_mode);
 		if (mode < 0)
 			return mode;
-		if (remote_arg->area_size > LONG_MAX / sizeof(unsigned long))
+		if ((unsigned long)remote_arg->area_size >
+		    LONG_MAX / sizeof(unsigned long))
 			return -EINVAL;
 		kcov->mode = mode;
 		t->kcov = kcov;
-- 
2.39.2