linux-kernel - [PATCH] x86: suppress sparse warning in copy_to

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Message-Id: <1475566428-22484-1-git-send-email-johannes@sipsolutions.net>
Date:   Tue,  4 Oct 2016 09:33:48 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     x86@...nel.org
Cc:     Jan Beulich <JBeulich@...e.com>, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH] x86: suppress sparse warning in copy_to_user()

From: Johannes Berg <johannes.berg@...el.com>

__compiletime_object_size() is simply defined to __builtin_object_size()
which gcc declares with (void *, int type) prototype. This is also done
by sparse, since it follows gcc, which leads it to warn, many times, on
any usage of copy_to_user(), about it:

  arch/x86/include/asm/uaccess.h:735:18: warning: incorrect type in argument 1 (different modifiers)
  arch/x86/include/asm/uaccess.h:735:18:    expected void *<noident>
  arch/x86/include/asm/uaccess.h:735:18:    got void const *from

Suppress this by adding a (void *) cast. The compiler probably should
have declared it as const, but as it doesn't this is necessary. If it
changes, then the cast also won't matter.

Fixes: 7a3d9b0f3abbe ("x86: Unify copy_to_user() and add size checking to it")
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 arch/x86/include/asm/uaccess.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 2131c4ce7d8a..0bd4a5a86199 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -732,7 +732,7 @@ copy_from_user(void *to, const void __user *from, unsigned long n)
 static __always_inline unsigned long __must_check
 copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	int sz = __compiletime_object_size(from);
+	int sz = __compiletime_object_size((void *)from);
 
 	kasan_check_read(from, n);
 
-- 
2.8.1