From 63a0895d960aa3d3653ef0ecad5bd8579388f14b Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Wed, 3 Jun 2020 13:09:38 -0700
Subject: [PATCH] compiler: Remove uninitialized_var() macro
Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.
As recommended[2] by[3] Linus[4], remove the macro. With the recent
change to disable -Wmaybe-uninitialized in v5.7 in commit 78a5255ffb6a
("Stop the ad-hoc games with -Wno-maybe-initialized"), this is likely
the best time to make this treewide change.
[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Bart van Assche <bvanassche@acm.org>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/linux/compiler-clang.h | 2 --
include/linux/compiler-gcc.h | 6 ------
tools/include/linux/compiler.h | 2 --
tools/virtio/linux/kernel.h | 2 --
4 files changed, 12 deletions(-)
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index 5e55302e3bf60..8a072d00e688d 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -5,8 +5,6 @@
/* Compiler specific definitions for Clang compiler */
-#define uninitialized_var(x) x = *(&(x))
-
/* same as gcc, this was present in clang-2.6 so we can assume it works
* with any version that can compile the kernel
*/
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 1c74464c80c65..4099ac8b7f100 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -59,12 +59,6 @@
(typeof(ptr)) (__ptr + (off)); \
})
-/*
- * A trick to suppress uninitialized variable warning without generating any
- * code
- */
-#define uninitialized_var(x) x = x
-
#ifdef CONFIG_RETPOLINE
#define __noretpoline __attribute__((__indirect_branch__("keep")))
#endif
diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index 9f9002734e192..2f2f4082225ec 100644
--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -111,8 +111,6 @@
# define noinline
#endif
-#define uninitialized_var(x) x = *(&(x))
-
#include <linux/types.h>
/*
diff --git a/tools/virtio/linux/kernel.h b/tools/virtio/linux/kernel.h
index caab980211a6d..315e85cabedab 100644
--- a/tools/virtio/linux/kernel.h
+++ b/tools/virtio/linux/kernel.h
@@ -110,8 +110,6 @@ static inline void free_page(unsigned long addr)
const typeof( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr - offsetof(type,member) );})
-#define uninitialized_var(x) x = x
-
# ifndef likely
# define likely(x) (__builtin_expect(!!(x), 1))
# endif
--
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