linux-hardened/include/linux/compiler-gcc4.h
Mikael Pettersson 9c695203a7 compiler-gcc.h: gcc-4.5 needs noclone and noinline on __naked functions
A __naked function is defined in C but with a body completely implemented
by asm(), including any prologue and epilogue.  These asm() bodies expect
standard calling conventions for parameter passing.  Older GCCs implement
that correctly, but 4.[56] currently do not, see GCC PR44290.  In the
Linux kernel this breaks ARM, causing most arch/arm/mm/copypage-*.c
modules to get miscompiled, resulting in kernel crashes during bootup.

Part of the kernel fix is to augment the __naked function attribute to
also imply noinline and noclone.  This patch implements that, and has been
verified to fix boot failures with gcc-4.5 compiled 2.6.34 and 2.6.35-rc1
kernels.  The patch is a no-op with older GCCs.

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-06-29 15:29:31 -07:00

65 lines
2.2 KiB
C

#ifndef __LINUX_COMPILER_H
#error "Please don't include <linux/compiler-gcc4.h> directly, include <linux/compiler.h> instead."
#endif
/* GCC 4.1.[01] miscompiles __weak */
#ifdef __KERNEL__
# if __GNUC_MINOR__ == 1 && __GNUC_PATCHLEVEL__ <= 1
# error Your version of gcc miscompiles the __weak directive
# endif
#endif
#define __used __attribute__((__used__))
#define __must_check __attribute__((warn_unused_result))
#define __compiler_offsetof(a,b) __builtin_offsetof(a,b)
#define __always_inline inline __attribute__((always_inline))
/*
* A trick to suppress uninitialized variable warning without generating any
* code
*/
#define uninitialized_var(x) x = x
#if __GNUC_MINOR__ >= 3
/* Mark functions as cold. gcc will assume any path leading to a call
to them will be unlikely. This means a lot of manual unlikely()s
are unnecessary now for any paths leading to the usual suspects
like BUG(), printk(), panic() etc. [but let's keep them for now for
older compilers]
Early snapshots of gcc 4.3 don't support this and we can't detect this
in the preprocessor, but we can live with this because they're unreleased.
Maketime probing would be overkill here.
gcc also has a __attribute__((__hot__)) to move hot functions into
a special section, but I don't see any sense in this right now in
the kernel context */
#define __cold __attribute__((__cold__))
#if __GNUC_MINOR__ >= 5
/*
* Mark a position in code as unreachable. This can be used to
* suppress control flow warnings after asm blocks that transfer
* control elsewhere.
*
* Early snapshots of gcc 4.5 don't support this and we can't detect
* this in the preprocessor, but we can live with this because they're
* unreleased. Really, we need to have autoconf for the kernel.
*/
#define unreachable() __builtin_unreachable()
/* Mark a function definition as prohibited from being cloned. */
#define __noclone __attribute__((__noclone__))
#endif
#endif
#if __GNUC_MINOR__ > 0
#define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
#endif
#if __GNUC_MINOR__ >= 4
#define __compiletime_warning(message) __attribute__((warning(message)))
#define __compiletime_error(message) __attribute__((error(message)))
#endif