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>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
index 94dea3ffbfa1..fcfa5b9a4317 100644
--- a/include/linux/compiler-gcc4.h
+++ b/include/linux/compiler-gcc4.h
@@ -48,6 +48,10 @@
  * 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