From 9c695203a7ddbe49dba5f22f4c941d24f47475df Mon Sep 17 00:00:00 2001 From: Mikael Pettersson Date: Tue, 29 Jun 2010 15:05:25 -0700 Subject: [PATCH] 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 Signed-off-by: Khem Raj Cc: Russell King Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/compiler-gcc.h | 10 +++++++++- include/linux/compiler-gcc4.h | 4 ++++ 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index 73dcf804bc94..0da5b187f124 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -58,8 +58,12 @@ * naked functions because then mcount is called without stack and frame pointer * being set up and there is no chance to restore the lr register to the value * before mcount was called. + * + * The asm() bodies of naked functions often depend on standard calling conventions, + * therefore they must be noinline and noclone. GCC 4.[56] currently fail to enforce + * this, so we must do so ourselves. See GCC PR44290. */ -#define __naked __attribute__((naked)) notrace +#define __naked __attribute__((naked)) noinline __noclone notrace #define __noreturn __attribute__((noreturn)) @@ -85,3 +89,7 @@ #define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h) #define gcc_header(x) _gcc_header(x) #include gcc_header(__GNUC__) + +#if !defined(__noclone) +#define __noclone /* not needed */ +#endif 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 -- 2.11.0