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Date: Fri, 4 Jun 2010 13:42:35 +0200 From: Mikael Pettersson <mikpe@...uu.se> To: linux-kernel@...r.kernel.org 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 <mikpe@...uu.se> Signed-off-by: Khem Raj <raj.khem@...il.com> Cc: stable@...nel.org --- This part of the fix touches code outside of arch/arm/ so RMK asked me to send it via LKML. Another fix for broken asm() is also needed on some machine types, but that's handled via the ARM tree. I can't find an obvious maintainer for include/linux/compiler-gcc.h. Does any core system maintainer want to handle this, or should I resend with cc: Linus? include/linux/compiler-gcc.h | 10 +++++++++- include/linux/compiler-gcc4.h | 4 ++++ 2 files changed, 13 insertions(+), 1 deletion(-) diff -rupN linux-2.6.35-rc1/include/linux/compiler-gcc.h linux-2.6.35-rc1.arm-gcc45-attribute-naked/include/linux/compiler-gcc.h --- linux-2.6.35-rc1/include/linux/compiler-gcc.h 2010-02-25 14:45:04.000000000 +0100 +++ linux-2.6.35-rc1.arm-gcc45-attribute-naked/include/linux/compiler-gcc.h 2010-06-01 20:18:33.000000000 +0200 @@ -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 -rupN linux-2.6.35-rc1/include/linux/compiler-gcc4.h linux-2.6.35-rc1.arm-gcc45-attribute-naked/include/linux/compiler-gcc4.h --- linux-2.6.35-rc1/include/linux/compiler-gcc4.h 2010-02-25 14:45:04.000000000 +0100 +++ linux-2.6.35-rc1.arm-gcc45-attribute-naked/include/linux/compiler-gcc4.h 2010-06-01 20:18:33.000000000 +0200 @@ -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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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