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9c695203a7
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>
96 lines
3.4 KiB
C
96 lines
3.4 KiB
C
#ifndef __LINUX_COMPILER_H
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#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
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#endif
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/*
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* Common definitions for all gcc versions go here.
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*/
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/* Optimization barrier */
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/* The "volatile" is due to gcc bugs */
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#define barrier() __asm__ __volatile__("": : :"memory")
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/*
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* This macro obfuscates arithmetic on a variable address so that gcc
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* shouldn't recognize the original var, and make assumptions about it.
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*
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* This is needed because the C standard makes it undefined to do
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* pointer arithmetic on "objects" outside their boundaries and the
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* gcc optimizers assume this is the case. In particular they
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* assume such arithmetic does not wrap.
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*
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* A miscompilation has been observed because of this on PPC.
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* To work around it we hide the relationship of the pointer and the object
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* using this macro.
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*
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* Versions of the ppc64 compiler before 4.1 had a bug where use of
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* RELOC_HIDE could trash r30. The bug can be worked around by changing
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* the inline assembly constraint from =g to =r, in this particular
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* case either is valid.
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*/
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#define RELOC_HIDE(ptr, off) \
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({ unsigned long __ptr; \
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__asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
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(typeof(ptr)) (__ptr + (off)); })
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/* &a[0] degrades to a pointer: a different type from an array */
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#define __must_be_array(a) \
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BUILD_BUG_ON_ZERO(__builtin_types_compatible_p(typeof(a), typeof(&a[0])))
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/*
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* Force always-inline if the user requests it so via the .config,
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* or if gcc is too old:
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*/
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#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
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!defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
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# define inline inline __attribute__((always_inline))
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# define __inline__ __inline__ __attribute__((always_inline))
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# define __inline __inline __attribute__((always_inline))
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#endif
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#define __deprecated __attribute__((deprecated))
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#define __packed __attribute__((packed))
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#define __weak __attribute__((weak))
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/*
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* it doesn't make sense on ARM (currently the only user of __naked) to trace
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* naked functions because then mcount is called without stack and frame pointer
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* being set up and there is no chance to restore the lr register to the value
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* before mcount was called.
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*
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* The asm() bodies of naked functions often depend on standard calling conventions,
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* therefore they must be noinline and noclone. GCC 4.[56] currently fail to enforce
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* this, so we must do so ourselves. See GCC PR44290.
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*/
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#define __naked __attribute__((naked)) noinline __noclone notrace
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#define __noreturn __attribute__((noreturn))
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/*
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* From the GCC manual:
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*
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* Many functions have no effects except the return value and their
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* return value depends only on the parameters and/or global
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* variables. Such a function can be subject to common subexpression
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* elimination and loop optimization just as an arithmetic operator
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* would be.
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* [...]
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*/
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#define __pure __attribute__((pure))
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#define __aligned(x) __attribute__((aligned(x)))
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#define __printf(a,b) __attribute__((format(printf,a,b)))
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#define noinline __attribute__((noinline))
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#define __attribute_const__ __attribute__((__const__))
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#define __maybe_unused __attribute__((unused))
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#define __always_unused __attribute__((unused))
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#define __gcc_header(x) #x
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#define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h)
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#define gcc_header(x) _gcc_header(x)
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#include gcc_header(__GNUC__)
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#if !defined(__noclone)
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#define __noclone /* not needed */
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#endif
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