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commit b53823fb2e upstream.
gcc and clang each have their own compiler bugs with respect to asm
goto. Implement a work-around for compiler versions known to have those
bugs.
gcc prior to 4.8.2 miscompiles asm goto.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
gcc prior to 8.1.0 miscompiles asm goto at O1.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103908
clang prior to version 13.0.1 miscompiles asm goto at O2.
https://github.com/llvm/llvm-project/issues/52735
Work around these issues by adding a volatile inline asm with
memory clobber in the fallthrough after the asm goto and at each
label target. Emit this for all compilers in case other similar
issues are found in the future.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220124171253.22072-14-mathieu.desnoyers@efficios.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
31 lines
912 B
C
31 lines
912 B
C
/* SPDX-License-Identifier: LGPL-2.1-only OR MIT */
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/*
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* rseq/compiler.h
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*
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* Work-around asm goto compiler bugs.
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*
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* (C) Copyright 2021 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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*/
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#ifndef RSEQ_COMPILER_H
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#define RSEQ_COMPILER_H
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/*
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* gcc prior to 4.8.2 miscompiles asm goto.
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* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
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*
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* gcc prior to 8.1.0 miscompiles asm goto at O1.
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* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103908
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*
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* clang prior to version 13.0.1 miscompiles asm goto at O2.
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* https://github.com/llvm/llvm-project/issues/52735
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*
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* Work around these issues by adding a volatile inline asm with
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* memory clobber in the fallthrough after the asm goto and at each
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* label target. Emit this for all compilers in case other similar
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* issues are found in the future.
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*/
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#define rseq_after_asm_goto() asm volatile ("" : : : "memory")
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#endif /* RSEQ_COMPILER_H_ */
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