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sync/atomic: trigger paging fault early on linux/arm
so that we don't need to traceback through __kuser_cmpxchg R=golang-dev, bradfitz CC=golang-dev https://golang.org/cl/12869043
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@ -32,6 +32,9 @@ TEXT ·CompareAndSwapInt32(SB),NOSPLIT,$0
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// Implement using kernel cas for portability.
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TEXT ·CompareAndSwapUint32(SB),NOSPLIT,$0-13
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MOVW addr+0(FP), R2
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// trigger potential paging fault here,
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// because we don't know how to traceback through __kuser_cmpxchg
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MOVW (R2), R0
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MOVW old+4(FP), R0
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casagain:
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MOVW new+8(FP), R1
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@ -102,6 +105,9 @@ TEXT cas64<>(SB),NOSPLIT,$0
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TEXT kernelCAS64<>(SB),NOSPLIT,$0-21
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// int (*__kuser_cmpxchg64_t)(const int64_t *oldval, const int64_t *newval, volatile int64_t *ptr);
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MOVW addr+0(FP), R2 // ptr
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// trigger potential paging fault here,
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// because we don't know how to traceback through __kuser_cmpxchg64
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MOVW (R2), R0
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// make unaligned atomic access panic
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AND.S $7, R2, R1
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BEQ 2(PC)
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