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sync/atomic: make unaligned 64-bit atomics crash on 386

Browse Source 
R=golang-dev, bradfitz, dvyukov
CC=golang-dev
https://golang.org/cl/7702043
This commit is contained in:
Russ Cox 2013-03-11 12:21:46 -04:00
parent b66df0e9ba
commit 14a295c817
2 changed files with 38 additions and 0 deletions
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12
src/pkg/sync/atomic/asm_386.s
View File

@ -28,6 +28,9 @@ TEXT ·CompareAndSwapInt64(SB),7,$0
TEXT ·CompareAndSwapUint64(SB),7,$0
MOVL addr+0(FP), BP
TESTL $7, BP
JZ 2(PC)
MOVL 0, AX // crash with nil ptr deref
MOVL old+4(FP), AX
MOVL old+8(FP), DX
MOVL new+12(FP), BX
@ -61,6 +64,9 @@ TEXT ·AddInt64(SB),7,$0
TEXT ·AddUint64(SB),7,$0
// no XADDQ so use CMPXCHG8B loop
MOVL addr+0(FP), BP
TESTL $7, BP
JZ 2(PC)
MOVL 0, AX // crash with nil ptr deref
// DI:SI = delta
MOVL delta+4(FP), SI
MOVL delta+8(FP), DI
@ -105,6 +111,9 @@ TEXT ·LoadInt64(SB),7,$0
TEXT ·LoadUint64(SB),7,$0
MOVL addr+0(FP), AX
TESTL $7, AX
JZ 2(PC)
MOVL 0, AX // crash with nil ptr deref
// MOVQ and EMMS were introduced on the Pentium MMX.
// MOVQ (%EAX), %MM0
BYTE $0x0f; BYTE $0x6f; BYTE $0x00
@ -133,6 +142,9 @@ TEXT ·StoreInt64(SB),7,$0
TEXT ·StoreUint64(SB),7,$0
MOVL addr+0(FP), AX
TESTL $7, AX
JZ 2(PC)
MOVL 0, AX // crash with nil ptr deref
// MOVQ and EMMS were introduced on the Pentium MMX.
// MOVQ 0x8(%ESP), %MM0
BYTE $0x0f; BYTE $0x6f; BYTE $0x44; BYTE $0x24; BYTE $0x08

26
src/pkg/sync/atomic/atomic_test.go
View File

@ -1177,3 +1177,29 @@ func TestStoreLoadRelAcq64(t *testing.T) {
<-c
<-c
}
func shouldPanic(t *testing.T, name string, f func()) {
defer func() {
if recover() == nil {
t.Errorf("%s did not panic", name)
}
}()
f()
}
func TestUnaligned64(t *testing.T) {
// Unaligned 64-bit atomics on 32-bit systems are
// a continual source of pain. Test that on 386 they crash
// instead of failing silently.
if runtime.GOARCH != "386" {
t.Skip("test only runs on 386")
}
x := make([]uint32, 4)
p := (*uint64)(unsafe.Pointer(&x[1])) // misaligned
shouldPanic(t, "LoadUint64", func() { LoadUint64(p) })
shouldPanic(t, "StoreUint64", func() { StoreUint64(p, 1) })
shouldPanic(t, "CompareAndSwapUint64", func() { CompareAndSwapUint64(p, 1, 2) })
shouldPanic(t, "AddUint64", func() { AddUint64(p, 3) })
}