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runtime: fix system memory allocator on plan9

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The following line in sysFree:
n += (n + memRound) &^ memRound
doubles value of n (n += n).
Which is wrong and can lead to memory corruption.

Fixes #9712

Change-Id: I3c141b71da11e38837c09408cf4f1d22e8f7f36e
Reviewed-on: https://go-review.googlesource.com/3602
Reviewed-by: David du Colombier <0intro@gmail.com>
This commit is contained in:
Dmitry Vyukov 2015-01-30 14:36:12 +03:00
parent 256116ad25
commit 3c3848ad92
2 changed files with 9 additions and 8 deletions
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13
src/runtime/mem_plan9.go
View File

@ -9,21 +9,24 @@ import "unsafe"
var bloc uintptr
var memlock mutex
const memRound = _PAGESIZE - 1
func memRound(p uintptr) uintptr {
return (p + _PAGESIZE - 1) &^ (_PAGESIZE - 1)
}
func initBloc() {
bloc = uintptr(unsafe.Pointer(&end))
bloc = memRound(uintptr(unsafe.Pointer(&end)))
}
func sbrk(n uintptr) unsafe.Pointer {
lock(&memlock)
// Plan 9 sbrk from /sys/src/libc/9sys/sbrk.c
bl := (bloc + memRound) &^ memRound
bl := bloc
n = memRound(n)
if brk_(unsafe.Pointer(bl+n)) < 0 {
unlock(&memlock)
return nil
}
bloc = bl + n
bloc += n
unlock(&memlock)
return unsafe.Pointer(bl)
}
@ -42,7 +45,7 @@ func sysFree(v unsafe.Pointer, n uintptr, stat *uint64) {
// from tiny/mem.c
// Push pointer back if this is a free
// of the most recent sysAlloc.
n += (n + memRound) &^ memRound
n = memRound(n)
if bloc == uintptr(v)+n {
bloc -= n
}

4
src/runtime/pprof/trace_test.go
View File

@ -20,8 +20,6 @@ func skipTraceTestsIfNeeded(t *testing.T) {
switch runtime.GOOS {
case "solaris":
t.Skip("skipping: solaris timer can go backwards (http://golang.org/issue/8976)")
case "plan9":
t.Skip("skipping: plan9 tests fail with out of memory (http://golang.org/issue/9712")
}
switch runtime.GOARCH {
@ -234,7 +232,7 @@ eventLoop:
for _, f := range ev.stk {
if strings.HasSuffix(f.file, "trace_test.go") &&
strings.HasSuffix(f.fn, "pprof_test.TestTraceSymbolize") &&
f.line == 218 {
f.line == 216 {
found = true
break eventLoop
}