Commit 0d6a2d5f authored by Ian Lance Taylor's avatar Ian Lance Taylor

runtime: skip writes to persistent memory in cgo checker

Fixes #23899
Fixes #28458

Change-Id: Ie177f2d4c399445d8d5e1a327f2419c7866cb45e
Reviewed-on: https://go-review.googlesource.com/c/155697
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: 's avatarAustin Clements <austin@google.com>
parent 95a6f112
......@@ -406,6 +406,24 @@ var ptrTests = []ptrTest{
body: `var b bytes.Buffer; b.WriteString("a"); C.f(unsafe.Pointer(&b.Bytes()[0]))`,
fail: false,
},
{
// Test that bgsweep releasing a finalizer is OK.
name: "finalizer",
c: `// Nothing to declare.`,
imports: []string{"os"},
support: `func open() { os.Open(os.Args[0]) }; var G [][]byte`,
body: `for i := 0; i < 10000; i++ { G = append(G, make([]byte, 4096)); if i % 100 == 0 { G = nil; open() } }`,
fail: false,
},
{
// Test that converting generated struct to interface is OK.
name: "structof",
c: `// Nothing to declare.`,
imports: []string{"reflect"},
support: `type MyInt int; func (i MyInt) Get() int { return int(i) }; type Getter interface { Get() int }`,
body: `t := reflect.StructOf([]reflect.StructField{{Name: "MyInt", Type: reflect.TypeOf(MyInt(0)), Anonymous: true}}); v := reflect.New(t).Elem(); v.Interface().(Getter).Get()`,
fail: false,
},
}
func TestPointerChecks(t *testing.T) {
......@@ -478,7 +496,7 @@ func testOne(t *testing.T, pt ptrTest) {
cmd := exec.Command("go", "build")
cmd.Dir = src
cmd.Env = addEnv("GOPATH", gopath)
cmd.Env = append(os.Environ(), "GOPATH="+gopath)
buf, err := cmd.CombinedOutput()
if err != nil {
t.Logf("%#q:\n%s", args(cmd), buf)
......@@ -550,16 +568,5 @@ func testOne(t *testing.T, pt ptrTest) {
}
func cgocheckEnv(val string) []string {
return addEnv("GODEBUG", "cgocheck="+val)
}
func addEnv(key, val string) []string {
env := []string{key + "=" + val}
look := key + "="
for _, e := range os.Environ() {
if !strings.HasPrefix(e, look) {
env = append(env, e)
}
}
return env
return append(os.Environ(), "GODEBUG=cgocheck="+val)
}
......@@ -43,6 +43,13 @@ func cgoCheckWriteBarrier(dst *uintptr, src uintptr) {
return
}
// It's OK if writing to memory allocated by persistentalloc.
// Do this check last because it is more expensive and rarely true.
// If it is false the expense doesn't matter since we are crashing.
if inPersistentAlloc(uintptr(unsafe.Pointer(dst))) {
return
}
systemstack(func() {
println("write of Go pointer", hex(src), "to non-Go memory", hex(uintptr(unsafe.Pointer(dst))))
throw(cgoWriteBarrierFail)
......
......@@ -1167,6 +1167,15 @@ var globalAlloc struct {
persistentAlloc
}
// persistentChunkSize is the number of bytes we allocate when we grow
// a persistentAlloc.
const persistentChunkSize = 256 << 10
// persistentChunks is a list of all the persistent chunks we have
// allocated. The list is maintained through the first word in the
// persistent chunk. This is updated atomically.
var persistentChunks *notInHeap
// Wrapper around sysAlloc that can allocate small chunks.
// There is no associated free operation.
// Intended for things like function/type/debug-related persistent data.
......@@ -1187,7 +1196,6 @@ func persistentalloc(size, align uintptr, sysStat *uint64) unsafe.Pointer {
//go:systemstack
func persistentalloc1(size, align uintptr, sysStat *uint64) *notInHeap {
const (
chunk = 256 << 10
maxBlock = 64 << 10 // VM reservation granularity is 64K on windows
)
......@@ -1218,15 +1226,24 @@ func persistentalloc1(size, align uintptr, sysStat *uint64) *notInHeap {
persistent = &globalAlloc.persistentAlloc
}
persistent.off = round(persistent.off, align)
if persistent.off+size > chunk || persistent.base == nil {
persistent.base = (*notInHeap)(sysAlloc(chunk, &memstats.other_sys))
if persistent.off+size > persistentChunkSize || persistent.base == nil {
persistent.base = (*notInHeap)(sysAlloc(persistentChunkSize, &memstats.other_sys))
if persistent.base == nil {
if persistent == &globalAlloc.persistentAlloc {
unlock(&globalAlloc.mutex)
}
throw("runtime: cannot allocate memory")
}
persistent.off = 0
// Add the new chunk to the persistentChunks list.
for {
chunks := uintptr(unsafe.Pointer(persistentChunks))
*(*uintptr)(unsafe.Pointer(persistent.base)) = chunks
if atomic.Casuintptr((*uintptr)(unsafe.Pointer(&persistentChunks)), chunks, uintptr(unsafe.Pointer(persistent.base))) {
break
}
}
persistent.off = sys.PtrSize
}
p := persistent.base.add(persistent.off)
persistent.off += size
......@@ -1242,6 +1259,21 @@ func persistentalloc1(size, align uintptr, sysStat *uint64) *notInHeap {
return p
}
// inPersistentAlloc reports whether p points to memory allocated by
// persistentalloc. This must be nosplit because it is called by the
// cgo checker code, which is called by the write barrier code.
//go:nosplit
func inPersistentAlloc(p uintptr) bool {
chunk := atomic.Loaduintptr((*uintptr)(unsafe.Pointer(&persistentChunks)))
for chunk != 0 {
if p >= chunk && p < chunk+persistentChunkSize {
return true
}
chunk = *(*uintptr)(unsafe.Pointer(chunk))
}
return false
}
// linearAlloc is a simple linear allocator that pre-reserves a region
// of memory and then maps that region as needed. The caller is
// responsible for locking.
......
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