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: Austin Clements <austin@google.com>
diff --git a/misc/cgo/errors/ptr_test.go b/misc/cgo/errors/ptr_test.go
index 165c2d4..254671f 100644
--- a/misc/cgo/errors/ptr_test.go
+++ b/misc/cgo/errors/ptr_test.go
@@ -406,6 +406,24 @@
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 @@
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 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)
}
diff --git a/src/runtime/cgocheck.go b/src/runtime/cgocheck.go
index ac57e03..7f3c4aa 100644
--- a/src/runtime/cgocheck.go
+++ b/src/runtime/cgocheck.go
@@ -43,6 +43,13 @@
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)
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 678e689..c1a89dc 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -1167,6 +1167,15 @@
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 @@
//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 @@
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 @@
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.
