cmd/compile: don't ICE on unaligned offsets for pointer writes

User code is unlikely to be correct, but don't crash the compiler
when the offset of a pointer in an object is not a multiple of the
pointer size.

Fixes #61187

Change-Id: Ie56bfcb38556c5dd6f702ae4ec1d4534c6acd420
Reviewed-on: https://go-review.googlesource.com/c/go/+/508555
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>

diff --git a/src/cmd/compile/internal/ssa/writebarrier.go b/src/cmd/compile/internal/ssa/writebarrier.go
index 5df65bfaa3cd5effcea67d33ea210eda9b21332c..bd9e0b826829a8f39e8cb3fed4bb0ede837d0c13 100644 (file)
--- a/src/cmd/compile/internal/ssa/writebarrier.go
+++ b/src/cmd/compile/internal/ssa/writebarrier.go
@@ -53,7 +53,10 @@ func mightContainHeapPointer(ptr *Value, size int64, mem *Value, zeroes map[ID]Z
        }
 
        ptrSize := ptr.Block.Func.Config.PtrSize
-       if off%ptrSize != 0 || size%ptrSize != 0 {
+       if off%ptrSize != 0 {
+               return true // see issue 61187
+       }
+       if size%ptrSize != 0 {
                ptr.Fatalf("unaligned pointer write")
        }
        if off < 0 || off+size > 64*ptrSize {
@@ -130,7 +133,7 @@ func needWBdst(ptr, mem *Value, zeroes map[ID]ZeroRegion) bool {
        }
        ptrSize := ptr.Block.Func.Config.PtrSize
        if off%ptrSize != 0 {
-               ptr.Fatalf("unaligned pointer write")
+               return true // see issue 61187
        }
        if off < 0 || off >= 64*ptrSize {
                // write goes off end of tracked offsets

diff --git a/test/fixedbugs/issue61187.go b/test/fixedbugs/issue61187.go
new file mode 100644 (file)
index 0000000..5e17628
--- /dev/null
+++ b/test/fixedbugs/issue61187.go
@@ -0,0 +1,22 @@
+// compile
+
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+       "fmt"
+       "reflect"
+       "unsafe"
+)
+
+var slice = []byte{'H', 'e', 'l', 'l', 'o', ','}
+
+func main() {
+       ptr := uintptr(unsafe.Pointer(&slice)) + 100
+       header := (*reflect.SliceHeader)(unsafe.Pointer(ptr))
+       header.Data += 1
+       fmt.Printf("%d %d\n", cap(slice), header.Cap)
+}