From 83317d9e3cb0674f71d1118d8814aefb31ac1239 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Thu, 15 Oct 2020 15:52:58 -0400 Subject: runtime/internal/atomic: panic nicely on unaligned 64-bit atomics On 386 and arm, unaligned 64-bit atomics aren't safe, so we check for this and panic. Currently, we panic by dereferencing nil, which may be expedient but is pretty user-hostile since it gives no hint of what the actual problem was. This CL replaces this with an actual panic. The only subtlety here is now the atomic assembly implementations are calling back into Go, so they have to play nicely with stack maps and stack scanning. On 386, this just requires declaring NO_LOCAL_POINTERS. On arm, this is somewhat more complicated: first, we have to move the alignment check into the functions that have Go signatures. Then we have to support both the tail call from these functions to the underlying implementation (which requires that they have no frame) and the call into Go to panic (which requires that they have a frame). We resolve this by forcing them to have no frame and setting up the frame manually just before the panic call. Change-Id: I19f1e860045df64088013db37a18acea47342c69 Reviewed-on: https://go-review.googlesource.com/c/go/+/262778 Trust: Austin Clements Run-TryBot: Austin Clements TryBot-Result: Go Bot Reviewed-by: Cherry Zhang Reviewed-by: Michael Knyszek --- src/sync/atomic/atomic_test.go | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'src/sync/atomic/atomic_test.go') diff --git a/src/sync/atomic/atomic_test.go b/src/sync/atomic/atomic_test.go index 83e7c8d763..eadc962f70 100644 --- a/src/sync/atomic/atomic_test.go +++ b/src/sync/atomic/atomic_test.go @@ -1397,8 +1397,15 @@ func TestStoreLoadRelAcq64(t *testing.T) { func shouldPanic(t *testing.T, name string, f func()) { defer func() { - if recover() == nil { + // Check that all GC maps are sane. + runtime.GC() + + err := recover() + want := "unaligned 64-bit atomic operation" + if err == nil { t.Errorf("%s did not panic", name) + } else if s, _ := err.(string); s != want { + t.Errorf("%s: wanted panic %q, got %q", name, want, err) } }() f() -- cgit v1.3