runtime: check alignment of 8-byte atomic loads and stores on 386
Currently, if we do an atomic{load,store}64 of an unaligned address on
386, we'll simply get a non-atomic load/store. This has been the
source of myriad bugs, so add alignment checks to these two
operations. These checks parallel the equivalent checks in
sync/atomic.
The alignment check is not necessary in cas64 because it uses a locked
instruction. The CPU will either execute this atomically or raise an
alignment fault (#AC)---depending on the alignment check flag---either
of which is fine.
This also fixes the two places in the runtime that trip the new
checks. One is in the runtime self-test and shouldn't have caused
real problems. The other is in tickspersecond and could, in
principle, have caused a misread of the ticks per second during
initialization.
Change-Id: If1796667012a6154f64f5e71d043c7f5fb3dd050
Reviewed-on: https://go-review.googlesource.com/3521
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/src/runtime/runtime.go b/src/runtime/runtime.go
index 2ce4618..ba9881f 100644
--- a/src/runtime/runtime.go
+++ b/src/runtime/runtime.go
@@ -10,6 +10,7 @@
var ticks struct {
lock mutex
+ pad uint32 // ensure 8-byte alignment of val on 386
val uint64
}
