runtime: add optional expensive check for invalid cgo pointer passing
If you set GODEBUG=cgocheck=2 the runtime package will use the write
barrier to detect cases where a Go program writes a Go pointer into
non-Go memory. In conjunction with the existing cgo checks, and the
not-yet-implemented cgo check for exported functions, this should
reliably detect all cases (that do not import the unsafe package) in
which a Go pointer is incorrectly shared with C code. This check is
optional because it turns on the write barrier at all times, which is
known to be expensive.
Update #12416.
Change-Id: I549d8b2956daa76eac853928e9280e615d6365f4
Reviewed-on: https://go-review.googlesource.com/16899
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/src/cmd/compile/internal/gc/builtin.go b/src/cmd/compile/internal/gc/builtin.go
index f1d2ac9..4199fb3 100644
--- a/src/cmd/compile/internal/gc/builtin.go
+++ b/src/cmd/compile/internal/gc/builtin.go
@@ -86,7 +86,7 @@
"func @\"\".chanrecv2 (@\"\".chanType·2 *byte, @\"\".hchan·3 <-chan any, @\"\".elem·4 *any) (? bool)\n" +
"func @\"\".chansend1 (@\"\".chanType·1 *byte, @\"\".hchan·2 chan<- any, @\"\".elem·3 *any)\n" +
"func @\"\".closechan (@\"\".hchan·1 any)\n" +
- "var @\"\".writeBarrierEnabled bool\n" +
+ "var @\"\".writeBarrier struct { @\"\".enabled bool; @\"\".needed bool; @\"\".cgo bool }\n" +
"func @\"\".writebarrierptr (@\"\".dst·1 *any, @\"\".src·2 any)\n" +
"func @\"\".writebarrierstring (@\"\".dst·1 *any, @\"\".src·2 any)\n" +
"func @\"\".writebarrierslice (@\"\".dst·1 *any, @\"\".src·2 any)\n" +
diff --git a/src/cmd/compile/internal/gc/builtin/runtime.go b/src/cmd/compile/internal/gc/builtin/runtime.go
index 9301757..a50fc2e 100644
--- a/src/cmd/compile/internal/gc/builtin/runtime.go
+++ b/src/cmd/compile/internal/gc/builtin/runtime.go
@@ -108,7 +108,11 @@
func chansend1(chanType *byte, hchan chan<- any, elem *any)
func closechan(hchan any)
-var writeBarrierEnabled bool
+var writeBarrier struct {
+ enabled bool
+ needed bool
+ cgo bool
+}
func writebarrierptr(dst *any, src any)
func writebarrierstring(dst *any, src any)
diff --git a/src/cmd/compile/internal/gc/cgen.go b/src/cmd/compile/internal/gc/cgen.go
index e2077ba..6456240 100644
--- a/src/cmd/compile/internal/gc/cgen.go
+++ b/src/cmd/compile/internal/gc/cgen.go
@@ -801,7 +801,9 @@
Cgenr(n, &src, nil)
}
- wbEnabled := syslook("writeBarrierEnabled", 0)
+ wbVar := syslook("writeBarrier", 0)
+ wbEnabled := Nod(ODOT, wbVar, newname(wbVar.Type.Type.Sym))
+ wbEnabled = typecheck(&wbEnabled, Erv)
pbr := Thearch.Ginscmp(ONE, Types[TUINT8], wbEnabled, Nodintconst(0), -1)
Thearch.Gins(Thearch.Optoas(OAS, Types[Tptr]), &src, &dst)
pjmp := Gbranch(obj.AJMP, nil, 0)
