1 files changed, 87 insertions, 0 deletions
diff --git a/src/runtime/cgo_sigaction.go b/src/runtime/cgo_sigaction.go
new file mode 100644
index 0000000..de634dc
--- /dev/null
+++ b/src/runtime/cgo_sigaction.go
@@ -0,0 +1,87 @@
+// Copyright 2016 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.
+
+// Support for memory sanitizer. See runtime/cgo/sigaction.go.
+
+// +build linux,amd64 freebsd,amd64 linux,arm64
+
+package runtime
+
+import "unsafe"
+
+// _cgo_sigaction is filled in by runtime/cgo when it is linked into the
+// program, so it is only non-nil when using cgo.
+//go:linkname _cgo_sigaction _cgo_sigaction
+var _cgo_sigaction unsafe.Pointer
+
+//go:nosplit
+//go:nowritebarrierrec
+func sigaction(sig uint32, new, old *sigactiont) {
+	// racewalk.go avoids adding sanitizing instrumentation to package runtime,
+	// but we might be calling into instrumented C functions here,
+	// so we need the pointer parameters to be properly marked.
+	//
+	// Mark the input as having been written before the call
+	// and the output as read after.
+	if msanenabled && new != nil {
+		msanwrite(unsafe.Pointer(new), unsafe.Sizeof(*new))
+	}
+
+	if _cgo_sigaction == nil || inForkedChild {
+		sysSigaction(sig, new, old)
+	} else {
+		// We need to call _cgo_sigaction, which means we need a big enough stack
+		// for C.  To complicate matters, we may be in libpreinit (before the
+		// runtime has been initialized) or in an asynchronous signal handler (with
+		// the current thread in transition between goroutines, or with the g0
+		// system stack already in use).
+
+		var ret int32
+
+		var g *g
+		if mainStarted {
+			g = getg()
+		}
+		sp := uintptr(unsafe.Pointer(&sig))
+		switch {
+		case g == nil:
+			// No g: we're on a C stack or a signal stack.
+			ret = callCgoSigaction(uintptr(sig), new, old)
+		case sp < g.stack.lo || sp >= g.stack.hi:
+			// We're no longer on g's stack, so we must be handling a signal.  It's
+			// possible that we interrupted the thread during a transition between g
+			// and g0, so we should stay on the current stack to avoid corrupting g0.
+			ret = callCgoSigaction(uintptr(sig), new, old)
+		default:
+			// We're running on g's stack, so either we're not in a signal handler or
+			// the signal handler has set the correct g.  If we're on gsignal or g0,
+			// systemstack will make the call directly; otherwise, it will switch to
+			// g0 to ensure we have enough room to call a libc function.
+			//
+			// The function literal that we pass to systemstack is not nosplit, but
+			// that's ok: we'll be running on a fresh, clean system stack so the stack
+			// check will always succeed anyway.
+			systemstack(func() {
+				ret = callCgoSigaction(uintptr(sig), new, old)
+			})
+		}
+
+		const EINVAL = 22
+		if ret == EINVAL {
+			// libc reserves certain signals — normally 32-33 — for pthreads, and
+			// returns EINVAL for sigaction calls on those signals.  If we get EINVAL,
+			// fall back to making the syscall directly.
+			sysSigaction(sig, new, old)
+		}
+	}
+
+	if msanenabled && old != nil {
+		msanread(unsafe.Pointer(old), unsafe.Sizeof(*old))
+	}
+}
+
+// callCgoSigaction calls the sigaction function in the runtime/cgo package
+// using the GCC calling convention. It is implemented in assembly.
+//go:noescape
+func callCgoSigaction(sig uintptr, new, old *sigactiont) int32