[dev.power64] code review 160200044: build: merge default into dev.power64

src/pkg/internal/syscall/getrandom_linux.go

Index: src/pkg/internal/syscall/getrandom_linux.go
===================================================================
new file mode 100644
--- /dev/null
+++ b/src/pkg/internal/syscall/getrandom_linux.go
@@ -0,0 +1,56 @@
+// Copyright 2014 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 syscall
+
+import (
+	"runtime"
+	"sync/atomic"
+	stdsyscall "syscall"
+	"unsafe"
+)
+
+var randomTrap = map[string]uintptr{
+	"386":   355,
+	"amd64": 318,
+	"arm":   384,
+}[runtime.GOARCH]
+
+var randomUnsupported int32 // atomic
+
+// GetRandomFlag is a flag supported by the getrandom system call.
+type GetRandomFlag uintptr
+
+const (
+	// GRND_NONBLOCK means return EAGAIN rather than blocking.
+	GRND_NONBLOCK GetRandomFlag = 0x0001
+
+	// GRND_RANDOM means use the /dev/random pool instead of /dev/urandom.
+	GRND_RANDOM GetRandomFlag = 0x0002
+)
+
+// GetRandom calls the Linux getrandom system call.
+// See https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c6e9d6f38894798696f23c8084ca7edbf16ee895
+func GetRandom(p []byte, flags GetRandomFlag) (n int, err error) {
+	if randomTrap == 0 {
+		return 0, stdsyscall.ENOSYS
+	}
+	if len(p) == 0 {
+		return 0, nil
+	}
+	if atomic.LoadInt32(&randomUnsupported) != 0 {
+		return 0, stdsyscall.ENOSYS
+	}
+	r1, _, errno := stdsyscall.Syscall(randomTrap,
+		uintptr(unsafe.Pointer(&p[0])),
+		uintptr(len(p)),
+		uintptr(flags))
+	if errno != 0 {
+		if errno == stdsyscall.ENOSYS {
+			atomic.StoreInt32(&randomUnsupported, 1)
+		}
+		return 0, errno
+	}
+	return int(r1), nil
+}