crypto/rand, internal/syscall/unix: add support for getrandom on NetBSD ≥ 10.0json-isValidNumber-before

The getrandom syscall was added to NetBSD in version 10.0, see
https://man.netbsd.org/NetBSD-10.0-STABLE/getrandom.2

Change-Id: I2714c1040791f7f4728be8d869058a38cbd93d4d
Reviewed-on: https://go-review.googlesource.com/c/go/+/463123
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>

1 files changed, 56 insertions, 0 deletions

diff --git a/src/internal/syscall/unix/getrandom_netbsd.go b/src/internal/syscall/unix/getrandom_netbsd.go
new file mode 100644
index 0000000000..724228b380
--- /dev/null
+++ b/src/internal/syscall/unix/getrandom_netbsd.go
@@ -0,0 +1,56 @@
+// Copyright 2023 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 unix
+
+import (
+	"sync"
+	"sync/atomic"
+	"syscall"
+	"unsafe"
+)
+
+// NetBSD getrandom system call number.
+const getrandomTrap uintptr = 91
+
+var getrandomUnsupported int32 // atomic
+
+// GetRandomFlag is a flag supported by the getrandom system call.
+type GetRandomFlag uintptr
+
+// GetRandom calls the getrandom system call.
+func GetRandom(p []byte, flags GetRandomFlag) (n int, err error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+	if atomic.LoadInt32(&getrandomUnsupported) != 0 {
+		return 0, syscall.ENOSYS
+	}
+	// getrandom(2) was added in NetBSD 10.0
+	if getOSRevision() < 1000000000 {
+		atomic.StoreInt32(&getrandomUnsupported, 1)
+		return 0, syscall.ENOSYS
+	}
+	r1, _, errno := syscall.Syscall(getrandomTrap,
+		uintptr(unsafe.Pointer(&p[0])),
+		uintptr(len(p)),
+		uintptr(flags))
+	if errno != 0 {
+		if errno == syscall.ENOSYS {
+			atomic.StoreInt32(&getrandomUnsupported, 1)
+		}
+		return 0, errno
+	}
+	return int(r1), nil
+}
+
+var (
+	osrevisionOnce sync.Once
+	osrevision     uint32
+)
+
+func getOSRevision() uint32 {
+	osrevisionOnce.Do(func() { osrevision, _ = syscall.SysctlUint32("kern.osrevision") })
+	return osrevision
+}