Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 61 insertions, 0 deletions

diff --git a/pkg/sentry/syscalls/linux/sys_syslog.go b/pkg/sentry/syscalls/linux/sys_syslog.go
new file mode 100644
index 000000000..792040c81
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_syslog.go
@@ -0,0 +1,61 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package linux
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+const (
+	_SYSLOG_ACTION_READ_ALL    = 3
+	_SYSLOG_ACTION_SIZE_BUFFER = 10
+)
+
+// logBufLen is the default syslog buffer size on Linux.
+const logBufLen = 1 << 17
+
+// Syslog implements part of Linux syscall syslog.
+//
+// Only the unpriviledged commands are implemented, allowing applications to
+// read a fun dmesg.
+func Syslog(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	command := args[0].Int()
+	buf := args[1].Pointer()
+	size := int(args[2].Int())
+
+	switch command {
+	case _SYSLOG_ACTION_READ_ALL:
+		if size < 0 {
+			return 0, nil, syserror.EINVAL
+		}
+		if size > logBufLen {
+			size = logBufLen
+		}
+
+		log := t.Kernel().Syslog().Log()
+		if len(log) > size {
+			log = log[:size]
+		}
+
+		n, err := t.CopyOutBytes(buf, log)
+		return uintptr(n), nil, err
+	case _SYSLOG_ACTION_SIZE_BUFFER:
+		return logBufLen, nil, nil
+	default:
+		return 0, nil, syserror.ENOSYS
+	}
+}