uname: add

This is a tiny package to check the Linux kernel version. It is taken
from the golang sources (src/internal/syscall/unix), with the irrelevant
parts, including FreeBSD and Solaris implementations, removed.

The code is covered by the "BSD 3-clause" license, which is compatible
with Apache license.

The history of the code before the fork can be seen here (oldest first):
 - https://go-review.googlesource.com/c/go/+/424896
 - https://go-review.googlesource.com/c/go/+/427675
 - https://go-review.googlesource.com/c/go/+/427676

This is aimed to replace the relevant containerd package
(github.com/containerd/containerd/pkg/kernelversion) and its forks.

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

uname/LICENSE.BSD

@@ -0,0 +1,27 @@
+Copyright 2009 The Go Authors.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google LLC nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

uname/go.mod

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+module github.com/moby/sys/uname
+
+go 1.18

uname/kernel_version_linux.go

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+// Copyright 2022 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.BSD file.
+
+package uname
+
+import (
+	"syscall"
+)
+
+// KernelVersion returns major and minor kernel version numbers
+// parsed from the [syscall.Uname] Release field, or (0, 0) if
+// the version can't be obtained or parsed.
+func KernelVersion() (major, minor int) {
+	var uname syscall.Utsname
+	if err := syscall.Uname(&uname); err != nil {
+		return
+	}
+
+	var (
+		values    [2]int
+		value, vi int
+	)
+	for _, c := range uname.Release {
+		if '0' <= c && c <= '9' {
+			value = (value * 10) + int(c-'0')
+		} else {
+			// Note that we're assuming N.N.N here.
+			// If we see anything else, we are likely to mis-parse it.
+			values[vi] = value
+			vi++
+			if vi >= len(values) {
+				break
+			}
+			value = 0
+		}
+	}
+
+	return values[0], values[1]
+}

uname/kernel_version_other.go

@@ -0,0 +1,11 @@
+// Copyright 2022 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.BSD file.
+
+//go:build !linux
+
+package uname
+
+func KernelVersion() (major int, minor int) {
+	return 0, 0
+}