talm

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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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package uki
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import (
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	"bytes"
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	"encoding/binary"
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	"errors"
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	"os"
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	"strings"
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)
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// DiscoverKernelVersion reads kernel version from the kernel image.
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//
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// This only works for x86 kernel images.
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//
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// Based on https://www.kernel.org/doc/html/v5.6/x86/boot.html.
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func DiscoverKernelVersion(kernelPath string) (string, error) {
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	f, err := os.Open(kernelPath)
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	if err != nil {
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		return "", err
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	}
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	defer f.Close() //nolint:errcheck
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	header := make([]byte, 1024)
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	_, err = f.Read(header)
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	if err != nil {
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		return "", err
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	}
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	// check header magic
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	if string(header[0x202:0x206]) != "HdrS" {
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		return "", errors.New("invalid kernel image")
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	}
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	setupSects := header[0x1f1]
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	versionOffset := binary.LittleEndian.Uint16(header[0x20e:0x210])
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	if versionOffset == 0 {
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		return "", errors.New("no kernel version")
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	}
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	if versionOffset > uint16(setupSects)*0x200 {
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		return "", errors.New("invalid kernel version offset")
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	}
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	versionOffset += 0x200
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	version := make([]byte, 256)
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	_, err = f.ReadAt(version, int64(versionOffset))
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	if err != nil {
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		return "", err
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	}
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	idx := bytes.IndexByte(version, 0)
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	if idx == -1 {
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		return "", errors.New("invalid kernel version")
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	}
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	versionString := string(version[:idx])
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	versionString, _, _ = strings.Cut(versionString, " ")
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	return versionString, nil
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}
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