プログラミング

QRコード写真からカーネルパニックをデコードする

Decode kernel panic from QR Code photo (gist.github.com)

7 pointsby modinfo2026年10月30日1 コメント

要約

この投稿では、Linuxカーネルパニック時に生成されるQRコードを、ZXingReaderというツールとPythonスクリプトを使用してデコードし、圧縮されたクラッシュログを復元する方法を紹介しています。スクリプトはQRコードをスキャンしてエンコードされたデータを抽出し、zlibで解凍してログを出力します。

全文翻訳

QRコード写真からカーネルパニックをデコードする

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［画像: @skorotkiewicz］

skorotkiewicz/decode-kernel-panic.py

Last active October 30, 2026 11:50

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decode kernel panic from QR code photo

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decode-kernel-panic.py


	#!/usr/bin/env python3
	"""
Scan a Linux panic QR code with ZXingReader and decompress its crash log.
./decode-kernel-panic.py screenshot.png -o panic.log
"""
	import argparse
	import json
	from pathlib import Path
	import subprocess
	import sys
	from urllib.parse import parse_qs, urlsplit
	import zlib


	def decode_panic_url(url):
	"""Decode the kernel's z parameter: 17 decimal digits per 7 little-endian bytes.

Format reference: https://github.com/kdj0c/panic_report
"""
| | parts = urlsplit(url) |
| | parameters = parse_qs(parts.query, keep_blank_values=True) |
| | if "z" not in parameters:
| | parameters = parse_qs(parts.fragment.lstrip("?"), keep_blank_values=True) |
| | if "z" not in parameters:
| | raise ValueError("QR code URL has no compressed panic data (z parameter)") |
| | if len(parameters["z"]) != 1:
| | raise ValueError("QR code URL has multiple z parameters") |
| | |
| | digits = parameters["z"][0] |
| | if not digits or not digits.isascii() or not digits.isdecimal(): |
| | raise ValueError("panic data must contain only decimal digits") |
| | |
| | # A final, partial group uses fewer digits and bytes.
| | byte_counts = {3: 1, 5: 2, 8: 3, 10: 4, 13: 5, 15: 6, 17: 7} |
| | compressed = bytearray() |
| | for offset in range(0, len(digits), 17):
| | chunk = digits[offset:offset + 17] |
| | if len(chunk) not in byte_counts:
| | raise ValueError("invalid length of encoded panic data") |
| | try:
| | compressed.extend(int(chunk).to_bytes(byte_counts[len(chunk)], "little")) |
| | except OverflowError as exc:
| | raise ValueError("encoded panic data contains an out-of-range chunk") from exc |
| | |
| | return zlib.decompress(compressed) |
| | |
| | |
| | def scan_image(image): |
| | if not image.is_file(): |
| | raise ValueError(f"image does not exist or is not a file: {image}") |
| | try:
| | result = subprocess.run(
| | ["ZXingReader", "-formats", "QRCode", "-json", str(image.resolve())],
| | capture_output=True,
| | text=True,
| | )
| | except FileNotFoundError as exc:
| | raise ValueError("ZXingReader is required; install it and put it on PATH") from exc |
| | if result.returncode != 0:
| | detail = result.stderr.strip() or "no readable QR code found"
| | raise ValueError(f"ZXingReader failed: {detail}") |
| | if not result.stdout.strip(): |
| | raise ValueError("no readable QR code found") |
| | try:
| | qr = json.loads(result.stdout) |
| | except json.JSONDecodeError as exc:
| | raise ValueError("expected one QR code in ZXingReader's JSON output") from exc |
| | if not isinstance(qr, dict) or not isinstance(qr.get("Text"), str):
| | raise ValueError("ZXingReader returned no QR code text") |
| | return qr["Text"] |
| | |
| | |
| | def main(): |
| | parser = argparse.ArgumentParser(
| | description="Scan a Linux panic screenshot with ZXingReader and decompress its log.",
| | epilog="Requires Python 3 and ZXingReader. Decoding runs locally without network access.",
| | )
| | parser.add_argument("image", type=Path, help="screenshot or photo containing the panic QR code") |
| | parser.add_argument("-o", "--output", type=Path, help="write the log to a file instead of stdout") |
| | args = parser.parse_args() |
| | try:
| | if args.output and args.output.resolve() == args.image.resolve(): |
| | raise ValueError("output must differ from the input image") |
| | log = decode_panic_url(scan_image(args.image)) |
| | if args.output:
| | args.output.write_bytes(log) |
| | else:
| | sys.stdout.buffer.write(log) |
| | except BrokenPipeError:
| | # Allow commands such as decode-kernel-panic screenshot.png | head.
| | import os |
| | os.dup2(os.open(os.devnull, os.O_WRONLY), sys.stdout.fileno()) |
| | return 0 |
| | except (OSError, ValueError, zlib.error) as exc:
| | print(f"{parser.prog}: {exc}", file=sys.stderr) |
| | return 1 |
| | return 0 |
| | |
| | |
| | if name == "main": |
| | sys.exit(main()) |

［画像: @skorotkiewicz］

skorotkiewicz commented Oct 30, 2026 •

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./decode-kernel-panic.py screenshot.png -o panic.log
［画像: 2026-10-30-12-26-18-715］

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