d0f7acf9eb
An x86-64 operating system built from xv6, now largely rewritten: SMP, a copy-on-write root filesystem (SchFS), PCI/USB/virtio drivers, a TTF rasteriser, and a Linux-numbered syscall ABI. No history before this point -- the tree was never under version control. This commit exists so the rename that follows has something to undo to.
85 lines
3 KiB
Python
85 lines
3 KiB
Python
#!/usr/bin/env python3
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"""Read the QR code back off a captured crash screen.
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This is the acceptance test for the crash channel, and it is deliberately
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end-to-end: it does not ask the encoder what it produced, it reads the pixels
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that were actually painted on the framebuffer. Everything in between -- payload
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construction in panic context, the encoder, the scaling into modules, the card
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and quiet zone -- is covered by whether this comes back as text.
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pwsh -File tools/crashshot.ps1 # crash on purpose, screendump it
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PYTHONPATH=<dir> python tools/crashqr.py
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Needs opencv-python-headless and numpy; see tools/qrcheck.py for the install.
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"""
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import sys
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try:
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import cv2
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import numpy as np
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except ImportError:
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sys.exit("crashqr: needs opencv-python-headless and numpy")
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PPM = sys.argv[1] if len(sys.argv) > 1 else "build/crashscreen.ppm"
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try:
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data = open(PPM, "rb").read()
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except OSError as e:
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sys.exit(f"crashqr: {e} -- run tools/crashshot.ps1 first")
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# PPM P6 header: three whitespace-separated fields after the magic. Parsed by
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# scanning rather than assuming a fixed length, because QEMU's is compact but
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# nothing guarantees that.
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pos, fields = 2, []
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while len(fields) < 3:
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while data[pos:pos + 1].isspace():
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pos += 1
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start = pos
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while not data[pos:pos + 1].isspace():
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pos += 1
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fields.append(int(data[start:pos]))
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pos += 1
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w, h = fields[0], fields[1]
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img = np.frombuffer(data[pos:pos + w * h * 3], np.uint8).reshape(h, w, 3)
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grey = cv2.cvtColor(img, cv2.COLOR_RGB2GRAY)
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# The symbol sits on the only light panel on an otherwise purple screen, so a
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# brightness threshold finds it without needing to know the layout. The white
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# report text passes the same threshold, which does not matter -- the detector
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# locates the symbol by its finder patterns, and handing it extra screen
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# costs nothing.
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mask = (grey > 240).astype(np.uint8)
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ys, xs = np.nonzero(mask)
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if len(xs) == 0:
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sys.exit("crashqr: no light region found -- was a crash screen captured?")
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crop = grey[ys.min():ys.max() + 1, xs.min():xs.max() + 1]
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# OpenCV's detector is sensitive to scale in ways unrelated to the encoding,
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# so try a few before concluding anything. See the note in tools/qrcheck.py.
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text = ""
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for scale in (1, 2, 3, 4):
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up = cv2.resize(crop, None, fx=scale, fy=scale, interpolation=cv2.INTER_NEAREST)
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up = cv2.copyMakeBorder(up, 40, 40, 40, 40, cv2.BORDER_CONSTANT, value=255)
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text, _, _ = cv2.QRCodeDetector().detectAndDecode(up)
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if text:
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break
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if not text:
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print("crashqr: FAILED -- the symbol on the crash screen did not decode")
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sys.exit(1)
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print("crashqr: decoded the crash screen's QR\n")
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for line in text.split("\n"):
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print(" ", line)
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# The payload is a contract with whatever reads these later, so check its shape
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# rather than only that something came back.
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lines = text.split("\n")
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ok = lines[0] == "SXPSOGM1"
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print()
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if not ok:
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print(f"crashqr: FAILED -- expected magic 'SXPSOGM1', got {lines[0]!r}")
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sys.exit(1)
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print(f"crashqr: passed ({len(text)} bytes, {len(lines)} fields)")
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