qemu and build: review fixes across the rig driver, boot script, and fetch helpers
Bounded waits and validated arguments in run.sh and ui-drive.sh, a seeded settings directory and root-only staged rootfs permissions with their own tests, qmp.py and imgtools.py hardening, the fetch scripts checking what they download, and ASCII typography throughout. Each fix carries its test under qemu/tests or tests/. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01N3G6m9Aw5RyVY4ZowtKzEj
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Noah
+48
-58
@@ -35,11 +35,10 @@ import json
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from PIL import Image, ImageFilter
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# occupancy thresholds for structural(): a downsampled cell counts as
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# "occupied" if it is meaningfully brighter than black, or sits on an edge.
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# Both are 0..255 greyscale/edge-magnitude averages over the cell.
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# structural(): a cell is occupied when its grey is this far from the crop's
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# median (its background) or its FIND_EDGES energy exceeds the edge threshold.
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# occupancy thresholds for structural(): a cell is occupied when its grey is
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# this far from the crop's median (its background), or its FIND_EDGES energy
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# exceeds the edge threshold. Both are 0..255 greyscale/edge-magnitude
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# averages over the cell.
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# Validated on real captures: a switch knob left/right differs in 240/256
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# cells, a dark card's icon and text stand out from its (7,13,29) ground.
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DEVIATION_THRESHOLD = 28
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@@ -53,64 +52,31 @@ EDGE_THRESHOLD = 24
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def load_ppm(path):
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"""Read a binary PPM (P6), return (w, h, rgb_bytes).
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QEMU's screendump writes a comment-free header ("P6\\nW H\\n255\\n"
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then raw bytes) but the token reader here handles the general P6
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grammar -- whitespace runs and '#' comments -- since that costs
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nothing extra and means any other producer of P6 files just works.
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Delegates to Pillow's own P6 decoder (Image.open, format auto-detected
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from the magic) instead of re-parsing the PPM grammar by hand: skipping
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whitespace runs and '#' comments, and normalising any maxval to 8-bit,
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are Pillow's problem here, not ours. convert("RGB") guarantees the
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tightly-packed 3-bytes-per-pixel layout every caller in this file
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assumes regardless of the source channel depth.
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"""
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with open(path, "rb") as f:
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data = f.read()
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def skip_ws_comments(p):
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while p < len(data):
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c = data[p]
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if c in b" \t\r\n":
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p += 1
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elif c == ord("#"):
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while p < len(data) and data[p] != ord("\n"):
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p += 1
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else:
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break
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return p
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def read_token(p):
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p = skip_ws_comments(p)
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start = p
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while p < len(data) and data[p] not in b" \t\r\n":
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p += 1
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return data[start:p], p
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pos = 0
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magic, pos = read_token(pos)
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if magic != b"P6":
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raise ValueError(f"{path}: not a P6 PPM (magic={magic!r})")
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w_tok, pos = read_token(pos)
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h_tok, pos = read_token(pos)
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maxval_tok, pos = read_token(pos)
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w, h, maxval = int(w_tok), int(h_tok), int(maxval_tok)
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if maxval != 255:
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raise ValueError(f"{path}: unsupported PPM maxval {maxval} (only 255 handled)")
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# exactly one whitespace byte separates the header from the binary data
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pos += 1
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need = w * h * 3
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pixels = data[pos:pos + need]
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if len(pixels) != need:
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raise ValueError(f"{path}: truncated PPM, want {need} bytes got {len(pixels)}")
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return w, h, pixels
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with Image.open(path) as im:
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im = im.convert("RGB")
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return im.width, im.height, im.tobytes()
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def crop(img, x, y, w, h):
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"""Crop (W,H,rgb) to the x,y,w,h box, return a new (w,h,rgb) image."""
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"""Crop (W,H,rgb) to the x,y,w,h box, return a new (w,h,rgb) image.
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The bounds check stays explicit and fails loudly (see main()'s own
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comment on that) rather than delegating to PIL's crop, which silently
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zero-pads a box that runs outside the source image instead of raising --
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exactly the kind of stale/mistyped region box this check exists to catch.
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"""
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width, height, data = img
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if x < 0 or y < 0 or w <= 0 or h <= 0 or x + w > width or y + h > height:
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raise ValueError(f"crop box {x},{y},{w}x{h} outside image {width}x{height}")
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row_bytes = w * 3
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out = bytearray(h * row_bytes)
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for row in range(h):
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src_off = ((y + row) * width + x) * 3
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dst_off = row * row_bytes
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out[dst_off:dst_off + row_bytes] = data[src_off:src_off + row_bytes]
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return w, h, bytes(out)
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cropped = _to_pil(img).crop((x, y, x + w, y + h))
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return w, h, cropped.tobytes()
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def _to_pil(img):
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@@ -188,7 +154,7 @@ def phash(img):
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def hamming(a, b):
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"""Bit-differences between two phash ints."""
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return bin(a ^ b).count("1")
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return (a ^ b).bit_count()
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# ---------------------------------------------------------------------------
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@@ -241,7 +207,7 @@ def _median_grey(grey):
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def _structural_diff(a, b):
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"""Count of differing bits between two 32-byte occupancy masks."""
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return sum(bin(x ^ y).count("1") for x, y in zip(a, b))
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return (int.from_bytes(a, "big") ^ int.from_bytes(b, "big")).bit_count()
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# ---------------------------------------------------------------------------
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@@ -405,6 +371,10 @@ def cmd_bench(argv):
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print(f"bench: {cw}x{ch} region, n={n} iterations")
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for label, fn in (("phash", lambda: phash(region)),
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("structural", lambda: structural(region))):
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for _ in range(5):
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fn() # warm up: first call can carry one-off costs (e.g. module-
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# level caches settling) that don't belong in the steady-state
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# population below
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samples = timeit.repeat(fn, repeat=n, number=1)
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lo, p50, p95, hi = percentiles(samples)
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print(f" {label:<10} min={lo * 1000:7.3f}ms p50={p50 * 1000:7.3f}ms "
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@@ -493,6 +463,26 @@ def selftest():
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check("crop keeps the drawn pixel in place",
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cropped[2][px_off:px_off + 3] == bytes((220, 20, 20)))
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# a header QEMU never writes but the P6 grammar allows: a '#'
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# comment line and a non-255 maxval. Pillow's decoder (load_ppm no
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# longer hand-parses the header) must still read it correctly.
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odd_path = os.path.join(tmp, "odd-header.ppm")
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with open(odd_path, "wb") as f:
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f.write(b"P6\n# generated for a selftest, not by QEMU\n2 2\n100\n")
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f.write(bytes((100, 0, 0, 0, 100, 0, 0, 0, 100, 100, 100, 100)))
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ow, oh, odata = load_ppm(odd_path)
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check("load_ppm reads width/height past a comment line", (ow, oh) == (2, 2))
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check("load_ppm scales a non-255 maxval channel to 8-bit",
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odata[0:3] == bytes((255, 0, 0)))
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# crop box outside the image must still fail loudly, not silently
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# zero-pad the way PIL's own Image.crop does
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try:
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crop((bw, bh, bdata), bw - 4, bh - 4, 32, 32)
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check("crop rejects a box past the image edge", False)
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except ValueError:
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check("crop rejects a box past the image edge", True)
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# _dct2d_32's _DCT_KEEP truncation must land on the exact same
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# coefficients an untruncated 32x32 DCT would produce
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small = _to_pil((bw, bh, bdata)).convert("L").resize((32, 32), Image.LANCZOS)
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