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eeae5466c4
While we only use stdin, the chardev is named 'stdio'. Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Reviewed-by: Alexander Bulekov <alxndr@bu.edu> Message-Id: <20210602170759.2500248-4-f4bug@amsat.org> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
104 lines
3.6 KiB
Python
Executable File
104 lines
3.6 KiB
Python
Executable File
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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"""
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Use this to convert qtest log info from a generic fuzzer input into a qtest
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trace that you can feed into a standard qemu-system process. Example usage:
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QEMU_FUZZ_ARGS="-machine q35,accel=qtest" QEMU_FUZZ_OBJECTS="*" \
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./i386-softmmu/qemu-fuzz-i386 --fuzz-target=generic-pci-fuzz
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# .. Finds some crash
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QTEST_LOG=1 FUZZ_SERIALIZE_QTEST=1 \
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QEMU_FUZZ_ARGS="-machine q35,accel=qtest" QEMU_FUZZ_OBJECTS="*" \
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./i386-softmmu/qemu-fuzz-i386 --fuzz-target=generic-pci-fuzz
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/path/to/crash 2> qtest_log_output
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scripts/oss-fuzz/reorder_fuzzer_qtest_trace.py qtest_log_output > qtest_trace
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./i386-softmmu/qemu-fuzz-i386 -machine q35,accel=qtest \
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-qtest stdio < qtest_trace
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### Details ###
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Some fuzzer make use of hooks that allow us to populate some memory range, just
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before a DMA read from that range. This means that the fuzzer can produce
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activity that looks like:
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[start] read from mmio addr
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[end] read from mmio addr
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[start] write to pio addr
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[start] fill a DMA buffer just in time
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[end] fill a DMA buffer just in time
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[start] fill a DMA buffer just in time
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[end] fill a DMA buffer just in time
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[end] write to pio addr
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[start] read from mmio addr
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[end] read from mmio addr
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We annotate these "nested" DMA writes, so with QTEST_LOG=1 the QTest trace
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might look something like:
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[R +0.028431] readw 0x10000
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[R +0.028434] outl 0xc000 0xbeef # Triggers a DMA read from 0xbeef and 0xbf00
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[DMA][R +0.034639] write 0xbeef 0x2 0xAAAA
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[DMA][R +0.034639] write 0xbf00 0x2 0xBBBB
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[R +0.028431] readw 0xfc000
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This script would reorder the above trace so it becomes:
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readw 0x10000
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write 0xbeef 0x2 0xAAAA
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write 0xbf00 0x2 0xBBBB
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outl 0xc000 0xbeef
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readw 0xfc000
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I.e. by the time, 0xc000 tries to read from DMA, those DMA buffers have already
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been set up, removing the need for the DMA hooks. We can simply provide this
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reordered trace via -qtest stdio to reproduce the input
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Note: this won't work for traces where the device tries to read from the same
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DMA region twice in between MMIO/PIO commands. E.g:
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[R +0.028434] outl 0xc000 0xbeef
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[DMA][R +0.034639] write 0xbeef 0x2 0xAAAA
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[DMA][R +0.034639] write 0xbeef 0x2 0xBBBB
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The fuzzer will annotate suspected double-fetches with [DOUBLE-FETCH]. This
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script looks for these tags and warns the users that the resulting trace might
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not reproduce the bug.
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"""
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import sys
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__author__ = "Alexander Bulekov <alxndr@bu.edu>"
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__copyright__ = "Copyright (C) 2020, Red Hat, Inc."
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__license__ = "GPL version 2 or (at your option) any later version"
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__maintainer__ = "Alexander Bulekov"
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__email__ = "alxndr@bu.edu"
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def usage():
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sys.exit("Usage: {} /path/to/qtest_log_output".format((sys.argv[0])))
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def main(filename):
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with open(filename, "r") as f:
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trace = f.readlines()
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# Leave only lines that look like logged qtest commands
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trace[:] = [x.strip() for x in trace if "[R +" in x
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or "[S +" in x and "CLOSED" not in x]
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for i in range(len(trace)):
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if i+1 < len(trace):
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if "[DMA]" in trace[i+1]:
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if "[DOUBLE-FETCH]" in trace[i+1]:
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sys.stderr.write("Warning: Likely double fetch on line"
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"{}.\n There will likely be problems "
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"reproducing behavior with the "
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"resulting qtest trace\n\n".format(i+1))
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trace[i], trace[i+1] = trace[i+1], trace[i]
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for line in trace:
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print(line.split("]")[-1].strip())
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if __name__ == '__main__':
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if len(sys.argv) == 1:
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usage()
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main(sys.argv[1])
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