1#!/usr/bin/env python3
2# -*- coding: utf-8 -*-
3
4"""
5This takes a crashing qtest trace and tries to remove superflous operations
6"""
7
8import sys
9import os
10import subprocess
11import time
12import struct
13
14QEMU_ARGS = None
15QEMU_PATH = None
16TIMEOUT = 5
17CRASH_TOKEN = None
18
19write_suffix_lookup = {"b": (1, "B"),
20                       "w": (2, "H"),
21                       "l": (4, "L"),
22                       "q": (8, "Q")}
23
24def usage():
25    sys.exit("""\
26Usage: QEMU_PATH="/path/to/qemu" QEMU_ARGS="args" {} input_trace output_trace
27By default, will try to use the second-to-last line in the output to identify
28whether the crash occred. Optionally, manually set a string that idenitifes the
29crash by setting CRASH_TOKEN=
30""".format((sys.argv[0])))
31
32deduplication_note = """\n\
33Note: While trimming the input, sometimes the mutated trace triggers a different
34type crash but indicates the same bug. Under this situation, our minimizer is
35incapable of recognizing and stopped from removing it. In the future, we may
36use a more sophisticated crash case deduplication method.
37\n"""
38
39def check_if_trace_crashes(trace, path):
40    with open(path, "w") as tracefile:
41        tracefile.write("".join(trace))
42
43    rc = subprocess.Popen("timeout -s 9 {timeout}s {qemu_path} {qemu_args} 2>&1\
44    < {trace_path}".format(timeout=TIMEOUT,
45                           qemu_path=QEMU_PATH,
46                           qemu_args=QEMU_ARGS,
47                           trace_path=path),
48                          shell=True,
49                          stdin=subprocess.PIPE,
50                          stdout=subprocess.PIPE,
51                          encoding="utf-8")
52    global CRASH_TOKEN
53    if CRASH_TOKEN is None:
54        try:
55            outs, _ = rc.communicate(timeout=5)
56            CRASH_TOKEN = " ".join(outs.splitlines()[-2].split()[0:3])
57        except subprocess.TimeoutExpired:
58            print("subprocess.TimeoutExpired")
59            return False
60        print("Identifying Crashes by this string: {}".format(CRASH_TOKEN))
61        global deduplication_note
62        print(deduplication_note)
63        return True
64
65    for line in iter(rc.stdout.readline, ""):
66        if "CLOSED" in line:
67            return False
68        if CRASH_TOKEN in line:
69            return True
70
71    print("\nWarning:")
72    print("  There is no 'CLOSED'or CRASH_TOKEN in the stdout of subprocess.")
73    print("  Usually this indicates a different type of crash.\n")
74    return False
75
76
77def minimize_trace(inpath, outpath):
78    global TIMEOUT
79    with open(inpath) as f:
80        trace = f.readlines()
81    start = time.time()
82    if not check_if_trace_crashes(trace, outpath):
83        sys.exit("The input qtest trace didn't cause a crash...")
84    end = time.time()
85    print("Crashed in {} seconds".format(end-start))
86    TIMEOUT = (end-start)*5
87    print("Setting the timeout for {} seconds".format(TIMEOUT))
88
89    i = 0
90    newtrace = trace[:]
91    # For each line
92    while i < len(newtrace):
93        # 1.) Try to remove it completely and reproduce the crash. If it works,
94        # we're done.
95        prior = newtrace[i]
96        print("Trying to remove {}".format(newtrace[i]))
97        # Try to remove the line completely
98        newtrace[i] = ""
99        if check_if_trace_crashes(newtrace, outpath):
100            i += 1
101            continue
102        newtrace[i] = prior
103
104        # 2.) Try to replace write{bwlq} commands with a write addr, len
105        # command. Since this can require swapping endianness, try both LE and
106        # BE options. We do this, so we can "trim" the writes in (3)
107        if (newtrace[i].startswith("write") and not
108            newtrace[i].startswith("write ")):
109            suffix = newtrace[i].split()[0][-1]
110            assert(suffix in write_suffix_lookup)
111            addr = int(newtrace[i].split()[1], 16)
112            value = int(newtrace[i].split()[2], 16)
113            for endianness in ['<', '>']:
114                data = struct.pack("{end}{size}".format(end=endianness,
115                                   size=write_suffix_lookup[suffix][1]),
116                                   value)
117                newtrace[i] = "write {addr} {size} 0x{data}\n".format(
118                    addr=hex(addr),
119                    size=hex(write_suffix_lookup[suffix][0]),
120                    data=data.hex())
121                if(check_if_trace_crashes(newtrace, outpath)):
122                    break
123            else:
124                newtrace[i] = prior
125
126        # 3.) If it is a qtest write command: write addr len data, try to split
127        # it into two separate write commands. If splitting the write down the
128        # middle does not work, try to move the pivot "left" and retry, until
129        # there is no space left. The idea is to prune unneccessary bytes from
130        # long writes, while accommodating arbitrary MemoryRegion access sizes
131        # and alignments.
132        if newtrace[i].startswith("write "):
133            addr = int(newtrace[i].split()[1], 16)
134            length = int(newtrace[i].split()[2], 16)
135            data = newtrace[i].split()[3][2:]
136            if length > 1:
137                leftlength = int(length/2)
138                rightlength = length - leftlength
139                newtrace.insert(i+1, "")
140                while leftlength > 0:
141                    newtrace[i] = "write {addr} {size} 0x{data}\n".format(
142                            addr=hex(addr),
143                            size=hex(leftlength),
144                            data=data[:leftlength*2])
145                    newtrace[i+1] = "write {addr} {size} 0x{data}\n".format(
146                            addr=hex(addr+leftlength),
147                            size=hex(rightlength),
148                            data=data[leftlength*2:])
149                    if check_if_trace_crashes(newtrace, outpath):
150                        break
151                    else:
152                        leftlength -= 1
153                        rightlength += 1
154                if check_if_trace_crashes(newtrace, outpath):
155                    i -= 1
156                else:
157                    newtrace[i] = prior
158                    del newtrace[i+1]
159        i += 1
160    check_if_trace_crashes(newtrace, outpath)
161
162
163if __name__ == '__main__':
164    if len(sys.argv) < 3:
165        usage()
166
167    QEMU_PATH = os.getenv("QEMU_PATH")
168    QEMU_ARGS = os.getenv("QEMU_ARGS")
169    if QEMU_PATH is None or QEMU_ARGS is None:
170        usage()
171    # if "accel" not in QEMU_ARGS:
172    #     QEMU_ARGS += " -accel qtest"
173    CRASH_TOKEN = os.getenv("CRASH_TOKEN")
174    QEMU_ARGS += " -qtest stdio -monitor none -serial none "
175    minimize_trace(sys.argv[1], sys.argv[2])
176