1DexFuzz
2=======
3
4DexFuzz is primarily a tool for fuzzing DEX files. Fuzzing is the introduction of
5subtle changes ("mutations") to a file to produce a new test case. These test cases
6can be used to test the various modes of execution available to ART (Interpreter,
7Quick compiler, Optimizing compiler) to check for bugs in these modes of execution.
8This is done by differential testing - each test file is executed with each mode of
9execution, and any differences between the resulting outputs may be an indication of
10a bug in one of the modes.
11
12For a wider overview of DexFuzz, see:
13
14http://community.arm.com/groups/android-community/blog/2014/11/26/the-art-of-fuzz-testing
15
16In typical operation, you provide DexFuzz with a set of DEX files that are the "seeds"
17for mutation - e.g. some tests taken from the ART test suite - and point it at an
18ADB-connected Android device, and it will fuzz these seed files, and execute the
19resulting new tests on the Android device.
20
21How to run DexFuzz
22==================
23
24DexFuzz can run its test programs on either an ADB-connected device, or a host-build of
25ART locally.
26
27Execution on an ADB-connected device
28------------------------------------
29
301. Build dexfuzz with mmma tools/dexfuzz from within art/.
312. Make sure you have an Android device connected via ADB, that is capable of
32   having DEX files pushed to it and executed with the dalvikvm command.
333. Make sure you're in the Android build environment!
34   (That is, . build/envsetup.sh && lunch)
354. Create a new directory, and place some DEX files in here. These are the seed files
36   that are mutated to form new tests.
375. Create a directory on your device that mutated test files can be pushed to and
38   executed in, using dalvikvm. For example, /data/art-test/
396. If you currently have multiple devices connected via ADB, find out the name of
40   your device using "adb devices -l".
417. Run this command:
42
43dexfuzz --inputs=<seeds dir> --execute --repeat=<attempts> \
44    --dump-output <combination of ISA(s) and and backend(s)>
45
46You MUST specify one of the following ISAs:
47  --arm
48  --arm64
49  --x86
50  --x86_64
51  --mips
52  --mips64
53
54And also at least two of the following backends:
55  --interpreter
56  --quick
57  --optimizing
58
59Note that if you wanted to test both ARM and ARM64 on an ARM64 device, you can use
60--allarm. Also in this case only one backend is needed, if i.e., you wanted to test
61ARM Quick Backend vs. ARM64 Quick Backend.
62
63Some legal examples:
64  --arm --quick --optimizing
65  --x86 --quick --optimizing --interpreter
66  --allarm --quick
67
68Add in --device=<device name, e.g. device:generic> if you want to specify a device.
69Add in --execute-dir=<dir on device> if you want to specify an execution directory.
70  (The default is /data/art-test/)
71
72Host Execution
73--------------
74
75DexFuzz now supports execution on your host machine.
76Follow steps 1, 3, 4, and 7 as above, but also observe the following:
77 - instead of specifying an ISA, use --host
78 - ANDROID_DATA must be set, pointing to a location where dex2oat will place
79   OAT files after compilation.
80 - Files will always be executed in the same directory where you are executing DexFuzz.
81
82Fuzzer Operation
83----------------
84
85As the fuzzer works, you'll see output like:
86
87|-----------------------------------------------------------------|
88|Iterations|VerifyFail|MutateFail|Timed Out |Successful|Divergence|
89|-----------------------------------------------------------------|
90| 48       | 37       | 4        | 0        | 6        | 1        |
91
92Iterations - number of attempts we've made to mutate DEX files.
93VerifyFail - the number of mutated files that ended up failing to verify, either
94             on the host, or the target.
95MutateFail - because mutation is a random process, and has attempt thresholds to
96             avoid attempting to mutate a file indefinitely, it is possible that
97             an attempt to mutate a file doesn't actually mutate it. This counts
98             those occurrences.
99Timed Out  - mutated files that timed out for one or more backends.
100             Current timeouts are:
101               Quick - 5 seconds
102               Optimizing - 5 seconds
103               Intepreter - 30 seconds
104              (use --short-timeouts to set all backends to 2 seconds.)
105Successful - mutated files that executed and all backends agreed on the resulting
106             output. NB: if all backends crashed with the same output, this would
107             be considered a success - proper detection of crashes is still to come.
108Divergence - mutated files that executed and some backend disagreed about the
109             resulting output. Divergent programs are run multiple times with a
110             single backend, to check if they diverge from themselves, and these are
111             not included in the count. If multiple architectures are being used
112             (ARM/ARM64), and the divergences align with different architectures,
113             these are also not included in the count.
114
1158. Check report.log for the full report, including input file and RNG seed for each
116   test program. This allows you to recreate a bad program with, e.g.:
117
118dexfuzz --input=<input file> --seed=<seed value>
119
120Check dexfuzz --help for the full list of options.
121
122NOTE: DEX files with unicode strings are not fully supported yet, and DEX files with
123JNI elements are not supported at all currently.
124
125Mutation Likelihoods
126====================
127
128Each bytecode mutation has a chance out of 100% of firing. Following is the listing
129of each mutation's probability. If you wish to easily adjust these values, copy
130these values into a file called likelihoods.txt, and run dexfuzz with
131--likelihoods=likelihoods.txt.
132
133ArithOpChanger 75
134BranchShifter 30
135CmpBiasChanger 30
136ConstantValueChanger 70
137ConversionRepeater 50
138FieldFlagChanger 40
139InstructionDeleter 40
140InstructionDuplicator 80
141InstructionSwapper 80
142NewMethodCaller 10
143NonsenseStringPrinter 10
144PoolIndexChanger 30
145RandomInstructionGenerator 30
146SwitchBranchShifter 30
147TryBlockShifter 40
148ValuePrinter 40
149VRegChanger 60
150