[test] Speed up fuzzing by ~200x when using afl-fuzz

Enable the `afl-clang-fast++` features deferred forkserver (`__AFL_INIT`) and persistent mode (`__AFL_LOOP(1000)`).

Before this patch:

```
$ afl-fuzz -i input -o output -m512 -- src/test/test_bitcoin_fuzzy
[*] Validating target binary...
[!] WARNING: The target binary is pretty slow! See /usr/local/share/doc/afl/perf_tips.txt.
[+] Here are some useful stats:

    Test case count : 1 favored, 0 variable, 1 total
       Bitmap range : 1072 to 1072 bits (average: 1072.00 bits)
        Exec timing : 20.4k to 20.4k us (average: 20.4k us)
…
exec speed : 57.58/sec (slow!)
exec speed : 48.35/sec (slow!)
exec speed : 53.78/sec (slow!)
```

After this patch:

```
$ afl-fuzz -i input -o output -m512 -- src/test/test_bitcoin_fuzzy
[*] Validating target binary...
[+] Persistent mode binary detected.
[+] Deferred forkserver binary detected.
[+] Here are some useful stats:

    Test case count : 1 favored, 0 variable, 1 total
       Bitmap range : 24 to 24 bits (average: 24.00 bits)
        Exec timing : 114 to 114 us (average: 114 us)
…
exec speed : 15.9k/sec
exec speed : 13.1k/sec
exec speed : 15.1k/sec
```
This commit is contained in:
practicalswift 2017-05-18 21:37:31 +02:00
parent 95546c859b
commit 693247b82b
2 changed files with 28 additions and 3 deletions

View file

@ -32,6 +32,13 @@ We disable ccache because we don't want to pollute the ccache with instrumented
objects, and similarly don't want to use non-instrumented cached objects linked objects, and similarly don't want to use non-instrumented cached objects linked
in. in.
The fuzzing can be sped up significantly (~200x) by using `afl-clang-fast` and
`afl-clang-fast++` in place of `afl-gcc` and `afl-g++` when compiling. When
compiling using `afl-clang-fast`/`afl-clang-fast++` the resulting
`test_bitcoin_fuzzy` binary will be instrumented in such a way that the AFL
features "persistent mode" and "deferred forkserver" can be used. See
https://github.com/mcarpenter/afl/tree/master/llvm_mode for details.
Preparing fuzzing Preparing fuzzing
------------------ ------------------
@ -63,4 +70,3 @@ $AFLPATH/afl-fuzz -i ${AFLIN} -o ${AFLOUT} -m52 -- test/test_bitcoin_fuzzy
You may have to change a few kernel parameters to test optimally - `afl-fuzz` You may have to change a few kernel parameters to test optimally - `afl-fuzz`
will print an error and suggestion if so. will print an error and suggestion if so.

View file

@ -59,9 +59,8 @@ bool read_stdin(std::vector<char> &data) {
return length==0; return length==0;
} }
int main(int argc, char **argv) int do_fuzz()
{ {
ECCVerifyHandle globalVerifyHandle;
std::vector<char> buffer; std::vector<char> buffer;
if (!read_stdin(buffer)) return 0; if (!read_stdin(buffer)) return 0;
@ -256,3 +255,23 @@ int main(int argc, char **argv)
return 0; return 0;
} }
int main(int argc, char **argv)
{
ECCVerifyHandle globalVerifyHandle;
#ifdef __AFL_INIT
// Enable AFL deferred forkserver mode. Requires compilation using
// afl-clang-fast++. See fuzzing.md for details.
__AFL_INIT();
#endif
#ifdef __AFL_LOOP
// Enable AFL persistent mode. Requires compilation using afl-clang-fast++.
// See fuzzing.md for details.
while (__AFL_LOOP(1000)) {
do_fuzz();
}
return 0;
#else
return do_fuzz();
#endif
}