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author | van Hauser <vh@thc.org> | 2021-03-09 21:13:41 +0100 |
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committer | GitHub <noreply@github.com> | 2021-03-09 21:13:41 +0100 |
commit | 9c9232b4e8cf9a4aa51fe4b3fd33df84b9d13171 (patch) | |
tree | f503a0ef85458feba2cc1052d620e8a99add5189 | |
parent | 0d6e5712372477a61a4ebee6995fb48d30e93304 (diff) | |
parent | 8628839c5583354f19045ca95aabb67cfa80b3ca (diff) | |
download | afl++-9c9232b4e8cf9a4aa51fe4b3fd33df84b9d13171.tar.gz |
Merge pull request #789 from wyattearp/dev
documentation correction & formatting
-rw-r--r-- | instrumentation/README.persistent_mode.md | 26 |
1 files changed, 13 insertions, 13 deletions
diff --git a/instrumentation/README.persistent_mode.md b/instrumentation/README.persistent_mode.md index 2cf76adf..24f81ea0 100644 --- a/instrumentation/README.persistent_mode.md +++ b/instrumentation/README.persistent_mode.md @@ -16,7 +16,7 @@ Examples can be found in [utils/persistent_mode](../utils/persistent_mode). ## 2) TLDR; Example `fuzz_target.c`: -``` +```c #include "what_you_need_for_your_target.h" __AFL_FUZZ_INIT(); @@ -60,14 +60,14 @@ The speed increase is usually x10 to x20. If you want to be able to compile the target without afl-clang-fast/lto then add this just after the includes: -``` +```c #ifndef __AFL_FUZZ_TESTCASE_LEN ssize_t fuzz_len; #define __AFL_FUZZ_TESTCASE_LEN fuzz_len unsigned char fuzz_buf[1024000]; #define __AFL_FUZZ_TESTCASE_BUF fuzz_buf #define __AFL_FUZZ_INIT() void sync(void); - #define __AFL_LOOP(x) ((fuzz_len = read(0, fuzz_buf, sizeof(fuzz_buf))) > 0 ? + #define __AFL_LOOP(x) ((fuzz_len = read(0, fuzz_buf, sizeof(fuzz_buf))) > 0 ? 1 : 0) #define __AFL_INIT() sync() #endif ``` @@ -75,7 +75,7 @@ add this just after the includes: ## 3) Deferred initialization AFL tries to optimize performance by executing the targeted binary just once, -stopping it just before main(), and then cloning this "main" process to get +stopping it just before `main()`, and then cloning this "main" process to get a steady supply of targets to fuzz. Although this approach eliminates much of the OS-, linker- and libc-level @@ -97,7 +97,7 @@ a location after: - The creation of any vital threads or child processes - since the forkserver can't clone them easily. - - The initialization of timers via setitimer() or equivalent calls. + - The initialization of timers via `setitimer()` or equivalent calls. - The creation of temporary files, network sockets, offset-sensitive file descriptors, and similar shared-state resources - but only provided that @@ -150,9 +150,9 @@ the impact of memory leaks and similar glitches; 1000 is a good starting point, and going much higher increases the likelihood of hiccups without giving you any real performance benefits. -A more detailed template is shown in ../utils/persistent_mode/. -Similarly to the previous mode, the feature works only with afl-clang-fast; #ifdef -guards can be used to suppress it when using other compilers. +A more detailed template is shown in `../utils/persistent_mode/.` +Similarly to the previous mode, the feature works only with afl-clang-fast; +`#ifdef` guards can be used to suppress it when using other compilers. Note that as with the previous mode, the feature is easy to misuse; if you do not fully reset the critical state, you may end up with false positives or @@ -161,7 +161,7 @@ wary of memory leaks and of the state of file descriptors. PS. Because there are task switches still involved, the mode isn't as fast as "pure" in-process fuzzing offered, say, by LLVM's LibFuzzer; but it is a lot -faster than the normal fork() model, and compared to in-process fuzzing, +faster than the normal `fork()` model, and compared to in-process fuzzing, should be a lot more robust. ## 5) Shared memory fuzzing @@ -174,17 +174,17 @@ Setting this up is very easy: After the includes set the following macro: -``` +```c __AFL_FUZZ_INIT(); ``` Directly at the start of main - or if you are using the deferred forkserver -with `__AFL_INIT()` then *after* `__AFL_INIT? : -``` +with `__AFL_INIT()` then *after* `__AFL_INIT()` : +```c unsigned char *buf = __AFL_FUZZ_TESTCASE_BUF; ``` Then as first line after the `__AFL_LOOP` while loop: -``` +```c int len = __AFL_FUZZ_TESTCASE_LEN; ``` and that is all! |