diff options
| -rw-r--r-- | docs/Changelog.md | 1 | ||||
| -rw-r--r-- | docs/env_variables.md | 5 | ||||
| -rw-r--r-- | instrumentation/README.llvm.md | 4 | ||||
| -rw-r--r-- | instrumentation/README.neverzero.md | 5 | ||||
| -rw-r--r-- | src/afl-cc.c | 1 |
5 files changed, 16 insertions, 0 deletions
diff --git a/docs/Changelog.md b/docs/Changelog.md index 9c9a3976..d8e96bf3 100644 --- a/docs/Changelog.md +++ b/docs/Changelog.md @@ -35,6 +35,7 @@ sending a mail to <afl-users+subscribe@googlegroups.com>. - Removed automatic linking with -lc++ for LTO mode - utils/aflpp_driver/aflpp_qemu_driver_hook fixed to work with qemu mode - add -d (add dead fuzzer stats) to afl-whatsup + - add thread safe counters for LLVM CLASSIC (set AFL_LLVM_THREADSAFE_INST) ### Version ++3.12c (release) - afl-fuzz: diff --git a/docs/env_variables.md b/docs/env_variables.md index 0100ffac..d9a774aa 100644 --- a/docs/env_variables.md +++ b/docs/env_variables.md @@ -231,6 +231,11 @@ Then there are a few specific features that are only available in instrumentatio See [instrumentation/README.instrument_list.md](../instrumentation/README.instrument_list.md) for more information. +### Thread safe instrumentation counters (in mode LLVM CLASSIC) + - Setting `AFL_LLVM_THREADSAFE_INST` will inject code that implements thread safe counters. + The overhead is a bit higher compared to the older non-thread safe case. + `AFL_LLVM_NOT_ZERO` and `AFL_LLVM_SKIP_NEVERZERO` are supported (see below). + ### NOT_ZERO - Setting `AFL_LLVM_NOT_ZERO=1` during compilation will use counters diff --git a/instrumentation/README.llvm.md b/instrumentation/README.llvm.md index adce6c1d..a9d51829 100644 --- a/instrumentation/README.llvm.md +++ b/instrumentation/README.llvm.md @@ -144,6 +144,10 @@ is not optimal and was only fixed in llvm 9. You can set this with AFL_LLVM_NOT_ZERO=1 See [README.neverzero.md](README.neverzero.md) +Support for thread safe counters has been added for mode LLVM CLASSIC. +Activate it with `AFL_LLVM_THREADSAFE_INST=1`. The tradeoff is better precision in +multi threaded apps for a slightly higher instrumentation overhead. + ## 4) Snapshot feature To speed up fuzzing you can use a linux loadable kernel module which enables diff --git a/instrumentation/README.neverzero.md b/instrumentation/README.neverzero.md index 49104e00..06334eab 100644 --- a/instrumentation/README.neverzero.md +++ b/instrumentation/README.neverzero.md @@ -33,3 +33,8 @@ AFL_LLVM_SKIP_NEVERZERO=1 ``` If the target does not have extensive loops or functions that are called a lot then this can give a small performance boost. + +Please note that the default counter implementations are not thread safe! + +Support for thread safe counters in mode LLVM CLASSIC can be activated with setting +`AFL_LLVM_THREADSAFE_INST=1`. \ No newline at end of file diff --git a/src/afl-cc.c b/src/afl-cc.c index 1f89bac5..132f5f83 100644 --- a/src/afl-cc.c +++ b/src/afl-cc.c @@ -1757,6 +1757,7 @@ int main(int argc, char **argv, char **envp) { SAYF( "\nLLVM/LTO/afl-clang-fast/afl-clang-lto specific environment " "variables:\n" + " AFL_LLVM_THREADSAFE_INST: instrument with thread safe counters\n" COUNTER_BEHAVIOUR |