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diff --git a/instrumentation/README.persistent_mode.md b/instrumentation/README.persistent_mode.md index 14e59f4a..8e4f6ae4 100644 --- a/instrumentation/README.persistent_mode.md +++ b/instrumentation/README.persistent_mode.md @@ -195,4 +195,34 @@ Then as first line after the `__AFL_LOOP` while loop: int len = __AFL_FUZZ_TESTCASE_LEN; ``` -And that is all! \ No newline at end of file +And that is all! + +## 6) Persistent record, and replay + +If your software under test requires keeping a state between persistent loop iterations (i.e., a stateful network stack), you can use the `AFL_PERSISTENT_RECORD` variable as described in the [environment variables documentation](../docs/env_variables.md). + +When `AFL_PERSISTENT_RECORD` is enabled, replay functionality is also included in the compiler-rt library. To replay a specific record, assign the record number to the AFL_PERSISTENT_REPLAY environment variable (i.e., `RECORD:XXXXX`` -> `AFL_PERSISTENT_REPLAY=XXXXX`), and run the test binary as you would normally do. +The directory where the record files live can be specified via the `AFL_PERSISTENT_DIR` environment varilable, otherwise by default it will be considered the current directory (`./`). + +If your harness reads the input files from arguments using the special `@@` argument you will need to include support by enabling `AFL_PERSISTENT_ARGPARSE` in `config.h`. + +In order to offer transparent support to harnesses using the `@@` command line argument, arguments are parsed by the `__afl_record_replay_init` init function. Since not all systems support passing arguments to initializers, this functionality is disabled by default, it's recommendable to use the `__AFL_FUZZ_TESTCASE_BUF/__AFL_FUZZ_TESTCASE_LEN` shared memory mechanism instead. + +## 7) Drop-in persistent loop replay replacement + +To use the replay functionality without having to use `afl-cc`, include the [include/record_compat.h](../include/afl-record_compat.h) header file. Together with the [include/afl-persistent-replay.h](../include/afl-persistent-replay.h) header included in it, `afl-record-compat.h` provides a drop-in replacement for the persistent loop mechanism. + +```c +#ifndef __AFL_FUZZ_TESTCASE_LEN + // #define AFL_PERSISTENT_REPLAY_ARGPARSE + #include "afl-record-compat.h" +#endif + +__AFL_FUZZ_INIT(); +``` + +A simple example is provided in [persistent_demo_replay.c](../utils/replay_record/persistent_demo_replay.c). + +Be aware that the [afl-record-compat.h](../include/afl-record-compat.h) header should only be included in a single compilation unit, or you will end up with clobbered functions and variables. + +If you need a cleaner solution, you'll have to move the functions and variables defined in [include/record_compat.h](../include/afl-record-compat.h) and [include/afl-persistent-replay.h](../include/afl-persistent-replay.h) in a C file, and add the relevant declarations to a header file. After including the new header file, the compilation unit resulting from compiling the C file can then be linked with your program. \ No newline at end of file |