2 files changed, 85 insertions, 2 deletions

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
diff --git a/instrumentation/afl-compiler-rt.o.c b/instrumentation/afl-compiler-rt.o.c
index caa3c3a8..a6982280 100644
--- a/instrumentation/afl-compiler-rt.o.c
+++ b/instrumentation/afl-compiler-rt.o.c
@@ -87,6 +87,10 @@ __attribute__((weak)) void __sanitizer_symbolize_pc(void *, const char *fmt,
 #include <sys/mman.h>
 #include <fcntl.h>
 
+#ifdef AFL_PERSISTENT_RECORD
+  #include "afl-persistent-replay.h"
+#endif
+
 /* Globals needed by the injected instrumentation. The __afl_area_initial region
    is used for instrumentation output before __afl_map_shm() has a chance to
    run. It will end up as .comm, so it shouldn't be too wasteful. */
@@ -1354,6 +1358,10 @@ int __afl_persistent_loop(unsigned int max_cnt) {
   static u8  first_pass = 1;
   static u32 cycle_cnt;
 
+#ifdef AFL_PERSISTENT_RECORD
+  char tcase[PATH_MAX];
+#endif
+
   if (first_pass) {
 
     /* Make sure that every iteration of __AFL_LOOP() starts with a clean slate.
@@ -1365,14 +1373,59 @@ int __afl_persistent_loop(unsigned int max_cnt) {
     __afl_area_ptr[0] = 1;
     memset(__afl_prev_loc, 0, NGRAM_SIZE_MAX * sizeof(PREV_LOC_T));
 
-    cycle_cnt = max_cnt;
     first_pass = 0;
     __afl_selective_coverage_temp = 1;
 
+#ifdef AFL_PERSISTENT_RECORD
+    if (unlikely(is_replay_record)) {
+
+      cycle_cnt = replay_record_cnt;
+      goto persistent_record;
+
+    } else
+
+#endif
+    {
+
+      cycle_cnt = max_cnt;
+
+    }
+
     return 1;
 
   } else if (--cycle_cnt) {
 
+#ifdef AFL_PERSISTENT_RECORD
+    if (unlikely(is_replay_record)) {
+
+    persistent_record:
+
+      snprintf(tcase, PATH_MAX, "%s/%s",
+               replay_record_dir ? replay_record_dir : "./",
+               record_list[replay_record_cnt - cycle_cnt]->d_name);
+
+  #ifdef AFL_PERSISTENT_REPLAY_ARGPARSE
+      if (unlikely(record_arg)) {
+
+        *record_arg = tcase;
+
+      } else
+
+  #endif  // AFL_PERSISTENT_REPLAY_ARGPARSE
+      {
+
+        int fd = open(tcase, O_RDONLY);
+        dup2(fd, 0);
+        close(fd);
+
+      }
+
+      return 1;
+
+    }
+
+#endif
+
     raise(SIGSTOP);
 
     __afl_area_ptr[0] = 1;