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Diffstat (limited to 'llvm_mode/README.persistent_mode.md')
| -rw-r--r-- | llvm_mode/README.persistent_mode.md | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/llvm_mode/README.persistent_mode.md b/llvm_mode/README.persistent_mode.md index 4f0bcb2e..7d2fd93b 100644 --- a/llvm_mode/README.persistent_mode.md +++ b/llvm_mode/README.persistent_mode.md @@ -115,6 +115,33 @@ will keep working normally when compiled with a tool other than afl-clang-fast. Finally, recompile the program with afl-clang-fast (afl-gcc or afl-clang will *not* generate a deferred-initialization binary) - and you should be all set! +*NOTE:* In the code between `main` and `__AFL_INIT()` should not be any code +run that is instrumented - otherwise a crash might occure. +In case this is useful (e.g. for expensive one time initialization) you can +try to do the following: + +Add after the includes: +``` +extern unsigned char *__afl_area_ptr; +#define MAX_DUMMY_SIZE 256000 + +__attribute__((constructor(1))) void __afl_protect(void) { +#ifdef MAP_FIXED_NOREPLACE + __afl_area_ptr = (unsigned char*) mmap((void *)0x10000, MAX_DUMMY_SIZE, PROT_READ | PROT_WRITE, MAP_FIXED_NOREPLACE | MAP_SHARED | MAP_ANONYMOUS, -1, 0); + if ((uint64_t)__afl_area_ptr == -1) +#endif + __afl_area_ptr = (unsigned char*) mmap((void *)0x10000, MAX_DUMMY_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); + if ((uint64_t)__afl_area_ptr == -1) + __afl_area_ptr = (unsigned char*) mmap(NULL, MAX_DUMMY_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); +} + +``` +and just before `__AFL_INIT()`: +``` + munmap(__afl_area_ptr, MAX_DUMMY_SIZE); + __afl_area_ptr = NULL; +``` + ## 4) persistent mode Some libraries provide APIs that are stateless, or whose state can be reset in |