On 25/07/19 05:23, Oleinik, Alexander wrote: > Intercept coverage buffer registration calls and use this information to > copy them to shared memory, if using fork() to avoid resetting device > state. > > Signed-off-by: Alexander Oleinik <alx...@bu.edu> > --- > tests/fuzz/fuzzer_hooks.c | 106 ++++++++++++++++++++++++++++++++++++++ > tests/fuzz/fuzzer_hooks.h | 9 ++++ > 2 files changed, 115 insertions(+) > create mode 100644 tests/fuzz/fuzzer_hooks.c > create mode 100644 tests/fuzz/fuzzer_hooks.h > > diff --git a/tests/fuzz/fuzzer_hooks.c b/tests/fuzz/fuzzer_hooks.c > new file mode 100644 > index 0000000000..5a0bbec413 > --- /dev/null > +++ b/tests/fuzz/fuzzer_hooks.c > @@ -0,0 +1,106 @@ > +#include "qemu/osdep.h" > +#include "qemu/units.h" > +#include "qapi/error.h" > +#include "qemu-common.h" > +#include "fuzzer_hooks.h" > + > +#include <dlfcn.h> > +#include <elf.h> > + > + > +extern void* _ZN6fuzzer3TPCE;
Would it make sense to make this a C++ source, so that you can avoid using the mangled names (in this case, "namespace fuzzer { extern void *TPC; }" and then using fuzzer::TPC)? Even if it's just a single symbol. > +// The libfuzzer handlers > +void __real___sanitizer_cov_8bit_counters_init(uint8_t*, uint8_t*); > +void __real___sanitizer_cov_trace_pc_guard_init(uint8_t*, uint8_t*); > + > +void __wrap___sanitizer_cov_8bit_counters_init(uint8_t *Start, uint8_t > *Stop); > +void __wrap___sanitizer_cov_trace_pc_guard_init(uint8_t *Start, uint8_t > *Stop); > + > + > +void* counter_shm; > + > +typedef struct CoverageRegion { > + uint8_t* start; > + size_t length; > + bool store; /* Set this if it needs to be copied to the forked process */ > +} CoverageRegion; > + > +CoverageRegion regions[10]; > +int region_index = 0; > + > +void __wrap___sanitizer_cov_8bit_counters_init(uint8_t *Start, uint8_t *Stop) > +{ > + regions[region_index].start = Start; > + regions[region_index].length = Stop-Start; > + regions[region_index].store = true; > + region_index++; > + __real___sanitizer_cov_8bit_counters_init(Start, Stop); > +} > + > +void __wrap___sanitizer_cov_trace_pc_guard_init(uint8_t *Start, uint8_t > *Stop) > +{ > + regions[region_index].start = Start; > + regions[region_index++].length = Stop-Start; > + regions[region_index].store = true; > + region_index++; > + __real___sanitizer_cov_trace_pc_guard_init(Start, Stop); > +} > + > +static void add_tpc_region(void) > +{ > + /* Got symbol and length from readelf. Horrible way to do this! */ > + regions[region_index].start = (uint8_t*)(&_ZN6fuzzer3TPCE); > + regions[region_index].length = 0x443c00; > + regions[region_index].store = true; > + region_index++; > +} > + > +void counter_shm_init(void) > +{ > + /* > + * Add the internal libfuzzer object that gets modified by cmp, etc > + * callbacks > + */ > + add_tpc_region(); > + > + size_t length = 0; > + for(int i=0; i<region_index; i++){ > + printf("%d %lx\n", i, length); > + length += regions[i].length; > + } > + > + /* > + * Map some shared memory. When we use a fork-server we can copy the > + * libfuzzer-related counters > + * */ > + counter_shm = mmap(NULL, length, PROT_READ | PROT_WRITE, > + MAP_SHARED | MAP_ANONYMOUS, -1, 0); > + if(counter_shm == MAP_FAILED) { > + printf("mmap() failed\n"); > + do { perror("error:"); exit(EXIT_FAILURE); } while (0); > + exit(-1); > + } > +} > + > +void counter_shm_store(void) > +{ > + size_t offset = 0; > + for(int i=0; i<region_index; i++) { > + if(regions[i].store) { > + memcpy(counter_shm + offset, regions[i].start, > regions[i].length); > + } > + offset+=regions[i].length; > + } > +} > + > +void counter_shm_load(void) > +{ > + size_t offset = 0; > + for(int i=0; i<region_index; i++) { > + if(regions[i].store) { > + memcpy(regions[i].start, counter_shm + offset, > regions[i].length); > + } > + offset+=regions[i].length; > + } > +} > + > diff --git a/tests/fuzz/fuzzer_hooks.h b/tests/fuzz/fuzzer_hooks.h > new file mode 100644 > index 0000000000..90dca254d4 > --- /dev/null > +++ b/tests/fuzz/fuzzer_hooks.h > @@ -0,0 +1,9 @@ > +#ifndef FUZZER_HOOKS_H > +#define FUZZER_HOOKS_H > + > +void counter_shm_init(void); > +void counter_shm_store(void); > +void counter_shm_load(void); > + > +#endif > + >