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#include <errno.h>
#include <sys/shm.h>
#include <sys/mman.h>
#include "frida-gumjs.h"
#include "debug.h"
#include "intercept.h"
#include "prefetch.h"
#include "stalker.h"
#define TRUST 0
#define PREFETCH_SIZE 65536
#define PREFETCH_ENTRIES ((PREFETCH_SIZE - sizeof(size_t)) / sizeof(void *))
typedef struct {
size_t count;
void * entry[PREFETCH_ENTRIES];
} prefetch_data_t;
gboolean prefetch_enable = TRUE;
static prefetch_data_t *prefetch_data = NULL;
static int prefetch_shm_id = -1;
/*
* We do this from the transformer since we need one anyway for coverage, this
* saves the need to use an event sink.
*/
void prefetch_write(void *addr) {
/* Bail if we aren't initialized */
if (prefetch_data == NULL) return;
/*
* Our shared memory IPC is large enough for about 1000 entries, we can fine
* tune this if we need to. But if we have more new blocks that this in a
* single run then we ignore them and we'll pick them up next time.
*/
if (prefetch_data->count >= PREFETCH_ENTRIES) return;
/*
* Write the block address to the SHM IPC and increment the number of entries.
*/
prefetch_data->entry[prefetch_data->count] = addr;
prefetch_data->count++;
}
/*
* Read the IPC region one block at the time and prefetch it
*/
void prefetch_read(void) {
GumStalker *stalker = stalker_get();
if (prefetch_data == NULL) return;
for (size_t i = 0; i < prefetch_data->count; i++) {
void *addr = prefetch_data->entry[i];
gum_stalker_prefetch(stalker, addr, 1);
}
/*
* Reset the entry count to indicate we have finished with it and it can be
* refilled by the child.
*/
prefetch_data->count = 0;
}
void prefetch_config(void) {
prefetch_enable = (getenv("AFL_FRIDA_INST_NO_PREFETCH") == NULL);
}
static int prefetch_on_fork(void) {
prefetch_read();
return fork();
}
static void prefetch_hook_fork(void) {
void *fork_addr =
GSIZE_TO_POINTER(gum_module_find_export_by_name(NULL, "fork"));
intercept_hook(fork_addr, prefetch_on_fork, NULL);
}
void prefetch_init(void) {
g_assert_cmpint(sizeof(prefetch_data_t), ==, PREFETCH_SIZE);
OKF("Instrumentation - prefetch [%c]", prefetch_enable ? 'X' : ' ');
if (!prefetch_enable) { return; }
/*
* Make our shared memory, we can attach before we fork, just like AFL does
* with the coverage bitmap region and fork will take care of ensuring both
* the parent and child see the same consistent memory region.
*/
prefetch_shm_id =
shmget(IPC_PRIVATE, sizeof(prefetch_data_t), IPC_CREAT | IPC_EXCL | 0600);
if (prefetch_shm_id < 0) {
FATAL("prefetch_shm_id < 0 - errno: %d\n", errno);
}
prefetch_data = shmat(prefetch_shm_id, NULL, 0);
g_assert(prefetch_data != MAP_FAILED);
/*
* Configure the shared memory region to be removed once the process dies.
*/
if (shmctl(prefetch_shm_id, IPC_RMID, NULL) < 0) {
FATAL("shmctl (IPC_RMID) < 0 - errno: %d\n", errno);
}
/* Clear it, not sure it's necessary, just seems like good practice */
memset(prefetch_data, '\0', sizeof(prefetch_data_t));
prefetch_hook_fork();
}
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