Add Android Ashmem stub header to libafl_targets forkserver.c (#1648)

* Add Android Ashmem stub header to libafl_targets forkserver.c

* clang-format

libafl_targets/src/android-ashmem.h

@@ -0,0 +1,81 @@
+/// On Android, this file redirects all (unsupported) shared memory calls out to
+/// Android's Ashmem. Source:
+/// <https://github.com/AFLplusplus/AFLplusplus/blob/stable/include/android-ashmem.h>
+#ifdef __ANDROID__
+  #ifndef _ANDROID_ASHMEM_H
+    #define _ANDROID_ASHMEM_H
+
+    // Not supported on Android.
+    #undef USEMMAP
+
+    #ifndef _GNU_SOURCE
+      #define _GNU_SOURCE
+    #endif
+    #include <sys/syscall.h>
+    #include <unistd.h>
+    #include <fcntl.h>
+    #include <linux/ashmem.h>
+    #include <sys/ioctl.h>
+    #include <sys/mman.h>
+    #include <sys/shm.h>
+    #include <stdio.h>
+    #define ASHMEM_DEVICE "/dev/ashmem"
+
+int shmdt(const void *address) {
+    #if defined(SYS_shmdt)
+  return syscall(SYS_shmdt, address);
+    #else
+  return syscall(SYS_ipc, SHMDT, 0, 0, 0, address, 0);
+    #endif
+}
+
+int shmctl(int __shmid, int __cmd, struct shmid_ds *__buf) {
+  int ret = 0;
+  if (__cmd == IPC_RMID) {
+    int               length = ioctl(__shmid, ASHMEM_GET_SIZE, NULL);
+    struct ashmem_pin pin = {0, length};
+    ret = ioctl(__shmid, ASHMEM_UNPIN, &pin);
+    close(__shmid);
+  }
+
+  return ret;
+}
+
+int shmget(key_t __key, size_t __size, int __shmflg) {
+  (void)__shmflg;
+  int  fd, ret;
+  char ourkey[11];
+
+  fd = open(ASHMEM_DEVICE, O_RDWR);
+  if (fd < 0) return fd;
+
+  sprintf(ourkey, "%d", __key);
+  ret = ioctl(fd, ASHMEM_SET_NAME, ourkey);
+  if (ret < 0) goto error;
+
+  ret = ioctl(fd, ASHMEM_SET_SIZE, __size);
+  if (ret < 0) goto error;
+
+  return fd;
+
+error:
+  close(fd);
+  return ret;
+}
+
+void *shmat(int __shmid, const void *__shmaddr, int __shmflg) {
+  (void)__shmflg;
+  int   size;
+  void *ptr;
+
+  size = ioctl(__shmid, ASHMEM_GET_SIZE, NULL);
+  if (size < 0) { return NULL; }
+
+  ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, __shmid, 0);
+  if (ptr == MAP_FAILED) { return NULL; }
+
+  return ptr;
+}
+
+  #endif /* !_ANDROID_ASHMEM_H */
+#endif   /* !__ANDROID__ */

libafl_targets/src/forkserver.c

@@ -1,5 +1,6 @@
 #include "common.h"
 
+#include "android-ashmem.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>