Add American Fuzzy Lop (afl) to third_party/afl/

third_party/afl/src/qemu_mode/patches/syscall.diff

Index: third_party/afl/src/qemu_mode/patches/syscall.diff
diff --git a/third_party/afl/src/qemu_mode/patches/syscall.diff b/third_party/afl/src/qemu_mode/patches/syscall.diff
new file mode 100644
index 0000000000000000000000000000000000000000..75d39386164eef7501298442c82083849649dc70
--- /dev/null
+++ b/third_party/afl/src/qemu_mode/patches/syscall.diff
@@ -0,0 +1,25 @@
+--- qemu-2.3.0/linux-user/syscall.c.orig	2014-12-09 14:45:43.000000000 +0000
++++ qemu-2.3.0/linux-user/syscall.c	2015-03-27 06:33:00.736000000 +0000
+@@ -227,7 +227,21 @@
+ _syscall3(int,sys_rt_sigqueueinfo,int,pid,int,sig,siginfo_t *,uinfo)
+ _syscall3(int,sys_syslog,int,type,char*,bufp,int,len)
+ #if defined(TARGET_NR_tgkill) && defined(__NR_tgkill)
+-_syscall3(int,sys_tgkill,int,tgid,int,pid,int,sig)
++
++extern unsigned int afl_forksrv_pid;
++
++static int sys_tgkill(int tgid, int pid, int sig) {
++
++  /* Workaround for -lpthread to make abort() work properly, without
++     killing the forkserver due to a prematurely cached PID. */
++
++  if (afl_forksrv_pid && afl_forksrv_pid == pid && sig == SIGABRT)
++    pid = tgid = getpid();
++
++  return syscall(__NR_sys_tgkill, pid, tgid, sig);
++
++}
++
+ #endif
+ #if defined(TARGET_NR_tkill) && defined(__NR_tkill)
+ _syscall2(int,sys_tkill,int,tid,int,sig)