fxsave / fxsave64 should store the floating point instruction pointer (fpip) (#1467)

* fxsave / fxsave64 should store the floating point instruction pointer (fpip)
- fxsave / fxsave64 happen to be used as GetPC code in exploits

* unit tests for the storage of FPIP in fxsave (x86) and fxsave64 (x64)

qemu/target-i386/fpu_helper.c

@@ -1127,12 +1127,12 @@ void helper_fxsave(CPUX86State *env, target_ulong ptr, int data64)
     cpu_stw_data(env, ptr + 4, fptag ^ 0xff);
 #ifdef TARGET_X86_64
     if (data64) {
-        cpu_stq_data(env, ptr + 0x08, 0); /* rip */
+        cpu_stq_data(env, ptr + 0x08, env->fpip); /* rip */
         cpu_stq_data(env, ptr + 0x10, 0); /* rdp */
     } else
 #endif
     {
-        cpu_stl_data(env, ptr + 0x08, 0); /* eip */
+        cpu_stl_data(env, ptr + 0x08, (uint32_t) env->fpip); /* eip */
         cpu_stl_data(env, ptr + 0x0c, 0); /* sel  */
         cpu_stl_data(env, ptr + 0x10, 0); /* dp */
         cpu_stl_data(env, ptr + 0x14, 0); /* sel  */