diff --git a/regress/rep_movsb.c b/regress/rep_movsb.c
new file mode 100644
index 00000000..ab49175b
--- /dev/null
+++ b/regress/rep_movsb.c
@@ -0,0 +1,183 @@
+/*
+
+rep movsb regression
+
+Copyright(c) 2015 Chris Eagle
+
+This program is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License
+version 2 as published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+
+*/
+
+#define __STDC_FORMAT_MACROS
+#include <inttypes.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#include <unicorn/unicorn.h>
+
+unsigned char PROGRAM[] =
+ "\xbe\x00\x00\x20\x00\xbf\x00\x10\x20\x00\xb9\x14\x00\x00\x00\xf3"
+ "\xa4\xf4";
+// total size: 18 bytes
+
+/*
+bits 32
+
+; assumes code section at 0x100000 r-x
+; assumes data section at 0x200000-0x202000, rw-
+
+mov esi, 0x200000
+mov edi, 0x201000
+mov ecx, 20
+rep movsb
+hlt
+*/
+
+static int log_num = 1;
+
+// callback for tracing instruction
+static void hook_code(uch handle, uint64_t addr, uint32_t size, void *user_data)
+{
+ uint8_t opcode;
+ if (uc_mem_read(handle, addr, &opcode, 1) != UC_ERR_OK) {
+ printf("not ok %d - uc_mem_read fail during hook_code callback, addr: 0x%" PRIx64 "\n", log_num++, addr);
+ _exit(-1);
+ }
+ switch (opcode) {
+ case 0xf4: //hlt
+ printf("# Handling HLT\n");
+ if (uc_emu_stop(handle) != UC_ERR_OK) {
+ printf("not ok %d - uc_emu_stop fail during hook_code callback, addr: 0x%" PRIx64 "\n", log_num++, addr);
+ _exit(-1);
+ }
+ else {
+ printf("ok %d - hlt encountered, uc_emu_stop called\n", log_num++);
+ }
+ break;
+ default: //all others
+ break;
+ }
+}
+
+// callback for tracing memory access (READ or WRITE)
+static void hook_mem_write(uch handle, uc_mem_type type,
+ uint64_t addr, int size, int64_t value, void *user_data)
+{
+ printf("# write to memory at 0x%"PRIx64 ", data size = %u, data value = 0x%"PRIx64 "\n", addr, size, value);
+ if (addr < 0x201000L) {
+ //this is actually a read, we don't write in this range
+ printf("not ok %d - write hook called for read of 0x%"PRIx64 ", data size = %u, data value = 0x%"PRIx64 "\n", log_num++, addr, size, value);
+ }
+ else {
+ printf("ok %d - write hook called for write of 0x%"PRIx64 ", data size = %u, data value = 0x%"PRIx64 "\n", log_num++, addr, size, value);
+ }
+}
+
+int main(int argc, char **argv, char **envp)
+{
+ uch handle, trace1, trace2;
+ uc_err err;
+ uint8_t buf1[100], readbuf[100];
+
+ printf("# rep movsb test\n");
+
+ memset(buf1, 'A', 20);
+
+ // Initialize emulator in X86-32bit mode
+ err = uc_open(UC_ARCH_X86, UC_MODE_32, &handle);
+ if (err) {
+ printf("not ok %d - Failed on uc_open() with error returned: %u\n", log_num++, err);
+ return 1;
+ }
+ else {
+ printf("ok %d - uc_open() success\n", log_num++);
+ }
+
+ uc_mem_map(handle, 0x100000, 0x1000, UC_PROT_READ);
+ uc_mem_map(handle, 0x200000, 0x2000, UC_PROT_READ | UC_PROT_WRITE);
+
+ // fill in the data that we want to copy
+ if (uc_mem_write(handle, 0x200000, (uint8_t*)buf1, 20)) {
+ printf("not ok %d - Failed to write read buffer to memory, quit!\n", log_num++);
+ return 2;
+ }
+ else {
+ printf("ok %d - Read buffer written to memory\n", log_num++);
+ }
+
+ // write machine code to be emulated to memory
+ if (uc_mem_write(handle, 0x100000, PROGRAM, sizeof(PROGRAM))) {
+ printf("not ok %d - Failed to write emulation code to memory, quit!\n", log_num++);
+ return 4;
+ }
+ else {
+ printf("ok %d - Program written to memory\n", log_num++);
+ }
+
+ if (uc_hook_add(handle, &trace2, UC_HOOK_CODE, hook_code, NULL, 1, 0) != UC_ERR_OK) {
+ printf("not ok %d - Failed to install UC_HOOK_CODE handler\n", log_num++);
+ return 5;
+ }
+ else {
+ printf("ok %d - UC_HOOK_CODE installed\n", log_num++);
+ }
+
+ // intercept memory write events only, NOT read events
+ if (uc_hook_add(handle, &trace1, UC_HOOK_MEM_WRITE, hook_mem_write, NULL) != UC_ERR_OK) {
+ printf("not ok %d - Failed to install UC_HOOK_MEM_WRITE handler\n", log_num++);
+ return 6;
+ }
+ else {
+ printf("ok %d - UC_HOOK_MEM_WRITE installed\n", log_num++);
+ }
+
+ // emulate machine code until told to stop by hook_code
+ printf("# BEGIN execution\n");
+ err = uc_emu_start(handle, 0x100000, 0x101000, 0, 0);
+ if (err != UC_ERR_OK) {
+ printf("not ok %d - Failure on uc_emu_start() with error %u:%s\n", log_num++, err, uc_strerror(err));
+ return 8;
+ }
+ else {
+ printf("ok %d - uc_emu_start complete\n", log_num++);
+ }
+ printf("# END execution\n");
+
+ //make sure that data got copied
+ // fill in sections that shouldn't get touched
+ if (uc_mem_read(handle, 0x201000, (uint8_t*)readbuf, 20)) {
+ printf("not ok %d - Failed to read random buffer 1 from memory\n", log_num++);
+ }
+ else {
+ printf("ok %d - Random buffer 1 read from memory\n", log_num++);
+ if (memcmp(buf1, readbuf, 20)) {
+ printf("not ok %d - write buffer contents are incorrect\n", log_num++);
+ }
+ else {
+ printf("ok %d - write buffer contents are correct\n", log_num++);
+ }
+ }
+
+ if (uc_close(&handle) == UC_ERR_OK) {
+ printf("ok %d - uc_close complete\n", log_num++);
+ }
+ else {
+ printf("not ok %d - uc_close complete\n", log_num++);
+ }
+
+ return 0;
+}