changes to PC from trace callbacks don't stick

regress/callback-pc.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+
+# reg_write() can't modify PC from within trace callbacks
+
+from __future__ import print_function
+from unicorn import *
+from unicorn.arm_const import *
+
+BASE_ADDRESS = 0x10000000
+
+# sub sp, #0xc
+THUMB_CODE = "\x83\xb0" * 5 
+
+# callback for tracing instructions
+def hook_code(uc, address, size, user_data):
+    print(">>> Tracing instruction at 0x%x, instruction size = %u" % (address, size))
+    mu = user_data
+    print(">>> Setting PC to 0xffffffff")
+    mu.reg_write(ARM_REG_PC, 0xffffffff)
+
+# callback for tracing basic blocks
+def hook_block(uc, address, size, user_data):
+    print(">>> Tracing basic block at 0x%x, block size = 0x%x" %(address, size))
+    mu = user_data
+    print(">>> Setting PC to 0xffffffff")
+    mu.reg_write(ARM_REG_PC, 0xffffffff)
+
+# set up emulation
+def instruction_trace_test():
+    try:
+        # initialize emulator in ARM's Thumb mode
+        mu = Uc(UC_ARCH_ARM, UC_MODE_THUMB)
+
+        # map some memory
+        mu.mem_map(BASE_ADDRESS, 2 * 1024 * 1024)
+
+        # write machine code to be emulated to memory
+        mu.mem_write(BASE_ADDRESS, THUMB_CODE)
+
+        # setup stack
+        mu.reg_write(ARM_REG_SP, BASE_ADDRESS + 2 * 1024 * 1024)
+
+        # tracing all instructions with customized callback
+        mu.hook_add(UC_HOOK_CODE, hook_code, user_data=mu)
+
+        # tracing all basic blocks with customized callback
+        mu.hook_add(UC_HOOK_BLOCK, hook_block, user_data=mu)
+
+        # emulate machine code in infinite time
+        mu.emu_start(BASE_ADDRESS, BASE_ADDRESS + len(THUMB_CODE))
+
+    except UcError as e:
+        print("ERROR: %s" % e)
+
+if __name__ == '__main__':
+    instruction_trace_test()