Support MIPS64 - write correct PC register width on uc_emu_start (#2111)

* Support mips64 - write correct pc register width on uc_emu_start

* Convert to UC_MODE_MIPS64

* Correctly select MIPS64 CPU model

* Simple 64-bit test - check it doesn't crash

* lint

* Comment

* Comment

* Add offset when indexing cpu model, makes tests work on older python

* Move test

* add PC check to test

* Fix test - add python version check

* Use RegressTest method for assert

tests/regress/mips64.py

@@ -0,0 +1,39 @@
+import sys
+import unittest
+import regress
+from unicorn import *
+from unicorn.mips_const import *
+
+
+class Mips64(regress.RegressTest):
+
+    @unittest.skipIf(sys.version_info < (3, 7), reason="requires python3.7 or higher")
+    def runTest(self):
+        # Two instructions:
+        #   daddu  $gp, $gp, $ra    # a 64-bit instruction. This is important - it ensures the selected CPU model is 64-bit, otherwise it would crash
+        #   move   $t1, $v0
+
+        code = b"\x03\x9f\xe0\x2d" + b"\x00\x40\x48\x25"
+
+        uc = Uc(UC_ARCH_MIPS, UC_MODE_MIPS64 + UC_MODE_BIG_ENDIAN)
+        # For MIPS64 to be able to reference addresses >= 0x80000000, you need to enable the virtual TLB
+        # See https://github.com/unicorn-engine/unicorn/pull/2111 for more details
+        uc.ctl_set_tlb_mode(UC_TLB_VIRTUAL)
+
+        ADDRESS = 0x0120003000
+
+        uc.reg_write(UC_MIPS_REG_PC, ADDRESS)
+        uc.reg_write(UC_MIPS_REG_GP, 0x123)
+        uc.reg_write(UC_MIPS_REG_RA, 0x456)
+
+        uc.mem_map(ADDRESS, 4 * 1024)
+        uc.mem_write(ADDRESS, code)
+
+        # This will raise an exception if MIPS64 fails
+        uc.emu_start(ADDRESS, 0, count=2)
+
+        self.assertEqual(uc.reg_read(UC_MIPS_REG_PC),0x0120003000 + 8)
+
+
+if __name__ == '__main__':
+    regress.main()