debug/gdbserver.py

   1 #!/usr/bin/python
   2
   3 import os
   4 import sys
   5 import argparse
   6 import testlib
   7 import unittest
   8 import tempfile
   9 import time
  10 import random
  11 import binascii
  12
  13
  14 MSTATUS_UIE = 0x00000001
  15 MSTATUS_SIE = 0x00000002
  16 MSTATUS_HIE = 0x00000004
  17 MSTATUS_MIE = 0x00000008
  18 MSTATUS_UPIE = 0x00000010
  19 MSTATUS_SPIE = 0x00000020
  20 MSTATUS_HPIE = 0x00000040
  21 MSTATUS_MPIE = 0x00000080
  22 MSTATUS_SPP = 0x00000100
  23 MSTATUS_HPP = 0x00000600
  24 MSTATUS_MPP = 0x00001800
  25 MSTATUS_FS = 0x00006000
  26 MSTATUS_XS = 0x00018000
  27 MSTATUS_MPRV = 0x00020000
  28 MSTATUS_PUM = 0x00040000
  29 MSTATUS_MXR = 0x00080000
  30 MSTATUS_VM = 0x1F000000
  31 MSTATUS32_SD = 0x80000000
  32 MSTATUS64_SD = 0x8000000000000000
  33
  34 def gdb(
  35         target=None,
  36         port=None,
  37         binary=None
  38         ):
  39
  40     gdb = None
  41     if parsed.gdb:
  42         gdb = testlib.Gdb(parsed.gdb)
  43     else:
  44         gdb = testlib.Gdb()
  45
  46     if binary:
  47         gdb.command("file %s" % binary)
  48     if target:
  49         gdb.command("set arch riscv:rv%d" % target.xlen)
  50         gdb.command("set remotetimeout %d" % target.timeout_sec)
  51     if port:
  52         gdb.command("target extended-remote localhost:%d" % port)
  53
  54     return gdb
  55
  56
  57 def ihex_line(address, record_type, data):
  58     assert len(data) < 128
  59     line = ":%02X%04X%02X" % (len(data), address, record_type)
  60     check = len(data)
  61     check += address % 256
  62     check += address >> 8
  63     check += record_type
  64     for char in data:
  65         value = ord(char)
  66         check += value
  67         line += "%02X" % value
  68     line += "%02X\n" % ((256-check)%256)
  69     return line
  70
  71 def ihex_parse(line):
  72     assert line.startswith(":")
  73     line = line[1:]
  74     data_len = int(line[:2], 16)
  75     address = int(line[2:6], 16)
  76     record_type = int(line[6:8], 16)
  77     data = ""
  78     for i in range(data_len):
  79         data += "%c" % int(line[8+2*i:10+2*i], 16)
  80     return record_type, address, data
  81
  82 def readable_binary_string(s):
  83     return "".join("%02x" % ord(c) for c in s)
  84
  85 class DeleteServer(unittest.TestCase):
  86     def tearDown(self):
  87         del self.server
  88
  89 class SimpleRegisterTest(DeleteServer):
  90     def setUp(self):
  91         self.server = target.server()
  92         self.gdb = gdb(target, self.server.port)
  93
  94         # 0x13 is nop
  95         self.gdb.command("p *((int*) 0x%x)=0x13" % target.ram)
  96         self.gdb.command("p *((int*) 0x%x)=0x13" % (target.ram + 4))
  97         self.gdb.command("p *((int*) 0x%x)=0x13" % (target.ram + 8))
  98         self.gdb.p("$pc=0x%x" % target.ram)
  99
 100     def check_reg(self, name):
 101         a = random.randrange(1<<target.xlen)
 102         b = random.randrange(1<<target.xlen)
 103         self.gdb.p("$%s=0x%x" % (name, a))
 104         self.gdb.stepi()
 105         self.assertEqual(self.gdb.p("$%s" % name), a)
 106         self.gdb.p("$%s=0x%x" % (name, b))
 107         self.gdb.stepi()
 108         self.assertEqual(self.gdb.p("$%s" % name), b)
 109
 110     def test_s0(self):
 111         # S0 is saved/restored in DSCRATCH
 112         self.check_reg("s0")
 113
 114     def test_s1(self):
 115         # S1 is saved/restored in Debug RAM
 116         self.check_reg("s1")
 117
 118     def test_t0(self):
 119         # T0 is not saved/restored at all
 120         self.check_reg("t2")
 121
 122     def test_t2(self):
 123         # T2 is not saved/restored at all
 124         self.check_reg("t2")
 125
 126 class SimpleMemoryTest(DeleteServer):
 127     def setUp(self):
 128         self.server = target.server()
 129         self.gdb = gdb(target, self.server.port)
 130
 131     def access_test(self, size, data_type):
 132         self.assertEqual(self.gdb.p("sizeof(%s)" % data_type),
 133                 size)
 134         a = 0x86753095555aaaa & ((1<<(size*8))-1)
 135         b = 0xdeadbeef12345678 & ((1<<(size*8))-1)
 136         self.gdb.p("*((%s*)0x%x) = 0x%x" % (data_type, target.ram, a))
 137         self.gdb.p("*((%s*)0x%x) = 0x%x" % (data_type, target.ram + size, b))
 138         self.assertEqual(self.gdb.p("*((%s*)0x%x)" % (data_type, target.ram)), a)
 139         self.assertEqual(self.gdb.p("*((%s*)0x%x)" % (data_type, target.ram + size)), b)
 140
 141     def test_8(self):
 142         self.access_test(1, 'char')
 143
 144     def test_16(self):
 145         self.access_test(2, 'short')
 146
 147     def test_32(self):
 148         self.access_test(4, 'int')
 149
 150     def test_64(self):
 151         self.access_test(8, 'long long')
 152
 153     def test_block(self):
 154         length = 1024
 155         line_length = 16
 156         a = tempfile.NamedTemporaryFile(suffix=".ihex")
 157         data = ""
 158         for i in range(length / line_length):
 159             line_data = "".join(["%c" % random.randrange(256) for _ in range(line_length)])
 160             data += line_data
 161             a.write(ihex_line(i * line_length, 0, line_data))
 162         a.flush()
 163
 164         self.gdb.command("restore %s 0x%x" % (a.name, target.ram))
 165         for offset in range(0, length, 19*4) + [length-4]:
 166             value = self.gdb.p("*((int*)0x%x)" % (target.ram + offset))
 167             written = ord(data[offset]) | \
 168                     (ord(data[offset+1]) << 8) | \
 169                     (ord(data[offset+2]) << 16) | \
 170                     (ord(data[offset+3]) << 24)
 171             self.assertEqual(value, written)
 172
 173         b = tempfile.NamedTemporaryFile(suffix=".ihex")
 174         self.gdb.command("dump ihex memory %s 0x%x 0x%x" % (b.name, target.ram,
 175             target.ram + length))
 176         for line in b:
 177             record_type, address, line_data = ihex_parse(line)
 178             if (record_type == 0):
 179                 self.assertEqual(readable_binary_string(line_data),
 180                         readable_binary_string(data[address:address+len(line_data)]))
 181
 182 class InstantHaltTest(DeleteServer):
 183     def setUp(self):
 184         self.server = target.server()
 185         self.gdb = gdb(target, self.server.port)
 186
 187     def test_instant_halt(self):
 188         self.assertEqual(target.reset_vector, self.gdb.p("$pc"))
 189         # mcycle and minstret have no defined reset value.
 190         mstatus = self.gdb.p("$mstatus")
 191         self.assertEqual(mstatus & (MSTATUS_MIE | MSTATUS_MPRV |
 192             MSTATUS_VM), 0)
 193
 194     def test_change_pc(self):
 195         """Change the PC right as we come out of reset."""
 196         # 0x13 is nop
 197         self.gdb.command("p *((int*) 0x%x)=0x13" % target.ram)
 198         self.gdb.command("p *((int*) 0x%x)=0x13" % (target.ram + 4))
 199         self.gdb.command("p *((int*) 0x%x)=0x13" % (target.ram + 8))
 200         self.gdb.p("$pc=0x%x" % target.ram)
 201         self.gdb.stepi()
 202         self.assertEqual((target.ram + 4), self.gdb.p("$pc"))
 203         self.gdb.stepi()
 204         self.assertEqual((target.ram + 8), self.gdb.p("$pc"))
 205
 206 class DebugTest(DeleteServer):
 207     def setUp(self):
 208         # Include malloc so that gdb can make function calls. I suspect this
 209         # malloc will silently blow through the memory set aside for it, so be
 210         # careful.
 211         self.binary = target.compile("programs/debug.c", "programs/checksum.c",
 212                 "programs/tiny-malloc.c", "-DDEFINE_MALLOC", "-DDEFINE_FREE")
 213         self.server = target.server()
 214         self.gdb = gdb(target, self.server.port, self.binary)
 215         self.gdb.load()
 216         self.gdb.b("_exit")
 217
 218     def exit(self, expected_result = 0xc86455d4):
 219         output = self.gdb.c()
 220         self.assertIn("Breakpoint", output)
 221         self.assertIn("_exit", output)
 222         self.assertEqual(self.gdb.p("status"), expected_result)
 223
 224     def test_function_call(self):
 225         self.gdb.b("main:start")
 226         self.gdb.c()
 227         self.assertEqual(self.gdb.p('fib(6)'), 8)
 228         self.assertEqual(self.gdb.p('fib(7)'), 13)
 229         self.exit()
 230
 231     def test_change_string(self):
 232         text = "This little piggy went to the market."
 233         self.gdb.b("main:start")
 234         self.gdb.c()
 235         self.gdb.p('fox = "%s"' % text)
 236         self.exit(0x43b497b8)
 237
 238     def test_turbostep(self):
 239         """Single step a bunch of times."""
 240         self.gdb.b("main:start")
 241         self.gdb.c()
 242         self.gdb.command("p i=0");
 243         last_pc = None
 244         advances = 0
 245         jumps = 0
 246         for _ in range(100):
 247             self.gdb.stepi()
 248             pc = self.gdb.p("$pc")
 249             self.assertNotEqual(last_pc, pc)
 250             if (last_pc and pc > last_pc and pc - last_pc <= 4):
 251                 advances += 1
 252             else:
 253                 jumps += 1
 254             last_pc = pc
 255         # Some basic sanity that we're not running between breakpoints or
 256         # something.
 257         self.assertGreater(jumps, 10)
 258         self.assertGreater(advances, 50)
 259
 260     def test_exit(self):
 261         self.exit()
 262
 263     def test_symbols(self):
 264         self.gdb.b("main")
 265         self.gdb.b("rot13")
 266         output = self.gdb.c()
 267         self.assertIn(", main ", output)
 268         output = self.gdb.c()
 269         self.assertIn(", rot13 ", output)
 270
 271     def test_breakpoint(self):
 272         self.gdb.b("rot13")
 273         # The breakpoint should be hit exactly 2 times.
 274         for i in range(2):
 275             output = self.gdb.c()
 276             self.gdb.p("$pc")
 277             self.assertIn("Breakpoint ", output)
 278             #TODO self.assertIn("rot13 ", output)
 279         self.exit()
 280
 281     def test_hwbp_1(self):
 282         if target.instruction_hardware_breakpoint_count < 1:
 283             return
 284
 285         self.gdb.hbreak("rot13")
 286         # The breakpoint should be hit exactly 2 times.
 287         for i in range(2):
 288             output = self.gdb.c()
 289             self.gdb.p("$pc")
 290             self.assertIn("Breakpoint ", output)
 291             #TODO self.assertIn("rot13 ", output)
 292         self.exit()
 293
 294     def test_hwbp_2(self):
 295         if target.instruction_hardware_breakpoint_count < 2:
 296             return
 297
 298         self.gdb.hbreak("main")
 299         self.gdb.hbreak("rot13")
 300         # We should hit 3 breakpoints.
 301         for i in range(3):
 302             output = self.gdb.c()
 303             self.gdb.p("$pc")
 304             self.assertIn("Breakpoint ", output)
 305             #TODO self.assertIn("rot13 ", output)
 306         self.exit()
 307
 308     def test_too_many_hwbp(self):
 309         for i in range(30):
 310             self.gdb.hbreak("*rot13 + %d" % (i * 4))
 311
 312         output = self.gdb.c()
 313         self.assertIn("Cannot insert hardware breakpoint", output)
 314         # Clean up, otherwise the hardware breakpoints stay set and future
 315         # tests may fail.
 316         self.gdb.command("D")
 317
 318     def test_registers(self):
 319         # Get to a point in the code where some registers have actually been
 320         # used.
 321         self.gdb.b("rot13")
 322         self.gdb.c()
 323         self.gdb.c()
 324         # Try both forms to test gdb.
 325         for cmd in ("info all-registers", "info registers all"):
 326             output = self.gdb.command(cmd)
 327             self.assertNotIn("Could not", output)
 328             for reg in ('zero', 'ra', 'sp', 'gp', 'tp'):
 329                 self.assertIn(reg, output)
 330
 331         #TODO
 332         # mcpuid is one of the few registers that should have the high bit set
 333         # (for rv64).
 334         # Leave this commented out until gdb and spike agree on the encoding of
 335         # mcpuid (which is going to be renamed to misa in any case).
 336         #self.assertRegexpMatches(output, ".*mcpuid *0x80")
 337
 338         #TODO:
 339         # The instret register should always be changing.
 340         #last_instret = None
 341         #for _ in range(5):
 342         #    instret = self.gdb.p("$instret")
 343         #    self.assertNotEqual(instret, last_instret)
 344         #    last_instret = instret
 345         #    self.gdb.stepi()
 346
 347         self.exit()
 348
 349     def test_interrupt(self):
 350         """Sending gdb ^C while the program is running should cause it to halt."""
 351         self.gdb.b("main:start")
 352         self.gdb.c()
 353         self.gdb.p("i=123");
 354         self.gdb.c(wait=False)
 355         time.sleep(0.1)
 356         output = self.gdb.interrupt()
 357         #TODO: assert "main" in output
 358         self.assertGreater(self.gdb.p("j"), 10)
 359         self.gdb.p("i=0");
 360         self.exit()
 361
 362 class StepTest(DeleteServer):
 363     def setUp(self):
 364         self.binary = target.compile("programs/step.S")
 365         self.server = target.server()
 366         self.gdb = gdb(target, self.server.port, self.binary)
 367         self.gdb.load()
 368         self.gdb.b("main")
 369         self.gdb.c()
 370
 371     def test_step(self):
 372         main = self.gdb.p("$pc")
 373         for expected in (4, 8, 0xc, 0x10, 0x18, 0x1c, 0x28, 0x20, 0x2c, 0x2c):
 374             self.gdb.stepi()
 375             pc = self.gdb.p("$pc")
 376             self.assertEqual("%x" % pc, "%x" % (expected + main))
 377
 378 class RegsTest(DeleteServer):
 379     def setUp(self):
 380         self.binary = target.compile("programs/regs.S")
 381         self.server = target.server()
 382         self.gdb = gdb(target, self.server.port, self.binary)
 383         self.gdb.load()
 384         self.gdb.b("main")
 385         self.gdb.b("handle_trap")
 386         self.gdb.c()
 387
 388     def test_write_gprs(self):
 389         regs = [("x%d" % n) for n in range(2, 32)]
 390
 391         self.gdb.p("$pc=write_regs")
 392         for i, r in enumerate(regs):
 393             self.gdb.p("$%s=%d" % (r, (0xdeadbeef<<i)+17))
 394         self.gdb.p("$x1=data")
 395         self.gdb.command("b all_done")
 396         output = self.gdb.c()
 397         self.assertIn("Breakpoint ", output)
 398
 399         # Just to get this data in the log.
 400         self.gdb.command("x/30gx data")
 401         self.gdb.command("info registers")
 402         for n in range(len(regs)):
 403             self.assertEqual(self.gdb.x("data+%d" % (8*n), 'g'),
 404                     ((0xdeadbeef<<n)+17) & ((1<<target.xlen)-1))
 405
 406     def test_write_csrs(self):
 407         # As much a test of gdb as of the simulator.
 408         self.gdb.p("$mscratch=0")
 409         self.gdb.stepi()
 410         self.assertEqual(self.gdb.p("$mscratch"), 0)
 411         self.gdb.p("$mscratch=123")
 412         self.gdb.stepi()
 413         self.assertEqual(self.gdb.p("$mscratch"), 123)
 414
 415         self.gdb.command("p $pc=write_regs")
 416         self.gdb.command("p $a0=data")
 417         self.gdb.command("b all_done")
 418         self.gdb.command("c")
 419
 420         self.assertEqual(123, self.gdb.p("$mscratch"))
 421         self.assertEqual(123, self.gdb.p("$x1"))
 422         self.assertEqual(123, self.gdb.p("$csr832"))
 423
 424 class DownloadTest(DeleteServer):
 425     def setUp(self):
 426         length = min(2**20, target.ram_size - 2048)
 427         download_c = tempfile.NamedTemporaryFile(prefix="download_", suffix=".c")
 428         download_c.write("#include <stdint.h>\n")
 429         download_c.write("unsigned int crc32a(uint8_t *message, unsigned int size);\n")
 430         download_c.write("uint32_t length = %d;\n" % length)
 431         download_c.write("uint8_t d[%d] = {\n" % length)
 432         self.crc = 0
 433         for i in range(length / 16):
 434             download_c.write("  /* 0x%04x */ " % (i * 16));
 435             for _ in range(16):
 436                 value = random.randrange(1<<8)
 437                 download_c.write("%d, " % value)
 438                 self.crc = binascii.crc32("%c" % value, self.crc)
 439             download_c.write("\n");
 440         download_c.write("};\n");
 441         download_c.write("uint8_t *data = &d[0];\n");
 442         download_c.write("uint32_t main() { return crc32a(data, length); }\n")
 443         download_c.flush()
 444
 445         if self.crc < 0:
 446             self.crc += 2**32
 447
 448         self.binary = target.compile(download_c.name, "programs/checksum.c")
 449         self.server = target.server()
 450         self.gdb = gdb(target, self.server.port, self.binary)
 451
 452     def test_download(self):
 453         output = self.gdb.load()
 454         self.gdb.command("b _exit")
 455         self.gdb.c()
 456         self.assertEqual(self.gdb.p("status"), self.crc)
 457
 458 class MprvTest(DeleteServer):
 459     def setUp(self):
 460         self.binary = target.compile("programs/mprv.S")
 461         self.server = target.server()
 462         self.gdb = gdb(target, self.server.port, self.binary)
 463         self.gdb.load()
 464
 465     def test_mprv(self):
 466         """Test that the debugger can access memory when MPRV is set."""
 467         self.gdb.c(wait=False)
 468         time.sleep(0.5)
 469         self.gdb.interrupt()
 470         output = self.gdb.command("p/x *(int*)(((char*)&data)-0x80000000)")
 471         self.assertIn("0xbead", output)
 472
 473 class PrivTest(DeleteServer):
 474     def setUp(self):
 475         self.binary = target.compile("programs/priv.S")
 476         self.server = target.server()
 477         self.gdb = gdb(target, self.server.port, self.binary)
 478         self.gdb.load()
 479
 480         misa = self.gdb.p("$misa")
 481         self.supported = set()
 482         if misa & (1<<20):
 483             self.supported.add(0)
 484         if misa & (1<<18):
 485             self.supported.add(1)
 486         if misa & (1<<7):
 487             self.supported.add(2)
 488         self.supported.add(3)
 489
 490     def test_rw(self):
 491         """Test reading/writing priv."""
 492         for privilege in range(4):
 493             self.gdb.p("$priv=%d" % privilege)
 494             self.gdb.stepi()
 495             actual = self.gdb.p("$priv")
 496             self.assertIn(actual, self.supported)
 497             if privilege in self.supported:
 498                 self.assertEqual(actual, privilege)
 499
 500     def test_change(self):
 501         """Test that the core's privilege level actually changes."""
 502
 503         if 0 not in self.supported:
 504             # TODO: return not applicable
 505             return
 506
 507         self.gdb.b("main")
 508         self.gdb.c()
 509
 510         # Machine mode
 511         self.gdb.p("$priv=3")
 512         main = self.gdb.p("$pc")
 513         self.gdb.stepi()
 514         self.assertEqual("%x" % self.gdb.p("$pc"), "%x" % (main+4))
 515
 516         # User mode
 517         self.gdb.p("$priv=0")
 518         self.gdb.stepi()
 519         # Should have taken an exception, so be nowhere near main.
 520         pc = self.gdb.p("$pc")
 521         self.assertTrue(pc < main or pc > main + 0x100)
 522
 523 class Target(object):
 524     directory = None
 525     timeout_sec = 2
 526
 527     def server(self):
 528         raise NotImplementedError
 529
 530     def compile(self, *sources):
 531         binary_name = "%s_%s-%d" % (
 532                 self.name,
 533                 os.path.basename(os.path.splitext(sources[0])[0]),
 534                 self.xlen)
 535         if parsed.isolate:
 536             self.temporary_binary = tempfile.NamedTemporaryFile(
 537                     prefix=binary_name + "_")
 538             binary_name = self.temporary_binary.name
 539         testlib.compile(sources +
 540                 ("programs/entry.S", "programs/init.c",
 541                     "-I", "../env",
 542                     "-T", "targets/%s/link.lds" % (self.directory or self.name),
 543                     "-nostartfiles",
 544                     "-mcmodel=medany",
 545                     "-o", binary_name),
 546                 xlen=self.xlen)
 547         return binary_name
 548
 549 class SpikeTarget(Target):
 550     directory = "spike"
 551     ram = 0x80010000
 552     ram_size = 5 * 1024 * 1024
 553     instruction_hardware_breakpoint_count = 0
 554     reset_vector = 0x1000
 555
 556 class Spike64Target(SpikeTarget):
 557     name = "spike64"
 558     xlen = 64
 559
 560     def server(self):
 561         return testlib.Spike(parsed.cmd, halted=True)
 562
 563 class Spike32Target(SpikeTarget):
 564     name = "spike32"
 565     xlen = 32
 566
 567     def server(self):
 568         return testlib.Spike(parsed.cmd, halted=True, xlen=32)
 569
 570 class FreedomE300Target(Target):
 571     name = "freedom-e300"
 572     xlen = 32
 573     ram = 0x80000000
 574     ram_size = 16 * 1024
 575     instruction_hardware_breakpoint_count = 2
 576
 577     def server(self):
 578         return testlib.Openocd(cmd=parsed.cmd,
 579                 config="targets/%s/openocd.cfg" % self.name)
 580
 581 class FreedomE300SimTarget(Target):
 582     name = "freedom-e300-sim"
 583     xlen = 32
 584     timeout_sec = 240
 585     ram = 0x80000000
 586     ram_size = 256 * 1024 * 1024
 587     instruction_hardware_breakpoint_count = 2
 588
 589     def server(self):
 590         sim = testlib.VcsSim(simv=parsed.run, debug=False)
 591         openocd = testlib.Openocd(cmd=parsed.cmd,
 592                             config="targets/%s/openocd.cfg" % self.name,
 593                             otherProcess = sim)
 594         time.sleep(20)
 595         return openocd
 596
 597 class FreedomU500Target(Target):
 598     name = "freedom-u500"
 599     xlen = 64
 600     ram = 0x80000000
 601     ram_size = 16 * 1024
 602     instruction_hardware_breakpoint_count = 2
 603
 604     def server(self):
 605         return testlib.Openocd(cmd=parsed.cmd,
 606                 config="targets/%s/openocd.cfg" % self.name)
 607
 608 class FreedomU500SimTarget(Target):
 609     name = "freedom-u500-sim"
 610     xlen = 64
 611     timeout_sec = 240
 612     ram = 0x80000000
 613     ram_size = 256 * 1024 * 1024
 614     instruction_hardware_breakpoint_count = 2
 615
 616     def server(self):
 617         sim = testlib.VcsSim(simv=parsed.run, debug=False)
 618         openocd = testlib.Openocd(cmd=parsed.cmd,
 619                             config="targets/%s/openocd.cfg" % self.name,
 620                             otherProcess = sim)
 621         time.sleep(20)
 622         return openocd
 623
 624 targets = [
 625         Spike32Target,
 626         Spike64Target,
 627         FreedomE300Target,
 628         FreedomU500Target,
 629         FreedomE300SimTarget,
 630         FreedomU500SimTarget]
 631
 632 def main():
 633     parser = argparse.ArgumentParser(
 634             epilog="""
 635             Example command line from the real world:
 636             Run all RegsTest cases against a physical FPGA, with custom openocd command:
 637             ./gdbserver.py --freedom-e-300 --cmd "$HOME/SiFive/openocd/src/openocd -s $HOME/SiFive/openocd/tcl -d" -- -vf RegsTest
 638             """)
 639     group = parser.add_mutually_exclusive_group(required=True)
 640     for t in targets:
 641         group.add_argument("--%s" % t.name, action="store_const", const=t,
 642                 dest="target")
 643     parser.add_argument("--run",
 644                         help="The command to use to start the actual target (e.g. simulation)")
 645     parser.add_argument("--cmd",
 646             help="The command to use to start the debug server.")
 647     parser.add_argument("--gdb",
 648             help="The command to use to start gdb.")
 649
 650     xlen_group = parser.add_mutually_exclusive_group()
 651     xlen_group.add_argument("--32", action="store_const", const=32, dest="xlen",
 652             help="Force the target to be 32-bit.")
 653     xlen_group.add_argument("--64", action="store_const", const=64, dest="xlen",
 654             help="Force the target to be 64-bit.")
 655
 656     parser.add_argument("--isolate", action="store_true",
 657             help="Try to run in such a way that multiple instances can run at "
 658             "the same time. This may make it harder to debug a failure if it "
 659             "does occur.")
 660
 661     parser.add_argument("unittest", nargs="*")
 662     global parsed
 663     parsed = parser.parse_args()
 664
 665     global target
 666     target = parsed.target()
 667
 668     if parsed.xlen:
 669         target.xlen = parsed.xlen
 670
 671     unittest.main(argv=[sys.argv[0]] + parsed.unittest)
 672
 673 # TROUBLESHOOTING TIPS
 674 # If a particular test fails, run just that one test, eg.:
 675 # ./gdbserver.py MprvTest.test_mprv
 676 # Then inspect gdb.log and spike.log to see what happened in more detail.
 677
 678 if __name__ == '__main__':
 679     sys.exit(main())