dump-guest-memory.py (20723B)
1 """ 2 This python script adds a new gdb command, "dump-guest-memory". It 3 should be loaded with "source dump-guest-memory.py" at the (gdb) 4 prompt. 5 6 Copyright (C) 2013, Red Hat, Inc. 7 8 Authors: 9 Laszlo Ersek <lersek@redhat.com> 10 Janosch Frank <frankja@linux.vnet.ibm.com> 11 12 This work is licensed under the terms of the GNU GPL, version 2 or later. See 13 the COPYING file in the top-level directory. 14 """ 15 16 import ctypes 17 import struct 18 19 try: 20 UINTPTR_T = gdb.lookup_type("uintptr_t") 21 except Exception as inst: 22 raise gdb.GdbError("Symbols must be loaded prior to sourcing dump-guest-memory.\n" 23 "Symbols may be loaded by 'attach'ing a QEMU process id or by " 24 "'load'ing a QEMU binary.") 25 26 TARGET_PAGE_SIZE = 0x1000 27 TARGET_PAGE_MASK = 0xFFFFFFFFFFFFF000 28 29 # Special value for e_phnum. This indicates that the real number of 30 # program headers is too large to fit into e_phnum. Instead the real 31 # value is in the field sh_info of section 0. 32 PN_XNUM = 0xFFFF 33 34 EV_CURRENT = 1 35 36 ELFCLASS32 = 1 37 ELFCLASS64 = 2 38 39 ELFDATA2LSB = 1 40 ELFDATA2MSB = 2 41 42 ET_CORE = 4 43 44 PT_LOAD = 1 45 PT_NOTE = 4 46 47 EM_386 = 3 48 EM_PPC = 20 49 EM_PPC64 = 21 50 EM_S390 = 22 51 EM_AARCH = 183 52 EM_X86_64 = 62 53 54 VMCOREINFO_FORMAT_ELF = 1 55 56 def le16_to_cpu(val): 57 return struct.unpack("<H", struct.pack("=H", val))[0] 58 59 def le32_to_cpu(val): 60 return struct.unpack("<I", struct.pack("=I", val))[0] 61 62 def le64_to_cpu(val): 63 return struct.unpack("<Q", struct.pack("=Q", val))[0] 64 65 class ELF(object): 66 """Representation of a ELF file.""" 67 68 def __init__(self, arch): 69 self.ehdr = None 70 self.notes = [] 71 self.segments = [] 72 self.notes_size = 0 73 self.endianness = None 74 self.elfclass = ELFCLASS64 75 76 if arch == 'aarch64-le': 77 self.endianness = ELFDATA2LSB 78 self.elfclass = ELFCLASS64 79 self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) 80 self.ehdr.e_machine = EM_AARCH 81 82 elif arch == 'aarch64-be': 83 self.endianness = ELFDATA2MSB 84 self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) 85 self.ehdr.e_machine = EM_AARCH 86 87 elif arch == 'X86_64': 88 self.endianness = ELFDATA2LSB 89 self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) 90 self.ehdr.e_machine = EM_X86_64 91 92 elif arch == '386': 93 self.endianness = ELFDATA2LSB 94 self.elfclass = ELFCLASS32 95 self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) 96 self.ehdr.e_machine = EM_386 97 98 elif arch == 's390': 99 self.endianness = ELFDATA2MSB 100 self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) 101 self.ehdr.e_machine = EM_S390 102 103 elif arch == 'ppc64-le': 104 self.endianness = ELFDATA2LSB 105 self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) 106 self.ehdr.e_machine = EM_PPC64 107 108 elif arch == 'ppc64-be': 109 self.endianness = ELFDATA2MSB 110 self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) 111 self.ehdr.e_machine = EM_PPC64 112 113 else: 114 raise gdb.GdbError("No valid arch type specified.\n" 115 "Currently supported types:\n" 116 "aarch64-be, aarch64-le, X86_64, 386, s390, " 117 "ppc64-be, ppc64-le") 118 119 self.add_segment(PT_NOTE, 0, 0) 120 121 def add_note(self, n_name, n_desc, n_type): 122 """Adds a note to the ELF.""" 123 124 note = get_arch_note(self.endianness, len(n_name), len(n_desc)) 125 note.n_namesz = len(n_name) + 1 126 note.n_descsz = len(n_desc) 127 note.n_name = n_name.encode() 128 note.n_type = n_type 129 130 # Desc needs to be 4 byte aligned (although the 64bit spec 131 # specifies 8 byte). When defining n_desc as uint32 it will be 132 # automatically aligned but we need the memmove to copy the 133 # string into it. 134 ctypes.memmove(note.n_desc, n_desc.encode(), len(n_desc)) 135 136 self.notes.append(note) 137 self.segments[0].p_filesz += ctypes.sizeof(note) 138 self.segments[0].p_memsz += ctypes.sizeof(note) 139 140 141 def add_vmcoreinfo_note(self, vmcoreinfo): 142 """Adds a vmcoreinfo note to the ELF dump.""" 143 # compute the header size, and copy that many bytes from the note 144 header = get_arch_note(self.endianness, 0, 0) 145 ctypes.memmove(ctypes.pointer(header), 146 vmcoreinfo, ctypes.sizeof(header)) 147 if header.n_descsz > 1 << 20: 148 print('warning: invalid vmcoreinfo size') 149 return 150 # now get the full note 151 note = get_arch_note(self.endianness, 152 header.n_namesz - 1, header.n_descsz) 153 ctypes.memmove(ctypes.pointer(note), vmcoreinfo, ctypes.sizeof(note)) 154 155 self.notes.append(note) 156 self.segments[0].p_filesz += ctypes.sizeof(note) 157 self.segments[0].p_memsz += ctypes.sizeof(note) 158 159 def add_segment(self, p_type, p_paddr, p_size): 160 """Adds a segment to the elf.""" 161 162 phdr = get_arch_phdr(self.endianness, self.elfclass) 163 phdr.p_type = p_type 164 phdr.p_paddr = p_paddr 165 phdr.p_vaddr = p_paddr 166 phdr.p_filesz = p_size 167 phdr.p_memsz = p_size 168 self.segments.append(phdr) 169 self.ehdr.e_phnum += 1 170 171 def to_file(self, elf_file): 172 """Writes all ELF structures to the passed file. 173 174 Structure: 175 Ehdr 176 Segment 0:PT_NOTE 177 Segment 1:PT_LOAD 178 Segment N:PT_LOAD 179 Note 0..N 180 Dump contents 181 """ 182 elf_file.write(self.ehdr) 183 off = ctypes.sizeof(self.ehdr) + \ 184 len(self.segments) * ctypes.sizeof(self.segments[0]) 185 186 for phdr in self.segments: 187 phdr.p_offset = off 188 elf_file.write(phdr) 189 off += phdr.p_filesz 190 191 for note in self.notes: 192 elf_file.write(note) 193 194 195 def get_arch_note(endianness, len_name, len_desc): 196 """Returns a Note class with the specified endianness.""" 197 198 if endianness == ELFDATA2LSB: 199 superclass = ctypes.LittleEndianStructure 200 else: 201 superclass = ctypes.BigEndianStructure 202 203 len_name = len_name + 1 204 205 class Note(superclass): 206 """Represents an ELF note, includes the content.""" 207 208 _fields_ = [("n_namesz", ctypes.c_uint32), 209 ("n_descsz", ctypes.c_uint32), 210 ("n_type", ctypes.c_uint32), 211 ("n_name", ctypes.c_char * len_name), 212 ("n_desc", ctypes.c_uint32 * ((len_desc + 3) // 4))] 213 return Note() 214 215 216 class Ident(ctypes.Structure): 217 """Represents the ELF ident array in the ehdr structure.""" 218 219 _fields_ = [('ei_mag0', ctypes.c_ubyte), 220 ('ei_mag1', ctypes.c_ubyte), 221 ('ei_mag2', ctypes.c_ubyte), 222 ('ei_mag3', ctypes.c_ubyte), 223 ('ei_class', ctypes.c_ubyte), 224 ('ei_data', ctypes.c_ubyte), 225 ('ei_version', ctypes.c_ubyte), 226 ('ei_osabi', ctypes.c_ubyte), 227 ('ei_abiversion', ctypes.c_ubyte), 228 ('ei_pad', ctypes.c_ubyte * 7)] 229 230 def __init__(self, endianness, elfclass): 231 self.ei_mag0 = 0x7F 232 self.ei_mag1 = ord('E') 233 self.ei_mag2 = ord('L') 234 self.ei_mag3 = ord('F') 235 self.ei_class = elfclass 236 self.ei_data = endianness 237 self.ei_version = EV_CURRENT 238 239 240 def get_arch_ehdr(endianness, elfclass): 241 """Returns a EHDR64 class with the specified endianness.""" 242 243 if endianness == ELFDATA2LSB: 244 superclass = ctypes.LittleEndianStructure 245 else: 246 superclass = ctypes.BigEndianStructure 247 248 class EHDR64(superclass): 249 """Represents the 64 bit ELF header struct.""" 250 251 _fields_ = [('e_ident', Ident), 252 ('e_type', ctypes.c_uint16), 253 ('e_machine', ctypes.c_uint16), 254 ('e_version', ctypes.c_uint32), 255 ('e_entry', ctypes.c_uint64), 256 ('e_phoff', ctypes.c_uint64), 257 ('e_shoff', ctypes.c_uint64), 258 ('e_flags', ctypes.c_uint32), 259 ('e_ehsize', ctypes.c_uint16), 260 ('e_phentsize', ctypes.c_uint16), 261 ('e_phnum', ctypes.c_uint16), 262 ('e_shentsize', ctypes.c_uint16), 263 ('e_shnum', ctypes.c_uint16), 264 ('e_shstrndx', ctypes.c_uint16)] 265 266 def __init__(self): 267 super(superclass, self).__init__() 268 self.e_ident = Ident(endianness, elfclass) 269 self.e_type = ET_CORE 270 self.e_version = EV_CURRENT 271 self.e_ehsize = ctypes.sizeof(self) 272 self.e_phoff = ctypes.sizeof(self) 273 self.e_phentsize = ctypes.sizeof(get_arch_phdr(endianness, elfclass)) 274 self.e_phnum = 0 275 276 277 class EHDR32(superclass): 278 """Represents the 32 bit ELF header struct.""" 279 280 _fields_ = [('e_ident', Ident), 281 ('e_type', ctypes.c_uint16), 282 ('e_machine', ctypes.c_uint16), 283 ('e_version', ctypes.c_uint32), 284 ('e_entry', ctypes.c_uint32), 285 ('e_phoff', ctypes.c_uint32), 286 ('e_shoff', ctypes.c_uint32), 287 ('e_flags', ctypes.c_uint32), 288 ('e_ehsize', ctypes.c_uint16), 289 ('e_phentsize', ctypes.c_uint16), 290 ('e_phnum', ctypes.c_uint16), 291 ('e_shentsize', ctypes.c_uint16), 292 ('e_shnum', ctypes.c_uint16), 293 ('e_shstrndx', ctypes.c_uint16)] 294 295 def __init__(self): 296 super(superclass, self).__init__() 297 self.e_ident = Ident(endianness, elfclass) 298 self.e_type = ET_CORE 299 self.e_version = EV_CURRENT 300 self.e_ehsize = ctypes.sizeof(self) 301 self.e_phoff = ctypes.sizeof(self) 302 self.e_phentsize = ctypes.sizeof(get_arch_phdr(endianness, elfclass)) 303 self.e_phnum = 0 304 305 # End get_arch_ehdr 306 if elfclass == ELFCLASS64: 307 return EHDR64() 308 else: 309 return EHDR32() 310 311 312 def get_arch_phdr(endianness, elfclass): 313 """Returns a 32 or 64 bit PHDR class with the specified endianness.""" 314 315 if endianness == ELFDATA2LSB: 316 superclass = ctypes.LittleEndianStructure 317 else: 318 superclass = ctypes.BigEndianStructure 319 320 class PHDR64(superclass): 321 """Represents the 64 bit ELF program header struct.""" 322 323 _fields_ = [('p_type', ctypes.c_uint32), 324 ('p_flags', ctypes.c_uint32), 325 ('p_offset', ctypes.c_uint64), 326 ('p_vaddr', ctypes.c_uint64), 327 ('p_paddr', ctypes.c_uint64), 328 ('p_filesz', ctypes.c_uint64), 329 ('p_memsz', ctypes.c_uint64), 330 ('p_align', ctypes.c_uint64)] 331 332 class PHDR32(superclass): 333 """Represents the 32 bit ELF program header struct.""" 334 335 _fields_ = [('p_type', ctypes.c_uint32), 336 ('p_offset', ctypes.c_uint32), 337 ('p_vaddr', ctypes.c_uint32), 338 ('p_paddr', ctypes.c_uint32), 339 ('p_filesz', ctypes.c_uint32), 340 ('p_memsz', ctypes.c_uint32), 341 ('p_flags', ctypes.c_uint32), 342 ('p_align', ctypes.c_uint32)] 343 344 # End get_arch_phdr 345 if elfclass == ELFCLASS64: 346 return PHDR64() 347 else: 348 return PHDR32() 349 350 351 def int128_get64(val): 352 """Returns low 64bit part of Int128 struct.""" 353 354 try: 355 assert val["hi"] == 0 356 return val["lo"] 357 except gdb.error: 358 u64t = gdb.lookup_type('uint64_t').array(2) 359 u64 = val.cast(u64t) 360 if sys.byteorder == 'little': 361 assert u64[1] == 0 362 return u64[0] 363 else: 364 assert u64[0] == 0 365 return u64[1] 366 367 368 def qlist_foreach(head, field_str): 369 """Generator for qlists.""" 370 371 var_p = head["lh_first"] 372 while var_p != 0: 373 var = var_p.dereference() 374 var_p = var[field_str]["le_next"] 375 yield var 376 377 378 def qemu_map_ram_ptr(block, offset): 379 """Returns qemu vaddr for given guest physical address.""" 380 381 return block["host"] + offset 382 383 384 def memory_region_get_ram_ptr(memory_region): 385 if memory_region["alias"] != 0: 386 return (memory_region_get_ram_ptr(memory_region["alias"].dereference()) 387 + memory_region["alias_offset"]) 388 389 return qemu_map_ram_ptr(memory_region["ram_block"], 0) 390 391 392 def get_guest_phys_blocks(): 393 """Returns a list of ram blocks. 394 395 Each block entry contains: 396 'target_start': guest block phys start address 397 'target_end': guest block phys end address 398 'host_addr': qemu vaddr of the block's start 399 """ 400 401 guest_phys_blocks = [] 402 403 print("guest RAM blocks:") 404 print("target_start target_end host_addr message " 405 "count") 406 print("---------------- ---------------- ---------------- ------- " 407 "-----") 408 409 current_map_p = gdb.parse_and_eval("address_space_memory.current_map") 410 current_map = current_map_p.dereference() 411 412 # Conversion to int is needed for python 3 413 # compatibility. Otherwise range doesn't cast the value itself and 414 # breaks. 415 for cur in range(int(current_map["nr"])): 416 flat_range = (current_map["ranges"] + cur).dereference() 417 memory_region = flat_range["mr"].dereference() 418 419 # we only care about RAM 420 if (not memory_region["ram"] or 421 memory_region["ram_device"] or 422 memory_region["nonvolatile"]): 423 continue 424 425 section_size = int128_get64(flat_range["addr"]["size"]) 426 target_start = int128_get64(flat_range["addr"]["start"]) 427 target_end = target_start + section_size 428 host_addr = (memory_region_get_ram_ptr(memory_region) 429 + flat_range["offset_in_region"]) 430 predecessor = None 431 432 # find continuity in guest physical address space 433 if len(guest_phys_blocks) > 0: 434 predecessor = guest_phys_blocks[-1] 435 predecessor_size = (predecessor["target_end"] - 436 predecessor["target_start"]) 437 438 # the memory API guarantees monotonically increasing 439 # traversal 440 assert predecessor["target_end"] <= target_start 441 442 # we want continuity in both guest-physical and 443 # host-virtual memory 444 if (predecessor["target_end"] < target_start or 445 predecessor["host_addr"] + predecessor_size != host_addr): 446 predecessor = None 447 448 if predecessor is None: 449 # isolated mapping, add it to the list 450 guest_phys_blocks.append({"target_start": target_start, 451 "target_end": target_end, 452 "host_addr": host_addr}) 453 message = "added" 454 else: 455 # expand predecessor until @target_end; predecessor's 456 # start doesn't change 457 predecessor["target_end"] = target_end 458 message = "joined" 459 460 print("%016x %016x %016x %-7s %5u" % 461 (target_start, target_end, host_addr.cast(UINTPTR_T), 462 message, len(guest_phys_blocks))) 463 464 return guest_phys_blocks 465 466 467 # The leading docstring doesn't have idiomatic Python formatting. It is 468 # printed by gdb's "help" command (the first line is printed in the 469 # "help data" summary), and it should match how other help texts look in 470 # gdb. 471 class DumpGuestMemory(gdb.Command): 472 """Extract guest vmcore from qemu process coredump. 473 474 The two required arguments are FILE and ARCH: 475 FILE identifies the target file to write the guest vmcore to. 476 ARCH specifies the architecture for which the core will be generated. 477 478 This GDB command reimplements the dump-guest-memory QMP command in 479 python, using the representation of guest memory as captured in the qemu 480 coredump. The qemu process that has been dumped must have had the 481 command line option "-machine dump-guest-core=on" which is the default. 482 483 For simplicity, the "paging", "begin" and "end" parameters of the QMP 484 command are not supported -- no attempt is made to get the guest's 485 internal paging structures (ie. paging=false is hard-wired), and guest 486 memory is always fully dumped. 487 488 Currently aarch64-be, aarch64-le, X86_64, 386, s390, ppc64-be, 489 ppc64-le guests are supported. 490 491 The CORE/NT_PRSTATUS and QEMU notes (that is, the VCPUs' statuses) are 492 not written to the vmcore. Preparing these would require context that is 493 only present in the KVM host kernel module when the guest is alive. A 494 fake ELF note is written instead, only to keep the ELF parser of "crash" 495 happy. 496 497 Dependent on how busted the qemu process was at the time of the 498 coredump, this command might produce unpredictable results. If qemu 499 deliberately called abort(), or it was dumped in response to a signal at 500 a halfway fortunate point, then its coredump should be in reasonable 501 shape and this command should mostly work.""" 502 503 def __init__(self): 504 super(DumpGuestMemory, self).__init__("dump-guest-memory", 505 gdb.COMMAND_DATA, 506 gdb.COMPLETE_FILENAME) 507 self.elf = None 508 self.guest_phys_blocks = None 509 510 def dump_init(self, vmcore): 511 """Prepares and writes ELF structures to core file.""" 512 513 # Needed to make crash happy, data for more useful notes is 514 # not available in a qemu core. 515 self.elf.add_note("NONE", "EMPTY", 0) 516 517 # We should never reach PN_XNUM for paging=false dumps, 518 # there's just a handful of discontiguous ranges after 519 # merging. 520 # The constant is needed to account for the PT_NOTE segment. 521 phdr_num = len(self.guest_phys_blocks) + 1 522 assert phdr_num < PN_XNUM 523 524 for block in self.guest_phys_blocks: 525 block_size = block["target_end"] - block["target_start"] 526 self.elf.add_segment(PT_LOAD, block["target_start"], block_size) 527 528 self.elf.to_file(vmcore) 529 530 def dump_iterate(self, vmcore): 531 """Writes guest core to file.""" 532 533 qemu_core = gdb.inferiors()[0] 534 for block in self.guest_phys_blocks: 535 cur = block["host_addr"] 536 left = block["target_end"] - block["target_start"] 537 print("dumping range at %016x for length %016x" % 538 (cur.cast(UINTPTR_T), left)) 539 540 while left > 0: 541 chunk_size = min(TARGET_PAGE_SIZE, left) 542 chunk = qemu_core.read_memory(cur, chunk_size) 543 vmcore.write(chunk) 544 cur += chunk_size 545 left -= chunk_size 546 547 def phys_memory_read(self, addr, size): 548 qemu_core = gdb.inferiors()[0] 549 for block in self.guest_phys_blocks: 550 if block["target_start"] <= addr \ 551 and addr + size <= block["target_end"]: 552 haddr = block["host_addr"] + (addr - block["target_start"]) 553 return qemu_core.read_memory(haddr, size) 554 return None 555 556 def add_vmcoreinfo(self): 557 if gdb.lookup_symbol("vmcoreinfo_realize")[0] is None: 558 return 559 vmci = 'vmcoreinfo_realize::vmcoreinfo_state' 560 if not gdb.parse_and_eval("%s" % vmci) \ 561 or not gdb.parse_and_eval("(%s)->has_vmcoreinfo" % vmci): 562 return 563 564 fmt = gdb.parse_and_eval("(%s)->vmcoreinfo.guest_format" % vmci) 565 addr = gdb.parse_and_eval("(%s)->vmcoreinfo.paddr" % vmci) 566 size = gdb.parse_and_eval("(%s)->vmcoreinfo.size" % vmci) 567 568 fmt = le16_to_cpu(fmt) 569 addr = le64_to_cpu(addr) 570 size = le32_to_cpu(size) 571 572 if fmt != VMCOREINFO_FORMAT_ELF: 573 return 574 575 vmcoreinfo = self.phys_memory_read(addr, size) 576 if vmcoreinfo: 577 self.elf.add_vmcoreinfo_note(bytes(vmcoreinfo)) 578 579 def invoke(self, args, from_tty): 580 """Handles command invocation from gdb.""" 581 582 # Unwittingly pressing the Enter key after the command should 583 # not dump the same multi-gig coredump to the same file. 584 self.dont_repeat() 585 586 argv = gdb.string_to_argv(args) 587 if len(argv) != 2: 588 raise gdb.GdbError("usage: dump-guest-memory FILE ARCH") 589 590 self.elf = ELF(argv[1]) 591 self.guest_phys_blocks = get_guest_phys_blocks() 592 self.add_vmcoreinfo() 593 594 with open(argv[0], "wb") as vmcore: 595 self.dump_init(vmcore) 596 self.dump_iterate(vmcore) 597 598 DumpGuestMemory()