| """ |
| This python script adds a new gdb command, "dump-guest-memory". It |
| should be loaded with "source dump-guest-memory.py" at the (gdb) |
| prompt. |
| |
| Copyright (C) 2013, Red Hat, Inc. |
| |
| Authors: |
| Laszlo Ersek <lersek@redhat.com> |
| Janosch Frank <frankja@linux.vnet.ibm.com> |
| |
| This work is licensed under the terms of the GNU GPL, version 2 or later. See |
| the COPYING file in the top-level directory. |
| """ |
| |
| import ctypes |
| |
| UINTPTR_T = gdb.lookup_type("uintptr_t") |
| |
| TARGET_PAGE_SIZE = 0x1000 |
| TARGET_PAGE_MASK = 0xFFFFFFFFFFFFF000 |
| |
| # Special value for e_phnum. This indicates that the real number of |
| # program headers is too large to fit into e_phnum. Instead the real |
| # value is in the field sh_info of section 0. |
| PN_XNUM = 0xFFFF |
| |
| EV_CURRENT = 1 |
| |
| ELFCLASS32 = 1 |
| ELFCLASS64 = 2 |
| |
| ELFDATA2LSB = 1 |
| ELFDATA2MSB = 2 |
| |
| ET_CORE = 4 |
| |
| PT_LOAD = 1 |
| PT_NOTE = 4 |
| |
| EM_386 = 3 |
| EM_PPC = 20 |
| EM_PPC64 = 21 |
| EM_S390 = 22 |
| EM_AARCH = 183 |
| EM_X86_64 = 62 |
| |
| class ELF(object): |
| """Representation of a ELF file.""" |
| |
| def __init__(self, arch): |
| self.ehdr = None |
| self.notes = [] |
| self.segments = [] |
| self.notes_size = 0 |
| self.endianness = None |
| self.elfclass = ELFCLASS64 |
| |
| if arch == 'aarch64-le': |
| self.endianness = ELFDATA2LSB |
| self.elfclass = ELFCLASS64 |
| self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) |
| self.ehdr.e_machine = EM_AARCH |
| |
| elif arch == 'aarch64-be': |
| self.endianness = ELFDATA2MSB |
| self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) |
| self.ehdr.e_machine = EM_AARCH |
| |
| elif arch == 'X86_64': |
| self.endianness = ELFDATA2LSB |
| self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) |
| self.ehdr.e_machine = EM_X86_64 |
| |
| elif arch == '386': |
| self.endianness = ELFDATA2LSB |
| self.elfclass = ELFCLASS32 |
| self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) |
| self.ehdr.e_machine = EM_386 |
| |
| elif arch == 's390': |
| self.endianness = ELFDATA2MSB |
| self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) |
| self.ehdr.e_machine = EM_S390 |
| |
| elif arch == 'ppc64-le': |
| self.endianness = ELFDATA2LSB |
| self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) |
| self.ehdr.e_machine = EM_PPC64 |
| |
| elif arch == 'ppc64-be': |
| self.endianness = ELFDATA2MSB |
| self.ehdr = get_arch_ehdr(self.endianness, self.elfclass) |
| self.ehdr.e_machine = EM_PPC64 |
| |
| else: |
| raise gdb.GdbError("No valid arch type specified.\n" |
| "Currently supported types:\n" |
| "aarch64-be, aarch64-le, X86_64, 386, s390, " |
| "ppc64-be, ppc64-le") |
| |
| self.add_segment(PT_NOTE, 0, 0) |
| |
| def add_note(self, n_name, n_desc, n_type): |
| """Adds a note to the ELF.""" |
| |
| note = get_arch_note(self.endianness, len(n_name), len(n_desc)) |
| note.n_namesz = len(n_name) + 1 |
| note.n_descsz = len(n_desc) |
| note.n_name = n_name.encode() |
| note.n_type = n_type |
| |
| # Desc needs to be 4 byte aligned (although the 64bit spec |
| # specifies 8 byte). When defining n_desc as uint32 it will be |
| # automatically aligned but we need the memmove to copy the |
| # string into it. |
| ctypes.memmove(note.n_desc, n_desc.encode(), len(n_desc)) |
| |
| self.notes.append(note) |
| self.segments[0].p_filesz += ctypes.sizeof(note) |
| self.segments[0].p_memsz += ctypes.sizeof(note) |
| |
| def add_segment(self, p_type, p_paddr, p_size): |
| """Adds a segment to the elf.""" |
| |
| phdr = get_arch_phdr(self.endianness, self.elfclass) |
| phdr.p_type = p_type |
| phdr.p_paddr = p_paddr |
| phdr.p_filesz = p_size |
| phdr.p_memsz = p_size |
| self.segments.append(phdr) |
| self.ehdr.e_phnum += 1 |
| |
| def to_file(self, elf_file): |
| """Writes all ELF structures to the the passed file. |
| |
| Structure: |
| Ehdr |
| Segment 0:PT_NOTE |
| Segment 1:PT_LOAD |
| Segment N:PT_LOAD |
| Note 0..N |
| Dump contents |
| """ |
| elf_file.write(self.ehdr) |
| off = ctypes.sizeof(self.ehdr) + \ |
| len(self.segments) * ctypes.sizeof(self.segments[0]) |
| |
| for phdr in self.segments: |
| phdr.p_offset = off |
| elf_file.write(phdr) |
| off += phdr.p_filesz |
| |
| for note in self.notes: |
| elf_file.write(note) |
| |
| |
| def get_arch_note(endianness, len_name, len_desc): |
| """Returns a Note class with the specified endianness.""" |
| |
| if endianness == ELFDATA2LSB: |
| superclass = ctypes.LittleEndianStructure |
| else: |
| superclass = ctypes.BigEndianStructure |
| |
| len_name = len_name + 1 |
| |
| class Note(superclass): |
| """Represents an ELF note, includes the content.""" |
| |
| _fields_ = [("n_namesz", ctypes.c_uint32), |
| ("n_descsz", ctypes.c_uint32), |
| ("n_type", ctypes.c_uint32), |
| ("n_name", ctypes.c_char * len_name), |
| ("n_desc", ctypes.c_uint32 * ((len_desc + 3) // 4))] |
| return Note() |
| |
| |
| class Ident(ctypes.Structure): |
| """Represents the ELF ident array in the ehdr structure.""" |
| |
| _fields_ = [('ei_mag0', ctypes.c_ubyte), |
| ('ei_mag1', ctypes.c_ubyte), |
| ('ei_mag2', ctypes.c_ubyte), |
| ('ei_mag3', ctypes.c_ubyte), |
| ('ei_class', ctypes.c_ubyte), |
| ('ei_data', ctypes.c_ubyte), |
| ('ei_version', ctypes.c_ubyte), |
| ('ei_osabi', ctypes.c_ubyte), |
| ('ei_abiversion', ctypes.c_ubyte), |
| ('ei_pad', ctypes.c_ubyte * 7)] |
| |
| def __init__(self, endianness, elfclass): |
| self.ei_mag0 = 0x7F |
| self.ei_mag1 = ord('E') |
| self.ei_mag2 = ord('L') |
| self.ei_mag3 = ord('F') |
| self.ei_class = elfclass |
| self.ei_data = endianness |
| self.ei_version = EV_CURRENT |
| |
| |
| def get_arch_ehdr(endianness, elfclass): |
| """Returns a EHDR64 class with the specified endianness.""" |
| |
| if endianness == ELFDATA2LSB: |
| superclass = ctypes.LittleEndianStructure |
| else: |
| superclass = ctypes.BigEndianStructure |
| |
| class EHDR64(superclass): |
| """Represents the 64 bit ELF header struct.""" |
| |
| _fields_ = [('e_ident', Ident), |
| ('e_type', ctypes.c_uint16), |
| ('e_machine', ctypes.c_uint16), |
| ('e_version', ctypes.c_uint32), |
| ('e_entry', ctypes.c_uint64), |
| ('e_phoff', ctypes.c_uint64), |
| ('e_shoff', ctypes.c_uint64), |
| ('e_flags', ctypes.c_uint32), |
| ('e_ehsize', ctypes.c_uint16), |
| ('e_phentsize', ctypes.c_uint16), |
| ('e_phnum', ctypes.c_uint16), |
| ('e_shentsize', ctypes.c_uint16), |
| ('e_shnum', ctypes.c_uint16), |
| ('e_shstrndx', ctypes.c_uint16)] |
| |
| def __init__(self): |
| super(superclass, self).__init__() |
| self.e_ident = Ident(endianness, elfclass) |
| self.e_type = ET_CORE |
| self.e_version = EV_CURRENT |
| self.e_ehsize = ctypes.sizeof(self) |
| self.e_phoff = ctypes.sizeof(self) |
| self.e_phentsize = ctypes.sizeof(get_arch_phdr(endianness, elfclass)) |
| self.e_phnum = 0 |
| |
| |
| class EHDR32(superclass): |
| """Represents the 32 bit ELF header struct.""" |
| |
| _fields_ = [('e_ident', Ident), |
| ('e_type', ctypes.c_uint16), |
| ('e_machine', ctypes.c_uint16), |
| ('e_version', ctypes.c_uint32), |
| ('e_entry', ctypes.c_uint32), |
| ('e_phoff', ctypes.c_uint32), |
| ('e_shoff', ctypes.c_uint32), |
| ('e_flags', ctypes.c_uint32), |
| ('e_ehsize', ctypes.c_uint16), |
| ('e_phentsize', ctypes.c_uint16), |
| ('e_phnum', ctypes.c_uint16), |
| ('e_shentsize', ctypes.c_uint16), |
| ('e_shnum', ctypes.c_uint16), |
| ('e_shstrndx', ctypes.c_uint16)] |
| |
| def __init__(self): |
| super(superclass, self).__init__() |
| self.e_ident = Ident(endianness, elfclass) |
| self.e_type = ET_CORE |
| self.e_version = EV_CURRENT |
| self.e_ehsize = ctypes.sizeof(self) |
| self.e_phoff = ctypes.sizeof(self) |
| self.e_phentsize = ctypes.sizeof(get_arch_phdr(endianness, elfclass)) |
| self.e_phnum = 0 |
| |
| # End get_arch_ehdr |
| if elfclass == ELFCLASS64: |
| return EHDR64() |
| else: |
| return EHDR32() |
| |
| |
| def get_arch_phdr(endianness, elfclass): |
| """Returns a 32 or 64 bit PHDR class with the specified endianness.""" |
| |
| if endianness == ELFDATA2LSB: |
| superclass = ctypes.LittleEndianStructure |
| else: |
| superclass = ctypes.BigEndianStructure |
| |
| class PHDR64(superclass): |
| """Represents the 64 bit ELF program header struct.""" |
| |
| _fields_ = [('p_type', ctypes.c_uint32), |
| ('p_flags', ctypes.c_uint32), |
| ('p_offset', ctypes.c_uint64), |
| ('p_vaddr', ctypes.c_uint64), |
| ('p_paddr', ctypes.c_uint64), |
| ('p_filesz', ctypes.c_uint64), |
| ('p_memsz', ctypes.c_uint64), |
| ('p_align', ctypes.c_uint64)] |
| |
| class PHDR32(superclass): |
| """Represents the 32 bit ELF program header struct.""" |
| |
| _fields_ = [('p_type', ctypes.c_uint32), |
| ('p_offset', ctypes.c_uint32), |
| ('p_vaddr', ctypes.c_uint32), |
| ('p_paddr', ctypes.c_uint32), |
| ('p_filesz', ctypes.c_uint32), |
| ('p_memsz', ctypes.c_uint32), |
| ('p_flags', ctypes.c_uint32), |
| ('p_align', ctypes.c_uint32)] |
| |
| # End get_arch_phdr |
| if elfclass == ELFCLASS64: |
| return PHDR64() |
| else: |
| return PHDR32() |
| |
| |
| def int128_get64(val): |
| """Returns low 64bit part of Int128 struct.""" |
| |
| assert val["hi"] == 0 |
| return val["lo"] |
| |
| |
| def qlist_foreach(head, field_str): |
| """Generator for qlists.""" |
| |
| var_p = head["lh_first"] |
| while var_p != 0: |
| var = var_p.dereference() |
| var_p = var[field_str]["le_next"] |
| yield var |
| |
| |
| def qemu_get_ram_block(ram_addr): |
| """Returns the RAMBlock struct to which the given address belongs.""" |
| |
| ram_blocks = gdb.parse_and_eval("ram_list.blocks") |
| |
| for block in qlist_foreach(ram_blocks, "next"): |
| if (ram_addr - block["offset"]) < block["used_length"]: |
| return block |
| |
| raise gdb.GdbError("Bad ram offset %x" % ram_addr) |
| |
| |
| def qemu_get_ram_ptr(ram_addr): |
| """Returns qemu vaddr for given guest physical address.""" |
| |
| block = qemu_get_ram_block(ram_addr) |
| return block["host"] + (ram_addr - block["offset"]) |
| |
| |
| def memory_region_get_ram_ptr(memory_region): |
| if memory_region["alias"] != 0: |
| return (memory_region_get_ram_ptr(memory_region["alias"].dereference()) |
| + memory_region["alias_offset"]) |
| |
| return qemu_get_ram_ptr(memory_region["ram_block"]["offset"]) |
| |
| |
| def get_guest_phys_blocks(): |
| """Returns a list of ram blocks. |
| |
| Each block entry contains: |
| 'target_start': guest block phys start address |
| 'target_end': guest block phys end address |
| 'host_addr': qemu vaddr of the block's start |
| """ |
| |
| guest_phys_blocks = [] |
| |
| print("guest RAM blocks:") |
| print("target_start target_end host_addr message " |
| "count") |
| print("---------------- ---------------- ---------------- ------- " |
| "-----") |
| |
| current_map_p = gdb.parse_and_eval("address_space_memory.current_map") |
| current_map = current_map_p.dereference() |
| |
| # Conversion to int is needed for python 3 |
| # compatibility. Otherwise range doesn't cast the value itself and |
| # breaks. |
| for cur in range(int(current_map["nr"])): |
| flat_range = (current_map["ranges"] + cur).dereference() |
| memory_region = flat_range["mr"].dereference() |
| |
| # we only care about RAM |
| if not memory_region["ram"]: |
| continue |
| |
| section_size = int128_get64(flat_range["addr"]["size"]) |
| target_start = int128_get64(flat_range["addr"]["start"]) |
| target_end = target_start + section_size |
| host_addr = (memory_region_get_ram_ptr(memory_region) |
| + flat_range["offset_in_region"]) |
| predecessor = None |
| |
| # find continuity in guest physical address space |
| if len(guest_phys_blocks) > 0: |
| predecessor = guest_phys_blocks[-1] |
| predecessor_size = (predecessor["target_end"] - |
| predecessor["target_start"]) |
| |
| # the memory API guarantees monotonically increasing |
| # traversal |
| assert predecessor["target_end"] <= target_start |
| |
| # we want continuity in both guest-physical and |
| # host-virtual memory |
| if (predecessor["target_end"] < target_start or |
| predecessor["host_addr"] + predecessor_size != host_addr): |
| predecessor = None |
| |
| if predecessor is None: |
| # isolated mapping, add it to the list |
| guest_phys_blocks.append({"target_start": target_start, |
| "target_end": target_end, |
| "host_addr": host_addr}) |
| message = "added" |
| else: |
| # expand predecessor until @target_end; predecessor's |
| # start doesn't change |
| predecessor["target_end"] = target_end |
| message = "joined" |
| |
| print("%016x %016x %016x %-7s %5u" % |
| (target_start, target_end, host_addr.cast(UINTPTR_T), |
| message, len(guest_phys_blocks))) |
| |
| return guest_phys_blocks |
| |
| |
| # The leading docstring doesn't have idiomatic Python formatting. It is |
| # printed by gdb's "help" command (the first line is printed in the |
| # "help data" summary), and it should match how other help texts look in |
| # gdb. |
| class DumpGuestMemory(gdb.Command): |
| """Extract guest vmcore from qemu process coredump. |
| |
| The two required arguments are FILE and ARCH: |
| FILE identifies the target file to write the guest vmcore to. |
| ARCH specifies the architecture for which the core will be generated. |
| |
| This GDB command reimplements the dump-guest-memory QMP command in |
| python, using the representation of guest memory as captured in the qemu |
| coredump. The qemu process that has been dumped must have had the |
| command line option "-machine dump-guest-core=on" which is the default. |
| |
| For simplicity, the "paging", "begin" and "end" parameters of the QMP |
| command are not supported -- no attempt is made to get the guest's |
| internal paging structures (ie. paging=false is hard-wired), and guest |
| memory is always fully dumped. |
| |
| Currently aarch64-be, aarch64-le, X86_64, 386, s390, ppc64-be, |
| ppc64-le guests are supported. |
| |
| The CORE/NT_PRSTATUS and QEMU notes (that is, the VCPUs' statuses) are |
| not written to the vmcore. Preparing these would require context that is |
| only present in the KVM host kernel module when the guest is alive. A |
| fake ELF note is written instead, only to keep the ELF parser of "crash" |
| happy. |
| |
| Dependent on how busted the qemu process was at the time of the |
| coredump, this command might produce unpredictable results. If qemu |
| deliberately called abort(), or it was dumped in response to a signal at |
| a halfway fortunate point, then its coredump should be in reasonable |
| shape and this command should mostly work.""" |
| |
| def __init__(self): |
| super(DumpGuestMemory, self).__init__("dump-guest-memory", |
| gdb.COMMAND_DATA, |
| gdb.COMPLETE_FILENAME) |
| self.elf = None |
| self.guest_phys_blocks = None |
| |
| def dump_init(self, vmcore): |
| """Prepares and writes ELF structures to core file.""" |
| |
| # Needed to make crash happy, data for more useful notes is |
| # not available in a qemu core. |
| self.elf.add_note("NONE", "EMPTY", 0) |
| |
| # We should never reach PN_XNUM for paging=false dumps, |
| # there's just a handful of discontiguous ranges after |
| # merging. |
| # The constant is needed to account for the PT_NOTE segment. |
| phdr_num = len(self.guest_phys_blocks) + 1 |
| assert phdr_num < PN_XNUM |
| |
| for block in self.guest_phys_blocks: |
| block_size = block["target_end"] - block["target_start"] |
| self.elf.add_segment(PT_LOAD, block["target_start"], block_size) |
| |
| self.elf.to_file(vmcore) |
| |
| def dump_iterate(self, vmcore): |
| """Writes guest core to file.""" |
| |
| qemu_core = gdb.inferiors()[0] |
| for block in self.guest_phys_blocks: |
| cur = block["host_addr"] |
| left = block["target_end"] - block["target_start"] |
| print("dumping range at %016x for length %016x" % |
| (cur.cast(UINTPTR_T), left)) |
| |
| while left > 0: |
| chunk_size = min(TARGET_PAGE_SIZE, left) |
| chunk = qemu_core.read_memory(cur, chunk_size) |
| vmcore.write(chunk) |
| cur += chunk_size |
| left -= chunk_size |
| |
| def invoke(self, args, from_tty): |
| """Handles command invocation from gdb.""" |
| |
| # Unwittingly pressing the Enter key after the command should |
| # not dump the same multi-gig coredump to the same file. |
| self.dont_repeat() |
| |
| argv = gdb.string_to_argv(args) |
| if len(argv) != 2: |
| raise gdb.GdbError("usage: dump-guest-memory FILE ARCH") |
| |
| self.elf = ELF(argv[1]) |
| self.guest_phys_blocks = get_guest_phys_blocks() |
| |
| with open(argv[0], "wb") as vmcore: |
| self.dump_init(vmcore) |
| self.dump_iterate(vmcore) |
| |
| DumpGuestMemory() |
