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[Qemu-devel] [PATCH 5/6] scripts/dump-guest-memory.py: Introduce multi-a
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From: |
Janosch Frank |
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Subject: |
[Qemu-devel] [PATCH 5/6] scripts/dump-guest-memory.py: Introduce multi-arch support |
|
Date: |
Fri, 22 Jan 2016 13:08:39 +0100 |
By modelling the ELF with ctypes we not only gain full python 3
support but can also create dumps for different architectures more easily.
Tested-by: Andrew Jones <address@hidden>
Acked-by: Laszlo Ersek <address@hidden>
Signed-off-by: Janosch Frank <address@hidden>
---
scripts/dump-guest-memory.py | 486 ++++++++++++++++++++++++++++---------------
1 file changed, 322 insertions(+), 164 deletions(-)
diff --git a/scripts/dump-guest-memory.py b/scripts/dump-guest-memory.py
index 2cf7365..7acce65 100644
--- a/scripts/dump-guest-memory.py
+++ b/scripts/dump-guest-memory.py
@@ -6,6 +6,7 @@
#
# Authors:
# Laszlo Ersek <address@hidden>
+# Janosch Frank <address@hidden>
#
# This work is licensed under the terms of the GNU GPL, version 2 or later. See
# the COPYING file in the top-level directory.
@@ -15,58 +16,303 @@
# "help data" summary), and it should match how other help texts look in
# gdb.
-import struct
+import ctypes
UINTPTR_T = gdb.lookup_type("uintptr_t")
TARGET_PAGE_SIZE = 0x1000
TARGET_PAGE_MASK = 0xFFFFFFFFFFFFF000
-# Various ELF constants
-EM_X86_64 = 62 # AMD x86-64 target machine
-ELFDATA2LSB = 1 # little endian
-ELFCLASS64 = 2
-ELFMAG = "\x7FELF"
-EV_CURRENT = 1
-ET_CORE = 4
-PT_LOAD = 1
-PT_NOTE = 4
-
# 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
-# Format strings for packing and header size calculation.
-ELF64_EHDR = ("4s" # e_ident/magic
- "B" # e_ident/class
- "B" # e_ident/data
- "B" # e_ident/version
- "B" # e_ident/osabi
- "8s" # e_ident/pad
- "H" # e_type
- "H" # e_machine
- "I" # e_version
- "Q" # e_entry
- "Q" # e_phoff
- "Q" # e_shoff
- "I" # e_flags
- "H" # e_ehsize
- "H" # e_phentsize
- "H" # e_phnum
- "H" # e_shentsize
- "H" # e_shnum
- "H" # e_shstrndx
- )
-ELF64_PHDR = ("I" # p_type
- "I" # p_flags
- "Q" # p_offset
- "Q" # p_vaddr
- "Q" # p_paddr
- "Q" # p_filesz
- "Q" # p_memsz
- "Q" # p_align
- )
+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.endianess = None
+ self.elfclass = ELFCLASS64
+
+ if arch == 'aarch64-le':
+ self.endianess = ELFDATA2LSB
+ self.elfclass = ELFCLASS64
+ self.ehdr = get_arch_ehdr(self.endianess, self.elfclass)
+ self.ehdr.e_machine = EM_AARCH
+
+ elif arch == 'aarch64-be':
+ self.endianess = ELFDATA2MSB
+ self.ehdr = get_arch_ehdr(self.endianess, self.elfclass)
+ self.ehdr.e_machine = EM_AARCH
+
+ elif arch == 'X86_64':
+ self.endianess = ELFDATA2LSB
+ self.ehdr = get_arch_ehdr(self.endianess, self.elfclass)
+ self.ehdr.e_machine = EM_X86_64
+
+ elif arch == '386':
+ self.endianess = ELFDATA2LSB
+ self.elfclass = ELFCLASS32
+ self.ehdr = get_arch_ehdr(self.endianess, self.elfclass)
+ self.ehdr.e_machine = EM_386
+
+ elif arch == 's390':
+ self.endianess = ELFDATA2MSB
+ self.ehdr = get_arch_ehdr(self.endianess, self.elfclass)
+ self.ehdr.e_machine = EM_S390
+
+ elif arch == 'ppc64-le':
+ self.endianess = ELFDATA2LSB
+ self.ehdr = get_arch_ehdr(self.endianess, self.elfclass)
+ self.ehdr.e_machine = EM_PPC64
+
+ elif arch == 'ppc64-be':
+ self.endianess = ELFDATA2MSB
+ self.ehdr = get_arch_ehdr(self.endianess, 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.endianess, 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.endianess, 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(endianess, len_name, len_desc):
+ """Returns a Note class with the specified endianess."""
+
+ if endianess == 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, endianess, 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 = endianess
+ self.ei_version = EV_CURRENT
+
+
+def get_arch_ehdr(endianess, elfclass):
+ """Returns a EHDR64 class with the specified endianess."""
+
+ if endianess == 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(endianess, 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(endianess,
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(endianess, 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(endianess,
elfclass))
+ self.e_phnum = 0
+
+ # End get_arch_ehdr
+ if elfclass == ELFCLASS64:
+ return EHDR64()
+ else:
+ return EHDR32()
+
+
+def get_arch_phdr(endianess, elfclass):
+ """Returns a 32 or 64 bit PHDR class with the specified endianess."""
+
+ if endianess == 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."""
@@ -188,20 +434,22 @@ def get_guest_phys_blocks():
class DumpGuestMemory(gdb.Command):
"""Extract guest vmcore from qemu process coredump.
-The sole argument is FILE, identifying the target file to write the
-guest vmcore to.
+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".
+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.
-Only x86_64 guests are supported.
+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
@@ -219,129 +467,39 @@ shape and this command should mostly work."""
super(DumpGuestMemory, self).__init__("dump-guest-memory",
gdb.COMMAND_DATA,
gdb.COMPLETE_FILENAME)
- self.elf64_ehdr_le = struct.Struct("<%s" % ELF64_EHDR)
- self.elf64_phdr_le = struct.Struct("<%s" % ELF64_PHDR)
+ self.elf = None
self.guest_phys_blocks = None
- def cpu_get_dump_info(self):
- # We can't synchronize the registers with KVM post-mortem, and
- # the bits in (first_x86_cpu->env.hflags) seem to be stale; they
- # may not reflect long mode for example. Hence just assume the
- # most common values. This also means that instruction pointer
- # etc. will be bogus in the dump, but at least the RAM contents
- # should be valid.
- self.dump_info = {"d_machine": EM_X86_64,
- "d_endian" : ELFDATA2LSB,
- "d_class" : ELFCLASS64}
+ def dump_init(self, vmcore):
+ """Prepares and writes ELF structures to core file."""
- def encode_elf64_ehdr_le(self):
- return self.elf64_ehdr_le.pack(
- ELFMAG, # e_ident/magic
- self.dump_info["d_class"], # e_ident/class
- self.dump_info["d_endian"], # e_ident/data
- EV_CURRENT, # e_ident/version
- 0, # e_ident/osabi
- "", # e_ident/pad
- ET_CORE, # e_type
- self.dump_info["d_machine"], # e_machine
- EV_CURRENT, # e_version
- 0, # e_entry
- self.elf64_ehdr_le.size, # e_phoff
- 0, # e_shoff
- 0, # e_flags
- self.elf64_ehdr_le.size, # e_ehsize
- self.elf64_phdr_le.size, # e_phentsize
- self.phdr_num, # e_phnum
- 0, # e_shentsize
- 0, # e_shnum
- 0 # e_shstrndx
- )
+ # Needed to make crash happy, data for more useful notes is
+ # not available in a qemu core.
+ self.elf.add_note("NONE", "EMPTY", 0)
- def encode_elf64_note_le(self):
- return self.elf64_phdr_le.pack(PT_NOTE, # p_type
- 0, # p_flags
- (self.memory_offset -
- len(self.note)), # p_offset
- 0, # p_vaddr
- 0, # p_paddr
- len(self.note), # p_filesz
- len(self.note), # p_memsz
- 0 # p_align
- )
+ # 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
- def encode_elf64_load_le(self, offset, start_hwaddr, range_size):
- return self.elf64_phdr_le.pack(PT_LOAD, # p_type
- 0, # p_flags
- offset, # p_offset
- 0, # p_vaddr
- start_hwaddr, # p_paddr
- range_size, # p_filesz
- range_size, # p_memsz
- 0 # p_align
- )
-
- def note_init(self, name, desc, type):
- # name must include a trailing NUL
- namesz = (len(name) + 1 + 3) / 4 * 4
- descsz = (len(desc) + 3) / 4 * 4
- fmt = ("<" # little endian
- "I" # n_namesz
- "I" # n_descsz
- "I" # n_type
- "%us" # name
- "%us" # desc
- % (namesz, descsz))
- self.note = struct.pack(fmt,
- len(name) + 1, len(desc), type, name, desc)
-
- def dump_init(self):
- self.guest_phys_blocks = get_guest_phys_blocks()
- self.cpu_get_dump_info()
- # we have no way to retrieve the VCPU status from KVM
- # post-mortem
- self.note_init("NONE", "EMPTY", 0)
-
- # Account for PT_NOTE.
- self.phdr_num = 1
-
- # We should never reach PN_XNUM for paging=false dumps: there's
- # just a handful of discontiguous ranges after merging.
- self.phdr_num += len(self.guest_phys_blocks)
- assert self.phdr_num < PN_XNUM
-
- # Calculate the ELF file offset where the memory dump commences:
- #
- # ELF header
- # PT_NOTE
- # PT_LOAD: 1
- # PT_LOAD: 2
- # ...
- # PT_LOAD: len(self.guest_phys_blocks)
- # ELF note
- # memory dump
- self.memory_offset = (self.elf64_ehdr_le.size +
- self.elf64_phdr_le.size * self.phdr_num +
- len(self.note))
-
- def dump_begin(self, vmcore):
- vmcore.write(self.encode_elf64_ehdr_le())
- vmcore.write(self.encode_elf64_note_le())
- running = self.memory_offset
for block in self.guest_phys_blocks:
- range_size = block["target_end"] - block["target_start"]
- vmcore.write(self.encode_elf64_load_le(running,
- block["target_start"],
- range_size))
- running += range_size
- vmcore.write(self.note)
+ 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)
@@ -349,22 +507,22 @@ shape and this command should mostly work."""
cur += chunk_size
left -= chunk_size
- def create_vmcore(self, filename):
- vmcore = open(filename, "wb")
- self.dump_begin(vmcore)
- self.dump_iterate(vmcore)
- vmcore.close()
-
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) != 1:
- raise gdb.GdbError("usage: dump-guest-memory FILE")
+ if len(argv) != 2:
+ raise gdb.GdbError("usage: dump-guest-memory FILE ARCH")
- self.dump_init()
- self.create_vmcore(argv[0])
+ 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()
--
2.3.0
- [Qemu-devel] [PATCH 0/6] scripts/dump-guest-memory.py: Add multi-arch support, Janosch Frank, 2016/01/22
- [Qemu-devel] [PATCH 5/6] scripts/dump-guest-memory.py: Introduce multi-arch support,
Janosch Frank <=
- [Qemu-devel] [PATCH 6/6] scripts/dump-guest-memory.py: Fix module docstring, Janosch Frank, 2016/01/22
- [Qemu-devel] [PATCH 4/6] scripts/dump-guest-memory.py: Cleanup functions, Janosch Frank, 2016/01/22
- [Qemu-devel] [PATCH 2/6] scripts/dump-guest-memory.py: Make methods functions, Janosch Frank, 2016/01/22
- [Qemu-devel] [PATCH 3/6] scripts/dump-guest-memory.py: Improve python 3 compatibility, Janosch Frank, 2016/01/22
- [Qemu-devel] [PATCH 1/6] scripts/dump-guest-memory.py: Move constants to the top, Janosch Frank, 2016/01/22
- Re: [Qemu-devel] [PATCH 0/6] scripts/dump-guest-memory.py: Add multi-arch support, Paolo Bonzini, 2016/01/22