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disassembler.py
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# Copyright 2019 Clevernet # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. from os import linesep import ctypes as ct from .table import get_table_type_name class OffsetUnion(ct.Union): _fields_ = [('offsetu', ct.c_uint16), ('offset', ct.c_int16)] class ImmUnion(ct.Union): _fields_ = [('immu', ct.c_uint32), ('imm', ct.c_int32)] class BPFInstrFields(ct.Structure): _pack_ = 1 _anonymous_ = ('o', 'i') _fields_ = [('opcode', ct.c_uint8), ('dst', ct.c_uint8, 4), ('src', ct.c_uint8, 4), ('o', OffsetUnion), ('i', ImmUnion)] class BPFInstr(ct.Union): _pack_ = 1 _anonymous_ = ('s') _fields_ = [('s', BPFInstrFields), ('instr', ct.c_uint64)] class BPFDecoder(): BPF_PSEUDO_CALL = 1 bpf_helpers = ['unspec', 'map_lookup_elem', 'map_update_elem', 'map_delete_elem', 'probe_read', 'ktime_get_ns', 'trace_printk', 'get_prandom_u32', 'get_smp_processor_id', 'skb_store_bytes', 'l3_csum_replace', 'l4_csum_replace', 'tail_call', 'clone_redirect', 'get_current_pid_tgid', 'get_current_uid_gid', 'get_current_comm', 'get_cgroup_classid', 'skb_vlan_push', 'skb_vlan_pop', 'skb_get_tunnel_key', 'skb_set_tunnel_key', 'perf_event_read', 'redirect', 'get_route_realm', 'perf_event_output', 'skb_load_bytes', 'get_stackid', 'csum_diff', 'skb_get_tunnel_opt', 'skb_set_tunnel_opt', 'skb_change_proto', 'skb_change_type', 'skb_under_cgroup', 'get_hash_recalc', 'get_current_task', 'probe_write_user', 'current_task_under_cgroup', 'skb_change_tail', 'skb_pull_data', 'csum_update', 'set_hash_invalid', 'get_numa_node_id', 'skb_change_head', 'xdp_adjust_head', 'probe_read_str', 'get_socket_cookie', 'get_socket_uid', 'set_hash', 'setsockopt', 'skb_adjust_room', 'redirect_map', 'sk_redirect_map', 'sock_map_update', 'xdp_adjust_meta', 'perf_event_read_value', 'perf_prog_read_value', 'getsockopt', 'override_return', 'sock_ops_cb_flags_set', 'msg_redirect_map', 'msg_apply_bytes', 'msg_cork_bytes', 'msg_pull_data', 'bind', 'xdp_adjust_tail', 'skb_get_xfrm_state', 'get_stack', 'skb_load_bytes_relative', 'fib_lookup', 'sock_hash_update', 'msg_redirect_hash', 'sk_redirect_hash', 'lwt_push_encap', 'lwt_seg6_store_bytes', 'lwt_seg6_adjust_srh', 'lwt_seg6_action', 'rc_repeat', 'rc_keydown', 'skb_cgroup_id', 'get_current_cgroup_id', 'get_local_storage', 'sk_select_reuseport', 'skb_ancestor_cgroup_id', 'sk_lookup_tcp', 'sk_lookup_udp', 'sk_release', 'map_push_elem', 'map_pop_elem', 'map_peek_elem', 'msg_push_data', 'msg_pop_data', 'rc_pointer_rel'] opcodes = {0x04: ('add32', 'dstimm', '+=', 32), 0x05: ('ja', 'joff', None, 64), 0x07: ('add', 'dstimm', '+=', 64), 0x0c: ('add32', 'dstsrc', '+=', 32), 0x0f: ('add', 'dstsrc', '+=', 64), 0x14: ('sub32', 'dstimm', '-=', 32), 0x15: ('jeq', 'jdstimmoff', '==', 64), 0x17: ('sub', 'dstimm', '-=', 64), 0x18: ('lddw', 'lddw', None, 64), 0x1c: ('sub32', 'dstsrc', '-=', 32), 0x1d: ('jeq', 'jdstsrcoff', '==', 64), 0x1f: ('sub', 'dstsrc', '-=', 64), 0x20: ('ldabsw', 'ldabs', None, 32), 0x24: ('mul32', 'dstimm', '*=', 32), 0x25: ('jgt', 'jdstimmoff', '>', 64), 0x27: ('mul', 'dstimm', '*=', 64), 0x28: ('ldabsh', 'ldabs', None, 16), 0x2c: ('mul32', 'dstsrc', '*=', 32), 0x2d: ('jgt', 'jdstsrcoff', '>', 64), 0x2f: ('mul', 'dstsrc', '*=', 64), 0x30: ('ldabsb', 'ldabs', None, 8), 0x34: ('div32', 'dstimm', '/=', 32), 0x35: ('jge', 'jdstimmoff', '>=', 64), 0x37: ('div', 'dstimm', '/=', 64), 0x38: ('ldabsdw', 'ldabs', None, 64), 0x3c: ('div32', 'dstsrc', '/=', 32), 0x3d: ('jge', 'jdstsrcoff', '>=', 64), 0x3f: ('div', 'dstsrc', '/=', 64), 0x40: ('ldindw', 'ldind', None, 32), 0x44: ('or32', 'dstimm_bw', '|=', 32), 0x45: ('jset', 'jdstimmoff', '&', 64), 0x47: ('or', 'dstimm_bw', '|=', 64), 0x48: ('ldindh', 'ldind', None, 16), 0x4c: ('or32', 'dstsrc', '|=', 32), 0x4d: ('jset', 'jdstsrcoff', '&', 64), 0x4f: ('or', 'dstsrc', '|=', 64), 0x50: ('ldindb', 'ldind', None, 8), 0x54: ('and32', 'dstimm_bw', '&=', 32), 0x55: ('jne', 'jdstimmoff', '!=', 64), 0x57: ('and', 'dstimm_bw', '&=', 64), 0x58: ('ldinddw', 'ldind', None, 64), 0x5c: ('and32', 'dstsrc', '&=', 32), 0x5d: ('jne', 'jdstsrcoff', '!=', 64), 0x5f: ('and', 'dstsrc', '&=', 64), 0x61: ('ldxw', 'ldstsrcoff', None, 32), 0x62: ('stw', 'sdstoffimm', None, 32), 0x63: ('stxw', 'sdstoffsrc', None, 32), 0x64: ('lsh32', 'dstimm', '<<=', 32), 0x65: ('jsgt', 'jdstimmoff', 's>', 64), 0x67: ('lsh', 'dstimm', '<<=', 64), 0x69: ('ldxh', 'ldstsrcoff', None, 16), 0x6a: ('sth', 'sdstoffimm', None, 16), 0x6b: ('stxh', 'sdstoffsrc', None, 16), 0x6c: ('lsh32', 'dstsrc', '<<=', 32), 0x6d: ('jsgt', 'jdstsrcoff', 's>', 64), 0x6f: ('lsh', 'dstsrc', '<<=', 64), 0x71: ('ldxb', 'ldstsrcoff', None, 8), 0x72: ('stb', 'sdstoffimm', None, 8), 0x73: ('stxb', 'sdstoffsrc', None, 8), 0x74: ('rsh32', 'dstimm', '>>=', 32), 0x75: ('jsge', 'jdstimmoff', 's>=', 64), 0x77: ('rsh', 'dstimm', '>>=', 64), 0x79: ('ldxdw', 'ldstsrcoff', None, 64), 0x7a: ('stdw', 'sdstoffimm', None, 64), 0x7b: ('stxdw', 'sdstoffsrc', None, 64), 0x7c: ('rsh32', 'dstsrc', '>>=', 32), 0x7d: ('jsge', 'jdstsrcoff', 's>=', 64), 0x7f: ('rsh', 'dstsrc', '>>=', 64), 0x84: ('neg32', 'dst', '~', 32), 0x85: ('call', 'call', None, 64), 0x87: ('neg', 'dst', '~', 64), 0x94: ('mod32', 'dstimm', '%=', 32), 0x95: ('exit', 'exit', None, 64), 0x97: ('mod', 'dstimm', '%=', 64), 0x9c: ('mod32', 'dstsrc', '%=', 32), 0x9f: ('mod', 'dstsrc', '%=', 64), 0xa4: ('xor32', 'dstimm_bw', '^=', 32), 0xa5: ('jlt', 'jdstimmoff', '<', 64), 0xa7: ('xor', 'dstimm_bw', '^=', 64), 0xac: ('xor32', 'dstsrc', '^=', 32), 0xad: ('jlt', 'jdstsrcoff', '<', 64), 0xaf: ('xor', 'dstsrc', '^=', 64), 0xb4: ('mov32', 'dstimm', '=', 32), 0xb5: ('jle', 'jdstimmoff', '<=', 64), 0xb7: ('mov', 'dstimm', '=', 64), 0xbc: ('mov32', 'dstsrc', '=', 32), 0xbd: ('jle', 'jdstsrcoff', '<=', 64), 0xbf: ('mov', 'dstsrc', '=', 64), 0xc4: ('arsh32', 'dstimm', 's>>=', 32), 0xc5: ('jslt', 'jdstimmoff', 's<', 64), 0xc7: ('arsh', 'dstimm', 's>>=', 64), 0xcc: ('arsh32', 'dstsrc', 's>>=', 32), 0xcd: ('jslt', 'jdstsrcoff', 's<', 64), 0xcf: ('arsh', 'dstsrc', 's>>=', 64), 0xd5: ('jsle', 'jdstimmoff', 's<=', 64), 0xdc: ('endian32', 'dstsrc', 'endian', 32), 0xdd: ('jsle', 'jdstimmoff', 's<=', 64),} @classmethod def decode(cls, i, w, w1): try: name, opclass, op, bits = cls.opcodes[w.opcode] if opclass == 'dstimm': return 'r%d %s %d' % (w.dst, op, w.imm), 0 elif opclass == 'dstimm_bw': return 'r%d %s 0x%x' % (w.dst, op, w.immu), 0 elif opclass == 'joff': return 'goto %s <%d>' % ('%+d' % (w.offset), i + w.offset + 1), 0 elif opclass == 'dstsrc': return 'r%d %s r%d' % (w.dst, op, w.src), 0 elif opclass == 'jdstimmoff': return 'if r%d %s %d goto pc%s <%d>' % (w.dst, op, w.imm, '%+d' % (w.offset), i + w.offset + 1), 0 elif opclass == 'jdstsrcoff': return 'if r%d %s r%d goto pc%s <%d>' % (w.dst, op, w.src, '%+d' % (w.offset), i + w.offset + 1), 0 elif opclass == 'lddw': # imm contains the file descriptor (FD) of the map being loaded; # the kernel will translate this into the proper address if w1 is None: raise Exception("lddw requires two instructions to be disassembled") if w1.imm == 0: return 'r%d = <map at fd #%d>' % (w.dst, w.imm), 1 imm = (w1.imm << 32) | w.imm return 'r%d = 0x%x' % (w.dst, imm), 1 elif opclass == 'ldabs': return 'r0 = *(u%s*)skb[%s]' % (bits, w.imm), 0 elif opclass == 'ldind': return 'r0 = *(u%d*)skb[r%d %s]' % (bits, w.src, '%+d' % (w.imm)), 0 elif opclass == 'ldstsrcoff': return 'r%d = *(u%d*)(r%d %s)' % (w.dst, bits, w.src, '%+d' % (w.offset)), 0 elif opclass == 'sdstoffimm': return '*(u%d*)(r%d %s) = %d' % (bits, w.dst, '%+d' % (w.offset), w.imm), 0 elif opclass == 'sdstoffsrc': return '*(u%d*)(r%d %s) = r%d' % (bits, w.dst, '%+d' % (w.offset), w.src), 0 elif opclass == 'dst': return 'r%d = %s (u%s)r%d' % (w.dst, op, bits, w.dst), 0 elif opclass == 'call': if w.src != cls.BPF_PSEUDO_CALL: try: return '%s bpf_%s#%d' % (name, cls.bpf_helpers[w.immu], w.immu), 0 except IndexError: return '%s <unknown helper #%d>' % (op, w.immu), 0 return '%s %s' % (name, '%+d' % (w.imm)), 0 elif opclass == 'exit': return name, 0 else: raise Exception('unknown opcode class') except KeyError: return 'unknown <0x%x>' % (w.opcode) def disassemble_instruction(i, w0, w1=None): instr, skip = BPFDecoder.decode(i, w0, w1) return "%4d: (%02x) %s" % (i, w0.opcode, instr), skip def disassemble_str(bpfstr): ptr = ct.cast(ct.c_char_p(bpfstr), ct.POINTER(BPFInstr)) numinstr = int(len(bpfstr) / 8) w0 = ptr[0] skip = 0 instr_list = [] for i in range(1, numinstr): w1 = ptr[i] if skip: skip -= 1 instr_str = "%4d: (64-bit upper word)" % (i) else: instr_str, skip = disassemble_instruction(i - 1, w0, w1) instr_list.append(instr_str) w0 = w1 instr_str, skip = disassemble_instruction(numinstr - 1, w0, None) instr_list.append(instr_str) return instr_list def disassemble_prog(func_name, bpfstr): instr_list = ["Disassemble of BPF program %s:" % (func_name)] instr_list += disassemble_str(bpfstr) return linesep.join(instr_list) class MapDecoder (): ctype2str = {ct.c_bool: u"_Bool", ct.c_char: u"char", ct.c_wchar: u"wchar_t", ct.c_ubyte: u"unsigned char", ct.c_short: u"short", ct.c_ushort: u"unsigned short", ct.c_int: u"int", ct.c_uint: u"unsigned int", ct.c_long: u"long", ct.c_ulong: u"unsigned long", ct.c_longlong: u"long long", ct.c_ulonglong: u"unsigned long long", ct.c_float: u"float", ct.c_double: u"double", ct.c_longdouble: u"long double", ct.c_int64 * 2: u"__int128", ct.c_uint64 * 2: u"unsigned __int128",} @classmethod def get_ct_name(cls, t): try: if issubclass(t, ct.Structure): field_type_name = "struct" elif issubclass(t, ct.Union): field_type_name = "union" elif issubclass(t, ct.Array): field_type_name = cls.ctype2str[t._type_] + "[" + str(t._length_) + "]" else: field_type_name = cls.ctype2str[t] except KeyError: field_type_name = str(t) return field_type_name @classmethod def format_size_info(cls, offset, size, enabled=False, bitoffset=None): if not enabled: return "" if bitoffset is not None: return "[%d,%d +%d bit]" % (offset, bitoffset, size) return "[%d +%d] " % (offset, size) @classmethod def print_ct_map(cls, t, indent="", offset=0, sizeinfo=False): map_lines = [] try: for field_name, field_type in t._fields_: is_structured = (issubclass(field_type, ct.Structure) or issubclass(field_type, ct.Union)) field_type_name = cls.get_ct_name(field_type) field_offset = getattr(t, field_name).offset field_size = ct.sizeof(field_type) sizedesc = cls.format_size_info(offset + field_offset, field_size, sizeinfo) if is_structured: map_lines.append("%s%s%s {" % (indent, sizedesc, field_type_name)) map_lines += cls.print_ct_map(field_type, indent + " ", offset + field_offset) map_lines.append("%s} %s;" % (indent, field_name)) else: map_lines.append("%s%s%s %s;" % (indent, sizedesc, field_type_name, field_name)) except ValueError: # is a bit field offset_bits = 0 for field in t._fields_: if len(field) == 3: field_name, field_type, field_bits = field field_type_name = cls.get_ct_name(field_type) sizedesc = cls.format_size_info(offset, offset_bits, sizeinfo, field_bits) map_lines.append("%s%s%s %s:%d;" % (indent, sizedesc, field_type_name, field_name, field_bits)) else: # end of previous bit field field_name, field_type = field field_type_name = cls.get_ct_name(field_type) field_offset = getattr(t, field_name).offset field_size = ct.sizeof(field_type) field_bits = 0 offset_bits = 0 sizedesc = cls.format_size_info(offset + field_offset, field_size, sizeinfo) map_lines.append("%s%s%s %s;" % (indent, sizedesc, field_type_name, field_name)) offset += field_offset offset_bits += field_bits return map_lines @classmethod def print_map_ctype(cls, t, field_name, sizeinfo): is_structured = (issubclass(t, ct.Structure) or issubclass(t, ct.Union)) type_name = cls.get_ct_name(t) if is_structured: map_lines = [" %s {" % (type_name)] map_lines += cls.print_ct_map(t, " ", sizeinfo=sizeinfo) map_lines.append(" } %s;" % (field_name)) else: map_lines = [" %s %s;" % (type_name, field_name)] return map_lines @classmethod def decode_map(cls, map_name, map_obj, map_type, sizeinfo=False): map_lines = ['Layout of BPF map %s (type %s, FD %d, ID %d):' % (map_name, map_type, map_obj.map_fd, map_obj.map_id)] map_lines += cls.print_map_ctype(map_obj.Key, 'key', sizeinfo=sizeinfo) map_lines += cls.print_map_ctype(map_obj.Leaf, 'value', sizeinfo=sizeinfo) return linesep.join(map_lines) def decode_map(map_name, map_obj, map_type, sizeinfo=False): map_type_name = get_table_type_name(map_type) return MapDecoder.decode_map(map_name, map_obj, map_type_name, sizeinfo=sizeinfo)