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# -------------------------------------------------------------------------------
# elftools: ehabi/decoder.py
#
# Decode ARM exception handler bytecode.
#
# LeadroyaL (leadroyal@qq.com)
# This code is in the public domain
# -------------------------------------------------------------------------------
from collections import namedtuple
class EHABIBytecodeDecoder(object):
""" Decoder of a sequence of ARM exception handler abi bytecode.
Reference:
https://github.com/llvm/llvm-project/blob/master/llvm/tools/llvm-readobj/ARMEHABIPrinter.h
https://developer.arm.com/documentation/ihi0038/b/
Accessible attributes:
mnemonic_array:
MnemonicItem array.
Parameters:
bytecode_array:
Integer array, raw data of bytecode.
"""
def __init__(self, bytecode_array):
self._bytecode_array = bytecode_array
self._index = None
self.mnemonic_array = None
self._decode()
def _decode(self):
""" Decode bytecode array, put result into mnemonic_array.
"""
self._index = 0
self.mnemonic_array = []
while self._index < len(self._bytecode_array):
for mask, value, handler in self.ring:
if (self._bytecode_array[self._index] & mask) == value:
start_idx = self._index
mnemonic = handler(self)
end_idx = self._index
self.mnemonic_array.append(
MnemonicItem(self._bytecode_array[start_idx: end_idx], mnemonic))
break
def _decode_00xxxxxx(self):
# SW.startLine() << format("0x%02X ; vsp = vsp + %u\n", Opcode,
# ((Opcode & 0x3f) << 2) + 4);
opcode = self._bytecode_array[self._index]
self._index += 1
return 'vsp = vsp + %u' % (((opcode & 0x3f) << 2) + 4)
def _decode_01xxxxxx(self):
# SW.startLine() << format("0x%02X ; vsp = vsp - %u\n", Opcode,
# ((Opcode & 0x3f) << 2) + 4);
opcode = self._bytecode_array[self._index]
self._index += 1
return 'vsp = vsp - %u' % (((opcode & 0x3f) << 2) + 4)
gpr_register_names = ("r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
"r8", "r9", "r10", "fp", "ip", "sp", "lr", "pc")
def _calculate_range(self, start, count):
return ((1 << (count + 1)) - 1) << start
def _printGPR(self, gpr_mask):
hits = [self.gpr_register_names[i] for i in range(32) if gpr_mask & (1 << i) != 0]
return '{%s}' % ', '.join(hits)
def _print_registers(self, vfp_mask, prefix):
hits = [prefix + str(i) for i in range(32) if vfp_mask & (1 << i) != 0]
return '{%s}' % ', '.join(hits)
def _decode_1000iiii_iiiiiiii(self):
op0 = self._bytecode_array[self._index]
self._index += 1
op1 = self._bytecode_array[self._index]
self._index += 1
# uint16_t GPRMask = (Opcode1 << 4) | ((Opcode0 & 0x0f) << 12);
# SW.startLine()
# << format("0x%02X 0x%02X ; %s",
# Opcode0, Opcode1, GPRMask ? "pop " : "refuse to unwind");
# if (GPRMask)
# PrintGPR(GPRMask);
gpr_mask = (op1 << 4) | ((op0 & 0x0f) << 12)
if gpr_mask == 0:
return 'refuse to unwind'
else:
return 'pop %s' % self._printGPR(gpr_mask)
def _decode_10011101(self):
self._index += 1
return 'reserved (ARM MOVrr)'
def _decode_10011111(self):
self._index += 1
return 'reserved (WiMMX MOVrr)'
def _decode_1001nnnn(self):
# SW.startLine() << format("0x%02X ; vsp = r%u\n", Opcode, (Opcode & 0x0f));
opcode = self._bytecode_array[self._index]
self._index += 1
return 'vsp = r%u' % (opcode & 0x0f)
def _decode_10100nnn(self):
# SW.startLine() << format("0x%02X ; pop ", Opcode);
# PrintGPR((((1 << ((Opcode & 0x7) + 1)) - 1) << 4));
opcode = self._bytecode_array[self._index]
self._index += 1
return 'pop %s' % self._printGPR(self._calculate_range(4, opcode & 0x07))
def _decode_10101nnn(self):
# SW.startLine() << format("0x%02X ; pop ", Opcode);
# PrintGPR((((1 << ((Opcode & 0x7) + 1)) - 1) << 4) | (1 << 14));
opcode = self._bytecode_array[self._index]
self._index += 1
return 'pop %s' % self._printGPR(self._calculate_range(4, opcode & 0x07) | (1 << 14))
def _decode_10110000(self):
# SW.startLine() << format("0x%02X ; finish\n", Opcode);
self._index += 1
return 'finish'
def _decode_10110001_0000iiii(self):
# SW.startLine()
# << format("0x%02X 0x%02X ; %s", Opcode0, Opcode1,
# ((Opcode1 & 0xf0) || Opcode1 == 0x00) ? "spare" : "pop ");
# if (((Opcode1 & 0xf0) == 0x00) && Opcode1)
# PrintGPR((Opcode1 & 0x0f));
self._index += 1 # skip constant byte
op1 = self._bytecode_array[self._index]
self._index += 1
if (op1 & 0xf0) != 0 or op1 == 0x00:
return 'spare'
else:
return 'pop %s' % self._printGPR((op1 & 0x0f))
def _decode_10110010_uleb128(self):
# SmallVector<uint8_t, 4> ULEB;
# do { ULEB.push_back(Opcodes[OI ^ 3]); } while (Opcodes[OI++ ^ 3] & 0x80);
# uint64_t Value = 0;
# for (unsigned BI = 0, BE = ULEB.size(); BI != BE; ++BI)
# Value = Value | ((ULEB[BI] & 0x7f) << (7 * BI));
# OS << format("; vsp = vsp + %" PRIu64 "\n", 0x204 + (Value << 2));
self._index += 1 # skip constant byte
uleb_buffer = [self._bytecode_array[self._index]]
self._index += 1
while self._bytecode_array[self._index] & 0x80 == 0:
uleb_buffer.append(self._bytecode_array[self._index])
self._index += 1
value = 0
for b in reversed(uleb_buffer):
value = (value << 7) + (b & 0x7F)
return 'vsp = vsp + %u' % (0x204 + (value << 2))
def _decode_10110011_sssscccc(self):
# these two decoders are equal
return self._decode_11001001_sssscccc()
def _decode_101101nn(self):
return self._spare()
def _decode_10111nnn(self):
# SW.startLine() << format("0x%02X ; pop ", Opcode);
# PrintRegisters((((1 << ((Opcode & 0x07) + 1)) - 1) << 8), "d");
opcode = self._bytecode_array[self._index]
self._index += 1
return 'pop %s' % self._print_registers(self._calculate_range(8, opcode & 0x07), "d")
def _decode_11000110_sssscccc(self):
# SW.startLine() << format("0x%02X 0x%02X ; pop ", Opcode0, Opcode1);
# uint8_t Start = ((Opcode1 & 0xf0) >> 4);
# uint8_t Count = ((Opcode1 & 0x0f) >> 0);
# PrintRegisters((((1 << (Count + 1)) - 1) << Start), "wR");
self._index += 1 # skip constant byte
op1 = self._bytecode_array[self._index]
self._index += 1
start = ((op1 & 0xf0) >> 4)
count = ((op1 & 0x0f) >> 0)
return 'pop %s' % self._print_registers(self._calculate_range(start, count), "wR")
def _decode_11000111_0000iiii(self):
# SW.startLine()
# << format("0x%02X 0x%02X ; %s", Opcode0, Opcode1,
# ((Opcode1 & 0xf0) || Opcode1 == 0x00) ? "spare" : "pop ");
# if ((Opcode1 & 0xf0) == 0x00 && Opcode1)
# PrintRegisters(Opcode1 & 0x0f, "wCGR");
self._index += 1 # skip constant byte
op1 = self._bytecode_array[self._index]
self._index += 1
if (op1 & 0xf0) != 0 or op1 == 0x00:
return 'spare'
else:
return 'pop %s' % self._print_registers(op1 & 0x0f, "wCGR")
def _decode_11001000_sssscccc(self):
# SW.startLine() << format("0x%02X 0x%02X ; pop ", Opcode0, Opcode1);
# uint8_t Start = 16 + ((Opcode1 & 0xf0) >> 4);
# uint8_t Count = ((Opcode1 & 0x0f) >> 0);
# PrintRegisters((((1 << (Count + 1)) - 1) << Start), "d");
self._index += 1 # skip constant byte
op1 = self._bytecode_array[self._index]
self._index += 1
start = 16 + ((op1 & 0xf0) >> 4)
count = ((op1 & 0x0f) >> 0)
return 'pop %s' % self._print_registers(self._calculate_range(start, count), "d")
def _decode_11001001_sssscccc(self):
# SW.startLine() << format("0x%02X 0x%02X ; pop ", Opcode0, Opcode1);
# uint8_t Start = ((Opcode1 & 0xf0) >> 4);
# uint8_t Count = ((Opcode1 & 0x0f) >> 0);
# PrintRegisters((((1 << (Count + 1)) - 1) << Start), "d");
self._index += 1 # skip constant byte
op1 = self._bytecode_array[self._index]
self._index += 1
start = ((op1 & 0xf0) >> 4)
count = ((op1 & 0x0f) >> 0)
return 'pop %s' % self._print_registers(self._calculate_range(start, count), "d")
def _decode_11001yyy(self):
return self._spare()
def _decode_11000nnn(self):
# SW.startLine() << format("0x%02X ; pop ", Opcode);
# PrintRegisters((((1 << ((Opcode & 0x07) + 1)) - 1) << 10), "wR");
opcode = self._bytecode_array[self._index]
self._index += 1
return 'pop %s' % self._print_registers(self._calculate_range(10, opcode & 0x07), "wR")
def _decode_11010nnn(self):
# these two decoders are equal
return self._decode_10111nnn()
def _decode_11xxxyyy(self):
return self._spare()
def _spare(self):
self._index += 1
return 'spare'
_DECODE_RECIPE_TYPE = namedtuple('_DECODE_RECIPE_TYPE', 'mask value handler')
ring = (
_DECODE_RECIPE_TYPE(mask=0xc0, value=0x00, handler=_decode_00xxxxxx),
_DECODE_RECIPE_TYPE(mask=0xc0, value=0x40, handler=_decode_01xxxxxx),
_DECODE_RECIPE_TYPE(mask=0xf0, value=0x80, handler=_decode_1000iiii_iiiiiiii),
_DECODE_RECIPE_TYPE(mask=0xff, value=0x9d, handler=_decode_10011101),
_DECODE_RECIPE_TYPE(mask=0xff, value=0x9f, handler=_decode_10011111),
_DECODE_RECIPE_TYPE(mask=0xf0, value=0x90, handler=_decode_1001nnnn),
_DECODE_RECIPE_TYPE(mask=0xf8, value=0xa0, handler=_decode_10100nnn),
_DECODE_RECIPE_TYPE(mask=0xf8, value=0xa8, handler=_decode_10101nnn),
_DECODE_RECIPE_TYPE(mask=0xff, value=0xb0, handler=_decode_10110000),
_DECODE_RECIPE_TYPE(mask=0xff, value=0xb1, handler=_decode_10110001_0000iiii),
_DECODE_RECIPE_TYPE(mask=0xff, value=0xb2, handler=_decode_10110010_uleb128),
_DECODE_RECIPE_TYPE(mask=0xff, value=0xb3, handler=_decode_10110011_sssscccc),
_DECODE_RECIPE_TYPE(mask=0xfc, value=0xb4, handler=_decode_101101nn),
_DECODE_RECIPE_TYPE(mask=0xf8, value=0xb8, handler=_decode_10111nnn),
_DECODE_RECIPE_TYPE(mask=0xff, value=0xc6, handler=_decode_11000110_sssscccc),
_DECODE_RECIPE_TYPE(mask=0xff, value=0xc7, handler=_decode_11000111_0000iiii),
_DECODE_RECIPE_TYPE(mask=0xff, value=0xc8, handler=_decode_11001000_sssscccc),
_DECODE_RECIPE_TYPE(mask=0xff, value=0xc9, handler=_decode_11001001_sssscccc),
_DECODE_RECIPE_TYPE(mask=0xc8, value=0xc8, handler=_decode_11001yyy),
_DECODE_RECIPE_TYPE(mask=0xf8, value=0xc0, handler=_decode_11000nnn),
_DECODE_RECIPE_TYPE(mask=0xf8, value=0xd0, handler=_decode_11010nnn),
_DECODE_RECIPE_TYPE(mask=0xc0, value=0xc0, handler=_decode_11xxxyyy),
)
class MnemonicItem(object):
""" Single mnemonic item.
"""
def __init__(self, bytecode, mnemonic):
self.bytecode = bytecode
self.mnemonic = mnemonic
def __repr__(self):
return '%s ; %s' % (' '.join(['0x%02x' % x for x in self.bytecode]), self.mnemonic)
|
