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Support memory slicing #1151

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Support memory slicing #1151

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2e8a703
Support memory slicing
wtdcode May 8, 2022
11224c3
Fix typo
wtdcode May 8, 2022
9f78b69
Check None correctly
wtdcode May 8, 2022
41d6d30
mimic bytearray
wtdcode May 9, 2022
295ea60
Enforce ql.mem[addr:] to be more intuitive
wtdcode May 10, 2022
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39 changes: 38 additions & 1 deletion qiling/os/memory.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
#

import os, re
from typing import Any, Callable, List, MutableSequence, Optional, Sequence, Tuple
from typing import Any, Callable, List, MutableSequence, Optional, Sequence, Tuple, Union

from unicorn import UC_PROT_NONE, UC_PROT_READ, UC_PROT_WRITE, UC_PROT_EXEC, UC_PROT_ALL

Expand Down Expand Up @@ -63,6 +63,43 @@ def __read_string(self, addr: int) -> str:
def __write_string(self, addr: int, s: str, encoding: str):
self.write(addr, bytes(s, encoding) + b'\x00')

def __getitem__(self, key: Union[slice, int]) -> bytearray:
if isinstance(key, slice):
start = key.start
stop = key.stop
step = key.step

if step is not None and step != 1:
# step != 1 means we have to do copy, don't allow it.
raise IndexError("Only support slicing continous memory")

return self.ql.mem.read(start, max(0, stop - start))
elif isinstance(key, int):
return self.ql.mem.read(key, 1)[0]
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@LukeSerne LukeSerne May 15, 2022 •
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This line returns an int, not bytearray, which is somewhat counterintuitive, inconsistent with the case where a slice is given as argument, and goes against the type annotation. I think you should remove the [0]. Also, I'm not sure why this code uses self.ql.mem instead of self. In this class, they reference / point to the same thing, right?

Suggested change
return self.ql.mem.read(key, 1)[0]
return self.read(key, 1)

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This line returns an int, not bytearray, which is somewhat counterintuitive. I think you should remove the [0].

Because we (try to) provide the same interface as bytearray, e.g.:

In [1]: a = bytearray(b"\x01\x02")

In [2]: type(a[0])
Out[2]: int

In [3]:

Also, I'm not sure why this code uses self.ql.mem instead of self. In this class, they reference / point to the same thing, right?

Good point.

else:
raise KeyError("Wrong type of key")

def __setitem__(self, key: Union[slice, int], value: bytes):
if isinstance(key, int):
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self.ql.mem.write(key, bytes([value]))
elif isinstance(key, slice):
start = key.start
stop = key.stop
step = key.step

if step is not None and step != 1:
raise IndexError("Only support slicing continous memory")

if start is None:
raise IndexError("The start of memory is not supplied")

if stop is not None and len(value) > stop - start:
raise IndexError("Bytes to write are more than sliced memory")

self.ql.mem.write(start, value)
else:
raise KeyError("Wrong type of key")

# TODO: this is an obsolete utility method that should not be used anymore
# and here for backward compatibility. use QlOsUtils.read_cstring instead
def string(self, addr: int, value=None, encoding='utf-8') -> Optional[str]:
Expand Down