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Fix RTT Control Block Search #1669

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Fix RTT Control Block Search #1669

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60 changes: 24 additions & 36 deletions pyocd/debug/rtt.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
# Copyright (C) 2021 Simon D. Levy <simon.d.levy@gmail.com>
# Copyright (C) 2022 Johan Carlsson <johan.carlsson@teenage.engineering>
# Copyright (c) 2022 Samuel Dewan
# Copyright (c) 2024 Ein Terakawa <applause@elfmimi.jp>
# SPDX-License-Identifier: Apache-2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
Expand Down Expand Up @@ -387,8 +388,8 @@ class GenericRTTControlBlock(RTTControlBlock):

target: SoCTarget
_cb_search_address: int
_cb_search_size_words: int
_control_block_id: Sequence[int]
_cb_search_size: int
_control_block_id: bytes

def __init__(self, target: SoCTarget, address: int = None,
size: int = None, control_block_id: bytes = b'SEGGER RTT'):
Expand Down Expand Up @@ -418,45 +419,32 @@ def __init__(self, target: SoCTarget, address: int = None,
if size is None:
# Address was specified, but size was not. Assume that the control
# block is located exactly at the provided address.
self._cb_search_size_words = 0
self._cb_search_size = 0
else:
self._cb_search_size_words = size // 4

extra_id_bytes = SEGGER_RTT_CB.acID.size - len(control_block_id)
control_block_bytes = control_block_id + b'\0' * extra_id_bytes
self._control_block_id = struct.unpack("<IIII", control_block_bytes)
self._cb_search_size = size
self._control_block_id = control_block_id

def _find_control_block(self) -> Optional[int]:
addr: int = self._cb_search_address & ~0x3
search_size: int = self._cb_search_size_words
if search_size < len(self._control_block_id):
search_size = len(self._control_block_id)
id_bytes: bytes = self._control_block_id
id_size: int = len(id_bytes)
addr: int = self._cb_search_address
search_size: int = max(self._cb_search_size, id_size)
carry_over_size: int = (1 - id_size) // 4 * 4 # it's negative!
chunk_size: int = 1024

data: bytes = b''
while search_size:
read_size: int = min(search_size, chunk_size)
prev: bytes = data[carry_over_size:]
data = bytes(self.target.read_memory_block8(addr, read_size))
idx: int = (prev + data).find(id_bytes)
if idx >= 0:
return addr - len(prev) + idx

id_len = len(self._control_block_id)
offset: int = 0
addr += read_size
search_size -= read_size

while search_size:
read_size = min(search_size, 32)
data = self.target.read_memory_block32(addr, read_size)

if not data:
break

for word in data:
if word == self._control_block_id[offset]:
offset += 1
if offset == id_len:
break
else:
num_skip_words = (offset + 1)
addr += (num_skip_words * 4)
search_size -= num_skip_words
offset = 0

if offset == id_len:
break

return addr if offset == id_len else None
return None

def start(self):
"""@brief Find the RTT control block on the target.
Expand Down