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# Copyright 2020 The Pigweed Authors
#
# 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
#
# https://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.
"""Tools to analyze Cortex-M CPU state context captured during an exception."""
from typing import Tuple
from pw_cpu_exception_cortex_m import cortex_m_constants
class CortexMExceptionAnalyzer:
"""This class provides helper functions to dump a ArmV7mCpuState proto."""
def __init__(self, cpu_state):
self._cpu_state = cpu_state
self._active_cfsr_fields = None
def active_cfsr_fields(self) -> Tuple[cortex_m_constants.BitField, ...]:
"""Returns a list of BitFields for each active CFSR flag."""
if self._active_cfsr_fields is not None:
return self._active_cfsr_fields
temp_field_list = []
if self._cpu_state.HasField('cfsr'):
for bit_field in cortex_m_constants.PW_CORTEX_M_CFSR_BIT_FIELDS:
if self._cpu_state.cfsr & bit_field.bit_mask:
temp_field_list.append(bit_field)
self._active_cfsr_fields = tuple(temp_field_list)
return self._active_cfsr_fields
def is_fault_active(self) -> bool:
"""Returns true if the current CPU state indicates a fault is active."""
if self._cpu_state.HasField('cfsr') and self._cpu_state.cfsr != 0:
return True
if self._cpu_state.HasField('icsr'):
exception_number = (
self._cpu_state.icsr
& cortex_m_constants.PW_CORTEX_M_ICSR_VECTACTIVE_MASK)
if (cortex_m_constants.PW_CORTEX_M_HARD_FAULT_ISR_NUM <=
exception_number <=
cortex_m_constants.PW_CORTEX_M_USAGE_FAULT_ISR_NUM):
return True
return False
def is_nested_fault(self) -> bool:
"""Returns true if the current CPU state indicates a nested fault."""
if not self.is_fault_active():
return False
if (self._cpu_state.HasField('hfsr') and self._cpu_state.hfsr
& cortex_m_constants.PW_CORTEX_M_HFSR_FORCED_MASK):
return True
return False
def exception_cause(self, show_active_cfsr_fields=True) -> str:
"""Analyzes CPU state to tries and classify the exception.
Examples:
show_active_cfsr_fields=False
unknown exception
memory management fault at 0x00000000
usage fault, imprecise bus fault
show_active_cfsr_fields=True
usage fault [DIVBYZERO]
memory management fault at 0x00000000 [DACCVIOL] [MMARVALID]
"""
cause = ''
# The CFSR can accumulate multiple exceptions.
split_major_cause = lambda cause: cause if not cause else cause + ', '
if self._cpu_state.HasField('cfsr') and self.is_fault_active():
if (self._cpu_state.cfsr
& cortex_m_constants.PW_CORTEX_M_CFSR_USAGE_FAULT_MASK):
cause += 'usage fault'
if (self._cpu_state.cfsr
& cortex_m_constants.PW_CORTEX_M_CFSR_MEM_FAULT_MASK):
cause = split_major_cause(cause)
cause += 'memory management fault'
if (self._cpu_state.cfsr
& cortex_m_constants.PW_CORTEX_M_CFSR_MMARVALID_MASK):
addr = '???' if not self._cpu_state.HasField(
'mmfar') else f'0x{self._cpu_state.mmfar:08x}'
cause += f' at {addr}'
if (self._cpu_state.cfsr
& cortex_m_constants.PW_CORTEX_M_CFSR_BUS_FAULT_MASK):
cause = split_major_cause(cause)
if (self._cpu_state.cfsr &
cortex_m_constants.PW_CORTEX_M_CFSR_IMPRECISERR_MASK):
cause += 'imprecise '
cause += 'bus fault'
if (self._cpu_state.cfsr
& cortex_m_constants.PW_CORTEX_M_CFSR_BFARVALID_MASK):
addr = '???' if not self._cpu_state.HasField(
'bfar') else f'0x{self._cpu_state.bfar:08x}'
cause += f' at {addr}'
if show_active_cfsr_fields:
for field in self.active_cfsr_fields():
cause += f' [{field.name}]'
return cause if cause else 'unknown exception'
def dump_registers(self) -> str:
"""Dumps all captured CPU registers as a multi-line string."""
registers = []
# TODO(amontanez): Do fancier decode of some registers like PC and LR.
for field in self._cpu_state.DESCRIPTOR.fields:
if self._cpu_state.HasField(field.name):
register_value = getattr(self._cpu_state, field.name)
registers.append(f'{field.name:<10} 0x{register_value:08x}')
return '\n'.join(registers)
def dump_active_active_cfsr_fields(self) -> str:
"""Dumps CFSR flags with their descriptions as a multi-line string."""
fields = []
for field in self.active_cfsr_fields():
fields.append(f'{field.name:<11} {field.description}')
return '\n'.join(fields)
def __str__(self):
dump = [f'Exception caused by a {self.exception_cause(False)}.', '']
if self.active_cfsr_fields():
dump.extend((
'Active Crash Fault Status Register (CFSR) fields:',
self.dump_active_active_cfsr_fields(),
'',
))
else:
dump.extend((
'No active Crash Fault Status Register (CFSR) fields.',
'',
))
dump.extend((
'All registers:',
self.dump_registers(),
))
return '\n'.join(dump)