#!/usr/bin/env python
# coding=utf-8
#
# A script which parses ESP-IDF panic handler output (registers & stack dump),
# and then acts as a GDB server over stdin/stdout, presenting the information
# from the panic handler to GDB.
# This allows for generating backtraces out of raw stack dumps on architectures
# where backtracing on the target side is not possible.
#
# Note that the "act as a GDB server" approach is somewhat a hack.
# A much nicer solution would have been to convert the panic handler output
# into a core file, and point GDB to the core file.
# However, RISC-V baremetal GDB currently lacks core dump support.
#
# The approach is inspired by Cesanta's ESP8266 GDB server:
# https://github.com/cesanta/mongoose-os/blob/27777c8977/platforms/esp8266/tools/serve_core.py
#
# Copyright 2020 Espressif Systems (Shanghai) Co. Ltd.
#
# 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.
#
import argparse
import binascii
import logging
import struct
import sys
from builtins import bytes
from collections import namedtuple
# Used for type annotations only. Silence linter warnings.
from pyparsing import (Combine, Group, Literal, OneOrMore, ParserElement, # noqa: F401 # pylint: disable=unused-import
ParseResults, Word, nums, srange)
try:
import typing # noqa: F401 # pylint: disable=unused-import
except ImportError:
pass
# pyparsing helper
hexnumber = srange('[0-9a-f]')
# List of registers to be passed to GDB, in the order GDB expects.
# The names should match those used in IDF panic handler.
# Registers not present in IDF panic handler output (like X0) will be assumed to be 0.
GDB_REGS_INFO_RISCV_ILP32 = [
'X0', 'RA', 'SP', 'GP',
'TP', 'T0', 'T1', 'T2',
'S0/FP', 'S1', 'A0', 'A1',
'A2', 'A3', 'A4', 'A5',
'A6', 'A7', 'S2', 'S3',
'S4', 'S5', 'S6', 'S7',
'S8', 'S9', 'S10', 'S11',
'T3', 'T4', 'T5', 'T6',
'MEPC'
]
GDB_REGS_INFO = {
'esp32c3': GDB_REGS_INFO_RISCV_ILP32
}
PanicInfo = namedtuple('PanicInfo', 'core_id regs stack_base_addr stack_data')
def build_riscv_panic_output_parser(): # type: () -> typing.Type[ParserElement]
"""Builds a parser for the panic handler output using pyparsing"""
# We don't match the first line, since "Guru Meditation" will not be printed in case of an abort:
# Guru Meditation Error: Core 0 panic'ed (Store access fault). Exception was unhandled.
# Core 0 register dump:
reg_dump_header = Group(Literal('Core') +
Word(nums)('core_id') +
Literal('register dump:'))('reg_dump_header')
# MEPC : 0x4200232c RA : 0x42009694 SP : 0x3fc93a80 GP : 0x3fc8b320
reg_name = Word(srange('[A-Z_0-9/-]'))('name')
hexnumber_with_0x = Combine(Literal('0x') + Word(hexnumber))
reg_value = hexnumber_with_0x('value')
reg_dump_one_reg = Group(reg_name + Literal(':') + reg_value) # not named because there will be OneOrMore
reg_dump_all_regs = Group(OneOrMore(reg_dump_one_reg))('regs')
reg_dump = Group(reg_dump_header + reg_dump_all_regs) # not named because there will be OneOrMore
reg_dumps = Group(OneOrMore(reg_dump))('reg_dumps')
# Stack memory:
# 3fc93a80: 0x00000030 0x00000021 0x3fc8aedc 0x4200232a 0xa5a5a5a5 0xa5a5a5a5 0x3fc8aedc 0x420099b0
stack_line = Group(Word(hexnumber)('base') + Literal(':') +
Group(OneOrMore(hexnumber_with_0x))('data'))
stack_dump = Group(Literal('Stack memory:') +
Group(OneOrMore(stack_line))('lines'))('stack_dump')
# Parser for the complete panic output:
panic_output = reg_dumps + stack_dump
return panic_output
def get_stack_addr_and_data(res): # type: (ParseResults) -> typing.Tuple[int, bytes]
""" Extract base address and bytes from the parsed stack dump """
stack_base_addr = 0 # First reported address in the dump
base_addr = 0 # keeps track of the address for the given line of the dump
bytes_in_line = 0 # bytes of stack parsed on the previous line; used to validate the next base address
stack_data = bytes(b'') # accumulates all the dumped stack data
for line in res.stack_dump.lines:
# update and validate the base address
prev_base_addr = base_addr
base_addr = int(line.base, 16)
if stack_base_addr == 0:
stack_base_addr = base_addr
else:
assert base_addr == prev_base_addr + bytes_in_line
# convert little-endian hex words to byte representation
words = [int(w, 16) for w in line.data]
line_data = bytes(b''.join([struct.pack('<I', w) for w in words]))
bytes_in_line = len(line_data)
# accumulate in the whole stack data
stack_data += line_data
return stack_base_addr, stack_data
def parse_idf_riscv_panic_output(panic_text): # type: (str) -> PanicInfo
""" Decode panic handler output from a file """
panic_output = build_riscv_panic_output_parser()
results = panic_output.searchString(panic_text)
if len(results) != 1:
raise ValueError("Couldn't parse panic handler output")
res = results[0]
if len(res.reg_dumps) > 1:
raise NotImplementedError('Handling of multi-core register dumps not implemented')
# Build a dict of register names/values
rd = res.reg_dumps[0]
core_id = int(rd.reg_dump_header.core_id)
regs = dict()
for reg in rd.regs:
reg_value = int(reg.value, 16)
regs[reg.name] = reg_value
stack_base_addr, stack_data = get_stack_addr_and_data(res)
return PanicInfo(core_id=core_id,
regs=regs,
stack_base_addr=stack_base_addr,
stack_data=stack_data)
PANIC_OUTPUT_PARSERS = {
'esp32c3': parse_idf_riscv_panic_output
}
class GdbServer(object):
def __init__(self, panic_info, target, log_file=None): # type: (PanicInfo, str, str) -> None
self.panic_info = panic_info
self.in_stream = sys.stdin
self.out_stream = sys.stdout
self.reg_list = GDB_REGS_INFO[target]
self.logger = logging.getLogger('GdbServer')
if log_file:
handler = logging.FileHandler(log_file, 'w+')
self.logger.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)
self.logger.addHandler(handler)
def run(self): # type: () -> None
""" Process GDB commands from stdin until GDB tells us to quit """
buffer = ''
while True:
buffer += self.in_stream.read(1)
if len(buffer) > 3 and buffer[-3] == '#':
self._handle_command(buffer)
buffer = ''
def _handle_command(self, buffer): # type: (str) -> None
command = buffer[1:-3] # ignore checksums
# Acknowledge the command
self.out_stream.write('+')
self.out_stream.flush()
self.logger.debug('Got command: %s', command)
if command == '?':
# report sigtrap as the stop reason; the exact reason doesn't matter for backtracing
self._respond('T05')
elif command.startswith('Hg') or command.startswith('Hc'):
# Select thread command
self._respond('OK')
elif command == 'qfThreadInfo':
# Get list of threads.
# Only one thread for now, can be extended to show one thread for each core,
# if we dump both cores (e.g. on an interrupt watchdog)
self._respond('m1')
elif command == 'qC':
# That single thread is selected.
self._respond('QC1')
elif command == 'g':
# Registers read
self._respond_regs()
elif command.startswith('m'):
# Memory read
addr, size = [int(v, 16) for v in command[1:].split(',')]
self._respond_mem(addr, size)
elif command.startswith('vKill') or command == 'k':
# Quit
self._respond('OK')
raise SystemExit(0)
else:
# Empty response required for any unknown command
self._respond('')
def _respond(self, data): # type: (str) -> None
# calculate checksum
data_bytes = bytes(data.encode('ascii')) # bytes() for Py2 compatibility
checksum = sum(data_bytes) & 0xff
# format and write the response
res = '${}#{:02x}'.format(data, checksum)
self.logger.debug('Wrote: %s', res)
self.out_stream.write(res)
self.out_stream.flush()
# get the result ('+' or '-')
ret = self.in_stream.read(1)
self.logger.debug('Response: %s', ret)
if ret != '+':
sys.stderr.write("GDB responded with '-' to {}".format(res))
raise SystemExit(1)
def _respond_regs(self): # type: () -> None
response = ''
for reg_name in self.reg_list:
# register values are reported as hexadecimal strings
# in target byte order (i.e. LSB first for RISC-V)
reg_val = self.panic_info.regs.get(reg_name, 0)
reg_bytes = struct.pack('<L', reg_val)
response += binascii.hexlify(reg_bytes).decode('ascii')
self._respond(response)
def _respond_mem(self, start_addr, size): # type: (int, int) -> None
stack_addr_min = self.panic_info.stack_base_addr
stack_data = self.panic_info.stack_data
stack_len = len(self.panic_info.stack_data)
stack_addr_max = stack_addr_min + stack_len
# For any memory address that is not on the stack, pretend the value is 0x00.
# GDB should never ask us for program memory, it will be obtained from the ELF file.
def in_stack(addr):
return stack_addr_min <= addr < stack_addr_max
result = ''
for addr in range(start_addr, start_addr + size):
if not in_stack(addr):
result += '00'
else:
result += '{:02x}'.format(stack_data[addr - stack_addr_min])
self._respond(result)
def main():
parser = argparse.ArgumentParser()
parser.add_argument('input_file', type=argparse.FileType('r'),
help='File containing the panic handler output')
parser.add_argument('--target', choices=GDB_REGS_INFO.keys(),
help='Chip to use (determines the architecture)')
parser.add_argument('--gdb-log', default=None,
help='If specified, the file for logging GDB server debug information')
args = parser.parse_args()
panic_info = PANIC_OUTPUT_PARSERS[args.target](args.input_file.read())
server = GdbServer(panic_info, target=args.target, log_file=args.gdb_log)
try:
server.run()
except KeyboardInterrupt:
sys.exit(0)
if __name__ == '__main__':
main()