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# FRR DWARF structure definition extractor
#
# Copyright (C) 2020 David Lamparter for NetDEF, Inc.
#
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the Free
# Software Foundation; either version 2 of the License, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
# more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; see the file COPYING; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
import sys
import os
import subprocess
import re
import argparse
import subprocess
import json
structs = ['xref', 'xref_logmsg', 'xref_threadsched', 'xref_install_element', 'xrefdata', 'xrefdata_logmsg', 'cmd_element']
def extract(filename='lib/.libs/libfrr.so'):
'''
Convert output from "pahole" to JSON.
Example pahole output:
$ pahole -C xref lib/.libs/libfrr.so
struct xref {
struct xrefdata * xrefdata; /* 0 8 */
enum xref_type type; /* 8 4 */
int line; /* 12 4 */
const char * file; /* 16 8 */
const char * func; /* 24 8 */
/* size: 32, cachelines: 1, members: 5 */
/* last cacheline: 32 bytes */
};
'''
pahole = subprocess.check_output(['pahole', '-C', ','.join(structs), filename]).decode('UTF-8')
struct_re = re.compile(r'^struct ([^ ]+) \{([^\}]+)};', flags=re.M | re.S)
field_re = re.compile(r'^\s*(?P<type>[^;\(]+)\s+(?P<name>[^;\[\]]+)(?:\[(?P<array>\d+)\])?;\s*\/\*(?P<comment>.*)\*\/\s*$')
comment_re = re.compile(r'^\s*\/\*.*\*\/\s*$')
pastructs = struct_re.findall(pahole)
out = {}
for sname, data in pastructs:
this = out.setdefault(sname, {})
fields = this.setdefault('fields', [])
lines = data.strip().splitlines()
next_offs = 0
for line in lines:
if line.strip() == '':
continue
m = comment_re.match(line)
if m is not None:
continue
m = field_re.match(line)
if m is not None:
offs, size = m.group('comment').strip().split()
offs = int(offs)
size = int(size)
typ_ = m.group('type').strip()
name = m.group('name')
if name.startswith('(*'):
# function pointer
typ_ = typ_ + ' *'
name = name[2:].split(')')[0]
data = {
'name': name,
'type': typ_,
# 'offset': offs,
# 'size': size,
}
if m.group('array'):
data['array'] = int(m.group('array'))
fields.append(data)
if offs != next_offs:
raise ValueError('%d padding bytes before struct %s.%s' % (offs - next_offs, sname, name))
next_offs = offs + size
continue
raise ValueError('cannot process line: %s' % line)
return out
class FieldApplicator(object):
'''
Fill ELFDissectStruct fields list from pahole/JSON
Uses the JSON file created by the above code to fill in the struct fields
in subclasses of ELFDissectStruct.
'''
# only what we really need. add more as needed.
packtypes = {
'int': 'i',
'uint8_t': 'B',
'uint16_t': 'H',
'uint32_t': 'I',
'char': 's',
}
def __init__(self, data):
self.data = data
self.classes = []
self.clsmap = {}
def add(self, cls):
self.classes.append(cls)
self.clsmap[cls.struct] = cls
def resolve(self, cls):
out = []
#offset = 0
fieldrename = getattr(cls, 'fieldrename', {})
def mkname(n):
return (fieldrename.get(n, n),)
for field in self.data[cls.struct]['fields']:
typs = field['type'].split()
typs = [i for i in typs if i not in ['const']]
# this will break reuse of xrefstructs.json across 32bit & 64bit
# platforms
#if field['offset'] != offset:
# assert offset < field['offset']
# out.append(('_pad', '%ds' % (field['offset'] - offset,)))
# pretty hacky C types handling, but covers what we need
ptrlevel = 0
while typs[-1] == '*':
typs.pop(-1)
ptrlevel += 1
if ptrlevel > 0:
packtype = ('P', None)
if ptrlevel == 1:
if typs[0] == 'char':
packtype = ('P', str)
elif typs[0] == 'struct' and typs[1] in self.clsmap:
packtype = ('P', self.clsmap[typs[1]])
elif typs[0] == 'enum':
packtype = ('I',)
elif typs[0] in self.packtypes:
packtype = (self.packtypes[typs[0]],)
elif typs[0] == 'struct':
if typs[1] in self.clsmap:
packtype = (self.clsmap[typs[1]],)
else:
raise ValueError('embedded struct %s not in extracted data' % (typs[1],))
else:
raise ValueError('cannot decode field %s in struct %s (%s)' % (
cls.struct, field['name'], field['type']))
if 'array' in field and typs[0] == 'char':
packtype = ('%ds' % field['array'],)
out.append(mkname(field['name']) + packtype)
elif 'array' in field:
for i in range(0, field['array']):
out.append(mkname('%s_%d' % (field['name'], i)) + packtype)
else:
out.append(mkname(field['name']) + packtype)
#offset = field['offset'] + field['size']
cls.fields = out
def __call__(self):
for cls in self.classes:
self.resolve(cls)
def main():
argp = argparse.ArgumentParser(description = 'FRR DWARF structure extractor')
argp.add_argument('-o', dest='output', type=str, help='write JSON output', default='python/xrefstructs.json')
argp.add_argument('-i', dest='input', type=str, help='ELF file to read', default='lib/.libs/libfrr.so')
args = argp.parse_args()
out = extract(args.input)
with open(args.output + '.tmp', 'w') as fd:
json.dump(out, fd, indent=2, sort_keys=True)
os.rename(args.output + '.tmp', args.output)
if __name__ == '__main__':
main()
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