X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=chiark-utils.git;a=blobdiff_plain;f=fishdescriptor%2Fpy%2Ffishdescriptor%2Findonor.py;h=20bc8071b6d0f7eb9b1223c8269e90e0c0a05ebe;hp=12f8c685e01cf4651f5b53bd163acce4f9bfe2d1;hb=cda1006ec229c3731fe48f412f6986588100c0c2;hpb=00ca8b27ab7bbea513959a13a93f98b1da14e2f9 diff --git a/fishdescriptor/py/fishdescriptor/indonor.py b/fishdescriptor/py/fishdescriptor/indonor.py index 12f8c68..20bc807 100644 --- a/fishdescriptor/py/fishdescriptor/indonor.py +++ b/fishdescriptor/py/fishdescriptor/indonor.py @@ -1,14 +1,42 @@ +# This file is part of chiark-utils, a collection of useful programs +# used on chiark.greenend.org.uk. +# +# This file is: +# Copyright 2018 Citrix Systems Ltd +# +# This 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 3, or (at your option) any later version. +# +# This 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; if not, consult the Free Software Foundation's +# website at www.fsf.org, or the GNU Project website at www.gnu.org. + # class for use inside gdb which is debugging the donor process +from __future__ import print_function + import gdb import copy import os import sys +import socket + +def _string_bytearray(s): + # gets us bytes in py2 and py3 + if not isinstance(s, bytes): + s = s.encode('utf-8') # sigh, python 2/3 compat + return bytearray(s) def _string_escape_for_c(s): out = '' - for c in bytearray(s): # gets us bytes in py2 and py3 + for c in _string_bytearray(s): if c == ord('\\') or c == ord('"') or c < 32 or c > 126: out += '\\x%02x' % c else: @@ -24,19 +52,17 @@ def _lit_aggregate_uncasted(val_lit_strs): return '{' + ', '.join(['(%s)' % v for v in val_lit_strs]) + ' }' def _lit_string_uncasted(s): - if not isinstance(s, bytes): - s = s.encode('utf-8') # sigh, python 2/3 compat - b = bytearray(s) - return _lit_aggregate_uncasted(map(_lit_integer, b) + [ '0' ]) + b = _string_bytearray(s) + return _lit_aggregate_uncasted([_lit_integer(x) for x in b] + [ '0' ]) def _lit_array(elemtype, val_lit_strs): return ( '((%s[%d])%s)' % - (elem_type, len(val_lit_strs), _lit_aggregate_uncasted(val_lit_strs)) + (elemtype, len(val_lit_strs), _lit_aggregate_uncasted(val_lit_strs)) ) def _lit_addressof(v): - return '&(%s)' % v + return '&(char[])(%s)' % v def _make_lit(v): if isinstance(v, int): @@ -53,15 +79,18 @@ def parse_eval(expr): class DonorStructLayout(): def __init__(l, typename): - x = parse_eval('(%s){ }' % typename) + x = gdb.lookup_type(typename) l._typename = typename l._template = [ ] l._posns = { } - for f in x.type.fields(): + for f in x.fields(): l._posns[f.name] = len(l._template) - try: f.type.fields(); blank = '{ }' + try: f.type.fields(); blank = '{ }' + except TypeError: blank = '0' except AttributeError: blank = '0' l._template.append(blank) + sys.stderr.write('## STRUCT %s template %s fields %s\n' + % (typename, l._template, l._posns)) def substitute(l, values): build = copy.deepcopy(l._template) @@ -74,21 +103,47 @@ class DonorImplementation(): di._structs = { } di._saved_errno = None di._result_stream = os.fdopen(3, 'w') + di._errno_workaround = None # assembling structs # sigh, we have to record the order of the arguments! - def _find_fields(typename): + def _find_fields(di, typename): try: fields = di._structs[typename] - except AttributeError: + except KeyError: fields = DonorStructLayout(typename) di._structs[typename] = fields return fields - def _make(typename, values): + def _make(di, typename, values): fields = di._find_fields(typename) return fields.substitute(values) + # hideous workaround + + def _parse_eval_errno(di, expr_pat): + # evaluates expr_pat % 'errno' + if di._errno_workaround is not True: + try: + x = parse_eval(expr_pat % 'errno') + di._errno_workaround = False + return x + except gdb.error as e: + if di._errno_workaround is False: + raise e + di._errno_workaround = True + # Incomprehensibly, gdb.parse_and_eval('errno') can sometimes + # fail with + # gdb.error: Cannot find thread-local variables on this target + # even though plain gdb `print errno' works while `print errno = 25' + # doesn't. OMG. This may be related to: + # https://github.com/cloudburst/libheap/issues/24 + # although I can't find it in the gdb bug db (which is half-broken + # in my browser). Also the error is very nonspecific :-/. + # This seems to happen on jessie, and is fixed in stretch. + # Anyway: + return parse_eval(expr_pat % '(*((int (*)(void))__errno_location)())') + # calling functions (need to cast the function name to the right # type in case maybe gdb doesn't know the type) @@ -99,7 +154,7 @@ class DonorImplementation(): def _must_func(di, functype, funcname, realargs): retval = di._func(functype, funcname, realargs) if retval < 0: - errnoval = parse_eval('errno') + errnoval = di._parse_eval_errno('%s') raise RuntimeError("%s gave errno=%d `%s'" % (funcname, errnoval, os.strerror(errnoval))) return retval @@ -107,10 +162,10 @@ class DonorImplementation(): # wrappers for the syscalls that do what we want def _sendmsg(di, carrier, control_msg): - iov_base = _lit_array('int', map(str,fds)) + iov_base = _lit_array('char', [1]) iov = di._make('struct iovec', { 'iov_base': iov_base, - 'iov_len' : len(fds), + 'iov_len' : 1, }) msg = di._make('struct msghdr', { @@ -121,7 +176,7 @@ class DonorImplementation(): }) di._must_func( - 'ssize_t (*)(int, const struct msghdr*, int flags)', + 'ssize_t (*)(int, const struct msghdr*, int)', 'sendmsg', '(%s, %s, 0)' % (carrier, _lit_addressof(msg)) ) @@ -156,7 +211,7 @@ class DonorImplementation(): '("%s", %d)' % (_string_escape_for_c(path), mode) ) if r < 0: - errnoval = parse_eval('errno') + errnoval = di._parse_eval_errno('%s') if errnoval != os.errno.EEXIST: raise RuntimeError("mkdir %s failed: `%s'" % (repr(path), os.strerror(errnoval))) @@ -164,13 +219,13 @@ class DonorImplementation(): return 1 def _errno_save(di): - di._saved_errno = parse_eval('errno') + di._saved_errno = di._parse_eval_errno('%s') def _errno_restore(di): to_restore = di._saved_errno di._saved_errno = None if to_restore is not None: - parse_eval('errno = %d' % to_restore) + di._parse_eval_errno('%%s = %d' % to_restore) def _result(di, output): sys.stderr.write("#> %s" % output) @@ -219,12 +274,18 @@ class DonorImplementation(): di._result('%d\n' % val) def _protocol_read(di): - input = sys.stdin.readline().rstrip('\n') + input = sys.stdin.readline() + if input == '': return None + input = input.rstrip('\n') sys.stderr.write("#< %s\n" % input) return input def eval_loop(di): + if not gdb.selected_inferior().was_attached: + print('gdb inferior not attached', file=sys.stderr) + sys.exit(0) while True: di._result('!\n') cmd = di._protocol_read() + if cmd is None: break eval(cmd)