1#!/usr/bin/python 2 3# GDB debugging support 4# 5# Copyright 2012 Red Hat, Inc. and/or its affiliates 6# 7# Authors: 8# Avi Kivity <avi@redhat.com> 9# 10# This work is licensed under the terms of the GNU GPL, version 2. See 11# the COPYING file in the top-level directory. 12# 13# Contributions after 2012-01-13 are licensed under the terms of the 14# GNU GPL, version 2 or (at your option) any later version. 15 16import gdb 17 18VOID_PTR = gdb.lookup_type('void').pointer() 19 20def get_fs_base(): 21 '''Fetch %fs base value using arch_prctl(ARCH_GET_FS). This is 22 pthread_self().''' 23 # %rsp - 120 is scratch space according to the SystemV ABI 24 old = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)') 25 gdb.execute('call arch_prctl(0x1003, $rsp - 120)', False, True) 26 fs_base = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)') 27 gdb.execute('set *(uint64_t*)($rsp - 120) = %s' % old, False, True) 28 return fs_base 29 30def pthread_self(): 31 '''Fetch pthread_self() from the glibc start_thread function.''' 32 f = gdb.newest_frame() 33 while f.name() != 'start_thread': 34 f = f.older() 35 if f is None: 36 return get_fs_base() 37 38 try: 39 return f.read_var("arg") 40 except ValueError: 41 return get_fs_base() 42 43def get_glibc_pointer_guard(): 44 '''Fetch glibc pointer guard value''' 45 fs_base = pthread_self() 46 return gdb.parse_and_eval('*(uint64_t*)((uint64_t)%s + 0x30)' % fs_base) 47 48def glibc_ptr_demangle(val, pointer_guard): 49 '''Undo effect of glibc's PTR_MANGLE()''' 50 return gdb.parse_and_eval('(((uint64_t)%s >> 0x11) | ((uint64_t)%s << (64 - 0x11))) ^ (uint64_t)%s' % (val, val, pointer_guard)) 51 52def get_jmpbuf_regs(jmpbuf): 53 JB_RBX = 0 54 JB_RBP = 1 55 JB_R12 = 2 56 JB_R13 = 3 57 JB_R14 = 4 58 JB_R15 = 5 59 JB_RSP = 6 60 JB_PC = 7 61 62 pointer_guard = get_glibc_pointer_guard() 63 return {'rbx': jmpbuf[JB_RBX], 64 'rbp': glibc_ptr_demangle(jmpbuf[JB_RBP], pointer_guard), 65 'rsp': glibc_ptr_demangle(jmpbuf[JB_RSP], pointer_guard), 66 'r12': jmpbuf[JB_R12], 67 'r13': jmpbuf[JB_R13], 68 'r14': jmpbuf[JB_R14], 69 'r15': jmpbuf[JB_R15], 70 'rip': glibc_ptr_demangle(jmpbuf[JB_PC], pointer_guard) } 71 72def bt_jmpbuf(jmpbuf): 73 '''Backtrace a jmpbuf''' 74 regs = get_jmpbuf_regs(jmpbuf) 75 old = dict() 76 77 for i in regs: 78 old[i] = gdb.parse_and_eval('(uint64_t)$%s' % i) 79 80 for i in regs: 81 gdb.execute('set $%s = %s' % (i, regs[i])) 82 83 gdb.execute('bt') 84 85 for i in regs: 86 gdb.execute('set $%s = %s' % (i, old[i])) 87 88def coroutine_to_jmpbuf(co): 89 coroutine_pointer = co.cast(gdb.lookup_type('CoroutineUContext').pointer()) 90 return coroutine_pointer['env']['__jmpbuf'] 91 92 93class CoroutineCommand(gdb.Command): 94 '''Display coroutine backtrace''' 95 def __init__(self): 96 gdb.Command.__init__(self, 'qemu coroutine', gdb.COMMAND_DATA, 97 gdb.COMPLETE_NONE) 98 99 def invoke(self, arg, from_tty): 100 argv = gdb.string_to_argv(arg) 101 if len(argv) != 1: 102 gdb.write('usage: qemu coroutine <coroutine-pointer>\n') 103 return 104 105 bt_jmpbuf(coroutine_to_jmpbuf(gdb.parse_and_eval(argv[0]))) 106 107class CoroutineSPFunction(gdb.Function): 108 def __init__(self): 109 gdb.Function.__init__(self, 'qemu_coroutine_sp') 110 111 def invoke(self, addr): 112 return get_jmpbuf_regs(coroutine_to_jmpbuf(addr))['rsp'].cast(VOID_PTR) 113 114class CoroutinePCFunction(gdb.Function): 115 def __init__(self): 116 gdb.Function.__init__(self, 'qemu_coroutine_pc') 117 118 def invoke(self, addr): 119 return get_jmpbuf_regs(coroutine_to_jmpbuf(addr))['rip'].cast(VOID_PTR) 120