1# 2# GDB debugging support 3# 4# Copyright 2012 Red Hat, Inc. and/or its affiliates 5# 6# Authors: 7# Avi Kivity <avi@redhat.com> 8# 9# This work is licensed under the terms of the GNU GPL, version 2 10# or later. See the COPYING file in the top-level directory. 11 12import gdb 13 14VOID_PTR = gdb.lookup_type('void').pointer() 15 16def get_fs_base(): 17 '''Fetch %fs base value using arch_prctl(ARCH_GET_FS). This is 18 pthread_self().''' 19 # %rsp - 120 is scratch space according to the SystemV ABI 20 old = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)') 21 gdb.execute('call (int)arch_prctl(0x1003, $rsp - 120)', False, True) 22 fs_base = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)') 23 gdb.execute('set *(uint64_t*)($rsp - 120) = %s' % old, False, True) 24 return fs_base 25 26def pthread_self(): 27 '''Fetch pthread_self() from the glibc start_thread function.''' 28 f = gdb.newest_frame() 29 while f.name() != 'start_thread': 30 f = f.older() 31 if f is None: 32 return get_fs_base() 33 34 try: 35 return f.read_var("arg") 36 except ValueError: 37 return get_fs_base() 38 39def get_glibc_pointer_guard(): 40 '''Fetch glibc pointer guard value''' 41 fs_base = pthread_self() 42 return gdb.parse_and_eval('*(uint64_t*)((uint64_t)%s + 0x30)' % fs_base) 43 44def glibc_ptr_demangle(val, pointer_guard): 45 '''Undo effect of glibc's PTR_MANGLE()''' 46 return gdb.parse_and_eval('(((uint64_t)%s >> 0x11) | ((uint64_t)%s << (64 - 0x11))) ^ (uint64_t)%s' % (val, val, pointer_guard)) 47 48def get_jmpbuf_regs(jmpbuf): 49 JB_RBX = 0 50 JB_RBP = 1 51 JB_R12 = 2 52 JB_R13 = 3 53 JB_R14 = 4 54 JB_R15 = 5 55 JB_RSP = 6 56 JB_PC = 7 57 58 pointer_guard = get_glibc_pointer_guard() 59 return {'rbx': jmpbuf[JB_RBX], 60 'rbp': glibc_ptr_demangle(jmpbuf[JB_RBP], pointer_guard), 61 'rsp': glibc_ptr_demangle(jmpbuf[JB_RSP], pointer_guard), 62 'r12': jmpbuf[JB_R12], 63 'r13': jmpbuf[JB_R13], 64 'r14': jmpbuf[JB_R14], 65 'r15': jmpbuf[JB_R15], 66 'rip': glibc_ptr_demangle(jmpbuf[JB_PC], pointer_guard) } 67 68def bt_jmpbuf(jmpbuf): 69 '''Backtrace a jmpbuf''' 70 regs = get_jmpbuf_regs(jmpbuf) 71 old = dict() 72 73 # remember current stack frame and select the topmost 74 # so that register modifications don't wreck it 75 selected_frame = gdb.selected_frame() 76 gdb.newest_frame().select() 77 78 for i in regs: 79 old[i] = gdb.parse_and_eval('(uint64_t)$%s' % i) 80 81 for i in regs: 82 gdb.execute('set $%s = %s' % (i, regs[i])) 83 84 gdb.execute('bt') 85 86 for i in regs: 87 gdb.execute('set $%s = %s' % (i, old[i])) 88 89 selected_frame.select() 90 91def co_cast(co): 92 return co.cast(gdb.lookup_type('CoroutineUContext').pointer()) 93 94def coroutine_to_jmpbuf(co): 95 coroutine_pointer = co_cast(co) 96 return coroutine_pointer['env']['__jmpbuf'] 97 98 99class CoroutineCommand(gdb.Command): 100 '''Display coroutine backtrace''' 101 def __init__(self): 102 gdb.Command.__init__(self, 'qemu coroutine', gdb.COMMAND_DATA, 103 gdb.COMPLETE_NONE) 104 105 def invoke(self, arg, from_tty): 106 argv = gdb.string_to_argv(arg) 107 if len(argv) != 1: 108 gdb.write('usage: qemu coroutine <coroutine-pointer>\n') 109 return 110 111 bt_jmpbuf(coroutine_to_jmpbuf(gdb.parse_and_eval(argv[0]))) 112 113class CoroutineBt(gdb.Command): 114 '''Display backtrace including coroutine switches''' 115 def __init__(self): 116 gdb.Command.__init__(self, 'qemu bt', gdb.COMMAND_STACK, 117 gdb.COMPLETE_NONE) 118 119 def invoke(self, arg, from_tty): 120 121 gdb.execute("bt") 122 123 if gdb.parse_and_eval("qemu_in_coroutine()") == False: 124 return 125 126 co_ptr = gdb.parse_and_eval("qemu_coroutine_self()") 127 128 while True: 129 co = co_cast(co_ptr) 130 co_ptr = co["base"]["caller"] 131 if co_ptr == 0: 132 break 133 gdb.write("Coroutine at " + str(co_ptr) + ":\n") 134 bt_jmpbuf(coroutine_to_jmpbuf(co_ptr)) 135 136class CoroutineSPFunction(gdb.Function): 137 def __init__(self): 138 gdb.Function.__init__(self, 'qemu_coroutine_sp') 139 140 def invoke(self, addr): 141 return get_jmpbuf_regs(coroutine_to_jmpbuf(addr))['rsp'].cast(VOID_PTR) 142 143class CoroutinePCFunction(gdb.Function): 144 def __init__(self): 145 gdb.Function.__init__(self, 'qemu_coroutine_pc') 146 147 def invoke(self, addr): 148 return get_jmpbuf_regs(coroutine_to_jmpbuf(addr))['rip'].cast(VOID_PTR) 149