xref: /qemu/scripts/qemugdb/coroutine.py (revision 138ca49a) 
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