xref: /qemu/scripts/qemugdb/coroutine.py (revision f2a3b549) 
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
11# or later.  See the COPYING file in the top-level directory.
12
13import gdb
14
15VOID_PTR = gdb.lookup_type('void').pointer()
16
17def get_fs_base():
18    '''Fetch %fs base value using arch_prctl(ARCH_GET_FS).  This is
19       pthread_self().'''
20    # %rsp - 120 is scratch space according to the SystemV ABI
21    old = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)')
22    gdb.execute('call (int)arch_prctl(0x1003, $rsp - 120)', False, True)
23    fs_base = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)')
24    gdb.execute('set *(uint64_t*)($rsp - 120) = %s' % old, False, True)
25    return fs_base
26
27def pthread_self():
28    '''Fetch pthread_self() from the glibc start_thread function.'''
29    f = gdb.newest_frame()
30    while f.name() != 'start_thread':
31        f = f.older()
32        if f is None:
33            return get_fs_base()
34
35    try:
36        return f.read_var("arg")
37    except ValueError:
38        return get_fs_base()
39
40def get_glibc_pointer_guard():
41    '''Fetch glibc pointer guard value'''
42    fs_base = pthread_self()
43    return gdb.parse_and_eval('*(uint64_t*)((uint64_t)%s + 0x30)' % fs_base)
44
45def glibc_ptr_demangle(val, pointer_guard):
46    '''Undo effect of glibc's PTR_MANGLE()'''
47    return gdb.parse_and_eval('(((uint64_t)%s >> 0x11) | ((uint64_t)%s << (64 - 0x11))) ^ (uint64_t)%s' % (val, val, pointer_guard))
48
49def get_jmpbuf_regs(jmpbuf):
50    JB_RBX  = 0
51    JB_RBP  = 1
52    JB_R12  = 2
53    JB_R13  = 3
54    JB_R14  = 4
55    JB_R15  = 5
56    JB_RSP  = 6
57    JB_PC   = 7
58
59    pointer_guard = get_glibc_pointer_guard()
60    return {'rbx': jmpbuf[JB_RBX],
61        'rbp': glibc_ptr_demangle(jmpbuf[JB_RBP], pointer_guard),
62        'rsp': glibc_ptr_demangle(jmpbuf[JB_RSP], pointer_guard),
63        'r12': jmpbuf[JB_R12],
64        'r13': jmpbuf[JB_R13],
65        'r14': jmpbuf[JB_R14],
66        'r15': jmpbuf[JB_R15],
67        'rip': glibc_ptr_demangle(jmpbuf[JB_PC], pointer_guard) }
68
69def bt_jmpbuf(jmpbuf):
70    '''Backtrace a jmpbuf'''
71    regs = get_jmpbuf_regs(jmpbuf)
72    old = dict()
73
74    for i in regs:
75        old[i] = gdb.parse_and_eval('(uint64_t)$%s' % i)
76
77    for i in regs:
78        gdb.execute('set $%s = %s' % (i, regs[i]))
79
80    gdb.execute('bt')
81
82    for i in regs:
83        gdb.execute('set $%s = %s' % (i, old[i]))
84
85def coroutine_to_jmpbuf(co):
86    coroutine_pointer = co.cast(gdb.lookup_type('CoroutineUContext').pointer())
87    return coroutine_pointer['env']['__jmpbuf']
88
89
90class CoroutineCommand(gdb.Command):
91    '''Display coroutine backtrace'''
92    def __init__(self):
93        gdb.Command.__init__(self, 'qemu coroutine', gdb.COMMAND_DATA,
94                             gdb.COMPLETE_NONE)
95
96    def invoke(self, arg, from_tty):
97        argv = gdb.string_to_argv(arg)
98        if len(argv) != 1:
99            gdb.write('usage: qemu coroutine <coroutine-pointer>\n')
100            return
101
102        bt_jmpbuf(coroutine_to_jmpbuf(gdb.parse_and_eval(argv[0])))
103
104class CoroutineSPFunction(gdb.Function):
105    def __init__(self):
106        gdb.Function.__init__(self, 'qemu_coroutine_sp')
107
108    def invoke(self, addr):
109        return get_jmpbuf_regs(coroutine_to_jmpbuf(addr))['rsp'].cast(VOID_PTR)
110
111class CoroutinePCFunction(gdb.Function):
112    def __init__(self):
113        gdb.Function.__init__(self, 'qemu_coroutine_pc')
114
115    def invoke(self, addr):
116        return get_jmpbuf_regs(coroutine_to_jmpbuf(addr))['rip'].cast(VOID_PTR)
117