xref: /openbmc/qemu/scripts/qemugdb/coroutine.py (revision dc5bd18f) 
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