LXR qemu/scripts/qemugdb/coroutine.py

   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