scripts/qemugdb/coroutine.py

   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
  12 import gdb
  13
  14 VOID_PTR = gdb.lookup_type('void').pointer()
  15
  16 def 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*)($rsp - 120) = %s' % old, False, True)
  24     return fs_base
  25
  26 def pthread_self():
  27     '''Fetch pthread_self() from the glibc start_thread function.'''
  28     f = gdb.newest_frame()
  29     while f.name() != 'start_thread':
  30         f = f.older()
  31         if f is None:
  32             return get_fs_base()
  33
  34     try:
  35         return f.read_var("arg")
  36     except ValueError:
  37         return get_fs_base()
  38
  39 def get_glibc_pointer_guard():
  40     '''Fetch glibc pointer guard value'''
  41     fs_base = pthread_self()
  42     return gdb.parse_and_eval('*(uint64_t*)((uint64_t)%s + 0x30)' % fs_base)
  43
  44 def glibc_ptr_demangle(val, pointer_guard):
  45     '''Undo effect of glibc's PTR_MANGLE()'''
  46     return gdb.parse_and_eval('(((uint64_t)%s >> 0x11) | ((uint64_t)%s << (64 - 0x11))) ^ (uint64_t)%s' % (val, val, pointer_guard))
  47
  48 def get_jmpbuf_regs(jmpbuf):
  49     JB_RBX  = 0
  50     JB_RBP  = 1
  51     JB_R12  = 2
  52     JB_R13  = 3
  53     JB_R14  = 4
  54     JB_R15  = 5
  55     JB_RSP  = 6
  56     JB_PC   = 7
  57
  58     pointer_guard = get_glibc_pointer_guard()
  59     return {'rbx': jmpbuf[JB_RBX],
  60         'rbp': glibc_ptr_demangle(jmpbuf[JB_RBP], pointer_guard),
  61         'rsp': glibc_ptr_demangle(jmpbuf[JB_RSP], pointer_guard),
  62         'r12': jmpbuf[JB_R12],
  63         'r13': jmpbuf[JB_R13],
  64         'r14': jmpbuf[JB_R14],
  65         'r15': jmpbuf[JB_R15],
  66         'rip': glibc_ptr_demangle(jmpbuf[JB_PC], pointer_guard) }
  67
  68 def bt_jmpbuf(jmpbuf):
  69     '''Backtrace a jmpbuf'''
  70     regs = get_jmpbuf_regs(jmpbuf)
  71     old = dict()
  72
  73     # remember current stack frame and select the topmost
  74     # so that register modifications don't wreck it
  75     selected_frame = gdb.selected_frame()
  76     gdb.newest_frame().select()
  77
  78     for i in regs:
  79         old[i] = gdb.parse_and_eval('(uint64_t)$%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
  91 def co_cast(co):
  92     return co.cast(gdb.lookup_type('CoroutineUContext').pointer())
  93
  94 def coroutine_to_jmpbuf(co):
  95     coroutine_pointer = co_cast(co)
  96     return coroutine_pointer['env']['__jmpbuf']
  97
  98
  99 class 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
 113 class 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
 136 class 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
 143 class 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)