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
  11 # or later.  See the COPYING file in the top-level directory.
  12
  13 import gdb
  14
  15 VOID_PTR = gdb.lookup_type('void').pointer()
  16
  17 def 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*)($rsp - 120) = %s' % old, False, True)
  25     return fs_base
  26
  27 def pthread_self():
  28     '''Fetch pthread_self() from the glibc start_thread function.'''
  29     f = gdb.newest_frame()
  30     while f.name() != 'start_thread':
  31         f = f.older()
  32         if f is None:
  33             return get_fs_base()
  34
  35     try:
  36         return f.read_var("arg")
  37     except ValueError:
  38         return get_fs_base()
  39
  40 def get_glibc_pointer_guard():
  41     '''Fetch glibc pointer guard value'''
  42     fs_base = pthread_self()
  43     return gdb.parse_and_eval('*(uint64_t*)((uint64_t)%s + 0x30)' % fs_base)
  44
  45 def glibc_ptr_demangle(val, pointer_guard):
  46     '''Undo effect of glibc's PTR_MANGLE()'''
  47     return gdb.parse_and_eval('(((uint64_t)%s >> 0x11) | ((uint64_t)%s << (64 - 0x11))) ^ (uint64_t)%s' % (val, val, pointer_guard))
  48
  49 def get_jmpbuf_regs(jmpbuf):
  50     JB_RBX  = 0
  51     JB_RBP  = 1
  52     JB_R12  = 2
  53     JB_R13  = 3
  54     JB_R14  = 4
  55     JB_R15  = 5
  56     JB_RSP  = 6
  57     JB_PC   = 7
  58
  59     pointer_guard = get_glibc_pointer_guard()
  60     return {'rbx': jmpbuf[JB_RBX],
  61         'rbp': glibc_ptr_demangle(jmpbuf[JB_RBP], pointer_guard),
  62         'rsp': glibc_ptr_demangle(jmpbuf[JB_RSP], pointer_guard),
  63         'r12': jmpbuf[JB_R12],
  64         'r13': jmpbuf[JB_R13],
  65         'r14': jmpbuf[JB_R14],
  66         'r15': jmpbuf[JB_R15],
  67         'rip': glibc_ptr_demangle(jmpbuf[JB_PC], pointer_guard) }
  68
  69 def bt_jmpbuf(jmpbuf):
  70     '''Backtrace a jmpbuf'''
  71     regs = get_jmpbuf_regs(jmpbuf)
  72     old = dict()
  73
  74     for i in regs:
  75         old[i] = gdb.parse_and_eval('(uint64_t)$%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
  85 def coroutine_to_jmpbuf(co):
  86     coroutine_pointer = co.cast(gdb.lookup_type('CoroutineUContext').pointer())
  87     return coroutine_pointer['env']['__jmpbuf']
  88
  89
  90 class 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
 104 class 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
 111 class 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)