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
  16 import gdb
  17
  18 VOID_PTR = gdb.lookup_type('void').pointer()
  19
  20 def 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*)($rsp - 120) = %s' % old, False, True)
  28     return fs_base
  29
  30 def pthread_self():
  31     '''Fetch pthread_self() from the glibc start_thread function.'''
  32     f = gdb.newest_frame()
  33     while f.name() != 'start_thread':
  34         f = f.older()
  35         if f is None:
  36             return get_fs_base()
  37
  38     try:
  39         return f.read_var("arg")
  40     except ValueError:
  41         return get_fs_base()
  42
  43 def get_glibc_pointer_guard():
  44     '''Fetch glibc pointer guard value'''
  45     fs_base = pthread_self()
  46     return gdb.parse_and_eval('*(uint64_t*)((uint64_t)%s + 0x30)' % fs_base)
  47
  48 def glibc_ptr_demangle(val, pointer_guard):
  49     '''Undo effect of glibc's PTR_MANGLE()'''
  50     return gdb.parse_and_eval('(((uint64_t)%s >> 0x11) | ((uint64_t)%s << (64 - 0x11))) ^ (uint64_t)%s' % (val, val, pointer_guard))
  51
  52 def get_jmpbuf_regs(jmpbuf):
  53     JB_RBX  = 0
  54     JB_RBP  = 1
  55     JB_R12  = 2
  56     JB_R13  = 3
  57     JB_R14  = 4
  58     JB_R15  = 5
  59     JB_RSP  = 6
  60     JB_PC   = 7
  61
  62     pointer_guard = get_glibc_pointer_guard()
  63     return {'rbx': jmpbuf[JB_RBX],
  64         'rbp': glibc_ptr_demangle(jmpbuf[JB_RBP], pointer_guard),
  65         'rsp': glibc_ptr_demangle(jmpbuf[JB_RSP], pointer_guard),
  66         'r12': jmpbuf[JB_R12],
  67         'r13': jmpbuf[JB_R13],
  68         'r14': jmpbuf[JB_R14],
  69         'r15': jmpbuf[JB_R15],
  70         'rip': glibc_ptr_demangle(jmpbuf[JB_PC], pointer_guard) }
  71
  72 def bt_jmpbuf(jmpbuf):
  73     '''Backtrace a jmpbuf'''
  74     regs = get_jmpbuf_regs(jmpbuf)
  75     old = dict()
  76
  77     for i in regs:
  78         old[i] = gdb.parse_and_eval('(uint64_t)$%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
  88 def coroutine_to_jmpbuf(co):
  89     coroutine_pointer = co.cast(gdb.lookup_type('CoroutineUContext').pointer())
  90     return coroutine_pointer['env']['__jmpbuf']
  91
  92
  93 class 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
 107 class 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
 114 class 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)