4cbf8efc5b
The code that dumps the stack frame works like that: * save current registers * overwrite current registers (including rip/rsp) with coroutine snapshot in the jmpbuf * print backtrace * restore the saved registers. If the user has currently selected a non topmost stack frame in gdb, the above code will still restore the selected frame registers, but the gdb will then lose the selected frame index, which makes it impossible to switch back to frame 0, to continue debugging the executable. Therefore switch temporarily to the topmost frame of the stack for the above code. Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20201217155436.927320-2-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
123 lines
3.6 KiB
Python
123 lines
3.6 KiB
Python
#
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# GDB debugging support
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#
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# Copyright 2012 Red Hat, Inc. and/or its affiliates
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#
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# Authors:
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# Avi Kivity <avi@redhat.com>
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#
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# This work is licensed under the terms of the GNU GPL, version 2
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# or later. See the COPYING file in the top-level directory.
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import gdb
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VOID_PTR = gdb.lookup_type('void').pointer()
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def get_fs_base():
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'''Fetch %fs base value using arch_prctl(ARCH_GET_FS). This is
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pthread_self().'''
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# %rsp - 120 is scratch space according to the SystemV ABI
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old = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)')
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gdb.execute('call (int)arch_prctl(0x1003, $rsp - 120)', False, True)
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fs_base = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)')
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gdb.execute('set *(uint64_t*)($rsp - 120) = %s' % old, False, True)
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return fs_base
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def pthread_self():
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'''Fetch pthread_self() from the glibc start_thread function.'''
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f = gdb.newest_frame()
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while f.name() != 'start_thread':
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f = f.older()
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if f is None:
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return get_fs_base()
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try:
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return f.read_var("arg")
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except ValueError:
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return get_fs_base()
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def get_glibc_pointer_guard():
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'''Fetch glibc pointer guard value'''
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fs_base = pthread_self()
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return gdb.parse_and_eval('*(uint64_t*)((uint64_t)%s + 0x30)' % fs_base)
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def glibc_ptr_demangle(val, pointer_guard):
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'''Undo effect of glibc's PTR_MANGLE()'''
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return gdb.parse_and_eval('(((uint64_t)%s >> 0x11) | ((uint64_t)%s << (64 - 0x11))) ^ (uint64_t)%s' % (val, val, pointer_guard))
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def get_jmpbuf_regs(jmpbuf):
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JB_RBX = 0
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JB_RBP = 1
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JB_R12 = 2
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JB_R13 = 3
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JB_R14 = 4
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JB_R15 = 5
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JB_RSP = 6
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JB_PC = 7
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pointer_guard = get_glibc_pointer_guard()
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return {'rbx': jmpbuf[JB_RBX],
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'rbp': glibc_ptr_demangle(jmpbuf[JB_RBP], pointer_guard),
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'rsp': glibc_ptr_demangle(jmpbuf[JB_RSP], pointer_guard),
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'r12': jmpbuf[JB_R12],
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'r13': jmpbuf[JB_R13],
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'r14': jmpbuf[JB_R14],
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'r15': jmpbuf[JB_R15],
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'rip': glibc_ptr_demangle(jmpbuf[JB_PC], pointer_guard) }
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def bt_jmpbuf(jmpbuf):
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'''Backtrace a jmpbuf'''
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regs = get_jmpbuf_regs(jmpbuf)
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old = dict()
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# remember current stack frame and select the topmost
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# so that register modifications don't wreck it
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selected_frame = gdb.selected_frame()
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gdb.newest_frame().select()
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for i in regs:
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old[i] = gdb.parse_and_eval('(uint64_t)$%s' % i)
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for i in regs:
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gdb.execute('set $%s = %s' % (i, regs[i]))
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gdb.execute('bt')
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for i in regs:
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gdb.execute('set $%s = %s' % (i, old[i]))
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selected_frame.select()
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def coroutine_to_jmpbuf(co):
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coroutine_pointer = co.cast(gdb.lookup_type('CoroutineUContext').pointer())
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return coroutine_pointer['env']['__jmpbuf']
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class CoroutineCommand(gdb.Command):
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'''Display coroutine backtrace'''
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def __init__(self):
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gdb.Command.__init__(self, 'qemu coroutine', gdb.COMMAND_DATA,
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gdb.COMPLETE_NONE)
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def invoke(self, arg, from_tty):
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argv = gdb.string_to_argv(arg)
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if len(argv) != 1:
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gdb.write('usage: qemu coroutine <coroutine-pointer>\n')
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return
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bt_jmpbuf(coroutine_to_jmpbuf(gdb.parse_and_eval(argv[0])))
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class CoroutineSPFunction(gdb.Function):
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def __init__(self):
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gdb.Function.__init__(self, 'qemu_coroutine_sp')
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def invoke(self, addr):
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return get_jmpbuf_regs(coroutine_to_jmpbuf(addr))['rsp'].cast(VOID_PTR)
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class CoroutinePCFunction(gdb.Function):
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def __init__(self):
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gdb.Function.__init__(self, 'qemu_coroutine_pc')
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def invoke(self, addr):
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return get_jmpbuf_regs(coroutine_to_jmpbuf(addr))['rip'].cast(VOID_PTR)
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