Re: [Qemu-devel] [PATCH 0/3] scripts/qemu-gdb: Add event tracing support

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2015-05-15 15:21, Markus Armbruster wrote:
> Jan Kiszka <jan.kiszka@siemens.com> writes:
> 
>> On 2015-05-15 14:18, Markus Armbruster wrote:
>>> Peter Maydell <peter.maydell@linaro.org> writes:
>>>
>>>> On 15 May 2015 at 08:58, Markus Armbruster <armbru@redhat.com> wrote:
>>>>> Since you're touching qemu-gdb.py anyway, could you stick in a brief
>>>>> comment explaining how to put it to use?
>>>>
>>>> Good idea. It turns out the answer is just "source it from gdb",
>>>> but it took me a little while to find that out, so worth commenting.
>>>> I also have a patch which makes it do the 'ignore SIGUSR1' bit
>>>> by doing 'handle SIGUSR1 pass noprint nostop' for you.
>>>
>>> Here's how to load scripts/qemu-gdb.py automatically:
>>>
>>> * Apply the appended patch to turn it into a gdb init file
>>>
>>>   That's what it is, after all.  It's not a standalone Python program.
>>>
>>> * Tell gdb to trust it
>>>
>>>   Add a line like
>>>
>>>       add-auto-load-safe-path ~/work/qemu/scripts/qemu-gdb.py
>>>
>>>   to your ~/.gdbinit
>>>
>>> * Link it into the directory where you run gdb --args qemu...
>>>
>>> * Verify it works:
>>>
>>>       $ gdb
>>>       [...]
>>>       (gdb) help qemu
>>>       Prefix for QEMU debug support commands
>>>
>>>       List of qemu subcommands:
>>>
>>>       qemu coroutine -- Display coroutine backtrace
>>>       qemu mtree -- Display the memory tree hierarchy
>>>
>>>       Type "help qemu" followed by qemu subcommand name for full documentation.
>>>       Type "apropos word" to search for commands related to "word".
>>>       Command name abbreviations are allowed if unambiguous.
>>>       (gdb) 
>>>
>>> If you know a better way to do this, please post it.
>>>
>>
>> Yep, that's the basic idea behind gdb python scripts: myapp-gdb.py gets
>> auto-pulled on "gdb myapp". Since some gdb 7.x, we have that security
>> feature above which prevents pulling from arbitrary sources.
>>
>>>
>>> diff --git a/scripts/qemu-gdb.py b/scripts/qemu-gdb.py
>>> index 6c7f4fb..ac3087c 100644
>>> --- a/scripts/qemu-gdb.py
>>> +++ b/scripts/qemu-gdb.py
>>> @@ -1,5 +1,3 @@
>>> -#!/usr/bin/python
>>> -
>>>  # GDB debugging support
>>>  #
>>>  # Copyright 2012 Red Hat, Inc. and/or its affiliates
>>> @@ -13,7 +11,7 @@
>>>  # Contributions after 2012-01-13 are licensed under the terms of the
>>>  # GNU GPL, version 2 or (at your option) any later version.
>>>  
>>> -
>>> +python
>>
>> What is this line doing?
> 
> Found here:
> https://stackoverflow.com/questions/16553283/python-code-in-gdb-init-file-gdbinit

The author there puts his code into .gdbinit, which is a gdb script, not
a python one.

> 
> It doesn't work for me without it.

When sourcing? Works fine here (gdb 7.7.something).

In any case, when you pull in the script via auto-load, that extra
non-python statement will break. Try "python python". ;)

Jan

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