Re: [PATCH] scripts/gdb: fix debugging modules on s390

From: Jan Kiszka
Date: Thu Oct 17 2019 - 03:06:25 EST

On 15.10.19 17:43, Ilya Leoshkevich wrote:
>> Am 15.10.2019 um 17:21 schrieb Jan Kiszka <jan.kiszka@xxxxxxxxxxx>:
>>> @@ -113,6 +113,12 @@ lx-symbols command."""
>>> if module_file:
>>> gdb.write("loading @{addr}: {filename}\n".format(
>>> addr=module_addr, filename=module_file))
>>> + if utils.is_target_arch('s390'):
>>> + # Module text is preceded by PLT stubs on s390.
>>> + module_arch = module['arch']
>>> + plt_offset = int(module_arch['plt_offset'])
>>> + plt_size = int(module_arch['plt_size'])
>>> + module_addr = hex(int(module_addr, 0) + plt_offset + plt_size)
>> Shouldn't we report the actual address above, ie. reorder this tuning
>> with the gdb.write?
> That's a tough question. I thought about this, and the argument for
> showing the fixed up address is that if someone does the math with
> symbol offsets from e.g. objdump, the result will be consistent with
> what gdb shows.
> On the other hand side, why would anyone do this? that's exactly what
> this gdb script is for. So showing the actual address at which the
> memory was allocated gives the user some additional information, and is
> also consistent with what cat /proc/modules would show.
> At the end of the day, I don't have a strong opinion on this, so if you
> think it's better to show the fixed up address, I'll send a v2.

One of the original ideas of the printout was to provide the information
needed to reproduce potential issues manually. From that perspective,
the fixed-up address would the the thing to print.

If you think the vanilla address has some value as well, we could make
an s390-specifi printout of both values.


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