Re: [PATCH v1 07/10] gdb/linux-tdep: migrate linux_find_memory_regions_full to file_reader_t

[Thiago Jung Bauermann <thiago.bauermann@linaro.org>]

Matthieu Longo <matthieu.longo@arm.com> writes:

> On 09/07/2026 07:36, Thiago Jung Bauermann wrote:
>> Matthieu Longo <matthieu.longo@arm.com> writes:
>> 
>>> The previous implementation of linux_find_memory_regions_full could
>>> still return success even when none of the /proc/PID/[s]maps files
>>> existed, or all reads returned 0 bytes (this last case can happen on
>>> Linux when the thread-group leader has exited).
>>> As a result, the function could incorrectly succeed, allowing core
>>> dump generation via the gcore command.
>>> This logical defect was allowing, by chance, the function to return
>>> success and hence, allowing fortuitously the codedump generation via
>>> gcore command (see gcore-stale-thread test for more details).
>> 
>> Did you run into this problem, or just noticed it by inspecting the
>> code? If the former, do you think it's worth adding a testcase to make
>> sure this problem doesn't appear again?
>> 
>
> The command stopped working after I migrated the function to file_reader_t.
> As Christina Schimpe mentioned it, bool operator () now returns false if the buffer is
> null, or if
> the size returned is 0. This last is a change with the previous behavior.
> When the thread-group leader exits, the /proc/pid/[s]maps files still exist, but become
> empty.
> In such a case, the function should return false instead of trying to parse an empty
> string, which
> results in no smaps data entry being processed, and so no callback called. This behavior is
> erroneous in my opinion.
>
> I don't think that it is worth adding a testcase for this, because the root cause was the
> wrong pid
> being used.

Ah, thanks for the explanation. I agree with you.

-- 
Thiago
(he/him)