[RFC PATCH 0/3] implement dlmopen hooks for gdb

[Florian Weimer]

* Daniel Walker:

> On Thu, Sep 17, 2020 at 09:53:30AM -0400, Carlos O'Donell wrote:
>> On 9/17/20 8:59 AM, Florian Weimer wrote:
>> > * Carlos O'Donell:
>> > 
>> >> You will always have .dynsym with a definition for _r_debug_dlmopen.
>> > 
>> > Note that this doesn't work if you just have a core file.  In order to
>> > find _r_debug (or _r_debug_dlmopen), a debugger needs the exact same
>> > copy of ld.so that was used by the executable, otherwise the symbol
>> > cannot be found in the image.
>> 
>> You are correct.
>> 
>> I followed up on my own email regarding this.
>> 
>> So in the end to get process and core file debugging we'll need:
>> 
>> * _r_debug_dlmopen
>> * DT_DEBUG_DLMOPEN
>> 
>
> It seems like adding DT_DEBUG_DLMOPEN into the gABI might take some
> effort. Have you considered this ? The last one which was added was
> DT_SYMTAB_SHNDX in 2018, and it looks like it did not come from glibc.

We are reviving GNU gABI maintenance.  There's been quite a bit of list
activity, and a proposal of a first ABI document:

  <https://sourceware.org/pipermail/gnu-gabi/2020q3/thread.html>

I have a feeling that we might be soon over this bump, and getting
things added should become easier.

In the meantime, can we demo this feature without DT_DEBUG_DLMOPEN?
With a patch glibc and gdb?  Incidentally, I have an LD_AUDIT issue I
need to debug. 8-)

Thanks,
Florian
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