Re: [PATCH] powerpc: Use FLAG_ELF_LIBC6 for 32-bit known libraries

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 02/03/2022 16:30, Raoni Fassina Firmino wrote:
> On Fri, Dec 03, 2021 at 11:51:29AM -0300, AL glibc-alpha wrote:
>>
>>
>> On 04/11/2021 15:10, Lucas A. M. Magalhaes via Libc-alpha wrote:
>>> In systems with more versions of the known libraries, i.e. on IBM
>>> Advance Toolchain, ldconfig will order them incorrectly on ld.cache.
>>>
>>> The issue only occurs with 32-bit libraries that don't depend on libc or
>>> libm. That's because process_elf32_file check if the elf depends on one
>>> of the libraries at known_libs to select the elf flag. For example, as
>>> libc.so.6 don't depend on itself or on libm it will be flagged as
>>> FLAG_ELF instead of FLAG_ELF_LIBC6 as expected.
>>
>> Wouldn't be simpler to check if the DT_SONAME matches any on 'known_libs' after
>> dynamic section parsing and set the appropriated flag on generic 'process_file'? 
> 
> But then it would touch every architecture, I think since this is only a
> problem affecting powerpc (BE 32bits) I don't think it is worth touch
> the generic code if will not help any other architecture.

Which is not a bad idea, removing arch-specific code and make the ldconfig
have a similar semantic interdependently of the ABI is a good move forward. 

> 
> 
>> (also powerpc SYSDEP_KNOWN_LIBRARY_NAMES seems redundant).
> 
> Seems to be the same as every other arch except i386. Lookin at Lucas's
> RFC for removal of libc.5 and libc.4 compatibility, maybe it being
> diferent in i386 is just that it was never really used anymore, and so
> never updated.

I think it would be better to send this change along the the RPC to
remove libc4/libc5 compatibility.  I am already proposing dropping some 
support for old lib5/aout files [1], which Florian thinks it is ok,
so I take that dropping all support for libc4/libc5 is a way forward.

In fact, with libc4/libc5 removal I think this patch is not really 
required.

[1] https://patchwork.sourceware.org/project/glibc/patch/20220304133801.1868553-4-adhemerval.zanella@linaro.org/