[PATCH] arm: Prevent GCC from using VFP registers in code used during dynamic linking

[Adhemerval Zanella Netto]

On 11/05/26 13:51, Aurelien Jarno wrote:
> On 2026-05-11 10:54, Adhemerval Zanella Netto wrote:
>>
>>
>> On 10/05/26 19:00, Aurelien Jarno wrote:
>>> Starting with GCC 15, VFP registers are used more aggressively on ARM,
>>> including in ld.so code involved in runtime linking. For instance d7 is
>>> used in _dl_lookup_symbol_, which clobbers the 8th floating point
>>> argument of a function on its first call.
>>
>> We added the --with-rtld-early-cflags configure option for avoid such issue,
>> couldn't this be used instead of specific flags to specific objects?
> 
> This is a configure option, so do you mean changing the default value 
> for arm?

I think it should a decision on which ISA do you want to deploy glibc. 
If you targetting armv7a system, runtime should be free to use any register
on dynamic loader.

> 
> Anyway is doesn't work as it misses dl-lookup.os and dl-runtime.os, but 
> works for dl-misc.os.
> 

I think it would be better to add $(rtld-early-cflags) for such objects
as well.

What I want to avoid is having multiple configurations on how to build
startup code. We already have the stack-protector, stack usage, ifunc
redirections to be aware.