[PATCH 2/2] aarch64: Add workaround for GDB bug handling string literals

[Yury Khrustalev]

On Tue, Jun 30, 2026 at 12:17:37PM -0300, Adhemerval Zanella Netto wrote:
> 
> On 30/06/26 11:15, Wilco Dijkstra wrote:
> > Hi,
> > 
> >> I don't like it either, but I don't see a better alternative to keep some
> >> compatibility with old gdb.
> >>
> >> But I also think this approach is fragile: it require some assumptions on how
> >> gdb implements this and adds some magic number.� I think a better alternative
> >> is invert the assumption: the only exactly legitimate caller of an IFUNC
> >> resolver is the the dynamic loader's relocation machinery
> >> (elf_ifunc_invoke / _dl_fixup):
> > 
> > On AArch64 we can just check for !(arg0 & IFUNC_ARG_HWCAP) since we always
> > invoke ifuncs with that bit set from GLIBC (obviously the value is way too large to
> > ever be a valid allocation). You could also check arg0 == GLRO (dl_hwcap) for other
> > targets.

Yes, we should do this, I'll make a patch.

> 
> This adds extra complexity for debuggers to have arch-specific knowledge of
> how ifunc works when called directly.  Doable, but it is essentially another
> undocumented semantic. 

The idea is to abort if !(arg0 & IFUNC_ARG_HWCAP) is true with a clear
error message. This is not to work-around the issue in GDB but to make
the error explicit and clear. No complexity, no arch-specific knowledge.

Thanks,
Yury