[PATCH v3] gas: add --reloc-section-sym={all, internal, none} option for ELF

[Fangrui Song]

On Sat, May 16, 2026 at 12:38 AM Fangrui Song <i@maskray.me> wrote:
>
> On Fri, May 15, 2026 at 5:05 AM Jan Beulich <jbeulich@suse.com> wrote:
> >
> > On 28.02.2026 07:19, Fangrui Song wrote:
> > > From: Fangrui Song <maskray@sourceware.org>
> > >
> > > When generating relocations for non-ifunc local symbols that satisfies
> > > several conditions, GAS converts them to reference the section symbol
> > > (STT_SECTION) instead, folding the original symbol's offset into the
> > > addend.  This allows the original local symbol to be omitted from
> > > .symtab, but the STT_SECTION symbol itself must be present, so the
> > > conversion saves .symtab entries only when a section has more than one
> > > local symbol referenced by relocations.
> > >
> > > Add --reloc-section-sym to control this conversion:
> > >
> > > - all (default): convert all eligible local symbols
> > > - internal: only convert compiler-generated locals (.L prefix)
> > > - none: never convert; keep all symbols as-is in relocations
> > >
> > > This is useful for debugging and for tools that benefit from preserved
> > > symbol names.
> > >
> > > PR gas/33885
> >
> > Okay, provided you checked the new tests pass for a wide range of targets.
> > In particular ...
>
> Thanks for taking a look.
>
> > > --- /dev/null
> > > +++ b/gas/testsuite/gas/elf/reloc-section-sym-all.d
> > > @@ -0,0 +1,12 @@
> > > +#source: reloc-section-sym.s
> > > +#as: --reloc-section-sym=all
> > > +#objdump: -rsj .data
> > > +#name: reloc-section-sym=all
> > > +
> > > +.*: +file format .*
> > > +
> > > +RELOCATION RECORDS FOR \[\.data\]:
> > > +OFFSET +TYPE +VALUE
> > > +0*0 [^ ]+ +\.text.*
> > > +0*4 [^ ]+ +\.text.*
> > > +#pass
> > > --- /dev/null
> > > +++ b/gas/testsuite/gas/elf/reloc-section-sym-internal.d
> > > @@ -0,0 +1,12 @@
> > > +#source: reloc-section-sym.s
> > > +#as: --reloc-section-sym=internal
> > > +#objdump: -rsj .data
> > > +#name: reloc-section-sym=internal
> > > +
> > > +.*: +file format .*
> > > +
> > > +RELOCATION RECORDS FOR \[\.data\]:
> > > +OFFSET +TYPE +VALUE
> > > +0*0 [^ ]+ +local.*
> > > +0*4 [^ ]+ +\.text.*
> > > +#pass
> > > --- /dev/null
> > > +++ b/gas/testsuite/gas/elf/reloc-section-sym-none.d
> > > @@ -0,0 +1,12 @@
> > > +#source: reloc-section-sym.s
> > > +#as: --reloc-section-sym=none
> > > +#objdump: -rsj .data
> > > +#name: reloc-section-sym=none
> > > +
> > > +.*: +file format .*
> > > +
> > > +RELOCATION RECORDS FOR \[\.data\]:
> > > +OFFSET +TYPE +VALUE
> > > +0*0 [^ ]+ +local.*
> > > +0*4 [^ ]+ +\.Ltemp.*
> > > +#pass
> > > --- /dev/null
> > > +++ b/gas/testsuite/gas/elf/reloc-section-sym.s
> > > @@ -0,0 +1,9 @@
> > > +     .text
> > > +local:
> > > +     .byte 0
> > > +.Ltemp:
> > > +     .byte 0
> > > +
> > > +     .data
> > > +     .long local + 16
> > > +     .long .Ltemp + 16
> >
> > ... here I wonder whether .dc.a wouldn't be the more portable directive to
> > use when it comes to relocations.
>
> With .long the relocation offset is target-agnostic. section5.s uses
> .long relocations as well, so I think .long relocations is portable.
>
> > > --- /dev/null
> > > +++ b/gas/testsuite/gas/i386/reloc-section-sym.s
> > > @@ -0,0 +1,14 @@
> > > +     .text
> > > +     nop
> > > +local:
> > > +     .byte 0
> >
> > Better "nop" here as well, just like ...
>
> I think `.byte 0` doesn't hurt here...
> .byte 0/int3/nop is to introduce some nuance. While it probably
> doesn't matter for this particular test, it helps in other tests when
> using objdump -s.
>
> > > +.Ltemp:
> > > +     nop
> >
> > ... you have it here?
> >
> > Which further reminds me to ask why in the generic test you don't use .nop
> > in favor of .byte.
> >
> > Jan
>
> I didn't realize that .nop is portable. However, .nop introduces
> target-dependent offsets, which is exactly what we want to avoid in a
> generic test.
> Sticking to explicit offsets like 0/4/8 IMHO is clearer than using .*

Hi Jan, are you happy with the patch as is ? :)