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

[Fangrui Song]

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 .*