Re: segfault in ld.elf_so

[RVP <rvp%SDF.ORG@localhost>]

On Wed, 4 Feb 2026, Thomas Klausner wrote:

> On Fri, Jan 30, 2026 at 11:44:47PM +0100, RVP wrote:
>
> > 2. Run the program with the new ld.elf_so and collect the (copious) debug
> >    output.
>
> It's not that much, really:
> [...]
> [1]   Segmentation fault (core dumped) /tmp/wip/webkit-gtk/work/webkitgtk-2.50.4/tmp-...

No, there should be a lot more debug output--esp. the reloc. stuff.
Uncomment: `-DDEBUG', `-DRTLD_DEBUG' and `-DRTLD_DEBUG_RELOC'.

> > 3. Run `readelf -Wa' on the program and the library it is crashing on when
> >    doing the PLT reloc. (if, indeed, it's crashing fixing up a library rather
> >    than the executable).
>
> This is more, yes:
> [...]
> Program Headers:
>  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg Align
>  PHDR           0x000040 0x0000000000400040 0x0000000000400040 0x0001f8 0x0001f8 R   0x8
>  INTERP         0x000238 0x0000000000400238 0x0000000000400238 0x000017 0x000017 R   0x1
>      [Requesting program interpreter: /usr/libexec/ld.elf_so]
>  LOAD           0x000000 0x0000000000400000 0x0000000000400000 0x004538 0x004538 R   0x1000
>  LOAD           0x005000 0x0000000000405000 0x0000000000405000 0x00248e 0x00248e R E 0x1000
>  LOAD           0x008000 0x0000000000408000 0x0000000000408000 0x000a7c 0x000a7c R   0x1000
>  LOAD           0x009000 0x0000000000409000 0x0000000000409000 0x000940 0x000988 RW  0x1000
>  DYNAMIC        0x009028 0x0000000000409028 0x0000000000409028 0x000290 0x000290 RW  0x8
>  NOTE           0x000250 0x0000000000400250 0x0000000000400250 0x00002c 0x00002c R   0x4
>  GNU_EH_FRAME   0x0087a8 0x00000000004087a8 0x00000000004087a8 0x00008c 0x00008c R   0x4

This is puzzling as well because,

a) there's no RELRO segment there (and there would've been one with if linked with `-Wl,-z,relro')

> Dynamic section at offset 0x9028 contains 36 entries:
>  Tag        Type                         Name/Value
> [...]
> 0x0000000000000003 (PLTGOT)             0x4092d8
> 0x0000000000000002 (PLTRELSZ)           1608 (bytes)
> 0x0000000000000014 (PLTREL)             RELA
> 0x0000000000000017 (JMPREL)             0x403ef0
> 0x0000000000000007 (RELA)               0x403350
> 0x0000000000000008 (RELASZ)             2976 (bytes)
> 0x0000000000000009 (RELAENT)            24 (bytes)
> 0x0000000000000000 (NULL)               0x0

and,

b) the binary doesn't seem to have been linked with `-Wl,-z,now'.

So how is this crashing?

I'll see if I can get pkgsrc running for this later this weekend.

-RVP