linux-kernel - Re: [RFC PATCH 3/9] tools/nolibc: Add basic ELF self-relocation support for static PIE

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Message-ID: <CAFr9PXkiwBLhiS+8o2gS2AkRXenv9SJRVmQUpidCjAWux+f_tA@mail.gmail.com>
Date: Mon, 2 Feb 2026 06:54:48 +0900
From: Daniel Palmer <daniel@...ngy.jp>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: w@....eu, kees@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 3/9] tools/nolibc: Add basic ELF self-relocation
 support for static PIE

Hi Thomas,

On Mon, 2 Feb 2026 at 01:42, Thomas Weißschuh <linux@...ssschuh.net> wrote:

> > +     /*
> > +      * Everything I could find said that the way to find the base for relocation
> > +      * should be done by searching for the first PT_LOAD and then using the ofset
> > +      * of that against the adressed of the program headers. So FIXME.
> > +      */
> > +     base = phdr_addr - sizeof(elf_ehdr);
>
> What was wrong with AT_BASE?

Apparently AT_BASE is the base of the interpreter
(https://man7.org/linux/man-pages/man3/getauxval.3.html).
I did try it and from what I remember it was 0 on m68k and x86. For
sparc and ppc there seems to be an issue with the address of the
dynamic section calculated from base so on those machines the current
way seems to be wrong either way.

Thank you for all of the other comments. I'll fix those up.

Cheers,

Daniel