linux-kernel - Re: [PATCH v3] kbuild: Strip runtime const RELA sections correctly

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Message-ID: <Z5Epcb+GnqFegstq@li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com>
Date: Wed, 22 Jan 2025 18:22:57 +0100
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        Ron Economos <re@...z.net>
Subject: Re: [PATCH v3] kbuild: Strip runtime const RELA sections correctly

On Wed, Jan 22, 2025 at 05:49:53PM +0100, Alexander Gordeev wrote:
> On Mon, Jan 13, 2025 at 04:53:07PM +0100, Ard Biesheuvel wrote:
> 
> Hi Ard,
> 
> > Due to the fact that runtime const ELF sections are named without a
> > leading period or double underscore, the RSTRIP logic that removes the
> > static RELA sections from vmlinux fails to identify them. This results
> > in a situation like below, where some sections that were supposed to get
> > removed are left behind.
> > 
> >   [Nr] Name                              Type            Address          Off     Size   ES Flg Lk Inf Al
> > 
> >   [58] runtime_shift_d_hash_shift        PROGBITS        ffffffff83500f50 2900f50 000014 00   A  0   0  1
> >   [59] .relaruntime_shift_d_hash_shift   RELA            0000000000000000 55b6f00 000078 18   I 70  58  8
> >   [60] runtime_ptr_dentry_hashtable      PROGBITS        ffffffff83500f68 2900f68 000014 00   A  0   0  1
> >   [61] .relaruntime_ptr_dentry_hashtable RELA            0000000000000000 55b6f78 000078 18   I 70  60  8
> >   [62] runtime_ptr_USER_PTR_MAX          PROGBITS        ffffffff83500f80 2900f80 000238 00   A  0   0  1
> >   [63] .relaruntime_ptr_USER_PTR_MAX     RELA            0000000000000000 55b6ff0 000d50 18   I 70  62  8
> > 
> > So tweak the match expression to strip all sections starting with .rel.
> > While at it, consolidate the logic used by RISC-V, s390 and x86 into a
> > single shared Makefile library command.
> 
> On s390 this is before:
> 
>   [32] .relaruntime[...] RELA             0000000000000000  13b3fe20
>   [34] .relaruntime[...] RELA             0000000000000000  13b3fe98
> 
> This is after:
> 
>   [ 2] .rela.text        RELA             0000000000000000  13b3fe20
...
>   [73] .rela.debug_[...] RELA             0000000000000000  298eb5a8

Sorry, I checked the wrong version. It works as expected.

Tested-by: Alexander Gordeev <agordeev@...ux.ibm.com>