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

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Message-ID: <Z5EhsaJOaRjjMEp4@li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com>
Date: Wed, 22 Jan 2025 17:49:53 +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 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
  [ 4] .rela.rodata      RELA             0000000000000000  142cf588
  [ 6] .rela__ksymtab    RELA             0000000000000000  142ece08
  [ 8] .rela__ksymt[...] RELA             0000000000000000  1433f200
  [13] .rela__param      RELA             0000000000000000  14432d40
  [15] .rela__modver     RELA             0000000000000000  14436358
  [17] .rela__ex_table   RELA             0000000000000000  14436538
  [20] .rela.data..[...] RELA             0000000000000000  14446228
  [22] .rela.data.rel.ro RELA             0000000000000000  144d9240
  [25] .rela.data        RELA             0000000000000000  14559148
  [27] .rela__bug_table  RELA             0000000000000000  145b4ae0
  [29] .rela.data.rel    RELA             0000000000000000  1461aab0
  [32] .rela.amode3[...] RELA             0000000000000000  146eb280
  [34] .rela.init.text   RELA             0000000000000000  146eb430
  [36] .rela.exit.text   RELA             0000000000000000  14750c20
  [38] .rela.altins[...] RELA             0000000000000000  14753d28
  [41] .rela.nospec[...] RELA             0000000000000000  1484ca58
  [43] .rela.nospec[...] RELA             0000000000000000  1487ef90
  [46] .rela.amode3[...] RELA             0000000000000000  14a0d168
  [48] .rela.amode3[...] RELA             0000000000000000  14a0d270
  [51] .rela.init.data   RELA             0000000000000000  14a0d330
  [53] .relaruntime[...] RELA             0000000000000000  14b5d6f0
  [55] .relaruntime[...] RELA             0000000000000000  14b5d768
  [57] .rela.data..[...] RELA             0000000000000000  14b5d7e0
  [61] .rela.debug_[...] RELA             0000000000000000  14b5d918
  [63] .rela.debug_info  RELA             0000000000000000  14b80478
  [66] .rela.debug_line  RELA             0000000000000000  250ef010
  [68] .rela.debug_frame RELA             0000000000000000  25123060
  [71] .rela.debug_loc   RELA             0000000000000000  253bb1a0
  [73] .rela.debug_[...] RELA             0000000000000000  298eb5a8

Thanks!