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From: "slyfox at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/99113] SHF_GNU_RETAIN doesn't work with Linux kernel
Date: Mon, 15 Feb 2021 18:54:55 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99113

Sergei Trofimovich <slyfox at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |slyfox at gcc dot gnu.org

--- Comment #2 from Sergei Trofimovich <slyfox at gcc dot gnu.org> ---
I have a few notes:

1. GCC should put SHF_GNU_RETAIN section into a different section from .data
anyway, right?

I think that means linux kernel would need to adapt in any case to merge new
.data.${SHF_GNU_RETAIN_name} section into appropriate place in it's linker
script.

Proposal: rename a section in an easily distinguishable prefix, like:

    NEW:    .data.retain.event_initcall_finish
    OLD:    .data.event_initcall_finish

That would simplify tweaking linux ldscript. For -fno-function-sections cas=
e it
could be just.
    .data.retain

Do we still have time for such a rename? Is it safe?

2. Linux kernel does support -ffunction-sections  with
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION. But it relies even more on naming
conventions:

  #ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
  #define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
  #define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX*
  #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
  #define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]*
  #define BSS_MAIN .bss .bss.[0-9a-zA-Z_]*
  #define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]*
  #else
  #define TEXT_MAIN .text
  #define DATA_MAIN .data
  #define SDATA_MAIN .sdata
  #define RODATA_MAIN .rodata
  #define BSS_MAIN .bss
  #define SBSS_MAIN .sbss
  #endif

  A variant of [1.] would allow for easier section ganthering in the script.

3. I tried to add '.data.event*' (and similar) to linux ldscript and it was=
 not
enough for me to built a kernel that does not crash. Which might hint at
binutils bug or linux loader bug (or at my bad attempt at adding sections).=