Re: [PATCH v2] arch: fix broken BuildID for arm64 and riscv

On Thu, Jan 5, 2023 at 6:27 PM Ard Biesheuvel [off-list ref] wrote:

On Thu, 5 Jan 2023 at 10:21, Andreas Schwab [off-list ref] wrote:

quoted

On Jan 05 2023, Masahiro Yamada wrote:

quoted

I do not understand why 99cb0d917ffa affected this.


I submitted a fix to shoot the error message "discarded section .exit.text"

https://lore.kernel.org/all/20230105031306.1455409-1-masahiroy@kernel.org/T/#u (local)

I do not understand the binutils commit either,
but it might have made something good
because EXIT_TEXT appears twice, in .exit.text, and /DISCARD/.

I think the issue is that the introdution of a second /DISCARD/
directive early in script changes the order of evaluation of the other
/DISCARD/ directive when binutils < 2.36 is used, so that the missing
RUNTIME_DISCARD_EXIT started to become relevant.  As long as /DISCARD/
only appears last, the effect of EXIT_TEXT inside it is always
overridden by its occurence in the .exit.exit output section directive.
When another /DISCARD/ occurs early (and binutils < 2.36 is used) the
effect of EXIT_TEXT inside the second /DISCARD/ (when merged with the
first) overrides its occurence in the .exit.text directive.  The
binutils commit changed that because the new /DISCARD/ directive no
longer affects the order of evaluation of the rest of the directives.

Exactly. The binutils change mentions output section merging, which
apparently applies to the /DISCARD/ pseudo section as well.

However, powerpc was also affected by this, and I suggested another
fix in the thread below

https://lore.kernel.org/all/20230103014535.GA313835@roeck-us.net/ (local)

Thanks for the pointer.

(and sorry, I did not notice that thread, and missed to reply promptly)


Your fix will work globally.
I left some comments in that thread.




-- 
Best Regards
Masahiro Yamada

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