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

From: Masahiro Yamada <masahiroy@kernel.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Andreas Schwab <schwab@linux-m68k.org>,
	Nathan Chancellor <nathan@kernel.org>,
	linux-arch@vger.kernel.org,  linux-kbuild@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	 Thorsten Leemhuis <regressions@leemhuis.info>,
	Catalin Marinas <catalin.marinas@arm.com>,
	 Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	 linux-riscv@lists.infradead.org,
	Dennis Gilmore <dennis@ausil.us>,
	 Albert Ou <aou@eecs.berkeley.edu>, Arnd Bergmann <arnd@arndb.de>,
	 Jisheng Zhang <jszhang@kernel.org>,
	Nicolas Schier <nicolas@fjasle.eu>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	llvm@lists.linux.dev
Subject: Re: [PATCH v2] arch: fix broken BuildID for arm64 and riscv
Date: Thu, 5 Jan 2023 22:49:46 +0900	[thread overview]
Message-ID: <CAK7LNASX4oJO+ciA6RRW35qDgD+39iWDVhW0LX_eQne+PDBVgA@mail.gmail.com> (raw)
In-Reply-To: <CAMj1kXGD3wQUPsRhvD7bO9xBJ6NR=Z+y8wXmKSCs57Oeh3MzGw@mail.gmail.com>

On Thu, Jan 5, 2023 at 6:27 PM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Thu, 5 Jan 2023 at 10:21, Andreas Schwab <schwab@linux-m68k.org> wrote:
> >
> > On Jan 05 2023, Masahiro Yamada wrote:
> >
> > > 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
> > >
> > > 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/

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