linux-kernel - Re: [PATCH v6 3/7] Adjust symbol ordering in text output section

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Message-ID: <CAF1bQ=QycziM6GQoTWSMQCGWPkZEDmAHMLfokoJ6k-vn7rCA=g@mail.gmail.com>
Date: Tue, 12 Nov 2024 12:13:22 -0800
From: Rong Xu <xur@...gle.com>
To: Klara Modin <klarasmodin@...il.com>
Cc: Alice Ryhl <aliceryhl@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Arnd Bergmann <arnd@...db.de>, Bill Wendling <morbo@...gle.com>, Borislav Petkov <bp@...en8.de>, 
	Breno Leitao <leitao@...ian.org>, Brian Gerst <brgerst@...il.com>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, David Li <davidxl@...gle.com>, 
	Han Shen <shenhan@...gle.com>, Heiko Carstens <hca@...ux.ibm.com>, "H. Peter Anvin" <hpa@...or.com>, 
	Ingo Molnar <mingo@...hat.com>, Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Juergen Gross <jgross@...e.com>, 
	Justin Stitt <justinstitt@...gle.com>, Kees Cook <kees@...nel.org>, 
	Masahiro Yamada <masahiroy@...nel.org>, "Mike Rapoport (IBM)" <rppt@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, 
	Nicolas Schier <nicolas@...sle.eu>, "Paul E. McKenney" <paulmck@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Wei Yang <richard.weiyang@...il.com>, 
	workflows@...r.kernel.org, Miguel Ojeda <miguel.ojeda.sandonis@...il.com>, 
	Maksim Panchenko <max4bolt@...il.com>, "David S. Miller" <davem@...emloft.net>, 
	Andreas Larsson <andreas@...sler.com>, Yonghong Song <yonghong.song@...ux.dev>, 
	Yabin Cui <yabinc@...gle.com>, Krzysztof Pszeniczny <kpszeniczny@...gle.com>, 
	Sriraman Tallam <tmsriram@...gle.com>, Stephane Eranian <eranian@...gle.com>, x86@...nel.org, 
	linux-arch@...r.kernel.org, sparclinux@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v6 3/7] Adjust symbol ordering in text output section

I sent the following patch for review:
https://lkml.org/lkml/2024/11/12/1565

Thanks!

-Rong

On Mon, Nov 11, 2024 at 11:45 PM Klara Modin <klarasmodin@...il.com> wrote:
>
> On 2024-11-12 06:38, Rong Xu wrote:
> > I compared the System.map files from Klara Modin. The linker script is
> > doing what I expected: relocating the unlikely executed functions to the
> > beginning of the .text section.
> >
> > However, the problem is with the _stext symbol. It belongs to the
> > .text section, so
> > it is positioned after the unlikely (or hot) functions. But it really
> > needs to be
> > the start of the text section.
> >
> > I checked all vmlinux.lds.S in arch/, I found that most archs
> > explicitly assign _stext to the same address as _text, with the
> > following 3 exceptions:
> >    arch/sh/kernel/vmlinux.lds.S
> >    arch/mips/kernel/vmlinux.lds.S
> >    arch/sparc/kernel/vmlinux.lds.S
> >
> > Note that we already partially handled arch/sparc/kernel/vmlinux.lds.S
> > for sparc64.
> > But we need to handle sparc32 also.
> >
> > Additionally, the boot/compressed/vmlinux.lds.S also the TEXT_TEXT
> > template. However,
> > I presume these files do not generate the .text.unlikely. or
> > .text.hot.* sections.
> >
> > I sent the following patch to Klara because I don't have an
> > environment to build and test.
> > ====================
> > diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
> > index 9ff55cb80a64..5f130af44247 100644
> > --- a/arch/mips/kernel/vmlinux.lds.S
> > +++ b/arch/mips/kernel/vmlinux.lds.S
> > @@ -61,6 +61,7 @@ SECTIONS
> >          /* read-only */
> >          _text = .;      /* Text and read-only data */
> >          .text : {
> > +               _stext = .;
> >                  TEXT_TEXT
> >                  SCHED_TEXT
> >                  LOCK_TEXT
> > ======================
> >
> > If Klara confirms the fix, I will send the patch for review.
> >
> > Thanks,
> >
> > -Rong
> >
>
> This does indeed fix the issue for me.
>
> Thanks,
> Tested-by: Klara Modin <klarasmodin@...il.com>