linux-kernel - Re: [PATCH v7 7/7] Add Propeller configuration for kernel build

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Message-ID: <CAF1bQ=TNOs7shXMbgY3UYzDZyF3ge=6hUdfEJvHV4LOo--tqVA@mail.gmail.com>
Date: Thu, 7 Nov 2024 13:54:06 -0800
From: Rong Xu <xur@...gle.com>
To: Nathan Chancellor <nathan@...nel.org>
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>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Nicolas Schier <nicolas@...sle.eu>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
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	Wei Yang <richard.weiyang@...il.com>, workflows@...r.kernel.org, 
	Miguel Ojeda <miguel.ojeda.sandonis@...il.com>, Maksim Panchenko <max4bolt@...il.com>, 
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	Yonghong Song <yonghong.song@...ux.dev>, Yabin Cui <yabinc@...gle.com>, 
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	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 v7 7/7] Add Propeller configuration for kernel build

Thanks Nathan for finding this out!

We changed the propeller option with this patch:
https://github.com/llvm/llvm-project/pull/110039

Currently, this patch is only in the ToT clang (v20) and not yet
released in v19.
I'll add a compiler version check to the patch: if the clang version >= 20,
use the new option.

If this patch is later released in v19.x clang, I'll have to update the check
accordingly.

If I don't hear objections, I'll send a fixup on top of Masahiro's branch.

Thanks,

-Rong

On Thu, Nov 7, 2024 at 12:45 PM Nathan Chancellor <nathan@...nel.org> wrote:
>
> Hi Rong,
>
> On Sat, Nov 02, 2024 at 10:51:14AM -0700, Rong Xu wrote:
> > diff --git a/scripts/Makefile.propeller b/scripts/Makefile.propeller
> > new file mode 100644
> > index 0000000000000..344190717e471
> > --- /dev/null
> > +++ b/scripts/Makefile.propeller
> > @@ -0,0 +1,28 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +# Enable available and selected Clang Propeller features.
> > +ifdef CLANG_PROPELLER_PROFILE_PREFIX
> > +  CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=list=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt -ffunction-sections
> > +  KBUILD_LDFLAGS += --symbol-ordering-file=$(CLANG_PROPELLER_PROFILE_PREFIX)_ld_profile.txt --no-warn-symbol-ordering
> > +else
> > +  CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=labels
> > +endif
>
> It appears that '-fbasic-block-sections=labels' has been deprecated in
> the main branch of LLVM, as I see a warning repeated over and over when
> building allmodconfig:
>
>   clang: warning: argument '-fbasic-block-sections=labels' is deprecated, use '-fbasic-block-address-map' instead [-Wdeprecated]
>
> https://github.com/llvm/llvm-project/commit/7b7747dc1d3da1a829503ea9505b4cecce4f5bda
>
> Sorry that I missed this during testing, as I was only using clang-19 at
> the time.
>
> I think you can send a fixup on top of Masahiro's branch:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/log/?h=kbuild
>
> > +# Propeller requires debug information to embed module names in the profiles.
> > +# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Skip this for AutoFDO,
> > +# as the option should already be set.
> > +ifndef CONFIG_DEBUG_INFO
> > +  ifndef CONFIG_AUTOFDO_CLANG
> > +    CFLAGS_PROPELLER_CLANG += -gmlt
> > +  endif
> > +endif
> > +
> > +ifdef CONFIG_LTO_CLANG_THIN
> > +  ifdef CLANG_PROPELLER_PROFILE_PREFIX
> > +    KBUILD_LDFLAGS += --lto-basic-block-sections=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt
> > +  else
> > +    KBUILD_LDFLAGS += --lto-basic-block-sections=labels
>
> I think this might have a similar problem but I have not tested.
>
> > +  endif
> > +endif
> > +
> > +export CFLAGS_PROPELLER_CLANG
>
> Cheers,
> Nathan