From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
"Kees Cook" <kees@kernel.org>,
"Nathan Chancellor" <nathan@kernel.org>,
"Nicolas Schier" <nsc@kernel.org>,
"Nick Desaulniers" <ndesaulniers@google.com>,
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"Masahiro Yamada" <masahiroy@kernel.org>,
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"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"Paul Walmsley" <pjw@kernel.org>,
"Palmer Dabbelt" <palmer@dabbelt.com>,
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"Jens Axboe" <axboe@kernel.dk>,
linux-hardening@vger.kernel.org
Subject: Re: [PATCH v2 00/21] kbuild: significantly speed up kernel builds
Date: Tue, 15 Sep 2026 12:35:53 +0100 [thread overview]
Message-ID: <aqks-ZmauZMcOELA@gremlin> (raw)
In-Reply-To: <7646eb0c-7c4a-4ec2-9562-66a74c4d9858@app.fastmail.com>
On Tue, Sep 15, 2026 at 10:53:51AM +0200, Arnd Bergmann wrote:
> On Mon, Sep 14, 2026, at 17:53, Linus Torvalds wrote:
> > On Mon, 14 Sept 2026 at 08:41, Kees Cook <kees@kernel.org> wrote:
> >>
> >> One area I think might solved via an LLM is the 3-pass kallsyms stuff.
> >> If we could get a deterministic kallsyms build in 1 pass, that would be
> >> very nice. A lot of people have tried, but it has eluded upstreaming.
> >
> > Even the three-pass one hasn't apparently always been entirely
> > deterministic. We've had random reports over the years of it failing
> > in some circumstances.
>
> This tends to break whenever a linker (rather than the compiler) starts
> creating a new type of symbols that show up in pass 2.
>
> > Maybe we've fixed it all, or maybe the failures just go imperceptibly
> > rare. Regardless, it has definitely been fragile.
>
> The rate seems to be once every few years, looking at the list
> of exceptions added to scripts/kallsyms.c (now scripts/mksysmap):
>
> efe6e3068067 ("kallsyms: fix nonconverging kallsyms table with lld")
> 516d980f8541 ("scripts/kallsyms: skip ppc compiler stub *.long_branch.* / *.plt_branch.*")
> b9b74be163a2 ("ARM: 8555/1: kallsyms: ignore ARM mode switching veneers")
>
> I'm sure there are other instances on architectures that get less
> build coverage.
Yeah, it's stuff like this that makes it more sensible in general to use
existing tooling where that makes sense, e.g. also the .mod.S stuff.
Though I also think dropping some of these arches would be a good idea ;)
*ahem*.
In any case, I think the bigger picture ideas like a single pass kallsyms is
stuff for the future.
The way I see it: grab the really low-hanging fruit (this series), then the
medium-hanging fruit, and only then enter the pits of hell to fight the
satanic hordes which clasp on to what remains.
>
> Arnd
--
Cheers, Lorenzo
next prev parent reply other threads:[~2026-09-15 11:36 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-14 9:21 Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 01/21] kbuild: do not allocate .modinfo in vmlinux Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 02/21] kallsyms: index symbols by token to speed up table compression Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 03/21] kallsyms: output binary data to speed output and kallsyms assembly Lorenzo Stoakes (ARM)
2026-09-14 20:16 ` Markus Elfring
2026-09-14 21:44 ` David Laight
2026-09-15 7:10 ` [v2 " Markus Elfring
2026-09-14 9:22 ` [PATCH v2 04/21] kbuild: do not sort nm output where the order is irrelevant Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 05/21] kbuild: only emit vmlinux relocations when required Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 06/21] elf-parse: add section flags, symbol binding and a read-only mapping Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 07/21] kallsyms: reimplement mksysmap in C Lorenzo Stoakes (ARM)
2026-09-14 16:33 ` Markus Elfring
2026-09-14 16:54 ` Markus Elfring
2026-09-14 17:01 ` Markus Elfring
2026-09-14 9:22 ` [PATCH v2 08/21] kbuild: cache list, composite object state per object Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 09/21] kbuild: implement and use depcheck to check dependency timestamps Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 10/21] kbuild: move the toolchain checks into init/Kconfig.toolchain Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 11/21] kbuild: avoid re-running compiler and linker probes Lorenzo Stoakes (ARM)
2026-09-14 15:02 ` John Stoffel
2026-09-14 15:24 ` Lorenzo Stoakes (ARM)
2026-09-15 11:01 ` Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 12/21] modpost: cache section relocation mismatch state Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 13/21] modpost: emit module descriptors as assembly Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 14/21] kbuild: batch module finalisation Lorenzo Stoakes (ARM)
2026-09-14 18:00 ` Kees Cook
2026-09-15 10:44 ` Lorenzo Stoakes (ARM)
2026-09-15 16:49 ` Kees Cook
2026-09-15 17:54 ` Lorenzo Stoakes (ARM)
2026-09-15 17:56 ` Nick Desaulniers
2026-09-14 9:22 ` [PATCH v2 15/21] objtool: cache relocations, do less work Lorenzo Stoakes (ARM)
2026-09-14 19:44 ` Josh Poimboeuf
2026-09-14 20:06 ` Linus Torvalds
2026-09-14 22:23 ` Josh Poimboeuf
2026-09-14 22:30 ` Linus Torvalds
2026-09-15 12:24 ` Lorenzo Stoakes (ARM)
2026-09-15 12:19 ` Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 16/21] objtool: size the instruction hash to the text Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 17/21] objtool: decode instructions and resolve branch targets in parallel Lorenzo Stoakes (ARM)
2026-09-14 18:20 ` Kees Cook
2026-09-15 10:09 ` Lorenzo Stoakes (ARM)
2026-09-15 11:29 ` David Laight
2026-09-15 15:04 ` Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 18/21] kbuild: rust: optionally parallelise rustc front end Lorenzo Stoakes (ARM)
2026-09-14 18:32 ` Kees Cook
2026-09-15 11:09 ` Lorenzo Stoakes (ARM)
2026-09-15 11:16 ` Lorenzo Stoakes (ARM)
2026-09-15 6:32 ` Miguel Ojeda
2026-09-15 11:15 ` Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 19/21] rust: make exports.o depend on the headers generated for it Lorenzo Stoakes (ARM)
2026-09-14 9:22 ` [PATCH v2 20/21] kbuild: build rust crates in parallel with the rest of the build Lorenzo Stoakes (ARM)
2026-09-14 18:37 ` Kees Cook
2026-09-15 11:58 ` Lorenzo Stoakes (ARM)
2026-09-15 16:52 ` Kees Cook
2026-09-14 9:22 ` [PATCH v2 21/21] kbuild: use pigz for gzip compression if available Lorenzo Stoakes (ARM)
2026-09-14 16:39 ` Kees Cook
2026-09-14 16:49 ` H. Peter Anvin
2026-09-14 17:50 ` Kees Cook
2026-09-15 14:30 ` Lorenzo Stoakes (ARM)
2026-09-15 17:31 ` Kees Cook
2026-09-15 17:47 ` Nick Desaulniers
2026-09-15 18:02 ` Arnd Bergmann
2026-09-14 15:41 ` [PATCH v2 00/21] kbuild: significantly speed up kernel builds Kees Cook
2026-09-14 15:53 ` Linus Torvalds
2026-09-15 8:53 ` Arnd Bergmann
2026-09-15 11:35 ` Lorenzo Stoakes (ARM) [this message]
2026-09-14 18:25 ` Lorenzo Stoakes (ARM)
2026-09-14 18:43 ` Kees Cook
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