From: David Laight <david.laight.linux@gmail.com>
To: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Cc: "Nicolas Schier" <n.schier@fritz.com>,
"Nathan Chancellor" <nathan@kernel.org>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Nick Desaulniers" <ndesaulniers@google.com>,
"Bill Wendling" <morbo@google.com>,
"Justin Stitt" <justinstitt@google.com>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Alexey Gladkov" <legion@kernel.org>,
"Thomas Gleixner" <tglx@kernel.org>,
"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>,
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linux-efi@vger.kernel.org, rust-for-linux@vger.kernel.org,
linux-doc@vger.kernel.org, "Jens Axboe" <axboe@kernel.dk>
Subject: Re: [PATCH 12/23] kbuild: avoid re-running compiler and linker probes
Date: Fri, 11 Sep 2026 22:01:02 +0100 [thread overview]
Message-ID: <20260911220102.1d3d696a@pumpkin> (raw)
In-Reply-To: <aqRGYXKDzXZMXmmp@gremlin>
On Fri, 11 Sep 2026 19:24:50 +0100
"Lorenzo Stoakes (ARM)" <ljs@kernel.org> wrote:
> On Fri, Sep 11, 2026 at 08:17:57PM +0200, Nicolas Schier wrote:
> > On Fri, Sep 11, 2026 at 06:33:33PM +0100, David Laight wrote:
> > > On Thu, 10 Sep 2026 17:42:35 +0200
> > > Nicolas Schier <n.schier@fritz.com> wrote:
> > >
> > > ...
> > > > Yes, skimming through the patch, I thought about that, too. Moving more
> > > > cc option checks to Kconfig will make building out-of-tree kmods with a
> > > > different compiler more dangerous. Maybe we will have to make the
> > > > warning in Makefile's prepare (external kmods) target a bit louder.
> > >
> > > One problem is that distributions have a nasty habit of shipping kernels
> > > that are compiled with a different compiler version to they actually
> > > ship as a compiler.
> > > In some cases the versions are clearly the same - but the version
> > > strings differ.
> >
> > yeah, I guess you hit the mark.
>
> I mean this is a problem that already exists for any flags already specified in
> Kconfig.
>
> Out-of-tree modules are historically something that we don't go to great lengths
> to support and haven't historically worried about breaking, either.
>
> I'm sure distros can find ways around this if a problem were to arise. But I
> don't think it's something to worry about all that much.
>
> I expect a _lot_ of these, in any case, would only require the compilers to be
> within a fair few major versions of one another anyway.
That is true at the moment when the version of the compiler being used
is checked.
For instance it doesn't matter if modules are compiled without 'asm goto
with output'.
But if you putting the options in Kconfig the compiler being used better
not be older - or it might not support the options.
It isn't too bad if the compile fails, but some are silent.
IIRC it is Ubuntu that has different version strings for the same compiler
version, and Oracle that ships kernels compiled with much newer compilers
that they install by default.
David
>
> >
> > --
> > Nicolas
>
> --
> Cheers, Lorenzo
next prev parent reply other threads:[~2026-09-11 21:01 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-08 20:55 [PATCH 00/23] kbuild: significantly speed up kernel builds Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 01/23] scripts/mksysmap: drop the MODULE_INFO() symbols from kallsyms Lorenzo Stoakes (ARM)
2026-09-09 19:47 ` Nicolas Schier
2026-09-10 11:00 ` Lorenzo Stoakes (ARM)
2026-09-10 4:19 ` Nathan Chancellor
2026-09-10 11:03 ` Lorenzo Stoakes (ARM)
2026-09-10 19:00 ` Nicolas Schier
2026-09-08 20:55 ` [PATCH 02/23] scripts/mksysmap: fix escape of '$' in the __pi_ pattern Lorenzo Stoakes (ARM)
2026-09-09 19:47 ` Nicolas Schier
2026-09-10 11:04 ` Lorenzo Stoakes (ARM)
2026-09-10 4:19 ` Nathan Chancellor
2026-09-10 11:21 ` Lorenzo Stoakes (ARM)
2026-09-10 19:00 ` Nicolas Schier
2026-09-08 20:55 ` [PATCH 03/23] kallsyms: index symbols by token to speed up table compression Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 04/23] kallsyms: output binary data to speed output and kallsyms assembly Lorenzo Stoakes (ARM)
2026-09-09 14:35 ` Linus Torvalds
2026-09-10 9:29 ` David Laight
2026-09-11 11:07 ` Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 05/23] kbuild: do not sort nm output where the order is irrelevant Lorenzo Stoakes (ARM)
2026-09-10 4:19 ` Nathan Chancellor
2026-09-08 20:55 ` [PATCH 06/23] kbuild: only emit vmlinux relocations when required Lorenzo Stoakes (ARM)
2026-09-10 4:19 ` Nathan Chancellor
2026-09-08 20:55 ` [PATCH 07/23] elf-parse: add section flags, symbol binding and a read-only mapping Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 08/23] kallsyms: reimplement mksysmap in C Lorenzo Stoakes (ARM)
2026-09-11 18:52 ` Markus Elfring
2026-09-11 19:15 ` Markus Elfring
2026-09-11 19:42 ` Markus Elfring
2026-09-08 20:55 ` [PATCH 09/23] kbuild: do not allocate .modinfo in vmlinux Lorenzo Stoakes (ARM)
2026-09-10 4:19 ` Nathan Chancellor
2026-09-10 10:59 ` Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 10/23] kbuild: cache list, composite object state per object Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 11/23] kbuild: implement and use depcheck to check dependency timestamps Lorenzo Stoakes (ARM)
2026-09-09 15:26 ` Linus Torvalds
2026-09-08 20:55 ` [PATCH 12/23] kbuild: avoid re-running compiler and linker probes Lorenzo Stoakes (ARM)
2026-09-10 4:19 ` Nathan Chancellor
2026-09-10 15:42 ` Nicolas Schier
2026-09-11 10:30 ` Lorenzo Stoakes (ARM)
2026-09-11 18:10 ` Nicolas Schier
2026-09-11 18:25 ` Lorenzo Stoakes (ARM)
2026-09-11 17:33 ` David Laight
2026-09-11 18:17 ` Nicolas Schier
2026-09-11 18:24 ` Lorenzo Stoakes (ARM)
2026-09-11 19:34 ` Nicolas Schier
2026-09-11 21:01 ` David Laight [this message]
2026-09-11 10:26 ` Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 13/23] modpost: hash module source per-file, not per-byte Lorenzo Stoakes (ARM)
2026-09-10 12:52 ` Petr Pavlu
2026-09-11 10:41 ` Lorenzo Stoakes (ARM)
2026-09-11 11:57 ` Petr Pavlu
2026-09-11 12:21 ` Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 14/23] modpost: cache section relocation mismatch state Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 15/23] modpost: emit module descriptors as assembly Lorenzo Stoakes (ARM)
2026-09-09 14:59 ` Linus Torvalds
2026-09-08 20:55 ` [PATCH 16/23] kbuild: batch module finalisation Lorenzo Stoakes (ARM)
2026-09-10 15:48 ` Nicolas Schier
2026-09-11 10:23 ` Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 17/23] modpost: perform srcversion hashing in parallel Lorenzo Stoakes (ARM)
2026-09-10 10:32 ` David Laight
2026-09-11 10:49 ` Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 18/23] objtool: cache relocations and function dead end state, do less work Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 19/23] objtool: decode instructions and resolve branch targets in parallel Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 20/23] kbuild: rust: parallelise rustc front end Lorenzo Stoakes (ARM)
2026-09-08 21:13 ` Miguel Ojeda
2026-09-09 14:22 ` Lorenzo Stoakes (ARM)
2026-09-09 10:22 ` Björn Baron
2026-09-09 12:59 ` Miguel Ojeda
2026-09-09 14:26 ` Lorenzo Stoakes (ARM)
2026-09-10 12:25 ` Nicolas Schier (FRITZ!)
2026-09-11 19:00 ` Nicolas Schier
2026-09-08 20:55 ` [PATCH 21/23] rust: make exports.o depend on the headers generated for it Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 22/23] kbuild: build rust crates in parallel with the rest of the build Lorenzo Stoakes (ARM)
2026-09-08 20:55 ` [PATCH 23/23] kbuild: use pigz for gzip compression if available Lorenzo Stoakes (ARM)
2026-09-10 4:19 ` Nathan Chancellor
2026-09-11 11:03 ` Lorenzo Stoakes (ARM)
2026-09-08 21:06 ` [PATCH 00/23] kbuild: significantly speed up kernel builds Nick Desaulniers
2026-09-09 14:17 ` Lorenzo Stoakes (ARM)
2026-09-09 22:09 ` Nick Desaulniers
2026-09-11 11:25 ` Lorenzo Stoakes (ARM)
2026-09-09 15:37 ` Linus Torvalds
2026-09-09 16:30 ` Lorenzo Stoakes (ARM)
2026-09-09 21:58 ` Florian Fainelli
2026-09-11 11:28 ` Lorenzo Stoakes (ARM)
2026-09-10 4:19 ` Nathan Chancellor
2026-09-11 11:13 ` Lorenzo Stoakes (ARM)
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