From: Mark Rutland <mark.rutland@arm.com>
To: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
lenb@kernel.org, linux-acpi@vger.kernel.org,
linux-kernel@vger.kernel.org, mhiramat@kernel.org,
ndesaulniers@google.com, ojeda@kernel.org, peterz@infradead.org,
rafael.j.wysocki@intel.com, revest@chromium.org,
robert.moore@intel.com, rostedt@goodmis.org, will@kernel.org
Subject: Re: [PATCH 1/8] Compiler attributes: GCC function alignment workarounds
Date: Thu, 12 Jan 2023 11:38:17 +0000 [thread overview]
Message-ID: <Y7/xKbOZYztcqz2b@FVFF77S0Q05N> (raw)
In-Reply-To: <Y77/qVgvaJidFpYt@FVFF77S0Q05N>
On Wed, Jan 11, 2023 at 06:27:53PM +0000, Mark Rutland wrote:
> On Mon, Jan 09, 2023 at 03:43:16PM +0100, Miguel Ojeda wrote:
> > On Mon, Jan 9, 2023 at 2:58 PM Mark Rutland <mark.rutland@arm.com> wrote:
> > >
> > > As far as I can tell, GCC doesn't respect '-falign-functions=N':
> > >
> > > * When the __weak__ attribute is used
> > >
> > > GCC seems to forget the alignment specified by '-falign-functions=N',
> > > but will respect the '__aligned__(N)' function attribute. Thus, we can
> > > work around this by explciitly setting the alignment for weak
> > > functions.
> > >
> > > * When the __cold__ attribute is used
> > >
> > > GCC seems to forget the alignment specified by '-falign-functions=N',
> > > and also doesn't seem to respect the '__aligned__(N)' function
> > > attribute. The only way to work around this is to not use the __cold__
> > > attibute.
> >
> > If you happen to have a reduced case, then it would be nice to link it
> > in the commit. A bug report to GCC would also be nice.
> >
> > I gave it a very quick try in Compiler Explorer, but I couldn't
> > reproduce it, so I guess it depends on flags, non-trivial functions or
> > something else.
>
> So having spent today coming up with tests, it turns out it's not quite as I
> described above, but in a sense worse. I'm posting a summary here for
> posterity; I'll try to get this to compiler folk shortly.
I've added the cold bits to an existing ticket:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345
I have not been able to reproduce the issue with __weak__, so I'll go dig into
that some more; it's likely I was mistaken there.
Thanks,
Mark.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2023-01-12 11:39 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-09 13:58 [PATCH 0/8] arm64/ftrace: Add support for DYNAMIC_FTRACE_WITH_CALL_OPS Mark Rutland
2023-01-09 13:58 ` [PATCH 1/8] Compiler attributes: GCC function alignment workarounds Mark Rutland
2023-01-09 14:43 ` Miguel Ojeda
2023-01-09 17:06 ` Mark Rutland
2023-01-09 22:35 ` Miguel Ojeda
2023-01-11 18:27 ` Mark Rutland
2023-01-12 11:38 ` Mark Rutland [this message]
2023-01-13 12:49 ` Mark Rutland
2023-01-15 21:32 ` Miguel Ojeda
2023-01-09 13:58 ` [PATCH 2/8] ACPI: Don't build ACPICA with '-Os' Mark Rutland
2023-01-10 13:45 ` Rafael J. Wysocki
2023-01-09 13:58 ` [PATCH 3/8] arm64: Extend support for CONFIG_FUNCTION_ALIGNMENT Mark Rutland
2023-01-10 20:35 ` Peter Zijlstra
2023-01-10 20:43 ` Will Deacon
2023-01-11 11:39 ` Mark Rutland
2023-01-11 11:36 ` Mark Rutland
2023-01-09 13:58 ` [PATCH 4/8] ftrace: Add DYNAMIC_FTRACE_WITH_CALL_OPS Mark Rutland
2023-01-12 6:48 ` Li Huafei
2023-01-12 11:00 ` Mark Rutland
2023-01-13 1:15 ` Li Huafei
2023-01-09 13:58 ` [PATCH 5/8] arm64: insn: Add helpers for BTI Mark Rutland
2023-01-09 13:58 ` [PATCH 6/8] arm64: patching: Add aarch64_insn_write_literal_u64() Mark Rutland
2023-01-09 13:58 ` [PATCH 7/8] arm64: ftrace: Update stale comment Mark Rutland
2023-01-09 13:58 ` [PATCH 8/8] arm64: Implement HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS Mark Rutland
2023-01-10 8:55 ` [PATCH 0/8] arm64/ftrace: Add support for DYNAMIC_FTRACE_WITH_CALL_OPS David Laight
2023-01-10 10:31 ` Mark Rutland
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Y7/xKbOZYztcqz2b@FVFF77S0Q05N \
--to=mark.rutland@arm.com \
--cc=catalin.marinas@arm.com \
--cc=lenb@kernel.org \
--cc=linux-acpi@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=miguel.ojeda.sandonis@gmail.com \
--cc=ndesaulniers@google.com \
--cc=ojeda@kernel.org \
--cc=peterz@infradead.org \
--cc=rafael.j.wysocki@intel.com \
--cc=revest@chromium.org \
--cc=robert.moore@intel.com \
--cc=rostedt@goodmis.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).