From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Jason Gerecke <killertofu@gmail.com>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Jason Baron <jbaron@akamai.com>,
Jason Gerecke <jason.gerecke@wacom.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH] RFC: x86/jump_label: Mark arguments as const to satisfy asm constraints
Date: Fri, 12 Feb 2021 10:14:39 -0600 [thread overview]
Message-ID: <20210212161439.pkrw6cpbfqhafrnk@treble> (raw)
In-Reply-To: <20210211214848.536626-1-jason.gerecke@wacom.com>
On Thu, Feb 11, 2021 at 01:48:48PM -0800, Jason Gerecke wrote:
> When compiling an external kernel module with `-O0` or `-O1`, the following
> compile error may be reported:
>
> ./arch/x86/include/asm/jump_label.h:25:2: error: impossible constraint in ‘asm’
> 25 | asm_volatile_goto("1:"
> | ^~~~~~~~~~~~~~~~~
>
> It appears that these lower optimization levels prevent GCC from detecting
> that the key/branch arguments can be treated as constants and used as
> immediate operands. To work around this, explicitly add the `const` label.
>
> Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> ---
> Marked RFC since I'm not familiar with this subsystem or the asm blocks that
> are impacted. Extra-close inspection would be appreciated.
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
--
Josh
next prev parent reply other threads:[~2021-02-12 16:16 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-11 21:48 Jason Gerecke
2021-02-12 14:40 ` Steven Rostedt
2021-02-12 15:27 ` Peter Zijlstra
2021-02-12 15:55 ` Jason Gerecke
2021-02-12 16:14 ` Josh Poimboeuf [this message]
2021-03-03 8:15 ` [tip: locking/core] " tip-bot2 for Jason Gerecke
2021-03-06 11:54 ` tip-bot2 for Jason Gerecke
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=20210212161439.pkrw6cpbfqhafrnk@treble \
--to=jpoimboe@redhat.com \
--cc=ardb@kernel.org \
--cc=jason.gerecke@wacom.com \
--cc=jbaron@akamai.com \
--cc=killertofu@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.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
all inboxes | Powered by JetHome®