From: David Laight <David.Laight@ACULAB.COM>
To: 'Christoph Hellwig' <hch@lst.de>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
"Arnd Bergmann" <arnd@arndb.de>,
Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Subject: Using asm_volatile_goto for get_user()
Date: Mon, 7 Sep 2020 08:49:27 +0000 [thread overview]
Message-ID: <39a56b046b104566922dd0d0ce7f794a@AcuMS.aculab.com> (raw)
I had an idea that might let 'asm_volatile_goto' be used for
get_user() even though gcc doesn't allow outputs.
What if (eg) 'register eax asm ("eax") is used for the
output and (probably) given in the 'clobber' list.
Such variables are usually used to get explicit registers
used when there is no suitable constraint.
I don't see why it shouldn't work for 'asm goto' as well
as just 'asm'.
While this forces the read value into a specific register
that probably doesn't make much difference to the code.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
reply other threads:[~2020-09-07 8:49 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
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=39a56b046b104566922dd0d0ce7f794a@AcuMS.aculab.com \
--to=david.laight@aculab.com \
--cc=arnd@arndb.de \
--cc=hch@lst.de \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=palmer@dabbelt.com \
--cc=paul.walmsley@sifive.com \
--cc=viro@zeniv.linux.org.uk \
/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®