From: Szabolcs Nagy <nsz@port70.net>
To: musl@lists.openwall.com
Subject: Re: TLSDESC register-preserving mess
Date: Wed, 10 Oct 2018 15:19:26 +0200 [thread overview]
Message-ID: <20181010131926.GT10209@port70.net> (raw)
In-Reply-To: <20181010012620.GL17110@brightrain.aerifal.cx>
* Rich Felker <dalias@libc.org> [2018-10-09 21:26:20 -0400]:
> As written, the aarch64 and arm asm save and restore float/vector
> registers around the call, but I don't think they're future-proof
> against ISA extensions that add more such registers; if libc were
at least on aarch64 for now the approach is to add new vector
registers to the tlsdesc clobber list in gcc (and document
this in the sysv abi, except that's not published yet).
the reasoning is that it makes it safe to use tlsdesc with
old dynamic linker (new vector registers overlap with old
ones so old dynamic linker can clobber them) without much
practical cost: it's unlikely that vector code needs to
access tls (in vectorized loops the address is hopefully
computed outside the loop and vector math code should not
use tls state in the fast path if it wants to be efficient)
next prev parent reply other threads:[~2018-10-10 13:19 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-10 1:26 Rich Felker
2018-10-10 2:35 ` Rich Felker
2018-10-10 13:19 ` Szabolcs Nagy [this message]
2018-10-10 13:52 ` Rich Felker
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=20181010131926.GT10209@port70.net \
--to=nsz@port70.net \
--cc=musl@lists.openwall.com \
/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.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
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).