From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Segher Boessenkool <segher@kernel.crashing.org>,
Joe Lawrence <joe.lawrence@redhat.com>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: vdso function descriptors (VDS64_HAS_DESCRIPTORS)?
Date: Mon, 24 Feb 2020 21:17:19 +1100 [thread overview]
Message-ID: <587a0a1765ba1264b92044f7b1f9937eb40731f1.camel@kernel.crashing.org> (raw)
In-Reply-To: <20200223000715.GW22482@gate.crashing.org>
On Sat, 2020-02-22 at 18:07 -0600, Segher Boessenkool wrote:
> >
> > so I don't believe they are ever used by default -- in this case
> > V_FUNCTION_BEGIN doesn't add to the .opd section with .name, .TOC base,
> > etc.
> >
> > Manually setting VDS64_HAS_DESCRIPTORS results in a vdso64.so in which
> > binutils tools like readelf properly report functions with symbol type
> > FUNC instead of NOTYPE.
> >
> > Are there pieces of the build/etc toolchain unprepared for function
> > descriptors? I'm just trying to figure out why the code defaults to
> > unsetting them.
>
> Because direct calls are faster than indirect calls? Ben might have a
> fuller explanation, cc:ing him.
I don't remember why :-) I think I didn't want to mess with the OPD
fixup in glibc back then.
Ben.
next prev parent reply other threads:[~2020-02-24 10:32 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-17 16:08 vdso function descriptors (VDS64_HAS_DESCRIPTORS)? Joe Lawrence
2020-02-23 0:07 ` Segher Boessenkool
2020-02-24 10:17 ` Benjamin Herrenschmidt [this message]
2020-02-24 15:20 ` Joe Lawrence
2020-02-24 15:34 ` Benjamin Herrenschmidt
2020-02-24 21:18 ` [PATCH] powerpc/vdso: remove deprecated VDS64_HAS_DESCRIPTORS references Joe Lawrence
2020-02-24 23:37 ` Michael Ellerman
2020-03-17 13:14 ` Michael Ellerman
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=587a0a1765ba1264b92044f7b1f9937eb40731f1.camel@kernel.crashing.org \
--to=benh@kernel.crashing.org \
--cc=joe.lawrence@redhat.com \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=segher@kernel.crashing.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).