From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Jann Horn <jannh@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Andrew Morton <akpm@linux-foundation.org>,
syzbot <syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Michal Marek <michal.lkml@markovi.net>,
linux-kbuild@vger.kernel.org
Subject: Re: [PATCH 2/2] x86/unwind: add hardcoded ORC entry for NULL
Date: Fri, 1 Mar 2019 10:29:11 -0600 [thread overview]
Message-ID: <20190301162911.ucd6diddioqnthc2@treble> (raw)
In-Reply-To: <20190301162418.sbhth5tycd6znxin@treble>
On Fri, Mar 01, 2019 at 10:24:18AM -0600, Josh Poimboeuf wrote:
> > Is there a reason why the top-level Makefile only sets
> > -fno-optimize-sibling-calls if CONFIG_FRAME_POINTER is set?
> > I suspect that this is just a historical thing, because reliable
> > unwinding didn't work without frame pointers until ORC came along.
> > I'm not quite sure how best to express "don't do tail optimization if
> > either frame pointers are used or ORC is used" in a Makefile, and
> > whether we want an indirection through Kconfig for that, so I'm not
> > doing anything about it in this series.
> > Can someone send a patch to deal with it properly?
>
> Why would sibling calls be a problem for ORC? Once a function does a
> sibling call, it has effectively returned and shouldn't show up on the
> stack trace anyway.
Answering my own question, I guess some people might find it confusing
to have a caller skipped in the stack trace. But nobody has ever
complained about it.
It's not a problem for livepatch since we only care about the return
path.
--
Josh
next prev parent reply other threads:[~2019-03-01 16:29 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-01 3:12 [PATCH 1/2] x86/unwind: handle NULL pointer calls better in frame unwinder Jann Horn
2019-03-01 3:12 ` [PATCH 2/2] x86/unwind: add hardcoded ORC entry for NULL Jann Horn
2019-03-01 16:24 ` Josh Poimboeuf
2019-03-01 16:29 ` Josh Poimboeuf [this message]
2019-03-01 16:55 ` Jann Horn
2019-03-01 4:22 ` [PATCH 1/2] x86/unwind: handle NULL pointer calls better in frame unwinder Josh Poimboeuf
2019-03-01 15:32 ` Sean Christopherson
2019-03-01 15:59 ` Jann Horn
2019-03-01 16:19 ` Josh Poimboeuf
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=20190301162911.ucd6diddioqnthc2@treble \
--to=jpoimboe@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=jannh@google.com \
--cc=linux-kbuild@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=michal.lkml@markovi.net \
--cc=mingo@redhat.com \
--cc=syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
--cc=yamada.masahiro@socionext.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.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox