From: Michael Ellerman <mpe@ellerman.id.au>
To: Matt Evans <matt@ozlabs.org>, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc: Clear branch trap (MSR.BE) before delivering SIGTRAP
Date: Wed, 28 Mar 2018 16:54:29 +1100 [thread overview]
Message-ID: <877epw3fu2.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <74EBF461-0D94-4C2D-ABA7-0B9BE010F173@ozlabs.org>
Matt Evans <matt@ozlabs.org> writes:
> When using SIG_DBG_BRANCH_TRACING, MSR.BE is left enabled in the
> user context when single_step_exception() prepares the SIGTRAP
> delivery. The resulting branch-trap-within-the-SIGTRAP-handler
> isn't healthy.
>
> Commit 2538c2d08f46141550a1e68819efa8fe31c6e3dc broke this, by
> replacing an MSR mask operation of ~(MSR_SE | MSR_BE) with a call
> to clear_single_step() which only clears MSR_SE.
>
> This patch adds a new helper, clear_br_trace(), which clears the
> debug trap before invoking the signal handler. This helper is a
> NOP for BookE as SIG_DBG_BRANCH_TRACING isn't supported on BookE.
>
> Signed-off-by: Matt Evans <matt@ozlabs.org>
Hi Matt!
It seems we might not be regularly testing this code :}
How did you hit/find the bug? And do you have a test case by any chance?
I found the test code at the bottom of:
https://lwn.net/Articles/114587/
But it didn't immediately work.
cheers
next prev parent reply other threads:[~2018-03-28 5:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-26 16:55 [PATCH] powerpc: Clear branch trap (MSR.BE) before delivering SIGTRAP Matt Evans
2018-03-28 5:54 ` Michael Ellerman [this message]
2018-03-28 10:36 ` Matt Evans
2018-03-29 11:54 ` Matt Evans
2018-04-04 6:11 ` Michael Ellerman
2018-04-03 16:03 ` 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=877epw3fu2.fsf@concordia.ellerman.id.au \
--to=mpe@ellerman.id.au \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=matt@ozlabs.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).