From: Steven Rostedt <rostedt@goodmis.org>
To: Robert Richter <robert.richter@amd.com>
Cc: wyang1 <Wei.Yang@windriver.com>, Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org,
oprofile-list@lists.sourceforge.net
Subject: Re: [PATCH] x86, 32-bit: Fix invalid stack address while in softirq
Date: Thu, 06 Sep 2012 11:14:42 -0400 [thread overview]
Message-ID: <1346944482.1680.28.camel@gandalf.local.home> (raw)
In-Reply-To: <20120906150246.GZ8285@erda.amd.com>
On Thu, 2012-09-06 at 17:02 +0200, Robert Richter wrote:
> > > --- a/arch/x86/oprofile/backtrace.c
> > > +++ b/arch/x86/oprofile/backtrace.c
> > > @@ -113,7 +113,7 @@ x86_backtrace(struct pt_regs * const regs, unsigned int depth)
> > >
> > > if (!user_mode_vm(regs)) {
> > > unsigned long stack = kernel_stack_pointer(regs);
> > > - if (depth)
> > > + if (depth & stack)
> >
> > Can other users of kernel_stack_pointer() be nailed by a return of NULL?
>
> It would be save here too, but dump_trace() falls back to the current
> stack in case there is no stack address given which we don't want with
> oprofile.
>
> I was looking at all users of kernel_stack_pointer() and could not
> find any direct pointer dereference of the sp. The only potential
> problems I found could arise here:
>
> arch/x86/kernel/kprobes.c:resume_execution()
> arch/x86/kernel/time.c:profile_pc()
>
> It is not quite clear if we really need code here that checks the
> pointer. Since a NULL pointer access has the same effect as if the
> stack address would be wrong which would be the case without the
> patch, I rather tend not to change the code here.
Then a comment should be in the oprofile code too. Something to the
effect that oprofile is special and can cause kernel_stack_pointer() to
return NULL in some cases, thus we need to check for it.
-- Steve
next prev parent reply other threads:[~2012-09-06 15:14 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-27 1:32 [PATCH 1/1] x86/oprofile: Fix the calltrace upon profiling some specified events with oprofile Wei.Yang
2012-08-28 9:17 ` Robert Richter
2012-09-03 5:28 ` wyang1
2012-09-04 10:24 ` Robert Richter
2012-09-06 1:30 ` wyang1
2012-09-06 10:04 ` [PATCH] x86, 32-bit: Fix invalid stack address while in softirq Robert Richter
2012-09-06 13:14 ` Steven Rostedt
2012-09-06 15:02 ` Robert Richter
2012-09-06 15:14 ` Steven Rostedt [this message]
2012-09-06 15:34 ` Robert Richter
2012-09-06 15:36 ` Robert Richter
2012-09-06 15:54 ` Steven Rostedt
2012-09-07 5:21 ` wyang1
2012-09-12 13:50 ` [PATCH -v2] " Robert Richter
2012-09-12 14:04 ` Steven Rostedt
2012-10-01 12:21 ` Robert Richter
2012-11-01 21:34 ` [tip:x86/urgent] x86-32: " tip-bot for Robert Richter
2012-11-13 15:17 ` Ingo Molnar
2012-11-13 15:56 ` Robert Richter
2012-11-15 21:53 ` tip-bot for Robert Richter
2012-11-21 7:34 ` tip-bot for Robert Richter
2012-11-21 7:35 ` [tip:x86/urgent] x86-32: Export kernel_stack_pointer() for modules tip-bot for H. Peter Anvin
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=1346944482.1680.28.camel@gandalf.local.home \
--to=rostedt@goodmis.org \
--cc=Wei.Yang@windriver.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=oprofile-list@lists.sourceforge.net \
--cc=peterz@infradead.org \
--cc=robert.richter@amd.com \
--cc=torvalds@linux-foundation.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).