linux-kernel - Re: [PATCH 00/14] tracing: add compat syscall support v3

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Message-ID: <20100521133117.GJ30108@nowhere>
Date:	Fri, 21 May 2010 15:31:19 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Jason Baron <jbaron@...hat.com>
Cc:	Ian Munsie <imunsie@....ibm.com>, mingo <mingo@...e.hu>,
	rostedt <rostedt@...dmis.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/14] tracing: add compat syscall support v3

On Fri, May 21, 2010 at 09:24:07AM -0400, Jason Baron wrote:
> On Fri, May 21, 2010 at 07:40:21PM +1000, Ian Munsie wrote:
> > Hi Jason,
> > 
> > I'm currently in the process of implementing syscall tracepoints for
> > PowerPC, and a considerable amount of my work is going to end up
> > requiring these patches of yours. I've reviewed and tested your patches
> > (and spent a good chunk of time rebasing them on top of
> > tip/tracing/core) and they all seem pretty good.
> > 
> > I *particularly* like the way in which they prevent ftrace syscalls from
> > reporting that sys_swapoff was constantly firing on x86_64 kernels with
> > a 32bit userspace ;)
> > 
> > Anyway, I'm just wondering if you have an ETA for the v4 patchset to
> > address the remaining issues that Frederic raised so that they can be
> > merged.
> > 
> > Cheers,
> > -Ian
> > 
> 
> hi Ian,
> 
> I think the main issue left was that I am using the same meta data for
> both the 32-bit and 64-bit table entries, when they reference the same
> syscall. for example, for x86 both the compat and underlying 64-bit
> kernel reference 'sys_rename'. Thus, i am pointing both perf events at
> the same meta data. Frederic was saying they need to be separate. I'm
> not sure i completely understand why, since the 32-bit are just sign
> extended to 64-bit in this case. Frederic, perhaps, you can explain this
> a bit more for me?
> 
> thanks,
> 
> -Jason


If they are pointing to the same function with the same parameters, then
yeah it's fine.

I think I worried about two different handlers that don't have the
exact same parameters (one having compat things, and the other having
not). But now that I think about it that's probably not what you did.

I'll give another shot to this patchset then, as I've probably confused
something, I just need to wait a bit for the giant patchset from Steve
on trace events to be applied, before applying this set. Should happen
soon.

Will look at this next week.
Thanks.

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