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

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Date:	Fri, 21 May 2010 09:24:07 -0400
From:	Jason Baron <jbaron@...hat.com>
To:	Ian Munsie <imunsie@....ibm.com>
Cc:	fweisbec <fweisbec@...il.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 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
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