linux-kernel - Re: [PATCH] perf: Handle compat ioctl

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Date:	Tue, 17 Jun 2014 14:19:03 +0100
From:	Pawel Moll <pawel.moll@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Drew Richardson <Drew.Richardson@....com>
Subject: Re: [PATCH] perf: Handle compat ioctl

On Tue, 2014-06-17 at 13:13 +0100, Peter Zijlstra wrote:
> On Fri, Jun 13, 2014 at 04:03:32PM +0100, Pawel Moll wrote:
> > When running a 32-bit userspace on a 64-bit kernel (eg. i386
> > application on x86_64 kernel or 32-bit arm userspace on arm64
> > kernel) some of the perf ioctls must be treated with special
> > care, as they have a pointer size encoded in the command.
> > 
> > For example, PERF_EVENT_IOC_ID in 32-bit world will be encoded
> > as 0x80042407, but 64-bit kernel will expect 0x80082407. In
> > result the ioctl will fail returning -ENOTTY.
> > 
> > This patch solves the problem by adding code fixing up the
> > size as compat_ioctl file operation.
> > 
> > Reported-by: Drew Richardson <drew.richardson@....com>
> > Signed-off-by: Pawel Moll <pawel.moll@....com>
> > ---
> 
> This gets me (on my favourite x86_64 .config):
> 
> kernel/events/core.c: In function ‘perf_compat_ioctl’:
> kernel/events/core.c:3726:32: error: ‘compat_uptr_t’ undeclared (first use in this function)
> kernel/events/core.c:3726:32: note: each undeclared identifier is reported only once for each function it appears in

Right, sorry. I've added the size check last minute and haven't
re-tested it with x86_64. #include for compat.h was missing (wonder
where was it included for arm64 ;-)

Already posted v2.

Pawel

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