linux-kernel - Re: [PATCH] LinuxPPS (with new syscalls API)

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Date:	Wed, 27 Jun 2007 14:58:02 +0200
From:	Rodolfo Giometti <giometti@...eenne.com>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] LinuxPPS (with new syscalls API)

On Wed, Jun 27, 2007 at 11:18:30AM +0100, David Woodhouse wrote:
> On Wed, 2007-06-27 at 12:14 +0200, Rodolfo Giometti wrote:
> > On Tue, Jun 26, 2007 at 06:38:40PM +0100, David Woodhouse wrote:
> > > 
> > > 64-bit kernels can run 32-bit userspace programs. But some structures
> > > come out _differently_ between 32-bit and 64-bit compilation, so the
> > > system call needs a special 'compat' handler instead of just running the
> > > normal 64-bit system call.
> > > 
> > > The 'struct timespec' is one structure which is sometimes different for
> > > 32-bit vs. 64-bit, so any system call taking a 'struct timespec' must
> > > have a separate compat_sys_xxxx() to handle that. See something like
> > > compat_sys_clock_settime() in kernel/compat.c for an example (but don't
> > > use set_fs() like it does; just see how it handles the compat_timespec).
> > 
> > Did you mean something like this?
> 
> How will 64-bit system calls work if you do it like that? You need to
> provide _both_ sys_time_pps_fetch() and compat_sys_time_pps_fetch().

Sorry, I'm new to this 32/64 bits issues...

Now is it correct?

diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index befe292..b9df17b 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -26,6 +26,7 @@
 #include <linux/init.h>
 #include <linux/linkage.h>
 #include <linux/sched.h>
+#include <linux/compat.h>
 #include <linux/pps.h>
 #include <asm/uaccess.h>
 
@@ -362,6 +363,22 @@ sys_time_pps_fetch_exit:
        return ret;
 }
 
+#ifdef CONFIG_COMPAT
+asmlinkage long compat_sys_time_pps_fetch(int source, const int tsformat,
+                               struct pps_info __user *info, 
+                               const struct compat_timespec __user *timeout)
+{
+       int ret;
+       struct timespec to;
+
+       ret = get_compat_timespec(&to, timeout);
+       if (ret)
+               return -EFAULT;
+       
+       return sys_time_pps_fetch(source, tsformat, info, &to);
+}
+#endif
+
 /*
  * Module staff
  */

Since I have no way to test this code maybe is better add no function
at all and simply using a warning message if someone try compiling
this code with CONFIG_COMPAT enabled...

Ciao,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail:    giometti@...eenne.com
Linux Device Driver                             giometti@...dd.com
Embedded Systems                     		giometti@...ux.it
UNIX programming                     phone:     +39 349 2432127
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