[IA64] fix ia64 syscall auditing

Attached is a patch against David's audit.17 kernel that adds checks
for the TIF_SYSCALL_AUDIT thread flag to the ia64 system call and
signal handling code paths.  The patch enables auditing of system
calls set up via fsys_bubble_down, as well as ensuring that
audit_syscall_exit() is called on return from sigreturn.

Neglecting to check for TIF_SYSCALL_AUDIT at these points results in
incorrect information in audit_context, causing frequent system panics
when system call auditing is enabled on an ia64 system.

I have tested this patch and have seen no problems with it.

[Original patch from Amy Griffis ported to current kernel by David Woodhouse]

From: Amy Griffis <amy.griffis@hp.com>
From: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/fsys.S

@@ -611,8 +611,10 @@ GLOBAL_ENTRY(fsys_bubble_down)
 	movl r2=ia64_ret_from_syscall
 	;;
 	mov rp=r2				// set the real return addr
-	tbit.z p8,p0=r3,TIF_SYSCALL_TRACE
+	and r3=_TIF_SYSCALL_TRACEAUDIT,r3
 	;;
+	cmp.eq p8,p0=r3,r0
+
 (p10)	br.cond.spnt.many ia64_ret_from_syscall	// p10==true means out registers are more than 8
 (p8)	br.call.sptk.many b6=b6		// ignore this return addr
 	br.cond.sptk ia64_trace_syscall

arch/ia64/kernel/signal.c

@@ -224,7 +224,8 @@ ia64_rt_sigreturn (struct sigscratch *scr)
 	 * could be corrupted.
 	 */
 	retval = (long) &ia64_leave_kernel;
-	if (test_thread_flag(TIF_SYSCALL_TRACE))
+	if (test_thread_flag(TIF_SYSCALL_TRACE)
+	    || test_thread_flag(TIF_SYSCALL_AUDIT))
 		/*
 		 * strace expects to be notified after sigreturn returns even though the
 		 * context to which we return may not be in the middle of a syscall.