[IA64] Fix convert_to_non_syscall() so gdb inferior calls work again

Fix convert_to_non_syscall() so it arranges for the kernel to be left
via ia64_leave_kernel() rather than ia64_leave_syscall().  The latter
no longer tolerates being called with pSys=0 and pNonSys=1.

Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/ptrace.c

@@ -705,12 +705,32 @@ convert_to_non_syscall (struct task_struct *child, struct pt_regs  *pt,
 			break;
 	}
 
+	/*
+	 * Note: at the time of this call, the target task is blocked
+	 * in notify_resume_user() and by clearling PRED_LEAVE_SYSCALL
+	 * (aka, "pLvSys") we redirect execution from
+	 * .work_pending_syscall_end to .work_processed_kernel.
+	 */
 	unw_get_pr(&prev_info, &pr);
-	pr &= ~(1UL << PRED_SYSCALL);
+	pr &= ~((1UL << PRED_SYSCALL) | (1UL << PRED_LEAVE_SYSCALL));
 	pr |=  (1UL << PRED_NON_SYSCALL);
 	unw_set_pr(&prev_info, pr);
 
 	pt->cr_ifs = (1UL << 63) | cfm;
+	/*
+	 * Clear the memory that is NOT written on syscall-entry to
+	 * ensure we do not leak kernel-state to user when execution
+	 * resumes.
+	 */
+	pt->r2 = 0;
+	pt->r3 = 0;
+	pt->r14 = 0;
+	memset(&pt->r16, 0, 16*8);	/* clear r16-r31 */
+	memset(&pt->f6, 0, 6*16);	/* clear f6-f11 */
+	pt->b7 = 0;
+	pt->ar_ccv = 0;
+	pt->ar_csd = 0;
+	pt->ar_ssd = 0;
 }
 
 static int