Fix some special cases for "sysenter" - some system calls depend on

doing a full register restore on return to user space, and thus require
the long system call exit path (ie "iret" instead of "sysexit").

 * execve() - we need to set edx/ecx correctly at process startup.
 * iopl() - needs iret to restore eflags with new IOPL levels.

arch/i386/kernel/ioport.c

@@ -14,6 +14,7 @@
 #include <linux/smp_lock.h>
 #include <linux/stddef.h>
 #include <linux/slab.h>
+#include <linux/thread_info.h>
 
 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */
 static void set_bitmap(unsigned long *bitmap, short base, short extent, int new_value)
@@ -122,5 +123,7 @@ asmlinkage int sys_iopl(unsigned long unused)
 			return -EPERM;
 	}
 	regs->eflags = (regs->eflags & 0xffffcfff) | (level << 12);
+	/* Make sure we return the long way (not sysenter) */
+	set_thread_flag(TIF_SIGPENDING);
 	return 0;
 }

arch/i386/kernel/process.c

@@ -558,8 +558,11 @@ asmlinkage int sys_execve(struct pt_regs regs)
 	if (IS_ERR(filename))
 		goto out;
 	error = do_execve(filename, (char **) regs.ecx, (char **) regs.edx, &regs);
-	if (error == 0)
+	if (error == 0) {
 		current->ptrace &= ~PT_DTRACE;
+		/* Make sure we don't return using sysenter.. */
+		set_thread_flag(TIF_SIGPENDING);
+	}
 	putname(filename);
 out:
 	return error;