sched: Add 'flags' argument to sched_{set,get}attr() syscalls

Because of a recent syscall design debate; its deemed appropriate for
each syscall to have a flags argument for future extension; without
immediately requiring new syscalls.

Cc: juri.lelli@gmail.com
Cc: Ingo Molnar <mingo@redhat.com>
Suggested-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140214161929.GL27965@twins.programming.kicks-ass.netSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/syscalls.h

@@ -281,13 +281,15 @@ asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
 asmlinkage long sys_sched_setparam(pid_t pid,
 					struct sched_param __user *param);
 asmlinkage long sys_sched_setattr(pid_t pid,
-					struct sched_attr __user *attr);
+					struct sched_attr __user *attr,
+					unsigned int flags);
 asmlinkage long sys_sched_getscheduler(pid_t pid);
 asmlinkage long sys_sched_getparam(pid_t pid,
 					struct sched_param __user *param);
 asmlinkage long sys_sched_getattr(pid_t pid,
 					struct sched_attr __user *attr,
-					unsigned int size);
+					unsigned int size,
+					unsigned int flags);
 asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
 					unsigned long __user *user_mask_ptr);
 asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,

kernel/sched/core.c

@@ -3661,13 +3661,14 @@ SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
  * @pid: the pid in question.
  * @uattr: structure containing the extended parameters.
  */
-SYSCALL_DEFINE2(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr)
+SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
+			       unsigned int, flags)
 {
 	struct sched_attr attr;
 	struct task_struct *p;
 	int retval;
 
-	if (!uattr || pid < 0)
+	if (!uattr || pid < 0 || flags)
 		return -EINVAL;
 
 	if (sched_copy_attr(uattr, &attr))
@@ -3804,8 +3805,8 @@ static int sched_read_attr(struct sched_attr __user *uattr,
  * @uattr: structure containing the extended parameters.
  * @size: sizeof(attr) for fwd/bwd comp.
  */
-SYSCALL_DEFINE3(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
-		unsigned int, size)
+SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
+		unsigned int, size, unsigned int, flags)
 {
 	struct sched_attr attr = {
 		.size = sizeof(struct sched_attr),
@@ -3814,7 +3815,7 @@ SYSCALL_DEFINE3(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
 	int retval;
 
 	if (!uattr || pid < 0 || size > PAGE_SIZE ||
-	    size < SCHED_ATTR_SIZE_VER0)
+	    size < SCHED_ATTR_SIZE_VER0 || flags)
 		return -EINVAL;
 
 	rcu_read_lock();