1 files changed, 79 insertions, 0 deletions
diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c
index 3c7a18f57ea9..61a80de6baf8 100644
--- a/arch/arm64/mm/gcs.c
+++ b/arch/arm64/mm/gcs.c
@@ -109,3 +109,82 @@ void gcs_free(struct task_struct *task)
 	task->thread.gcs_base = 0;
 	task->thread.gcs_size = 0;
 }
+
+int arch_set_shadow_stack_status(struct task_struct *task, unsigned long arg)
+{
+	unsigned long gcs, size;
+	int ret;
+
+	if (!system_supports_gcs())
+		return -EINVAL;
+
+	if (is_compat_thread(task_thread_info(task)))
+		return -EINVAL;
+
+	/* Reject unknown flags */
+	if (arg & ~PR_SHADOW_STACK_SUPPORTED_STATUS_MASK)
+		return -EINVAL;
+
+	ret = gcs_check_locked(task, arg);
+	if (ret != 0)
+		return ret;
+
+	/* If we are enabling GCS then make sure we have a stack */
+	if (arg & PR_SHADOW_STACK_ENABLE &&
+	    !task_gcs_el0_enabled(task)) {
+		/* Do not allow GCS to be reenabled */
+		if (task->thread.gcs_base || task->thread.gcspr_el0)
+			return -EINVAL;
+
+		if (task != current)
+			return -EBUSY;
+
+		size = gcs_size(0);
+		gcs = alloc_gcs(0, size);
+		if (!gcs)
+			return -ENOMEM;
+
+		task->thread.gcspr_el0 = gcs + size - sizeof(u64);
+		task->thread.gcs_base = gcs;
+		task->thread.gcs_size = size;
+		if (task == current)
+			write_sysreg_s(task->thread.gcspr_el0,
+				       SYS_GCSPR_EL0);
+	}
+
+	task->thread.gcs_el0_mode = arg;
+	if (task == current)
+		gcs_set_el0_mode(task);
+
+	return 0;
+}
+
+int arch_get_shadow_stack_status(struct task_struct *task,
+				 unsigned long __user *arg)
+{
+	if (!system_supports_gcs())
+		return -EINVAL;
+
+	if (is_compat_thread(task_thread_info(task)))
+		return -EINVAL;
+
+	return put_user(task->thread.gcs_el0_mode, arg);
+}
+
+int arch_lock_shadow_stack_status(struct task_struct *task,
+				  unsigned long arg)
+{
+	if (!system_supports_gcs())
+		return -EINVAL;
+
+	if (is_compat_thread(task_thread_info(task)))
+		return -EINVAL;
+
+	/*
+	 * We support locking unknown bits so applications can prevent
+	 * any changes in a future proof manner.
+	 */
+	task->thread.gcs_el0_locked |= arg;
+
+	return 0;
+}