From: Eugene Syromiatnikov <esyr@redhat.com>
Date: Wed, 25 Aug 2021 19:06:13 +0200
Subject: uapi/linux/prctl: provide macro definitions for the PR_SCHED_CORE
 type argument
Git-commit: 61bc346ce64a3864ac55f5d18bdc1572cda4fb18
Patch-mainline: v5.16-rc1
References: bsc#1194659

Commit 7ac592aa35a684ff ("sched: prctl() core-scheduling interface")
made use of enum pid_type in prctl's arg4; this type and the associated
enumeration definitions are not exposed to userspace.  Christian
has suggested to provide additional macro definitions that convey
the meaning of the type argument more in alignment with its actual
usage, and this patch does exactly that.

Link: https://lore.kernel.org/r/20210825170613.GA3884@asgard.redhat.com
Suggested-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
Complements: 7ac592aa35a684ff ("sched: prctl() core-scheduling interface")
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Dario Faggioli <dfaggioli@suse.com>
---
 Documentation/admin-guide/hw-vuln/core-scheduling.rst | 5 +++--
 include/uapi/linux/prctl.h                            | 3 +++
 kernel/sched/core_sched.c                             | 4 ++++
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/core-scheduling.rst b/Documentation/admin-guide/hw-vuln/core-scheduling.rst
index 0febe458597c..cf1eeefdfc32 100644
--- a/Documentation/admin-guide/hw-vuln/core-scheduling.rst
+++ b/Documentation/admin-guide/hw-vuln/core-scheduling.rst
@@ -61,8 +61,9 @@ arg3:
     ``pid`` of the task for which the operation applies.
 
 arg4:
-    ``pid_type`` for which the operation applies. It is of type ``enum pid_type``.
-    For example, if arg4 is ``PIDTYPE_TGID``, then the operation of this command
+    ``pid_type`` for which the operation applies. It is one of
+    ``PR_SCHED_CORE_SCOPE_``-prefixed macro constants.  For example, if arg4
+    is ``PR_SCHED_CORE_SCOPE_THREAD_GROUP``, then the operation of this command
     will be performed for all tasks in the task group of ``pid``.
 
 arg5:
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 43bd7f713c39..b2e4dc1449b9 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -268,5 +268,8 @@ struct prctl_mm_map {
 # define PR_SCHED_CORE_SHARE_TO		2 /* push core_sched cookie to pid */
 # define PR_SCHED_CORE_SHARE_FROM	3 /* pull core_sched cookie to pid */
 # define PR_SCHED_CORE_MAX		4
+# define PR_SCHED_CORE_SCOPE_THREAD		0
+# define PR_SCHED_CORE_SCOPE_THREAD_GROUP	1
+# define PR_SCHED_CORE_SCOPE_PROCESS_GROUP	2
 
 #endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sched/core_sched.c b/kernel/sched/core_sched.c
index 9a80e9a474c0..20f640949450 100644
--- a/kernel/sched/core_sched.c
+++ b/kernel/sched/core_sched.c
@@ -134,6 +134,10 @@ int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type type,
 	if (!static_branch_likely(&sched_smt_present))
 		return -ENODEV;
 
+	BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_THREAD != PIDTYPE_PID);
+	BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_THREAD_GROUP != PIDTYPE_TGID);
+	BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_PROCESS_GROUP != PIDTYPE_PGID);
+
 	if (type > PIDTYPE_PGID || cmd >= PR_SCHED_CORE_MAX || pid < 0 ||
 	    (cmd != PR_SCHED_CORE_GET && uaddr))
 		return -EINVAL;