Unverified Commit a4c746f0 authored by Christian Brauner's avatar Christian Brauner
Browse files

uapi/fcntl: mark range as reserved 

Mark the range from -10000 to -40000 as a range reserved for special
in-kernel values. Move the PIDFD_SELF_*/PIDFD_THREAD_* sentinels over so
all the special values are in one place.

Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-6-d02a04858fe3@kernel.org


Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 1c548439

include/uapi/linux/fcntl.h

+16 −0
Original line number Diff line number Diff line
@@ -90,10 +90,26 @@ 
#define DN_ATTRIB	0x00000020	/* File changed attibutes */

#define DN_MULTISHOT	0x80000000	/* Don't remove notifier */



/* Reserved kernel ranges [-100], [-10000, -40000]. */

#define AT_FDCWD		-100    /* Special value for dirfd used to

					   indicate openat should use the

					   current working directory. */



/*

 * The concept of process and threads in userland and the kernel is a confusing

 * one - within the kernel every thread is a 'task' with its own individual PID,

 * however from userland's point of view threads are grouped by a single PID,

 * which is that of the 'thread group leader', typically the first thread

 * spawned.

 *

 * To cut the Gideon knot, for internal kernel usage, we refer to

 * PIDFD_SELF_THREAD to refer to the current thread (or task from a kernel

 * perspective), and PIDFD_SELF_THREAD_GROUP to refer to the current thread

 * group leader...

 */

#define PIDFD_SELF_THREAD		-10000 /* Current thread. */

#define PIDFD_SELF_THREAD_GROUP		-20000 /* Current thread group leader. */





/* Generic flags for the *at(2) family of syscalls. */

include/uapi/linux/pidfd.h

+0 −15
Original line number Diff line number Diff line
@@ -42,21 +42,6 @@ 
#define PIDFD_COREDUMP_USER	(1U << 2) /* coredump was done as the user. */

#define PIDFD_COREDUMP_ROOT	(1U << 3) /* coredump was done as root. */



/*

 * The concept of process and threads in userland and the kernel is a confusing

 * one - within the kernel every thread is a 'task' with its own individual PID,

 * however from userland's point of view threads are grouped by a single PID,

 * which is that of the 'thread group leader', typically the first thread

 * spawned.

 *

 * To cut the Gideon knot, for internal kernel usage, we refer to

 * PIDFD_SELF_THREAD to refer to the current thread (or task from a kernel

 * perspective), and PIDFD_SELF_THREAD_GROUP to refer to the current thread

 * group leader...

 */

#define PIDFD_SELF_THREAD		-10000 /* Current thread. */

#define PIDFD_SELF_THREAD_GROUP		-20000 /* Current thread group leader. */



/*

 * ...and for userland we make life simpler - PIDFD_SELF refers to the current

 * thread, PIDFD_SELF_PROCESS refers to the process thread group leader.