mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-10-29 23:53:32 +00:00
bfe3911a91
Userspace has discovered the functionality offered by SYS_kcmp and has started to depend upon it. In particular, Mesa uses SYS_kcmp for os_same_file_description() in order to identify when two fd (e.g. device or dmabuf) point to the same struct file. Since they depend on it for core functionality, lift SYS_kcmp out of the non-default CONFIG_CHECKPOINT_RESTORE into the selectable syscall category. Rasmus Villemoes also pointed out that systemd uses SYS_kcmp to deduplicate the per-service file descriptor store. Note that some distributions such as Ubuntu are already enabling CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp. References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Will Drewry <wad@chromium.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Lucas Stach <l.stach@pengutronix.de> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Cyrill Gorcunov <gorcunov@gmail.com> Cc: stable@vger.kernel.org Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> # DRM depends on kcmp Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> # systemd uses kcmp Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Thomas Zimmermann <tzimmermann@suse.de> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20210205220012.1983-1-chris@chris-wilson.co.uk
71 lines
1.9 KiB
C
71 lines
1.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
|
|
/*
|
|
* include/linux/eventpoll.h ( Efficient event polling implementation )
|
|
* Copyright (C) 2001,...,2006 Davide Libenzi
|
|
*
|
|
* Davide Libenzi <davidel@xmailserver.org>
|
|
*/
|
|
#ifndef _LINUX_EVENTPOLL_H
|
|
#define _LINUX_EVENTPOLL_H
|
|
|
|
#include <uapi/linux/eventpoll.h>
|
|
#include <uapi/linux/kcmp.h>
|
|
|
|
|
|
/* Forward declarations to avoid compiler errors */
|
|
struct file;
|
|
|
|
|
|
#ifdef CONFIG_EPOLL
|
|
|
|
#ifdef CONFIG_KCMP
|
|
struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
|
|
#endif
|
|
|
|
/* Used to release the epoll bits inside the "struct file" */
|
|
void eventpoll_release_file(struct file *file);
|
|
|
|
/*
|
|
* This is called from inside fs/file_table.c:__fput() to unlink files
|
|
* from the eventpoll interface. We need to have this facility to cleanup
|
|
* correctly files that are closed without being removed from the eventpoll
|
|
* interface.
|
|
*/
|
|
static inline void eventpoll_release(struct file *file)
|
|
{
|
|
|
|
/*
|
|
* Fast check to avoid the get/release of the semaphore. Since
|
|
* we're doing this outside the semaphore lock, it might return
|
|
* false negatives, but we don't care. It'll help in 99.99% of cases
|
|
* to avoid the semaphore lock. False positives simply cannot happen
|
|
* because the file in on the way to be removed and nobody ( but
|
|
* eventpoll ) has still a reference to this file.
|
|
*/
|
|
if (likely(!file->f_ep))
|
|
return;
|
|
|
|
/*
|
|
* The file is being closed while it is still linked to an epoll
|
|
* descriptor. We need to handle this by correctly unlinking it
|
|
* from its containers.
|
|
*/
|
|
eventpoll_release_file(file);
|
|
}
|
|
|
|
int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds,
|
|
bool nonblock);
|
|
|
|
/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
|
|
static inline int ep_op_has_event(int op)
|
|
{
|
|
return op != EPOLL_CTL_DEL;
|
|
}
|
|
|
|
#else
|
|
|
|
static inline void eventpoll_release(struct file *file) {}
|
|
|
|
#endif
|
|
|
|
#endif /* #ifndef _LINUX_EVENTPOLL_H */
|