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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
72 lines
1.9 KiB
C
72 lines
1.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* include/linux/eventpoll.h ( Efficient event polling implementation )
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* Copyright (C) 2001,...,2006 Davide Libenzi
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*
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* Davide Libenzi <davidel@xmailserver.org>
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*/
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#ifndef _LINUX_EVENTPOLL_H
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#define _LINUX_EVENTPOLL_H
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#include <uapi/linux/eventpoll.h>
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#include <uapi/linux/kcmp.h>
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/* Forward declarations to avoid compiler errors */
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struct file;
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#ifdef CONFIG_EPOLL
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#ifdef CONFIG_KCMP
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struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
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#endif
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/* Used to release the epoll bits inside the "struct file" */
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void eventpoll_release_file(struct file *file);
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/*
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* This is called from inside fs/file_table.c:__fput() to unlink files
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* from the eventpoll interface. We need to have this facility to cleanup
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* correctly files that are closed without being removed from the eventpoll
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* interface.
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*/
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static inline void eventpoll_release(struct file *file)
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{
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/*
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* Fast check to avoid the get/release of the semaphore. Since
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* we're doing this outside the semaphore lock, it might return
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* false negatives, but we don't care. It'll help in 99.99% of cases
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* to avoid the semaphore lock. False positives simply cannot happen
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* because the file in on the way to be removed and nobody ( but
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* eventpoll ) has still a reference to this file.
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*/
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if (likely(!file->f_ep))
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return;
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/*
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* The file is being closed while it is still linked to an epoll
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* descriptor. We need to handle this by correctly unlinking it
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* from its containers.
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*/
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eventpoll_release_file(file);
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}
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int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds,
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bool nonblock);
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/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
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static inline int ep_op_has_event(int op)
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{
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return op != EPOLL_CTL_DEL;
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}
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#else
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static inline void eventpoll_release(struct file *file) {}
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#endif
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#endif /* #ifndef _LINUX_EVENTPOLL_H */
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