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ddb9fd7a54
A while ago, we changed the way that select() and poll() preallocate
a temporary buffer just under the size of the static warning limit of
1024 bytes, as clang was frequently going slightly above that limit.
The warnings have recently returned and I took another look. As it turns
out, clang is not actually inherently worse at reserving stack space,
it just happens to inline do_select() into core_sys_select(), while gcc
never inlines it.
Annotate do_select() to never be inlined and in turn remove the special
case for the allocation size. This should give the same behavior for
both clang and gcc all the time and once more avoids those warnings.
Fixes: ad312f95d4 ("fs/select: avoid clang stack usage warning")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20240216202352.2492798-1-arnd@kernel.org
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
144 lines
3.9 KiB
C
144 lines
3.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_POLL_H
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#define _LINUX_POLL_H
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#include <linux/compiler.h>
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#include <linux/ktime.h>
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#include <linux/wait.h>
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#include <linux/string.h>
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#include <linux/fs.h>
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#include <linux/uaccess.h>
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#include <uapi/linux/poll.h>
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#include <uapi/linux/eventpoll.h>
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/* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
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additional memory. */
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#define MAX_STACK_ALLOC 832
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#define FRONTEND_STACK_ALLOC 256
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#define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC
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#define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC
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#define WQUEUES_STACK_ALLOC (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
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#define N_INLINE_POLL_ENTRIES (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
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#define DEFAULT_POLLMASK (EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM)
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struct poll_table_struct;
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/*
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* structures and helpers for f_op->poll implementations
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*/
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typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
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/*
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* Do not touch the structure directly, use the access functions
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* poll_does_not_wait() and poll_requested_events() instead.
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*/
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typedef struct poll_table_struct {
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poll_queue_proc _qproc;
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__poll_t _key;
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} poll_table;
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static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
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{
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if (p && p->_qproc && wait_address)
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p->_qproc(filp, wait_address, p);
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}
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/*
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* Return true if it is guaranteed that poll will not wait. This is the case
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* if the poll() of another file descriptor in the set got an event, so there
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* is no need for waiting.
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*/
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static inline bool poll_does_not_wait(const poll_table *p)
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{
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return p == NULL || p->_qproc == NULL;
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}
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/*
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* Return the set of events that the application wants to poll for.
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* This is useful for drivers that need to know whether a DMA transfer has
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* to be started implicitly on poll(). You typically only want to do that
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* if the application is actually polling for POLLIN and/or POLLOUT.
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*/
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static inline __poll_t poll_requested_events(const poll_table *p)
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{
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return p ? p->_key : ~(__poll_t)0;
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}
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static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
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{
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pt->_qproc = qproc;
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pt->_key = ~(__poll_t)0; /* all events enabled */
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}
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static inline bool file_can_poll(struct file *file)
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{
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return file->f_op->poll;
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}
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static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
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{
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if (unlikely(!file->f_op->poll))
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return DEFAULT_POLLMASK;
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return file->f_op->poll(file, pt);
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}
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struct poll_table_entry {
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struct file *filp;
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__poll_t key;
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wait_queue_entry_t wait;
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wait_queue_head_t *wait_address;
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};
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/*
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* Structures and helpers for select/poll syscall
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*/
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struct poll_wqueues {
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poll_table pt;
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struct poll_table_page *table;
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struct task_struct *polling_task;
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int triggered;
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int error;
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int inline_index;
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struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
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};
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extern void poll_initwait(struct poll_wqueues *pwq);
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extern void poll_freewait(struct poll_wqueues *pwq);
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extern u64 select_estimate_accuracy(struct timespec64 *tv);
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#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
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extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
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fd_set __user *exp, struct timespec64 *end_time);
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extern int poll_select_set_timeout(struct timespec64 *to, time64_t sec,
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long nsec);
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#define __MAP(v, from, to) \
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(from < to ? (v & from) * (to/from) : (v & from) / (from/to))
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static inline __u16 mangle_poll(__poll_t val)
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{
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__u16 v = (__force __u16)val;
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#define M(X) __MAP(v, (__force __u16)EPOLL##X, POLL##X)
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return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
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M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
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M(HUP) | M(RDHUP) | M(MSG);
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#undef M
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}
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static inline __poll_t demangle_poll(u16 val)
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{
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#define M(X) (__force __poll_t)__MAP(val, POLL##X, (__force __u16)EPOLL##X)
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return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
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M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
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M(HUP) | M(RDHUP) | M(MSG);
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#undef M
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}
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#undef __MAP
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#endif /* _LINUX_POLL_H */
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