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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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ad312f95d4
The select() implementation is carefully tuned to put a sensible amount of data on the stack for holding a copy of the user space fd_set, but not too large to risk overflowing the kernel stack. When building a 32-bit kernel with clang, we need a little more space than with gcc, which often triggers a warning: fs/select.c:619:5: error: stack frame size of 1048 bytes in function 'core_sys_select' [-Werror,-Wframe-larger-than=] int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, I experimentally found that for 32-bit ARM, reducing the maximum stack usage by 64 bytes keeps us reliably under the warning limit again. Link: http://lkml.kernel.org/r/20190307090146.1874906-1-arnd@arndb.de Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Andi Kleen <ak@linux.intel.com> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Eric Dumazet <edumazet@google.com> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
150 lines
4.1 KiB
C
150 lines
4.1 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/sysctl.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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extern struct ctl_table epoll_table[]; /* for sysctl */
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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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#ifdef __clang__
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#define MAX_STACK_ALLOC 768
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#else
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#define MAX_STACK_ALLOC 832
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#endif
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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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