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Diffstat (limited to 'fs/select.c')
| -rw-r--r-- | fs/select.c | 1448 |
1 files changed, 1448 insertions, 0 deletions
diff --git a/fs/select.c b/fs/select.c new file mode 100644 index 000000000..5edffee11 --- /dev/null +++ b/fs/select.c @@ -0,0 +1,1448 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * This file contains the procedures for the handling of select and poll + * + * Created for Linux based loosely upon Mathius Lattner's minix + * patches by Peter MacDonald. Heavily edited by Linus. + * + * 4 February 1994 + * COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS + * flag set in its personality we do *not* modify the given timeout + * parameter to reflect time remaining. + * + * 24 January 2000 + * Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation + * of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian). + */ + +#include <linux/kernel.h> +#include <linux/sched/signal.h> +#include <linux/sched/rt.h> +#include <linux/syscalls.h> +#include <linux/export.h> +#include <linux/slab.h> +#include <linux/poll.h> +#include <linux/personality.h> /* for STICKY_TIMEOUTS */ +#include <linux/file.h> +#include <linux/fdtable.h> +#include <linux/fs.h> +#include <linux/rcupdate.h> +#include <linux/hrtimer.h> +#include <linux/freezer.h> +#include <net/busy_poll.h> +#include <linux/vmalloc.h> + +#include <linux/uaccess.h> + + +/* + * Estimate expected accuracy in ns from a timeval. + * + * After quite a bit of churning around, we've settled on + * a simple thing of taking 0.1% of the timeout as the + * slack, with a cap of 100 msec. + * "nice" tasks get a 0.5% slack instead. + * + * Consider this comment an open invitation to come up with even + * better solutions.. + */ + +#define MAX_SLACK (100 * NSEC_PER_MSEC) + +static long __estimate_accuracy(struct timespec64 *tv) +{ + long slack; + int divfactor = 1000; + + if (tv->tv_sec < 0) + return 0; + + if (task_nice(current) > 0) + divfactor = divfactor / 5; + + if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor)) + return MAX_SLACK; + + slack = tv->tv_nsec / divfactor; + slack += tv->tv_sec * (NSEC_PER_SEC/divfactor); + + if (slack > MAX_SLACK) + return MAX_SLACK; + + return slack; +} + +u64 select_estimate_accuracy(struct timespec64 *tv) +{ + u64 ret; + struct timespec64 now; + + /* + * Realtime tasks get a slack of 0 for obvious reasons. + */ + + if (rt_task(current)) + return 0; + + ktime_get_ts64(&now); + now = timespec64_sub(*tv, now); + ret = __estimate_accuracy(&now); + if (ret < current->timer_slack_ns) + return current->timer_slack_ns; + return ret; +} + + + +struct poll_table_page { + struct poll_table_page * next; + struct poll_table_entry * entry; + struct poll_table_entry entries[]; +}; + +#define POLL_TABLE_FULL(table) \ + ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table)) + +/* + * Ok, Peter made a complicated, but straightforward multiple_wait() function. + * I have rewritten this, taking some shortcuts: This code may not be easy to + * follow, but it should be free of race-conditions, and it's practical. If you + * understand what I'm doing here, then you understand how the linux + * sleep/wakeup mechanism works. + * + * Two very simple procedures, poll_wait() and poll_freewait() make all the + * work. poll_wait() is an inline-function defined in <linux/poll.h>, + * as all select/poll functions have to call it to add an entry to the + * poll table. + */ +static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, + poll_table *p); + +void poll_initwait(struct poll_wqueues *pwq) +{ + init_poll_funcptr(&pwq->pt, __pollwait); + pwq->polling_task = current; + pwq->triggered = 0; + pwq->error = 0; + pwq->table = NULL; + pwq->inline_index = 0; +} +EXPORT_SYMBOL(poll_initwait); + +static void free_poll_entry(struct poll_table_entry *entry) +{ + remove_wait_queue(entry->wait_address, &entry->wait); + fput(entry->filp); +} + +void poll_freewait(struct poll_wqueues *pwq) +{ + struct poll_table_page * p = pwq->table; + int i; + for (i = 0; i < pwq->inline_index; i++) + free_poll_entry(pwq->inline_entries + i); + while (p) { + struct poll_table_entry * entry; + struct poll_table_page *old; + + entry = p->entry; + do { + entry--; + free_poll_entry(entry); + } while (entry > p->entries); + old = p; + p = p->next; + free_page((unsigned long) old); + } +} +EXPORT_SYMBOL(poll_freewait); + +static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p) +{ + struct poll_table_page *table = p->table; + + if (p->inline_index < N_INLINE_POLL_ENTRIES) + return p->inline_entries + p->inline_index++; + + if (!table || POLL_TABLE_FULL(table)) { + struct poll_table_page *new_table; + + new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL); + if (!new_table) { + p->error = -ENOMEM; + return NULL; + } + new_table->entry = new_table->entries; + new_table->next = table; + p->table = new_table; + table = new_table; + } + + return table->entry++; +} + +static int __pollwake(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) +{ + struct poll_wqueues *pwq = wait->private; + DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task); + + /* + * Although this function is called under waitqueue lock, LOCK + * doesn't imply write barrier and the users expect write + * barrier semantics on wakeup functions. The following + * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up() + * and is paired with smp_store_mb() in poll_schedule_timeout. + */ + smp_wmb(); + pwq->triggered = 1; + + /* + * Perform the default wake up operation using a dummy + * waitqueue. + * + * TODO: This is hacky but there currently is no interface to + * pass in @sync. @sync is scheduled to be removed and once + * that happens, wake_up_process() can be used directly. + */ + return default_wake_function(&dummy_wait, mode, sync, key); +} + +static int pollwake(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) +{ + struct poll_table_entry *entry; + + entry = container_of(wait, struct poll_table_entry, wait); + if (key && !(key_to_poll(key) & entry->key)) + return 0; + return __pollwake(wait, mode, sync, key); +} + +/* Add a new entry */ +static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, + poll_table *p) +{ + struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt); + struct poll_table_entry *entry = poll_get_entry(pwq); + if (!entry) + return; + entry->filp = get_file(filp); + entry->wait_address = wait_address; + entry->key = p->_key; + init_waitqueue_func_entry(&entry->wait, pollwake); + entry->wait.private = pwq; + add_wait_queue(wait_address, &entry->wait); +} + +static int poll_schedule_timeout(struct poll_wqueues *pwq, int state, + ktime_t *expires, unsigned long slack) +{ + int rc = -EINTR; + + set_current_state(state); + if (!pwq->triggered) + rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS); + __set_current_state(TASK_RUNNING); + + /* + * Prepare for the next iteration. + * + * The following smp_store_mb() serves two purposes. First, it's + * the counterpart rmb of the wmb in pollwake() such that data + * written before wake up is always visible after wake up. + * Second, the full barrier guarantees that triggered clearing + * doesn't pass event check of the next iteration. Note that + * this problem doesn't exist for the first iteration as + * add_wait_queue() has full barrier semantics. + */ + smp_store_mb(pwq->triggered, 0); + + return rc; +} + +/** + * poll_select_set_timeout - helper function to setup the timeout value + * @to: pointer to timespec64 variable for the final timeout + * @sec: seconds (from user space) + * @nsec: nanoseconds (from user space) + * + * Note, we do not use a timespec for the user space value here, That + * way we can use the function for timeval and compat interfaces as well. + * + * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0. + */ +int poll_select_set_timeout(struct timespec64 *to, time64_t sec, long nsec) +{ + struct timespec64 ts = {.tv_sec = sec, .tv_nsec = nsec}; + + if (!timespec64_valid(&ts)) + return -EINVAL; + + /* Optimize for the zero timeout value here */ + if (!sec && !nsec) { + to->tv_sec = to->tv_nsec = 0; + } else { + ktime_get_ts64(to); + *to = timespec64_add_safe(*to, ts); + } + return 0; +} + +enum poll_time_type { + PT_TIMEVAL = 0, + PT_OLD_TIMEVAL = 1, + PT_TIMESPEC = 2, + PT_OLD_TIMESPEC = 3, +}; + +static int poll_select_finish(struct timespec64 *end_time, + void __user *p, + enum poll_time_type pt_type, int ret) +{ + struct timespec64 rts; + + restore_saved_sigmask_unless(ret == -ERESTARTNOHAND); + + if (!p) + return ret; + + if (current->personality & STICKY_TIMEOUTS) + goto sticky; + + /* No update for zero timeout */ + if (!end_time->tv_sec && !end_time->tv_nsec) + return ret; + + ktime_get_ts64(&rts); + rts = timespec64_sub(*end_time, rts); + if (rts.tv_sec < 0) + rts.tv_sec = rts.tv_nsec = 0; + + + switch (pt_type) { + case PT_TIMEVAL: + { + struct __kernel_old_timeval rtv; + + if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec)) + memset(&rtv, 0, sizeof(rtv)); + rtv.tv_sec = rts.tv_sec; + rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; + if (!copy_to_user(p, &rtv, sizeof(rtv))) + return ret; + } + break; + case PT_OLD_TIMEVAL: + { + struct old_timeval32 rtv; + + rtv.tv_sec = rts.tv_sec; + rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; + if (!copy_to_user(p, &rtv, sizeof(rtv))) + return ret; + } + break; + case PT_TIMESPEC: + if (!put_timespec64(&rts, p)) + return ret; + break; + case PT_OLD_TIMESPEC: + if (!put_old_timespec32(&rts, p)) + return ret; + break; + default: + BUG(); + } + /* + * If an application puts its timeval in read-only memory, we + * don't want the Linux-specific update to the timeval to + * cause a fault after the select has completed + * successfully. However, because we're not updating the + * timeval, we can't restart the system call. + */ + +sticky: + if (ret == -ERESTARTNOHAND) + ret = -EINTR; + return ret; +} + +/* + * Scalable version of the fd_set. + */ + +typedef struct { + unsigned long *in, *out, *ex; + unsigned long *res_in, *res_out, *res_ex; +} fd_set_bits; + +/* + * How many longwords for "nr" bits? + */ +#define FDS_BITPERLONG (8*sizeof(long)) +#define FDS_LONGS(nr) (((nr)+FDS_BITPERLONG-1)/FDS_BITPERLONG) +#define FDS_BYTES(nr) (FDS_LONGS(nr)*sizeof(long)) + +/* + * Use "unsigned long" accesses to let user-mode fd_set's be long-aligned. + */ +static inline +int get_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset) +{ + nr = FDS_BYTES(nr); + if (ufdset) + return copy_from_user(fdset, ufdset, nr) ? -EFAULT : 0; + + memset(fdset, 0, nr); + return 0; +} + +static inline unsigned long __must_check +set_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset) +{ + if (ufdset) + return __copy_to_user(ufdset, fdset, FDS_BYTES(nr)); + return 0; +} + +static inline +void zero_fd_set(unsigned long nr, unsigned long *fdset) +{ + memset(fdset, 0, FDS_BYTES(nr)); +} + +#define FDS_IN(fds, n) (fds->in + n) +#define FDS_OUT(fds, n) (fds->out + n) +#define FDS_EX(fds, n) (fds->ex + n) + +#define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n)) + +static int max_select_fd(unsigned long n, fd_set_bits *fds) +{ + unsigned long *open_fds; + unsigned long set; + int max; + struct fdtable *fdt; + + /* handle last in-complete long-word first */ + set = ~(~0UL << (n & (BITS_PER_LONG-1))); + n /= BITS_PER_LONG; + fdt = files_fdtable(current->files); + open_fds = fdt->open_fds + n; + max = 0; + if (set) { + set &= BITS(fds, n); + if (set) { + if (!(set & ~*open_fds)) + goto get_max; + return -EBADF; + } + } + while (n) { + open_fds--; + n--; + set = BITS(fds, n); + if (!set) + continue; + if (set & ~*open_fds) + return -EBADF; + if (max) + continue; +get_max: + do { + max++; + set >>= 1; + } while (set); + max += n * BITS_PER_LONG; + } + + return max; +} + +#define POLLIN_SET (EPOLLRDNORM | EPOLLRDBAND | EPOLLIN | EPOLLHUP | EPOLLERR |\ + EPOLLNVAL) +#define POLLOUT_SET (EPOLLWRBAND | EPOLLWRNORM | EPOLLOUT | EPOLLERR |\ + EPOLLNVAL) +#define POLLEX_SET (EPOLLPRI | EPOLLNVAL) + +static inline void wait_key_set(poll_table *wait, unsigned long in, + unsigned long out, unsigned long bit, + __poll_t ll_flag) +{ + wait->_key = POLLEX_SET | ll_flag; + if (in & bit) + wait->_key |= POLLIN_SET; + if (out & bit) + wait->_key |= POLLOUT_SET; +} + +static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time) +{ + ktime_t expire, *to = NULL; + struct poll_wqueues table; + poll_table *wait; + int retval, i, timed_out = 0; + u64 slack = 0; + __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0; + unsigned long busy_start = 0; + + rcu_read_lock(); + retval = max_select_fd(n, fds); + rcu_read_unlock(); + + if (retval < 0) + return retval; + n = retval; + + poll_initwait(&table); + wait = &table.pt; + if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { + wait->_qproc = NULL; + timed_out = 1; + } + + if (end_time && !timed_out) + slack = select_estimate_accuracy(end_time); + + retval = 0; + for (;;) { + unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp; + bool can_busy_loop = false; + + inp = fds->in; outp = fds->out; exp = fds->ex; + rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex; + + for (i = 0; i < n; ++rinp, ++routp, ++rexp) { + unsigned long in, out, ex, all_bits, bit = 1, j; + unsigned long res_in = 0, res_out = 0, res_ex = 0; + __poll_t mask; + + in = *inp++; out = *outp++; ex = *exp++; + all_bits = in | out | ex; + if (all_bits == 0) { + i += BITS_PER_LONG; + continue; + } + + for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) { + struct fd f; + if (i >= n) + break; + if (!(bit & all_bits)) + continue; + mask = EPOLLNVAL; + f = fdget(i); + if (f.file) { + wait_key_set(wait, in, out, bit, + busy_flag); + mask = vfs_poll(f.file, wait); + + fdput(f); + } + if ((mask & POLLIN_SET) && (in & bit)) { + res_in |= bit; + retval++; + wait->_qproc = NULL; + } + if ((mask & POLLOUT_SET) && (out & bit)) { + res_out |= bit; + retval++; + wait->_qproc = NULL; + } + if ((mask & POLLEX_SET) && (ex & bit)) { + res_ex |= bit; + retval++; + wait->_qproc = NULL; + } + /* got something, stop busy polling */ + if (retval) { + can_busy_loop = false; + busy_flag = 0; + + /* + * only remember a returned + * POLL_BUSY_LOOP if we asked for it + */ + } else if (busy_flag & mask) + can_busy_loop = true; + + } + if (res_in) + *rinp = res_in; + if (res_out) + *routp = res_out; + if (res_ex) + *rexp = res_ex; + cond_resched(); + } + wait->_qproc = NULL; + if (retval || timed_out || signal_pending(current)) + break; + if (table.error) { + retval = table.error; + break; + } + + /* only if found POLL_BUSY_LOOP sockets && not out of time */ + if (can_busy_loop && !need_resched()) { + if (!busy_start) { + busy_start = busy_loop_current_time(); + continue; + } + if (!busy_loop_timeout(busy_start)) + continue; + } + busy_flag = 0; + + /* + * If this is the first loop and we have a timeout + * given, then we convert to ktime_t and set the to + * pointer to the expiry value. + */ + if (end_time && !to) { + expire = timespec64_to_ktime(*end_time); + to = &expire; + } + + if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE, + to, slack)) + timed_out = 1; + } + + poll_freewait(&table); + + return retval; +} + +/* + * We can actually return ERESTARTSYS instead of EINTR, but I'd + * like to be certain this leads to no problems. So I return + * EINTR just for safety. + * + * Update: ERESTARTSYS breaks at least the xview clock binary, so + * I'm trying ERESTARTNOHAND which restart only when you want to. + */ +int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, + fd_set __user *exp, struct timespec64 *end_time) +{ + fd_set_bits fds; + void *bits; + int ret, max_fds; + size_t size, alloc_size; + struct fdtable *fdt; + /* Allocate small arguments on the stack to save memory and be faster */ + long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; + + ret = -EINVAL; + if (n < 0) + goto out_nofds; + + /* max_fds can increase, so grab it once to avoid race */ + rcu_read_lock(); + fdt = files_fdtable(current->files); + max_fds = fdt->max_fds; + rcu_read_unlock(); + if (n > max_fds) + n = max_fds; + + /* + * We need 6 bitmaps (in/out/ex for both incoming and outgoing), + * since we used fdset we need to allocate memory in units of + * long-words. + */ + size = FDS_BYTES(n); + bits = stack_fds; + if (size > sizeof(stack_fds) / 6) { + /* Not enough space in on-stack array; must use kmalloc */ + ret = -ENOMEM; + if (size > (SIZE_MAX / 6)) + goto out_nofds; + + alloc_size = 6 * size; + bits = kvmalloc(alloc_size, GFP_KERNEL); + if (!bits) + goto out_nofds; + } + fds.in = bits; + fds.out = bits + size; + fds.ex = bits + 2*size; + fds.res_in = bits + 3*size; + fds.res_out = bits + 4*size; + fds.res_ex = bits + 5*size; + + if ((ret = get_fd_set(n, inp, fds.in)) || + (ret = get_fd_set(n, outp, fds.out)) || + (ret = get_fd_set(n, exp, fds.ex))) + goto out; + zero_fd_set(n, fds.res_in); + zero_fd_set(n, fds.res_out); + zero_fd_set(n, fds.res_ex); + + ret = do_select(n, &fds, end_time); + + if (ret < 0) + goto out; + if (!ret) { + ret = -ERESTARTNOHAND; + if (signal_pending(current)) + goto out; + ret = 0; + } + + if (set_fd_set(n, inp, fds.res_in) || + set_fd_set(n, outp, fds.res_out) || + set_fd_set(n, exp, fds.res_ex)) + ret = -EFAULT; + +out: + if (bits != stack_fds) + kvfree(bits); +out_nofds: + return ret; +} + +static int kern_select(int n, fd_set __user *inp, fd_set __user *outp, + fd_set __user *exp, struct __kernel_old_timeval __user *tvp) +{ + struct timespec64 end_time, *to = NULL; + struct __kernel_old_timeval tv; + int ret; + + if (tvp) { + if (copy_from_user(&tv, tvp, sizeof(tv))) + return -EFAULT; + + to = &end_time; + if (poll_select_set_timeout(to, + tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), + (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) + return -EINVAL; + } + + ret = core_sys_select(n, inp, outp, exp, to); + return poll_select_finish(&end_time, tvp, PT_TIMEVAL, ret); +} + +SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp, + fd_set __user *, exp, struct __kernel_old_timeval __user *, tvp) +{ + return kern_select(n, inp, outp, exp, tvp); +} + +static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp, + fd_set __user *exp, void __user *tsp, + const sigset_t __user *sigmask, size_t sigsetsize, + enum poll_time_type type) +{ + struct timespec64 ts, end_time, *to = NULL; + int ret; + + if (tsp) { + switch (type) { + case PT_TIMESPEC: + if (get_timespec64(&ts, tsp)) + return -EFAULT; + break; + case PT_OLD_TIMESPEC: + if (get_old_timespec32(&ts, tsp)) + return -EFAULT; + break; + default: + BUG(); + } + + to = &end_time; + if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) + return -EINVAL; + } + + ret = set_user_sigmask(sigmask, sigsetsize); + if (ret) + return ret; + + ret = core_sys_select(n, inp, outp, exp, to); + return poll_select_finish(&end_time, tsp, type, ret); +} + +/* + * Most architectures can't handle 7-argument syscalls. So we provide a + * 6-argument version where the sixth argument is a pointer to a structure + * which has a pointer to the sigset_t itself followed by a size_t containing + * the sigset size. + */ +struct sigset_argpack { + sigset_t __user *p; + size_t size; +}; + +static inline int get_sigset_argpack(struct sigset_argpack *to, + struct sigset_argpack __user *from) +{ + // the path is hot enough for overhead of copy_from_user() to matter + if (from) { + if (!user_read_access_begin(from, sizeof(*from))) + return -EFAULT; + unsafe_get_user(to->p, &from->p, Efault); + unsafe_get_user(to->size, &from->size, Efault); + user_read_access_end(); + } + return 0; +Efault: + user_access_end(); + return -EFAULT; +} + +SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp, + fd_set __user *, exp, struct __kernel_timespec __user *, tsp, + void __user *, sig) +{ + struct sigset_argpack x = {NULL, 0}; + + if (get_sigset_argpack(&x, sig)) + return -EFAULT; + + return do_pselect(n, inp, outp, exp, tsp, x.p, x.size, PT_TIMESPEC); +} + +#if defined(CONFIG_COMPAT_32BIT_TIME) && !defined(CONFIG_64BIT) + +SYSCALL_DEFINE6(pselect6_time32, int, n, fd_set __user *, inp, fd_set __user *, outp, + fd_set __user *, exp, struct old_timespec32 __user *, tsp, + void __user *, sig) +{ + struct sigset_argpack x = {NULL, 0}; + + if (get_sigset_argpack(&x, sig)) + return -EFAULT; + + return do_pselect(n, inp, outp, exp, tsp, x.p, x.size, PT_OLD_TIMESPEC); +} + +#endif + +#ifdef __ARCH_WANT_SYS_OLD_SELECT +struct sel_arg_struct { + unsigned long n; + fd_set __user *inp, *outp, *exp; + struct __kernel_old_timeval __user *tvp; +}; + +SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg) +{ + struct sel_arg_struct a; + + if (copy_from_user(&a, arg, sizeof(a))) + return -EFAULT; + return kern_select(a.n, a.inp, a.outp, a.exp, a.tvp); +} +#endif + +struct poll_list { + struct poll_list *next; + int len; + struct pollfd entries[]; +}; + +#define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) + +/* + * Fish for pollable events on the pollfd->fd file descriptor. We're only + * interested in events matching the pollfd->events mask, and the result + * matching that mask is both recorded in pollfd->revents and returned. The + * pwait poll_table will be used by the fd-provided poll handler for waiting, + * if pwait->_qproc is non-NULL. + */ +static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait, + bool *can_busy_poll, + __poll_t busy_flag) +{ + int fd = pollfd->fd; + __poll_t mask = 0, filter; + struct fd f; + + if (fd < 0) + goto out; + mask = EPOLLNVAL; + f = fdget(fd); + if (!f.file) + goto out; + + /* userland u16 ->events contains POLL... bitmap */ + filter = demangle_poll(pollfd->events) | EPOLLERR | EPOLLHUP; + pwait->_key = filter | busy_flag; + mask = vfs_poll(f.file, pwait); + if (mask & busy_flag) + *can_busy_poll = true; + mask &= filter; /* Mask out unneeded events. */ + fdput(f); + +out: + /* ... and so does ->revents */ + pollfd->revents = mangle_poll(mask); + return mask; +} + +static int do_poll(struct poll_list *list, struct poll_wqueues *wait, + struct timespec64 *end_time) +{ + poll_table* pt = &wait->pt; + ktime_t expire, *to = NULL; + int timed_out = 0, count = 0; + u64 slack = 0; + __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0; + unsigned long busy_start = 0; + + /* Optimise the no-wait case */ + if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { + pt->_qproc = NULL; + timed_out = 1; + } + + if (end_time && !timed_out) + slack = select_estimate_accuracy(end_time); + + for (;;) { + struct poll_list *walk; + bool can_busy_loop = false; + + for (walk = list; walk != NULL; walk = walk->next) { + struct pollfd * pfd, * pfd_end; + + pfd = walk->entries; + pfd_end = pfd + walk->len; + for (; pfd != pfd_end; pfd++) { + /* + * Fish for events. If we found one, record it + * and kill poll_table->_qproc, so we don't + * needlessly register any other waiters after + * this. They'll get immediately deregistered + * when we break out and return. + */ + if (do_pollfd(pfd, pt, &can_busy_loop, + busy_flag)) { + count++; + pt->_qproc = NULL; + /* found something, stop busy polling */ + busy_flag = 0; + can_busy_loop = false; + } + } + } + /* + * All waiters have already been registered, so don't provide + * a poll_table->_qproc to them on the next loop iteration. + */ + pt->_qproc = NULL; + if (!count) { + count = wait->error; + if (signal_pending(current)) + count = -ERESTARTNOHAND; + } + if (count || timed_out) + break; + + /* only if found POLL_BUSY_LOOP sockets && not out of time */ + if (can_busy_loop && !need_resched()) { + if (!busy_start) { + busy_start = busy_loop_current_time(); + continue; + } + if (!busy_loop_timeout(busy_start)) + continue; + } + busy_flag = 0; + + /* + * If this is the first loop and we have a timeout + * given, then we convert to ktime_t and set the to + * pointer to the expiry value. + */ + if (end_time && !to) { + expire = timespec64_to_ktime(*end_time); + to = &expire; + } + + if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack)) + timed_out = 1; + } + return count; +} + +#define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ + sizeof(struct pollfd)) + +static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, + struct timespec64 *end_time) +{ + struct poll_wqueues table; + int err = -EFAULT, fdcount, len; + /* Allocate small arguments on the stack to save memory and be + faster - use long to make sure the buffer is aligned properly + on 64 bit archs to avoid unaligned access */ + long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; + struct poll_list *const head = (struct poll_list *)stack_pps; + struct poll_list *walk = head; + unsigned long todo = nfds; + + if (nfds > rlimit(RLIMIT_NOFILE)) + return -EINVAL; + + len = min_t(unsigned int, nfds, N_STACK_PPS); + for (;;) { + walk->next = NULL; + walk->len = len; + if (!len) + break; + + if (copy_from_user(walk->entries, ufds + nfds-todo, + sizeof(struct pollfd) * walk->len)) + goto out_fds; + + todo -= walk->len; + if (!todo) + break; + + len = min(todo, POLLFD_PER_PAGE); + walk = walk->next = kmalloc(struct_size(walk, entries, len), + GFP_KERNEL); + if (!walk) { + err = -ENOMEM; + goto out_fds; + } + } + + poll_initwait(&table); + fdcount = do_poll(head, &table, end_time); + poll_freewait(&table); + + if (!user_write_access_begin(ufds, nfds * sizeof(*ufds))) + goto out_fds; + + for (walk = head; walk; walk = walk->next) { + struct pollfd *fds = walk->entries; + int j; + + for (j = walk->len; j; fds++, ufds++, j--) + unsafe_put_user(fds->revents, &ufds->revents, Efault); + } + user_write_access_end(); + + err = fdcount; +out_fds: + walk = head->next; + while (walk) { + struct poll_list *pos = walk; + walk = walk->next; + kfree(pos); + } + + return err; + +Efault: + user_write_access_end(); + err = -EFAULT; + goto out_fds; +} + +static long do_restart_poll(struct restart_block *restart_block) +{ + struct pollfd __user *ufds = restart_block->poll.ufds; + int nfds = restart_block->poll.nfds; + struct timespec64 *to = NULL, end_time; + int ret; + + if (restart_block->poll.has_timeout) { + end_time.tv_sec = restart_block->poll.tv_sec; + end_time.tv_nsec = restart_block->poll.tv_nsec; + to = &end_time; + } + + ret = do_sys_poll(ufds, nfds, to); + + if (ret == -ERESTARTNOHAND) + ret = set_restart_fn(restart_block, do_restart_poll); + + return ret; +} + +SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds, + int, timeout_msecs) +{ + struct timespec64 end_time, *to = NULL; + int ret; + + if (timeout_msecs >= 0) { + to = &end_time; + poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC, + NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC)); + } + + ret = do_sys_poll(ufds, nfds, to); + + if (ret == -ERESTARTNOHAND) { + struct restart_block *restart_block; + + restart_block = ¤t->restart_block; + restart_block->poll.ufds = ufds; + restart_block->poll.nfds = nfds; + + if (timeout_msecs >= 0) { + restart_block->poll.tv_sec = end_time.tv_sec; + restart_block->poll.tv_nsec = end_time.tv_nsec; + restart_block->poll.has_timeout = 1; + } else + restart_block->poll.has_timeout = 0; + + ret = set_restart_fn(restart_block, do_restart_poll); + } + return ret; +} + +SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, + struct __kernel_timespec __user *, tsp, const sigset_t __user *, sigmask, + size_t, sigsetsize) +{ + struct timespec64 ts, end_time, *to = NULL; + int ret; + + if (tsp) { + if (get_timespec64(&ts, tsp)) + return -EFAULT; + + to = &end_time; + if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) + return -EINVAL; + } + + ret = set_user_sigmask(sigmask, sigsetsize); + if (ret) + return ret; + + ret = do_sys_poll(ufds, nfds, to); + return poll_select_finish(&end_time, tsp, PT_TIMESPEC, ret); +} + +#if defined(CONFIG_COMPAT_32BIT_TIME) && !defined(CONFIG_64BIT) + +SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds, unsigned int, nfds, + struct old_timespec32 __user *, tsp, const sigset_t __user *, sigmask, + size_t, sigsetsize) +{ + struct timespec64 ts, end_time, *to = NULL; + int ret; + + if (tsp) { + if (get_old_timespec32(&ts, tsp)) + return -EFAULT; + + to = &end_time; + if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) + return -EINVAL; + } + + ret = set_user_sigmask(sigmask, sigsetsize); + if (ret) + return ret; + + ret = do_sys_poll(ufds, nfds, to); + return poll_select_finish(&end_time, tsp, PT_OLD_TIMESPEC, ret); +} +#endif + +#ifdef CONFIG_COMPAT +#define __COMPAT_NFDBITS (8 * sizeof(compat_ulong_t)) + +/* + * Ooo, nasty. We need here to frob 32-bit unsigned longs to + * 64-bit unsigned longs. + */ +static +int compat_get_fd_set(unsigned long nr, compat_ulong_t __user *ufdset, + unsigned long *fdset) +{ + if (ufdset) { + return compat_get_bitmap(fdset, ufdset, nr); + } else { + zero_fd_set(nr, fdset); + return 0; + } +} + +static +int compat_set_fd_set(unsigned long nr, compat_ulong_t __user *ufdset, + unsigned long *fdset) +{ + if (!ufdset) + return 0; + return compat_put_bitmap(ufdset, fdset, nr); +} + + +/* + * This is a virtual copy of sys_select from fs/select.c and probably + * should be compared to it from time to time + */ + +/* + * We can actually return ERESTARTSYS instead of EINTR, but I'd + * like to be certain this leads to no problems. So I return + * EINTR just for safety. + * + * Update: ERESTARTSYS breaks at least the xview clock binary, so + * I'm trying ERESTARTNOHAND which restart only when you want to. + */ +static int compat_core_sys_select(int n, compat_ulong_t __user *inp, + compat_ulong_t __user *outp, compat_ulong_t __user *exp, + struct timespec64 *end_time) +{ + fd_set_bits fds; + void *bits; + int size, max_fds, ret = -EINVAL; + struct fdtable *fdt; + long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; + + if (n < 0) + goto out_nofds; + + /* max_fds can increase, so grab it once to avoid race */ + rcu_read_lock(); + fdt = files_fdtable(current->files); + max_fds = fdt->max_fds; + rcu_read_unlock(); + if (n > max_fds) + n = max_fds; + + /* + * We need 6 bitmaps (in/out/ex for both incoming and outgoing), + * since we used fdset we need to allocate memory in units of + * long-words. + */ + size = FDS_BYTES(n); + bits = stack_fds; + if (size > sizeof(stack_fds) / 6) { + bits = kmalloc_array(6, size, GFP_KERNEL); + ret = -ENOMEM; + if (!bits) + goto out_nofds; + } + fds.in = (unsigned long *) bits; + fds.out = (unsigned long *) (bits + size); + fds.ex = (unsigned long *) (bits + 2*size); + fds.res_in = (unsigned long *) (bits + 3*size); + fds.res_out = (unsigned long *) (bits + 4*size); + fds.res_ex = (unsigned long *) (bits + 5*size); + + if ((ret = compat_get_fd_set(n, inp, fds.in)) || + (ret = compat_get_fd_set(n, outp, fds.out)) || + (ret = compat_get_fd_set(n, exp, fds.ex))) + goto out; + zero_fd_set(n, fds.res_in); + zero_fd_set(n, fds.res_out); + zero_fd_set(n, fds.res_ex); + + ret = do_select(n, &fds, end_time); + + if (ret < 0) + goto out; + if (!ret) { + ret = -ERESTARTNOHAND; + if (signal_pending(current)) + goto out; + ret = 0; + } + + if (compat_set_fd_set(n, inp, fds.res_in) || + compat_set_fd_set(n, outp, fds.res_out) || + compat_set_fd_set(n, exp, fds.res_ex)) + ret = -EFAULT; +out: + if (bits != stack_fds) + kfree(bits); +out_nofds: + return ret; +} + +static int do_compat_select(int n, compat_ulong_t __user *inp, + compat_ulong_t __user *outp, compat_ulong_t __user *exp, + struct old_timeval32 __user *tvp) +{ + struct timespec64 end_time, *to = NULL; + struct old_timeval32 tv; + int ret; + + if (tvp) { + if (copy_from_user(&tv, tvp, sizeof(tv))) + return -EFAULT; + + to = &end_time; + if (poll_select_set_timeout(to, + tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), + (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) + return -EINVAL; + } + + ret = compat_core_sys_select(n, inp, outp, exp, to); + return poll_select_finish(&end_time, tvp, PT_OLD_TIMEVAL, ret); +} + +COMPAT_SYSCALL_DEFINE5(select, int, n, compat_ulong_t __user *, inp, + compat_ulong_t __user *, outp, compat_ulong_t __user *, exp, + struct old_timeval32 __user *, tvp) +{ + return do_compat_select(n, inp, outp, exp, tvp); +} + +struct compat_sel_arg_struct { + compat_ulong_t n; + compat_uptr_t inp; + compat_uptr_t outp; + compat_uptr_t exp; + compat_uptr_t tvp; +}; + +COMPAT_SYSCALL_DEFINE1(old_select, struct compat_sel_arg_struct __user *, arg) +{ + struct compat_sel_arg_struct a; + + if (copy_from_user(&a, arg, sizeof(a))) + return -EFAULT; + return do_compat_select(a.n, compat_ptr(a.inp), compat_ptr(a.outp), + compat_ptr(a.exp), compat_ptr(a.tvp)); +} + +static long do_compat_pselect(int n, compat_ulong_t __user *inp, + compat_ulong_t __user *outp, compat_ulong_t __user *exp, + void __user *tsp, compat_sigset_t __user *sigmask, + compat_size_t sigsetsize, enum poll_time_type type) +{ + struct timespec64 ts, end_time, *to = NULL; + int ret; + + if (tsp) { + switch (type) { + case PT_OLD_TIMESPEC: + if (get_old_timespec32(&ts, tsp)) + return -EFAULT; + break; + case PT_TIMESPEC: + if (get_timespec64(&ts, tsp)) + return -EFAULT; + break; + default: + BUG(); + } + + to = &end_time; + if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) + return -EINVAL; + } + + ret = set_compat_user_sigmask(sigmask, sigsetsize); + if (ret) + return ret; + + ret = compat_core_sys_select(n, inp, outp, exp, to); + return poll_select_finish(&end_time, tsp, type, ret); +} + +struct compat_sigset_argpack { + compat_uptr_t p; + compat_size_t size; +}; +static inline int get_compat_sigset_argpack(struct compat_sigset_argpack *to, + struct compat_sigset_argpack __user *from) +{ + if (from) { + if (!user_read_access_begin(from, sizeof(*from))) + return -EFAULT; + unsafe_get_user(to->p, &from->p, Efault); + unsafe_get_user(to->size, &from->size, Efault); + user_read_access_end(); + } + return 0; +Efault: + user_access_end(); + return -EFAULT; +} + +COMPAT_SYSCALL_DEFINE6(pselect6_time64, int, n, compat_ulong_t __user *, inp, + compat_ulong_t __user *, outp, compat_ulong_t __user *, exp, + struct __kernel_timespec __user *, tsp, void __user *, sig) +{ + struct compat_sigset_argpack x = {0, 0}; + + if (get_compat_sigset_argpack(&x, sig)) + return -EFAULT; + + return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(x.p), + x.size, PT_TIMESPEC); +} + +#if defined(CONFIG_COMPAT_32BIT_TIME) + +COMPAT_SYSCALL_DEFINE6(pselect6_time32, int, n, compat_ulong_t __user *, inp, + compat_ulong_t __user *, outp, compat_ulong_t __user *, exp, + struct old_timespec32 __user *, tsp, void __user *, sig) +{ + struct compat_sigset_argpack x = {0, 0}; + + if (get_compat_sigset_argpack(&x, sig)) + return -EFAULT; + + return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(x.p), + x.size, PT_OLD_TIMESPEC); +} + +#endif + +#if defined(CONFIG_COMPAT_32BIT_TIME) +COMPAT_SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds, + unsigned int, nfds, struct old_timespec32 __user *, tsp, + const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize) +{ + struct timespec64 ts, end_time, *to = NULL; + int ret; + + if (tsp) { + if (get_old_timespec32(&ts, tsp)) + return -EFAULT; + + to = &end_time; + if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) + return -EINVAL; + } + + ret = set_compat_user_sigmask(sigmask, sigsetsize); + if (ret) + return ret; + + ret = do_sys_poll(ufds, nfds, to); + return poll_select_finish(&end_time, tsp, PT_OLD_TIMESPEC, ret); +} +#endif + +/* New compat syscall for 64 bit time_t*/ +COMPAT_SYSCALL_DEFINE5(ppoll_time64, struct pollfd __user *, ufds, + unsigned int, nfds, struct __kernel_timespec __user *, tsp, + const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize) +{ + struct timespec64 ts, end_time, *to = NULL; + int ret; + + if (tsp) { + if (get_timespec64(&ts, tsp)) + return -EFAULT; + + to = &end_time; + if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) + return -EINVAL; + } + + ret = set_compat_user_sigmask(sigmask, sigsetsize); + if (ret) + return ret; + + ret = do_sys_poll(ufds, nfds, to); + return poll_select_finish(&end_time, tsp, PT_TIMESPEC, ret); +} + +#endif |