/* * 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/syscalls.h> #include <linux/module.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 <asm/uaccess.h> struct poll_table_page { struct poll_table_page * next; struct poll_table_entry * entry; struct poll_table_entry entries[0]; }; #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->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(poll_table *_p) { struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt); 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; __set_current_state(TASK_RUNNING); return NULL; } new_table->entry = new_table->entries; new_table->next = table; p->table = new_table; table = new_table; } return table->entry++; } /* Add a new entry */ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, poll_table *p) { struct poll_table_entry *entry = poll_get_entry(p); if (!entry) return; get_file(filp); entry->filp = filp; entry->wait_address = wait_address; init_waitqueue_entry(&entry->wait, current); add_wait_queue(wait_address, &entry->wait); } #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 & (__NFDBITS-1))); n /= __NFDBITS; fdt = files_fdtable(current->files); open_fds = fdt->open_fds->fds_bits+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 * __NFDBITS; } return max; } #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR) #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR) #define POLLEX_SET (POLLPRI) int do_select(int n, fd_set_bits *fds, s64 *timeout) { struct poll_wqueues table; poll_table *wait; int retval, i; 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 (!*timeout) wait = NULL; retval = 0; for (;;) { unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp; long __timeout; set_current_state(TASK_INTERRUPTIBLE); 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, mask, j; unsigned long res_in = 0, res_out = 0, res_ex = 0; const struct file_operations *f_op = NULL; struct file *file = NULL; in = *inp++; out = *outp++; ex = *exp++; all_bits = in | out | ex; if (all_bits == 0) { i += __NFDBITS; continue; } for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) { int fput_needed; if (i >= n) break; if (!(bit & all_bits)) continue; file = fget_light(i, &fput_needed); if (file) { f_op = file->f_op; mask = DEFAULT_POLLMASK; if (f_op && f_op->poll) mask = (*f_op->poll)(file, retval ? NULL : wait); fput_light(file, fput_needed); if ((mask & POLLIN_SET) && (in & bit)) { res_in |= bit; retval++; } if ((mask & POLLOUT_SET) && (out & bit)) { res_out |= bit; retval++; } if ((mask & POLLEX_SET) && (ex & bit)) { res_ex |= bit; retval++; } } cond_resched(); } if (res_in) *rinp = res_in; if (res_out) *routp = res_out; if (res_ex) *rexp = res_ex; } wait = NULL; if (retval || !*timeout || signal_pending(current)) break; if (table.error) { retval = table.error; break; } if (*timeout < 0) { /* Wait indefinitely */ __timeout = MAX_SCHEDULE_TIMEOUT; } else if (unlikely(*timeout >= (s64)MAX_SCHEDULE_TIMEOUT - 1)) { /* Wait for longer than MAX_SCHEDULE_TIMEOUT. Do it in a loop */ __timeout = MAX_SCHEDULE_TIMEOUT - 1; *timeout -= __timeout; } else { __timeout = *timeout; *timeout = 0; } __timeout = schedule_timeout(__timeout); if (*timeout >= 0) *timeout += __timeout; } __set_current_state(TASK_RUNNING); 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. */ #define MAX_SELECT_SECONDS \ ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1) int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, s64 *timeout) { fd_set_bits fds; void *bits; int ret, max_fds; unsigned int 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; bits = kmalloc(6 * 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, timeout); 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) kfree(bits); out_nofds: return ret; } asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct timeval __user *tvp) { s64 timeout = -1; struct timeval tv; int ret; if (tvp) { if (copy_from_user(&tv, tvp, sizeof(tv))) return -EFAULT; if (tv.tv_sec < 0 || tv.tv_usec < 0) return -EINVAL; /* Cast to u64 to make GCC stop complaining */ if ((u64)tv.tv_sec >= (u64)MAX_INT64_SECONDS) timeout = -1; /* infinite */ else { timeout = DIV_ROUND_UP(tv.tv_usec, USEC_PER_SEC/HZ); timeout += tv.tv_sec * HZ; } } ret = core_sys_select(n, inp, outp, exp, &timeout); if (tvp) { struct timeval rtv; if (current->personality & STICKY_TIMEOUTS) goto sticky; rtv.tv_usec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)); rtv.tv_sec = timeout; if (timeval_compare(&rtv, &tv) >= 0) rtv = tv; if (copy_to_user(tvp, &rtv, sizeof(rtv))) { sticky: /* * 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. */ if (ret == -ERESTARTNOHAND) ret = -EINTR; } } return ret; } #ifdef HAVE_SET_RESTORE_SIGMASK asmlinkage long sys_pselect7(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct timespec __user *tsp, const sigset_t __user *sigmask, size_t sigsetsize) { s64 timeout = MAX_SCHEDULE_TIMEOUT; sigset_t ksigmask, sigsaved; struct timespec ts; int ret; if (tsp) { if (copy_from_user(&ts, tsp, sizeof(ts))) return -EFAULT; if (ts.tv_sec < 0 || ts.tv_nsec < 0) return -EINVAL; /* Cast to u64 to make GCC stop complaining */ if ((u64)ts.tv_sec >= (u64)MAX_INT64_SECONDS) timeout = -1; /* infinite */ else { timeout = DIV_ROUND_UP(ts.tv_nsec, NSEC_PER_SEC/HZ); timeout += ts.tv_sec * HZ; } } if (sigmask) { /* XXX: Don't preclude handling different sized sigset_t's. */ if (sigsetsize != sizeof(sigset_t)) return -EINVAL; if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) return -EFAULT; sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); } ret = core_sys_select(n, inp, outp, exp, &timeout); if (tsp) { struct timespec rts; if (current->personality & STICKY_TIMEOUTS) goto sticky; rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) * 1000; rts.tv_sec = timeout; if (timespec_compare(&rts, &ts) >= 0) rts = ts; if (copy_to_user(tsp, &rts, sizeof(rts))) { sticky: /* * 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. */ if (ret == -ERESTARTNOHAND) ret = -EINTR; } } if (ret == -ERESTARTNOHAND) { /* * Don't restore the signal mask yet. Let do_signal() deliver * the signal on the way back to userspace, before the signal * mask is restored. */ if (sigmask) { memcpy(¤t->saved_sigmask, &sigsaved, sizeof(sigsaved)); set_restore_sigmask(); } } else if (sigmask) sigprocmask(SIG_SETMASK, &sigsaved, NULL); return 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. */ asmlinkage long sys_pselect6(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct timespec __user *tsp, void __user *sig) { size_t sigsetsize = 0; sigset_t __user *up = NULL; if (sig) { if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t)) || __get_user(up, (sigset_t __user * __user *)sig) || __get_user(sigsetsize, (size_t __user *)(sig+sizeof(void *)))) return -EFAULT; } return sys_pselect7(n, inp, outp, exp, tsp, up, sigsetsize); } #endif /* HAVE_SET_RESTORE_SIGMASK */ struct poll_list { struct poll_list *next; int len; struct pollfd entries[0]; }; #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 non-NULL. */ static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait) { unsigned int mask; int fd; mask = 0; fd = pollfd->fd; if (fd >= 0) { int fput_needed; struct file * file; file = fget_light(fd, &fput_needed); mask = POLLNVAL; if (file != NULL) { mask = DEFAULT_POLLMASK; if (file->f_op && file->f_op->poll) mask = file->f_op->poll(file, pwait); /* Mask out unneeded events. */ mask &= pollfd->events | POLLERR | POLLHUP; fput_light(file, fput_needed); } } pollfd->revents = mask; return mask; } static int do_poll(unsigned int nfds, struct poll_list *list, struct poll_wqueues *wait, s64 *timeout) { int count = 0; poll_table* pt = &wait->pt; /* Optimise the no-wait case */ if (!(*timeout)) pt = NULL; for (;;) { struct poll_list *walk; long __timeout; set_current_state(TASK_INTERRUPTIBLE); 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 the poll_table, 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)) { count++; pt = NULL; } } } /* * All waiters have already been registered, so don't provide * a poll_table to them on the next loop iteration. */ pt = NULL; if (!count) { count = wait->error; if (signal_pending(current)) count = -EINTR; } if (count || !*timeout) break; if (*timeout < 0) { /* Wait indefinitely */ __timeout = MAX_SCHEDULE_TIMEOUT; } else if (unlikely(*timeout >= (s64)MAX_SCHEDULE_TIMEOUT-1)) { /* * Wait for longer than MAX_SCHEDULE_TIMEOUT. Do it in * a loop */ __timeout = MAX_SCHEDULE_TIMEOUT - 1; *timeout -= __timeout; } else { __timeout = *timeout; *timeout = 0; } __timeout = schedule_timeout(__timeout); if (*timeout >= 0) *timeout += __timeout; } __set_current_state(TASK_RUNNING); return count; } #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ sizeof(struct pollfd)) int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout) { struct poll_wqueues table; int err = -EFAULT, fdcount, len, size; /* 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 > current->signal->rlim[RLIMIT_NOFILE].rlim_cur) 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); size = sizeof(struct poll_list) + sizeof(struct pollfd) * len; walk = walk->next = kmalloc(size, GFP_KERNEL); if (!walk) { err = -ENOMEM; goto out_fds; } } poll_initwait(&table); fdcount = do_poll(nfds, head, &table, timeout); poll_freewait(&table); for (walk = head; walk; walk = walk->next) { struct pollfd *fds = walk->entries; int j; for (j = 0; j < walk->len; j++, ufds++) if (__put_user(fds[j].revents, &ufds->revents)) goto out_fds; } err = fdcount; out_fds: walk = head->next; while (walk) { struct poll_list *pos = walk; walk = walk->next; kfree(pos); } return err; } static long do_restart_poll(struct restart_block *restart_block) { struct pollfd __user *ufds = (struct pollfd __user*)restart_block->arg0; int nfds = restart_block->arg1; s64 timeout = ((s64)restart_block->arg3<<32) | (s64)restart_block->arg2; int ret; ret = do_sys_poll(ufds, nfds, &timeout); if (ret == -EINTR) { restart_block->fn = do_restart_poll; restart_block->arg2 = timeout & 0xFFFFFFFF; restart_block->arg3 = (u64)timeout >> 32; ret = -ERESTART_RESTARTBLOCK; } return ret; } asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds, long timeout_msecs) { s64 timeout_jiffies; int ret; if (timeout_msecs > 0) { #if HZ > 1000 /* We can only overflow if HZ > 1000 */ if (timeout_msecs / 1000 > (s64)0x7fffffffffffffffULL / (s64)HZ) timeout_jiffies = -1; else #endif timeout_jiffies = msecs_to_jiffies(timeout_msecs) + 1; } else { /* Infinite (< 0) or no (0) timeout */ timeout_jiffies = timeout_msecs; } ret = do_sys_poll(ufds, nfds, &timeout_jiffies); if (ret == -EINTR) { struct restart_block *restart_block; restart_block = ¤t_thread_info()->restart_block; restart_block->fn = do_restart_poll; restart_block->arg0 = (unsigned long)ufds; restart_block->arg1 = nfds; restart_block->arg2 = timeout_jiffies & 0xFFFFFFFF; restart_block->arg3 = (u64)timeout_jiffies >> 32; ret = -ERESTART_RESTARTBLOCK; } return ret; } #ifdef HAVE_SET_RESTORE_SIGMASK asmlinkage long sys_ppoll(struct pollfd __user *ufds, unsigned int nfds, struct timespec __user *tsp, const sigset_t __user *sigmask, size_t sigsetsize) { sigset_t ksigmask, sigsaved; struct timespec ts; s64 timeout = -1; int ret; if (tsp) { if (copy_from_user(&ts, tsp, sizeof(ts))) return -EFAULT; /* Cast to u64 to make GCC stop complaining */ if ((u64)ts.tv_sec >= (u64)MAX_INT64_SECONDS) timeout = -1; /* infinite */ else { timeout = DIV_ROUND_UP(ts.tv_nsec, NSEC_PER_SEC/HZ); timeout += ts.tv_sec * HZ; } } if (sigmask) { /* XXX: Don't preclude handling different sized sigset_t's. */ if (sigsetsize != sizeof(sigset_t)) return -EINVAL; if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) return -EFAULT; sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); } ret = do_sys_poll(ufds, nfds, &timeout); /* We can restart this syscall, usually */ if (ret == -EINTR) { /* * Don't restore the signal mask yet. Let do_signal() deliver * the signal on the way back to userspace, before the signal * mask is restored. */ if (sigmask) { memcpy(¤t->saved_sigmask, &sigsaved, sizeof(sigsaved)); set_restore_sigmask(); } ret = -ERESTARTNOHAND; } else if (sigmask) sigprocmask(SIG_SETMASK, &sigsaved, NULL); if (tsp && timeout >= 0) { struct timespec rts; if (current->personality & STICKY_TIMEOUTS) goto sticky; /* Yes, we know it's actually an s64, but it's also positive. */ rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) * 1000; rts.tv_sec = timeout; if (timespec_compare(&rts, &ts) >= 0) rts = ts; if (copy_to_user(tsp, &rts, sizeof(rts))) { sticky: /* * 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. */ if (ret == -ERESTARTNOHAND && timeout >= 0) ret = -EINTR; } } return ret; } #endif /* HAVE_SET_RESTORE_SIGMASK */