// SPDX-License-Identifier: GPL-2.0 /* * Provide access to virtual console memory. * /dev/vcs: the screen as it is being viewed right now (possibly scrolled) * /dev/vcsN: the screen of /dev/ttyN (1 <= N <= 63) * [minor: N] * * /dev/vcsaN: idem, but including attributes, and prefixed with * the 4 bytes lines,columns,x,y (as screendump used to give). * Attribute/character pair is in native endianity. * [minor: N+128] * * /dev/vcsuN: similar to /dev/vcsaN but using 4-byte unicode values * instead of 1-byte screen glyph values. * [minor: N+64] * * /dev/vcsuaN: same idea as /dev/vcsaN for unicode (not yet implemented). * * This replaces screendump and part of selection, so that the system * administrator can control access using file system permissions. * * aeb@cwi.nl - efter Friedas begravelse - 950211 * * machek@k332.feld.cvut.cz - modified not to send characters to wrong console * - fixed some fatal off-by-one bugs (0-- no longer == -1 -> looping and looping and looping...) * - making it shorter - scr_readw are macros which expand in PRETTY long code */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define HEADER_SIZE 4u #define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE) /* * Our minor space: * * 0 ... 63 glyph mode without attributes * 64 ... 127 unicode mode without attributes * 128 ... 191 glyph mode with attributes * 192 ... 255 unused (reserved for unicode with attributes) * * This relies on MAX_NR_CONSOLES being <= 63, meaning 63 actual consoles * with minors 0, 64, 128 and 192 being proxies for the foreground console. */ #if MAX_NR_CONSOLES > 63 #warning "/dev/vcs* devices may not accommodate more than 63 consoles" #endif #define console(inode) (iminor(inode) & 63) #define use_unicode(inode) (iminor(inode) & 64) #define use_attributes(inode) (iminor(inode) & 128) struct vcs_poll_data { struct notifier_block notifier; unsigned int cons_num; int event; wait_queue_head_t waitq; struct fasync_struct *fasync; }; static int vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param) { struct vt_notifier_param *param = _param; struct vc_data *vc = param->vc; struct vcs_poll_data *poll = container_of(nb, struct vcs_poll_data, notifier); int currcons = poll->cons_num; int fa_band; switch (code) { case VT_UPDATE: fa_band = POLL_PRI; break; case VT_DEALLOCATE: fa_band = POLL_HUP; break; default: return NOTIFY_DONE; } if (currcons == 0) currcons = fg_console; else currcons--; if (currcons != vc->vc_num) return NOTIFY_DONE; poll->event = code; wake_up_interruptible(&poll->waitq); kill_fasync(&poll->fasync, SIGIO, fa_band); return NOTIFY_OK; } static void vcs_poll_data_free(struct vcs_poll_data *poll) { unregister_vt_notifier(&poll->notifier); kfree(poll); } static struct vcs_poll_data * vcs_poll_data_get(struct file *file) { struct vcs_poll_data *poll = file->private_data, *kill = NULL; if (poll) return poll; poll = kzalloc(sizeof(*poll), GFP_KERNEL); if (!poll) return NULL; poll->cons_num = console(file_inode(file)); init_waitqueue_head(&poll->waitq); poll->notifier.notifier_call = vcs_notifier; /* * In order not to lose any update event, we must pretend one might * have occurred before we have a chance to register our notifier. * This is also how user space has come to detect which kernels * support POLLPRI on /dev/vcs* devices i.e. using poll() with * POLLPRI and a zero timeout. */ poll->event = VT_UPDATE; if (register_vt_notifier(&poll->notifier) != 0) { kfree(poll); return NULL; } /* * This code may be called either through ->poll() or ->fasync(). * If we have two threads using the same file descriptor, they could * both enter this function, both notice that the structure hasn't * been allocated yet and go ahead allocating it in parallel, but * only one of them must survive and be shared otherwise we'd leak * memory with a dangling notifier callback. */ spin_lock(&file->f_lock); if (!file->private_data) { file->private_data = poll; } else { /* someone else raced ahead of us */ kill = poll; poll = file->private_data; } spin_unlock(&file->f_lock); if (kill) vcs_poll_data_free(kill); return poll; } /** * vcs_vc - return VC for @inode * @inode: inode for which to return a VC * @viewed: returns whether this console is currently foreground (viewed) * * Must be called with console_lock. */ static struct vc_data *vcs_vc(struct inode *inode, bool *viewed) { unsigned int currcons = console(inode); WARN_CONSOLE_UNLOCKED(); if (currcons == 0) { currcons = fg_console; if (viewed) *viewed = true; } else { currcons--; if (viewed) *viewed = false; } return vc_cons[currcons].d; } /** * vcs_size - return size for a VC in @vc * @vc: which VC * @attr: does it use attributes? * @unicode: is it unicode? * * Must be called with console_lock. */ static int vcs_size(const struct vc_data *vc, bool attr, bool unicode) { int size; WARN_CONSOLE_UNLOCKED(); size = vc->vc_rows * vc->vc_cols; if (attr) { if (unicode) return -EOPNOTSUPP; size = 2 * size + HEADER_SIZE; } else if (unicode) size *= 4; return size; } static loff_t vcs_lseek(struct file *file, loff_t offset, int orig) { struct inode *inode = file_inode(file); struct vc_data *vc; int size; console_lock(); vc = vcs_vc(inode, NULL); if (!vc) { console_unlock(); return -ENXIO; } size = vcs_size(vc, use_attributes(inode), use_unicode(inode)); console_unlock(); if (size < 0) return size; return fixed_size_llseek(file, offset, orig, size); } static int vcs_read_buf_uni(struct vc_data *vc, char *con_buf, unsigned int pos, unsigned int count, bool viewed) { unsigned int nr, row, col, maxcol = vc->vc_cols; int ret; ret = vc_uniscr_check(vc); if (ret) return ret; pos /= 4; row = pos / maxcol; col = pos % maxcol; nr = maxcol - col; do { if (nr > count / 4) nr = count / 4; vc_uniscr_copy_line(vc, con_buf, viewed, row, col, nr); con_buf += nr * 4; count -= nr * 4; row++; col = 0; nr = maxcol; } while (count); return 0; } static void vcs_read_buf_noattr(const struct vc_data *vc, char *con_buf, unsigned int pos, unsigned int count, bool viewed) { u16 *org; unsigned int col, maxcol = vc->vc_cols; org = screen_pos(vc, pos, viewed); col = pos % maxcol; pos += maxcol - col; while (count-- > 0) { *con_buf++ = (vcs_scr_readw(vc, org++) & 0xff); if (++col == maxcol) { org = screen_pos(vc, pos, viewed); col = 0; pos += maxcol; } } } static unsigned int vcs_read_buf(const struct vc_data *vc, char *con_buf, unsigned int pos, unsigned int count, bool viewed, unsigned int *skip) { u16 *org, *con_buf16; unsigned int col, maxcol = vc->vc_cols; unsigned int filled = count; if (pos < HEADER_SIZE) { /* clamp header values if they don't fit */ con_buf[0] = min(vc->vc_rows, 0xFFu); con_buf[1] = min(vc->vc_cols, 0xFFu); getconsxy(vc, con_buf + 2); *skip += pos; count += pos; if (count > CON_BUF_SIZE) { count = CON_BUF_SIZE; filled = count - pos; } /* Advance state pointers and move on. */ count -= min(HEADER_SIZE, count); pos = HEADER_SIZE; con_buf += HEADER_SIZE; /* If count >= 0, then pos is even... */ } else if (pos & 1) { /* * Skip first byte for output if start address is odd. Update * region sizes up/down depending on free space in buffer. */ (*skip)++; if (count < CON_BUF_SIZE) count++; else filled--; } if (!count) return filled; pos -= HEADER_SIZE; pos /= 2; col = pos % maxcol; org = screen_pos(vc, pos, viewed); pos += maxcol - col; /* * Buffer has even length, so we can always copy character + attribute. * We do not copy last byte to userspace if count is odd. */ count = (count + 1) / 2; con_buf16 = (u16 *)con_buf; while (count) { *con_buf16++ = vcs_scr_readw(vc, org++); count--; if (++col == maxcol) { org = screen_pos(vc, pos, viewed); col = 0; pos += maxcol; } } return filled; } static ssize_t vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { struct inode *inode = file_inode(file); struct vc_data *vc; struct vcs_poll_data *poll; unsigned int read; ssize_t ret; char *con_buf; loff_t pos; bool viewed, attr, uni_mode; con_buf = (char *) __get_free_page(GFP_KERNEL); if (!con_buf) return -ENOMEM; pos = *ppos; /* Select the proper current console and verify * sanity of the situation under the console lock. */ console_lock(); uni_mode = use_unicode(inode); attr = use_attributes(inode); ret = -EINVAL; if (pos < 0) goto unlock_out; /* we enforce 32-bit alignment for pos and count in unicode mode */ if (uni_mode && (pos | count) & 3) goto unlock_out; poll = file->private_data; if (count && poll) poll->event = 0; read = 0; ret = 0; while (count) { unsigned int this_round, skip = 0; int size; vc = vcs_vc(inode, &viewed); if (!vc) { ret = -ENXIO; break; } /* Check whether we are above size each round, * as copy_to_user at the end of this loop * could sleep. */ size = vcs_size(vc, attr, uni_mode); if (size < 0) { ret = size; break; } if (pos >= size) break; if (count > size - pos) count = size - pos; this_round = count; if (this_round > CON_BUF_SIZE) this_round = CON_BUF_SIZE; /* Perform the whole read into the local con_buf. * Then we can drop the console spinlock and safely * attempt to move it to userspace. */ if (uni_mode) { ret = vcs_read_buf_uni(vc, con_buf, pos, this_round, viewed); if (ret) break; } else if (!attr) { vcs_read_buf_noattr(vc, con_buf, pos, this_round, viewed); } else { this_round = vcs_read_buf(vc, con_buf, pos, this_round, viewed, &skip); } /* Finally, release the console semaphore while we push * all the data to userspace from our temporary buffer. * * AKPM: Even though it's a semaphore, we should drop it because * the pagefault handling code may want to call printk(). */ console_unlock(); ret = copy_to_user(buf, con_buf + skip, this_round); console_lock(); if (ret) { read += this_round - ret; ret = -EFAULT; break; } buf += this_round; pos += this_round; read += this_round; count -= this_round; } *ppos += read; if (read) ret = read; unlock_out: console_unlock(); free_page((unsigned long) con_buf); return ret; } static u16 *vcs_write_buf_noattr(struct vc_data *vc, const char *con_buf, unsigned int pos, unsigned int count, bool viewed, u16 **org0) { u16 *org; unsigned int col, maxcol = vc->vc_cols; *org0 = org = screen_pos(vc, pos, viewed); col = pos % maxcol; pos += maxcol - col; while (count > 0) { unsigned char c = *con_buf++; count--; vcs_scr_writew(vc, (vcs_scr_readw(vc, org) & 0xff00) | c, org); org++; if (++col == maxcol) { org = screen_pos(vc, pos, viewed); col = 0; pos += maxcol; } } return org; } /* * Compilers (gcc 10) are unable to optimize the swap in cpu_to_le16. So do it * the poor man way. */ static inline u16 vc_compile_le16(u8 hi, u8 lo) { #ifdef __BIG_ENDIAN return (lo << 8u) | hi; #else return (hi << 8u) | lo; #endif } static u16 *vcs_write_buf(struct vc_data *vc, const char *con_buf, unsigned int pos, unsigned int count, bool viewed, u16 **org0) { u16 *org; unsigned int col, maxcol = vc->vc_cols; unsigned char c; /* header */ if (pos < HEADER_SIZE) { char header[HEADER_SIZE]; getconsxy(vc, header + 2); while (pos < HEADER_SIZE && count > 0) { count--; header[pos++] = *con_buf++; } if (!viewed) putconsxy(vc, header + 2); } if (!count) return NULL; pos -= HEADER_SIZE; col = (pos/2) % maxcol; *org0 = org = screen_pos(vc, pos/2, viewed); /* odd pos -- the first single character */ if (pos & 1) { count--; c = *con_buf++; vcs_scr_writew(vc, vc_compile_le16(c, vcs_scr_readw(vc, org)), org); org++; pos++; if (++col == maxcol) { org = screen_pos(vc, pos/2, viewed); col = 0; } } pos /= 2; pos += maxcol - col; /* even pos -- handle attr+character pairs */ while (count > 1) { unsigned short w; w = get_unaligned(((unsigned short *)con_buf)); vcs_scr_writew(vc, w, org++); con_buf += 2; count -= 2; if (++col == maxcol) { org = screen_pos(vc, pos, viewed); col = 0; pos += maxcol; } } if (!count) return org; /* odd pos -- the remaining character */ c = *con_buf++; vcs_scr_writew(vc, vc_compile_le16(vcs_scr_readw(vc, org) >> 8, c), org); return org; } static ssize_t vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { struct inode *inode = file_inode(file); struct vc_data *vc; char *con_buf; u16 *org0, *org; unsigned int written; int size; ssize_t ret; loff_t pos; bool viewed, attr; if (use_unicode(inode)) return -EOPNOTSUPP; con_buf = (char *) __get_free_page(GFP_KERNEL); if (!con_buf) return -ENOMEM; pos = *ppos; /* Select the proper current console and verify * sanity of the situation under the console lock. */ console_lock(); attr = use_attributes(inode); ret = -ENXIO; vc = vcs_vc(inode, &viewed); if (!vc) goto unlock_out; size = vcs_size(vc, attr, false); if (size < 0) { ret = size; goto unlock_out; } ret = -EINVAL; if (pos < 0 || pos > size) goto unlock_out; if (count > size - pos) count = size - pos; written = 0; while (count) { unsigned int this_round = count; if (this_round > CON_BUF_SIZE) this_round = CON_BUF_SIZE; /* Temporarily drop the console lock so that we can read * in the write data from userspace safely. */ console_unlock(); ret = copy_from_user(con_buf, buf, this_round); console_lock(); if (ret) { this_round -= ret; if (!this_round) { /* Abort loop if no data were copied. Otherwise * fail with -EFAULT. */ if (written) break; ret = -EFAULT; goto unlock_out; } } /* The vc might have been freed or vcs_size might have changed * while we slept to grab the user buffer, so recheck. * Return data written up to now on failure. */ vc = vcs_vc(inode, &viewed); if (!vc) { if (written) break; ret = -ENXIO; goto unlock_out; } size = vcs_size(vc, attr, false); if (size < 0) { if (written) break; ret = size; goto unlock_out; } if (pos >= size) break; if (this_round > size - pos) this_round = size - pos; /* OK, now actually push the write to the console * under the lock using the local kernel buffer. */ if (attr) org = vcs_write_buf(vc, con_buf, pos, this_round, viewed, &org0); else org = vcs_write_buf_noattr(vc, con_buf, pos, this_round, viewed, &org0); count -= this_round; written += this_round; buf += this_round; pos += this_round; if (org) update_region(vc, (unsigned long)(org0), org - org0); } *ppos += written; ret = written; if (written) vcs_scr_updated(vc); unlock_out: console_unlock(); free_page((unsigned long) con_buf); return ret; } static __poll_t vcs_poll(struct file *file, poll_table *wait) { struct vcs_poll_data *poll = vcs_poll_data_get(file); __poll_t ret = DEFAULT_POLLMASK|EPOLLERR; if (poll) { poll_wait(file, &poll->waitq, wait); switch (poll->event) { case VT_UPDATE: ret = DEFAULT_POLLMASK|EPOLLPRI; break; case VT_DEALLOCATE: ret = DEFAULT_POLLMASK|EPOLLHUP|EPOLLERR; break; case 0: ret = DEFAULT_POLLMASK; break; } } return ret; } static int vcs_fasync(int fd, struct file *file, int on) { struct vcs_poll_data *poll = file->private_data; if (!poll) { /* don't allocate anything if all we want is disable fasync */ if (!on) return 0; poll = vcs_poll_data_get(file); if (!poll) return -ENOMEM; } return fasync_helper(fd, file, on, &poll->fasync); } static int vcs_open(struct inode *inode, struct file *filp) { unsigned int currcons = console(inode); bool attr = use_attributes(inode); bool uni_mode = use_unicode(inode); int ret = 0; /* we currently don't support attributes in unicode mode */ if (attr && uni_mode) return -EOPNOTSUPP; console_lock(); if(currcons && !vc_cons_allocated(currcons-1)) ret = -ENXIO; console_unlock(); return ret; } static int vcs_release(struct inode *inode, struct file *file) { struct vcs_poll_data *poll = file->private_data; if (poll) vcs_poll_data_free(poll); return 0; } static const struct file_operations vcs_fops = { .llseek = vcs_lseek, .read = vcs_read, .write = vcs_write, .poll = vcs_poll, .fasync = vcs_fasync, .open = vcs_open, .release = vcs_release, }; static const struct class vc_class = { .name = "vc", }; void vcs_make_sysfs(int index) { device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, index + 1), NULL, "vcs%u", index + 1); device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, index + 65), NULL, "vcsu%u", index + 1); device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, index + 129), NULL, "vcsa%u", index + 1); } void vcs_remove_sysfs(int index) { device_destroy(&vc_class, MKDEV(VCS_MAJOR, index + 1)); device_destroy(&vc_class, MKDEV(VCS_MAJOR, index + 65)); device_destroy(&vc_class, MKDEV(VCS_MAJOR, index + 129)); } int __init vcs_init(void) { unsigned int i; if (register_chrdev(VCS_MAJOR, "vcs", &vcs_fops)) panic("unable to get major %d for vcs device", VCS_MAJOR); if (class_register(&vc_class)) panic("unable to create vc_class"); device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, 0), NULL, "vcs"); device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, 64), NULL, "vcsu"); device_create(&vc_class, NULL, MKDEV(VCS_MAJOR, 128), NULL, "vcsa"); for (i = 0; i < MIN_NR_CONSOLES; i++) vcs_make_sysfs(i); return 0; }