| /* |
| * Tty buffer allocation management |
| */ |
| |
| #include <linux/types.h> |
| #include <linux/errno.h> |
| #include <linux/tty.h> |
| #include <linux/tty_driver.h> |
| #include <linux/tty_flip.h> |
| #include <linux/timer.h> |
| #include <linux/string.h> |
| #include <linux/slab.h> |
| #include <linux/sched.h> |
| #include <linux/init.h> |
| #include <linux/wait.h> |
| #include <linux/bitops.h> |
| #include <linux/delay.h> |
| #include <linux/module.h> |
| #include <linux/ratelimit.h> |
| |
| #define TTY_MAX_BUF 131072 |
| /** |
| * tty_buffer_free_all - free buffers used by a tty |
| * @tty: tty to free from |
| * |
| * Remove all the buffers pending on a tty whether queued with data |
| * or in the free ring. Must be called when the tty is no longer in use |
| * |
| * Locking: none |
| */ |
| |
| void tty_buffer_free_all(struct tty_port *port) |
| { |
| struct tty_bufhead *buf = &port->buf; |
| struct tty_buffer *thead; |
| |
| while ((thead = buf->head) != NULL) { |
| buf->head = thead->next; |
| kfree(thead); |
| } |
| while ((thead = buf->free) != NULL) { |
| buf->free = thead->next; |
| kfree(thead); |
| } |
| buf->tail = NULL; |
| buf->memory_used = 0; |
| } |
| |
| /** |
| * tty_buffer_alloc - allocate a tty buffer |
| * @tty: tty device |
| * @size: desired size (characters) |
| * |
| * Allocate a new tty buffer to hold the desired number of characters. |
| * Return NULL if out of memory or the allocation would exceed the |
| * per device queue |
| * |
| * Locking: Caller must hold tty->buf.lock |
| */ |
| |
| static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) |
| { |
| struct tty_buffer *p; |
| |
| if (port->buf.memory_used + size > TTY_MAX_BUF) |
| return NULL; |
| p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); |
| if (p == NULL) |
| return NULL; |
| p->used = 0; |
| p->size = size; |
| p->next = NULL; |
| p->commit = 0; |
| p->read = 0; |
| p->char_buf_ptr = (char *)(p->data); |
| p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size; |
| port->buf.memory_used += size; |
| return p; |
| } |
| |
| /** |
| * tty_buffer_free - free a tty buffer |
| * @tty: tty owning the buffer |
| * @b: the buffer to free |
| * |
| * Free a tty buffer, or add it to the free list according to our |
| * internal strategy |
| * |
| * Locking: Caller must hold tty->buf.lock |
| */ |
| |
| static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b) |
| { |
| struct tty_bufhead *buf = &port->buf; |
| |
| /* Dumb strategy for now - should keep some stats */ |
| buf->memory_used -= b->size; |
| WARN_ON(buf->memory_used < 0); |
| |
| if (b->size >= 512) |
| kfree(b); |
| else { |
| b->next = buf->free; |
| buf->free = b; |
| } |
| } |
| |
| /** |
| * __tty_buffer_flush - flush full tty buffers |
| * @tty: tty to flush |
| * |
| * flush all the buffers containing receive data. Caller must |
| * hold the buffer lock and must have ensured no parallel flush to |
| * ldisc is running. |
| * |
| * Locking: Caller must hold tty->buf.lock |
| */ |
| |
| static void __tty_buffer_flush(struct tty_port *port) |
| { |
| struct tty_bufhead *buf = &port->buf; |
| struct tty_buffer *thead; |
| |
| if (unlikely(buf->head == NULL)) |
| return; |
| while ((thead = buf->head->next) != NULL) { |
| tty_buffer_free(port, buf->head); |
| buf->head = thead; |
| } |
| WARN_ON(buf->head != buf->tail); |
| buf->head->read = buf->head->commit; |
| } |
| |
| /** |
| * tty_buffer_flush - flush full tty buffers |
| * @tty: tty to flush |
| * |
| * flush all the buffers containing receive data. If the buffer is |
| * being processed by flush_to_ldisc then we defer the processing |
| * to that function |
| * |
| * Locking: none |
| */ |
| |
| void tty_buffer_flush(struct tty_struct *tty) |
| { |
| struct tty_port *port = tty->port; |
| struct tty_bufhead *buf = &port->buf; |
| unsigned long flags; |
| |
| spin_lock_irqsave(&buf->lock, flags); |
| |
| /* If the data is being pushed to the tty layer then we can't |
| process it here. Instead set a flag and the flush_to_ldisc |
| path will process the flush request before it exits */ |
| if (test_bit(TTYP_FLUSHING, &port->iflags)) { |
| set_bit(TTYP_FLUSHPENDING, &port->iflags); |
| spin_unlock_irqrestore(&buf->lock, flags); |
| wait_event(tty->read_wait, |
| test_bit(TTYP_FLUSHPENDING, &port->iflags) == 0); |
| return; |
| } else |
| __tty_buffer_flush(port); |
| spin_unlock_irqrestore(&buf->lock, flags); |
| } |
| |
| /** |
| * tty_buffer_find - find a free tty buffer |
| * @tty: tty owning the buffer |
| * @size: characters wanted |
| * |
| * Locate an existing suitable tty buffer or if we are lacking one then |
| * allocate a new one. We round our buffers off in 256 character chunks |
| * to get better allocation behaviour. |
| * |
| * Locking: Caller must hold tty->buf.lock |
| */ |
| |
| static struct tty_buffer *tty_buffer_find(struct tty_port *port, size_t size) |
| { |
| struct tty_buffer **tbh = &port->buf.free; |
| while ((*tbh) != NULL) { |
| struct tty_buffer *t = *tbh; |
| if (t->size >= size) { |
| *tbh = t->next; |
| t->next = NULL; |
| t->used = 0; |
| t->commit = 0; |
| t->read = 0; |
| port->buf.memory_used += t->size; |
| return t; |
| } |
| tbh = &((*tbh)->next); |
| } |
| /* Round the buffer size out */ |
| size = (size + 0xFF) & ~0xFF; |
| return tty_buffer_alloc(port, size); |
| /* Should possibly check if this fails for the largest buffer we |
| have queued and recycle that ? */ |
| } |
| /** |
| * tty_buffer_request_room - grow tty buffer if needed |
| * @tty: tty structure |
| * @size: size desired |
| * |
| * Make at least size bytes of linear space available for the tty |
| * buffer. If we fail return the size we managed to find. |
| * |
| * Locking: Takes port->buf.lock |
| */ |
| int tty_buffer_request_room(struct tty_port *port, size_t size) |
| { |
| struct tty_bufhead *buf = &port->buf; |
| struct tty_buffer *b, *n; |
| int left; |
| unsigned long flags; |
| spin_lock_irqsave(&buf->lock, flags); |
| /* OPTIMISATION: We could keep a per tty "zero" sized buffer to |
| remove this conditional if its worth it. This would be invisible |
| to the callers */ |
| b = buf->tail; |
| if (b != NULL) |
| left = b->size - b->used; |
| else |
| left = 0; |
| |
| if (left < size) { |
| /* This is the slow path - looking for new buffers to use */ |
| if ((n = tty_buffer_find(port, size)) != NULL) { |
| if (b != NULL) { |
| b->next = n; |
| b->commit = b->used; |
| } else |
| buf->head = n; |
| buf->tail = n; |
| } else |
| size = left; |
| } |
| spin_unlock_irqrestore(&buf->lock, flags); |
| return size; |
| } |
| EXPORT_SYMBOL_GPL(tty_buffer_request_room); |
| |
| /** |
| * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer |
| * @port: tty port |
| * @chars: characters |
| * @flag: flag value for each character |
| * @size: size |
| * |
| * Queue a series of bytes to the tty buffering. All the characters |
| * passed are marked with the supplied flag. Returns the number added. |
| * |
| * Locking: Called functions may take port->buf.lock |
| */ |
| |
| int tty_insert_flip_string_fixed_flag(struct tty_port *port, |
| const unsigned char *chars, char flag, size_t size) |
| { |
| int copied = 0; |
| do { |
| int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
| int space = tty_buffer_request_room(port, goal); |
| struct tty_buffer *tb = port->buf.tail; |
| /* If there is no space then tb may be NULL */ |
| if (unlikely(space == 0)) { |
| break; |
| } |
| memcpy(tb->char_buf_ptr + tb->used, chars, space); |
| memset(tb->flag_buf_ptr + tb->used, flag, space); |
| tb->used += space; |
| copied += space; |
| chars += space; |
| /* There is a small chance that we need to split the data over |
| several buffers. If this is the case we must loop */ |
| } while (unlikely(size > copied)); |
| return copied; |
| } |
| EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag); |
| |
| /** |
| * tty_insert_flip_string_flags - Add characters to the tty buffer |
| * @port: tty port |
| * @chars: characters |
| * @flags: flag bytes |
| * @size: size |
| * |
| * Queue a series of bytes to the tty buffering. For each character |
| * the flags array indicates the status of the character. Returns the |
| * number added. |
| * |
| * Locking: Called functions may take port->buf.lock |
| */ |
| |
| int tty_insert_flip_string_flags(struct tty_port *port, |
| const unsigned char *chars, const char *flags, size_t size) |
| { |
| int copied = 0; |
| do { |
| int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
| int space = tty_buffer_request_room(port, goal); |
| struct tty_buffer *tb = port->buf.tail; |
| /* If there is no space then tb may be NULL */ |
| if (unlikely(space == 0)) { |
| break; |
| } |
| memcpy(tb->char_buf_ptr + tb->used, chars, space); |
| memcpy(tb->flag_buf_ptr + tb->used, flags, space); |
| tb->used += space; |
| copied += space; |
| chars += space; |
| flags += space; |
| /* There is a small chance that we need to split the data over |
| several buffers. If this is the case we must loop */ |
| } while (unlikely(size > copied)); |
| return copied; |
| } |
| EXPORT_SYMBOL(tty_insert_flip_string_flags); |
| |
| /** |
| * tty_schedule_flip - push characters to ldisc |
| * @port: tty port to push from |
| * |
| * Takes any pending buffers and transfers their ownership to the |
| * ldisc side of the queue. It then schedules those characters for |
| * processing by the line discipline. |
| * Note that this function can only be used when the low_latency flag |
| * is unset. Otherwise the workqueue won't be flushed. |
| * |
| * Locking: Takes port->buf.lock |
| */ |
| |
| void tty_schedule_flip(struct tty_port *port) |
| { |
| struct tty_bufhead *buf = &port->buf; |
| unsigned long flags; |
| WARN_ON(port->low_latency); |
| |
| spin_lock_irqsave(&buf->lock, flags); |
| if (buf->tail != NULL) |
| buf->tail->commit = buf->tail->used; |
| spin_unlock_irqrestore(&buf->lock, flags); |
| schedule_work(&buf->work); |
| } |
| EXPORT_SYMBOL(tty_schedule_flip); |
| |
| /** |
| * tty_prepare_flip_string - make room for characters |
| * @port: tty port |
| * @chars: return pointer for character write area |
| * @size: desired size |
| * |
| * Prepare a block of space in the buffer for data. Returns the length |
| * available and buffer pointer to the space which is now allocated and |
| * accounted for as ready for normal characters. This is used for drivers |
| * that need their own block copy routines into the buffer. There is no |
| * guarantee the buffer is a DMA target! |
| * |
| * Locking: May call functions taking port->buf.lock |
| */ |
| |
| int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars, |
| size_t size) |
| { |
| int space = tty_buffer_request_room(port, size); |
| if (likely(space)) { |
| struct tty_buffer *tb = port->buf.tail; |
| *chars = tb->char_buf_ptr + tb->used; |
| memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space); |
| tb->used += space; |
| } |
| return space; |
| } |
| EXPORT_SYMBOL_GPL(tty_prepare_flip_string); |
| |
| /** |
| * tty_prepare_flip_string_flags - make room for characters |
| * @port: tty port |
| * @chars: return pointer for character write area |
| * @flags: return pointer for status flag write area |
| * @size: desired size |
| * |
| * Prepare a block of space in the buffer for data. Returns the length |
| * available and buffer pointer to the space which is now allocated and |
| * accounted for as ready for characters. This is used for drivers |
| * that need their own block copy routines into the buffer. There is no |
| * guarantee the buffer is a DMA target! |
| * |
| * Locking: May call functions taking port->buf.lock |
| */ |
| |
| int tty_prepare_flip_string_flags(struct tty_port *port, |
| unsigned char **chars, char **flags, size_t size) |
| { |
| int space = tty_buffer_request_room(port, size); |
| if (likely(space)) { |
| struct tty_buffer *tb = port->buf.tail; |
| *chars = tb->char_buf_ptr + tb->used; |
| *flags = tb->flag_buf_ptr + tb->used; |
| tb->used += space; |
| } |
| return space; |
| } |
| EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags); |
| |
| |
| |
| /** |
| * flush_to_ldisc |
| * @work: tty structure passed from work queue. |
| * |
| * This routine is called out of the software interrupt to flush data |
| * from the buffer chain to the line discipline. |
| * |
| * Locking: holds tty->buf.lock to guard buffer list. Drops the lock |
| * while invoking the line discipline receive_buf method. The |
| * receive_buf method is single threaded for each tty instance. |
| */ |
| |
| static void flush_to_ldisc(struct work_struct *work) |
| { |
| struct tty_port *port = container_of(work, struct tty_port, buf.work); |
| struct tty_bufhead *buf = &port->buf; |
| struct tty_struct *tty; |
| unsigned long flags; |
| struct tty_ldisc *disc; |
| |
| tty = port->itty; |
| if (tty == NULL) |
| return; |
| |
| disc = tty_ldisc_ref(tty); |
| if (disc == NULL) |
| return; |
| |
| spin_lock_irqsave(&buf->lock, flags); |
| |
| if (!test_and_set_bit(TTYP_FLUSHING, &port->iflags)) { |
| struct tty_buffer *head; |
| while ((head = buf->head) != NULL) { |
| int count; |
| char *char_buf; |
| unsigned char *flag_buf; |
| |
| count = head->commit - head->read; |
| if (!count) { |
| if (head->next == NULL) |
| break; |
| buf->head = head->next; |
| tty_buffer_free(port, head); |
| continue; |
| } |
| if (!tty->receive_room) |
| break; |
| if (count > tty->receive_room) |
| count = tty->receive_room; |
| char_buf = head->char_buf_ptr + head->read; |
| flag_buf = head->flag_buf_ptr + head->read; |
| head->read += count; |
| spin_unlock_irqrestore(&buf->lock, flags); |
| disc->ops->receive_buf(tty, char_buf, |
| flag_buf, count); |
| spin_lock_irqsave(&buf->lock, flags); |
| /* Ldisc or user is trying to flush the buffers. |
| We may have a deferred request to flush the |
| input buffer, if so pull the chain under the lock |
| and empty the queue */ |
| if (test_bit(TTYP_FLUSHPENDING, &port->iflags)) { |
| __tty_buffer_flush(port); |
| clear_bit(TTYP_FLUSHPENDING, &port->iflags); |
| wake_up(&tty->read_wait); |
| break; |
| } |
| } |
| clear_bit(TTYP_FLUSHING, &port->iflags); |
| } |
| |
| spin_unlock_irqrestore(&buf->lock, flags); |
| |
| tty_ldisc_deref(disc); |
| } |
| |
| /** |
| * tty_flush_to_ldisc |
| * @tty: tty to push |
| * |
| * Push the terminal flip buffers to the line discipline. |
| * |
| * Must not be called from IRQ context. |
| */ |
| void tty_flush_to_ldisc(struct tty_struct *tty) |
| { |
| if (!tty->port->low_latency) |
| flush_work(&tty->port->buf.work); |
| } |
| |
| /** |
| * tty_flip_buffer_push - terminal |
| * @port: tty port to push |
| * |
| * Queue a push of the terminal flip buffers to the line discipline. This |
| * function must not be called from IRQ context if port->low_latency is |
| * set. |
| * |
| * In the event of the queue being busy for flipping the work will be |
| * held off and retried later. |
| * |
| * Locking: tty buffer lock. Driver locks in low latency mode. |
| */ |
| |
| void tty_flip_buffer_push(struct tty_port *port) |
| { |
| struct tty_bufhead *buf = &port->buf; |
| unsigned long flags; |
| |
| spin_lock_irqsave(&buf->lock, flags); |
| if (buf->tail != NULL) |
| buf->tail->commit = buf->tail->used; |
| spin_unlock_irqrestore(&buf->lock, flags); |
| |
| if (port->low_latency) |
| flush_to_ldisc(&buf->work); |
| else |
| schedule_work(&buf->work); |
| } |
| EXPORT_SYMBOL(tty_flip_buffer_push); |
| |
| /** |
| * tty_buffer_init - prepare a tty buffer structure |
| * @tty: tty to initialise |
| * |
| * Set up the initial state of the buffer management for a tty device. |
| * Must be called before the other tty buffer functions are used. |
| * |
| * Locking: none |
| */ |
| |
| void tty_buffer_init(struct tty_port *port) |
| { |
| struct tty_bufhead *buf = &port->buf; |
| |
| spin_lock_init(&buf->lock); |
| buf->head = NULL; |
| buf->tail = NULL; |
| buf->free = NULL; |
| buf->memory_used = 0; |
| INIT_WORK(&buf->work, flush_to_ldisc); |
| } |
| |