n_tty: Use separate head and tail indices for echo_buf
Instead of using a single index to track the current echo_buf position, use a head index when adding to the buffer and a tail index when consuming from the buffer. Allow these head and tail indices to wrap at max representable value; perform modulo reduction via helper functions when accessing the buffer. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley
Greg Kroah-Hartman
Родитель
ae56f33041
Коммит
addaebccf6
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@ -108,7 +108,8 @@ struct n_tty_data {
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/* protected by echo_lock */
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unsigned char *echo_buf;
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unsigned int echo_pos;
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size_t echo_head;
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size_t echo_tail;
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unsigned int echo_cnt;
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/* protected by output lock */
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@ -135,6 +136,16 @@ static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
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return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
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}
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static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
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{
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return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
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}
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static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
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{
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return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
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}
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static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
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unsigned char __user *ptr)
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{
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@ -325,7 +336,7 @@ static void reset_buffer_flags(struct n_tty_data *ldata)
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ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
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mutex_lock(&ldata->echo_lock);
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ldata->echo_pos = ldata->echo_cnt = 0;
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ldata->echo_head = ldata->echo_tail = ldata->echo_cnt = 0;
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mutex_unlock(&ldata->echo_lock);
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ldata->erasing = 0;
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@ -640,8 +651,8 @@ static void process_echoes(struct tty_struct *tty)
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{
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struct n_tty_data *ldata = tty->disc_data;
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int space, nr;
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size_t tail;
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unsigned char c;
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unsigned char *cp, *buf_end;
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if (!ldata->echo_cnt)
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return;
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@ -651,14 +662,12 @@ static void process_echoes(struct tty_struct *tty)
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space = tty_write_room(tty);
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buf_end = ldata->echo_buf + N_TTY_BUF_SIZE;
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cp = ldata->echo_buf + ldata->echo_pos;
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tail = ldata->echo_tail;
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nr = ldata->echo_cnt;
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while (nr > 0) {
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c = *cp;
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c = echo_buf(ldata, tail);
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if (c == ECHO_OP_START) {
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unsigned char op;
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unsigned char *opp;
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int no_space_left = 0;
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/*
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@ -666,18 +675,13 @@ static void process_echoes(struct tty_struct *tty)
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* operation, get the next byte, which is either the
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* op code or a control character value.
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*/
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opp = cp + 1;
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if (opp == buf_end)
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opp -= N_TTY_BUF_SIZE;
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op = *opp;
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op = echo_buf(ldata, tail + 1);
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switch (op) {
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unsigned int num_chars, num_bs;
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case ECHO_OP_ERASE_TAB:
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if (++opp == buf_end)
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opp -= N_TTY_BUF_SIZE;
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num_chars = *opp;
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num_chars = echo_buf(ldata, tail + 2);
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/*
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* Determine how many columns to go back
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@ -703,20 +707,20 @@ static void process_echoes(struct tty_struct *tty)
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if (ldata->column > 0)
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ldata->column--;
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}
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cp += 3;
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tail += 3;
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nr -= 3;
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break;
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case ECHO_OP_SET_CANON_COL:
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ldata->canon_column = ldata->column;
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cp += 2;
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tail += 2;
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nr -= 2;
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break;
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case ECHO_OP_MOVE_BACK_COL:
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if (ldata->column > 0)
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ldata->column--;
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cp += 2;
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tail += 2;
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nr -= 2;
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break;
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@ -729,7 +733,7 @@ static void process_echoes(struct tty_struct *tty)
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tty_put_char(tty, ECHO_OP_START);
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ldata->column++;
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space--;
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cp += 2;
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tail += 2;
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nr -= 2;
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break;
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@ -751,7 +755,7 @@ static void process_echoes(struct tty_struct *tty)
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tty_put_char(tty, op ^ 0100);
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ldata->column += 2;
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space -= 2;
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cp += 2;
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tail += 2;
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nr -= 2;
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}
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@ -769,24 +773,13 @@ static void process_echoes(struct tty_struct *tty)
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tty_put_char(tty, c);
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space -= 1;
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}
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cp += 1;
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tail += 1;
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nr -= 1;
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}
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/* When end of circular buffer reached, wrap around */
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if (cp >= buf_end)
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cp -= N_TTY_BUF_SIZE;
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}
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if (nr == 0) {
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ldata->echo_pos = 0;
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ldata->echo_cnt = 0;
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} else {
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int num_processed = ldata->echo_cnt - nr;
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ldata->echo_pos += num_processed;
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ldata->echo_pos &= N_TTY_BUF_SIZE - 1;
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ldata->echo_cnt = nr;
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}
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ldata->echo_tail = tail;
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ldata->echo_cnt = nr;
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mutex_unlock(&ldata->echo_lock);
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mutex_unlock(&ldata->output_lock);
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@ -807,37 +800,26 @@ static void process_echoes(struct tty_struct *tty)
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static void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
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{
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int new_byte_pos;
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if (ldata->echo_cnt == N_TTY_BUF_SIZE) {
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/* Circular buffer is already at capacity */
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new_byte_pos = ldata->echo_pos;
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size_t head = ldata->echo_head;
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/*
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* Since the buffer start position needs to be advanced,
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* be sure to step by a whole operation byte group.
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*/
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if (ldata->echo_buf[ldata->echo_pos] == ECHO_OP_START) {
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if (ldata->echo_buf[(ldata->echo_pos + 1) &
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(N_TTY_BUF_SIZE - 1)] ==
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ECHO_OP_ERASE_TAB) {
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ldata->echo_pos += 3;
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if (echo_buf(ldata, head) == ECHO_OP_START) {
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if (echo_buf(ldata, head + 1) == ECHO_OP_ERASE_TAB) {
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ldata->echo_tail += 3;
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ldata->echo_cnt -= 2;
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} else {
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ldata->echo_pos += 2;
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ldata->echo_tail += 2;
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ldata->echo_cnt -= 1;
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}
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} else {
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ldata->echo_pos++;
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}
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ldata->echo_pos &= N_TTY_BUF_SIZE - 1;
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} else {
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new_byte_pos = ldata->echo_pos + ldata->echo_cnt;
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new_byte_pos &= N_TTY_BUF_SIZE - 1;
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} else
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ldata->echo_tail++;
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} else
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ldata->echo_cnt++;
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}
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ldata->echo_buf[new_byte_pos] = c;
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*echo_buf_addr(ldata, ldata->echo_head++) = c;
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}
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/**
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