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n_tty: Don't wrap input buffer indices at buffer size
Wrap read_buf indices (read_head, read_tail, canon_head) at max representable value, instead of at the N_TTY_BUF_SIZE. This step is necessary to allow lockless reads of these shared variables (by updating the variables atomically). 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
parent
ce74117a18
commit
bc5a5e3f45
1 changed files with 60 additions and 51 deletions
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@ -96,8 +96,8 @@ struct n_tty_data {
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DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
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char *read_buf;
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int read_head;
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int read_tail;
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size_t read_head;
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size_t read_tail;
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int read_cnt;
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int minimum_to_wake;
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@ -106,7 +106,7 @@ struct n_tty_data {
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unsigned int echo_cnt;
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int canon_data;
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unsigned long canon_head;
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size_t canon_head;
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unsigned int canon_column;
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struct mutex atomic_read_lock;
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@ -120,6 +120,16 @@ static inline size_t read_cnt(struct n_tty_data *ldata)
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return ldata->read_cnt;
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}
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static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
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{
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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 *read_buf_addr(struct n_tty_data *ldata, size_t i)
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{
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return &ldata->read_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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@ -186,8 +196,8 @@ static void n_tty_set_room(struct tty_struct *tty)
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static void put_tty_queue_nolock(unsigned char c, struct n_tty_data *ldata)
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{
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if (read_cnt(ldata) < N_TTY_BUF_SIZE) {
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ldata->read_buf[ldata->read_head] = c;
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ldata->read_head = (ldata->read_head + 1) & (N_TTY_BUF_SIZE-1);
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*read_buf_addr(ldata, ldata->read_head) = c;
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ldata->read_head++;
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ldata->read_cnt++;
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}
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}
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@ -289,13 +299,10 @@ static ssize_t chars_in_buffer(struct tty_struct *tty)
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ssize_t n = 0;
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raw_spin_lock_irqsave(&ldata->read_lock, flags);
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if (!ldata->icanon) {
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if (!ldata->icanon)
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n = read_cnt(ldata);
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} else if (ldata->canon_data) {
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n = (ldata->canon_head > ldata->read_tail) ?
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ldata->canon_head - ldata->read_tail :
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ldata->canon_head + (N_TTY_BUF_SIZE - ldata->read_tail);
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}
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else
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n = ldata->canon_head - ldata->read_tail;
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raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
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return n;
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}
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@ -918,7 +925,9 @@ static void eraser(unsigned char c, struct tty_struct *tty)
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{
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struct n_tty_data *ldata = tty->disc_data;
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enum { ERASE, WERASE, KILL } kill_type;
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int head, seen_alnums, cnt;
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size_t head;
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size_t cnt;
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int seen_alnums;
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unsigned long flags;
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/* FIXME: locking needed ? */
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@ -962,8 +971,8 @@ static void eraser(unsigned char c, struct tty_struct *tty)
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/* erase a single possibly multibyte character */
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do {
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head = (head - 1) & (N_TTY_BUF_SIZE-1);
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c = ldata->read_buf[head];
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head--;
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c = read_buf(ldata, head);
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} while (is_continuation(c, tty) && head != ldata->canon_head);
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/* do not partially erase */
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@ -977,7 +986,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
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else if (seen_alnums)
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break;
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}
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cnt = (ldata->read_head - head) & (N_TTY_BUF_SIZE-1);
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cnt = ldata->read_head - head;
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raw_spin_lock_irqsave(&ldata->read_lock, flags);
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ldata->read_head = head;
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ldata->read_cnt -= cnt;
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@ -991,9 +1000,8 @@ static void eraser(unsigned char c, struct tty_struct *tty)
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/* if cnt > 1, output a multi-byte character */
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echo_char(c, tty);
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while (--cnt > 0) {
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head = (head+1) & (N_TTY_BUF_SIZE-1);
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echo_char_raw(ldata->read_buf[head],
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ldata);
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head++;
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echo_char_raw(read_buf(ldata, head), ldata);
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echo_move_back_col(ldata);
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}
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} else if (kill_type == ERASE && !L_ECHOE(tty)) {
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@ -1001,7 +1009,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
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} else if (c == '\t') {
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unsigned int num_chars = 0;
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int after_tab = 0;
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unsigned long tail = ldata->read_head;
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size_t tail = ldata->read_head;
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/*
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* Count the columns used for characters
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@ -1011,8 +1019,8 @@ static void eraser(unsigned char c, struct tty_struct *tty)
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* number of columns.
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*/
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while (tail != ldata->canon_head) {
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tail = (tail-1) & (N_TTY_BUF_SIZE-1);
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c = ldata->read_buf[tail];
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tail--;
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c = read_buf(ldata, tail);
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if (c == '\t') {
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after_tab = 1;
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break;
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@ -1296,14 +1304,14 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
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}
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if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
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L_IEXTEN(tty)) {
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unsigned long tail = ldata->canon_head;
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size_t tail = ldata->canon_head;
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finish_erasing(ldata);
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echo_char(c, tty);
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echo_char_raw('\n', ldata);
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while (tail != ldata->read_head) {
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echo_char(ldata->read_buf[tail], tty);
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tail = (tail+1) & (N_TTY_BUF_SIZE-1);
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echo_char(read_buf(ldata, tail), tty);
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tail++;
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}
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process_echoes(tty);
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return;
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@ -1356,7 +1364,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
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handle_newline:
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raw_spin_lock_irqsave(&ldata->read_lock, flags);
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set_bit(ldata->read_head, ldata->read_flags);
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set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
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put_tty_queue_nolock(c, ldata);
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ldata->canon_head = ldata->read_head;
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ldata->canon_data++;
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@ -1436,19 +1444,19 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
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if (ldata->real_raw) {
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raw_spin_lock_irqsave(&ldata->read_lock, cpuflags);
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i = min(N_TTY_BUF_SIZE - read_cnt(ldata),
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N_TTY_BUF_SIZE - ldata->read_head);
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N_TTY_BUF_SIZE - (ldata->read_head & (N_TTY_BUF_SIZE - 1)));
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i = min(count, i);
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memcpy(ldata->read_buf + ldata->read_head, cp, i);
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ldata->read_head = (ldata->read_head + i) & (N_TTY_BUF_SIZE-1);
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memcpy(read_buf_addr(ldata, ldata->read_head), cp, i);
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ldata->read_head += i;
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ldata->read_cnt += i;
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cp += i;
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count -= i;
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i = min(N_TTY_BUF_SIZE - read_cnt(ldata),
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N_TTY_BUF_SIZE - ldata->read_head);
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N_TTY_BUF_SIZE - (ldata->read_head & (N_TTY_BUF_SIZE - 1)));
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i = min(count, i);
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memcpy(ldata->read_buf + ldata->read_head, cp, i);
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ldata->read_head = (ldata->read_head + i) & (N_TTY_BUF_SIZE-1);
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memcpy(read_buf_addr(ldata, ldata->read_head), cp, i);
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ldata->read_head += i;
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ldata->read_cnt += i;
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raw_spin_unlock_irqrestore(&ldata->read_lock, cpuflags);
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} else {
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@ -1739,21 +1747,21 @@ static int copy_from_read_buf(struct tty_struct *tty,
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size_t n;
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unsigned long flags;
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bool is_eof;
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size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
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retval = 0;
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raw_spin_lock_irqsave(&ldata->read_lock, flags);
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n = min(read_cnt(ldata), N_TTY_BUF_SIZE - ldata->read_tail);
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n = min(read_cnt(ldata), N_TTY_BUF_SIZE - tail);
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n = min(*nr, n);
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raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
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if (n) {
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retval = copy_to_user(*b, &ldata->read_buf[ldata->read_tail], n);
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retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
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n -= retval;
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is_eof = n == 1 &&
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ldata->read_buf[ldata->read_tail] == EOF_CHAR(tty);
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tty_audit_add_data(tty, &ldata->read_buf[ldata->read_tail], n,
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is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
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tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
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ldata->icanon);
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raw_spin_lock_irqsave(&ldata->read_lock, flags);
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ldata->read_tail = (ldata->read_tail + n) & (N_TTY_BUF_SIZE-1);
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ldata->read_tail += n;
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ldata->read_cnt -= n;
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/* Turn single EOF into zero-length read */
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if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))
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@ -1785,8 +1793,9 @@ static int canon_copy_from_read_buf(struct tty_struct *tty,
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struct n_tty_data *ldata = tty->disc_data;
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unsigned long flags;
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size_t n, size, more, c;
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unsigned long eol;
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int ret, tail, found = 0;
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size_t eol;
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size_t tail;
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int ret, found = 0;
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/* N.B. avoid overrun if nr == 0 */
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@ -1798,10 +1807,10 @@ static int canon_copy_from_read_buf(struct tty_struct *tty,
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return 0;
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}
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tail = ldata->read_tail;
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tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
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size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
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n_tty_trace("%s: nr:%zu tail:%d n:%zu size:%zu\n",
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n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
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__func__, *nr, tail, n, size);
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eol = find_next_bit(ldata->read_flags, size, tail);
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@ -1818,21 +1827,21 @@ static int canon_copy_from_read_buf(struct tty_struct *tty,
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n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
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c = n;
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if (found && ldata->read_buf[eol] == __DISABLED_CHAR)
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if (found && read_buf(ldata, eol) == __DISABLED_CHAR)
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n--;
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n_tty_trace("%s: eol:%lu found:%d n:%zu c:%zu size:%zu more:%zu\n",
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n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
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__func__, eol, found, n, c, size, more);
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raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
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if (n > size) {
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ret = copy_to_user(*b, &ldata->read_buf[tail], size);
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ret = copy_to_user(*b, read_buf_addr(ldata, tail), size);
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if (ret)
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return -EFAULT;
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ret = copy_to_user(*b + size, ldata->read_buf, n - size);
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} else
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ret = copy_to_user(*b, &ldata->read_buf[tail], n);
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ret = copy_to_user(*b, read_buf_addr(ldata, tail), n);
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if (ret)
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return -EFAULT;
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@ -1840,7 +1849,7 @@ static int canon_copy_from_read_buf(struct tty_struct *tty,
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*nr -= n;
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raw_spin_lock_irqsave(&ldata->read_lock, flags);
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ldata->read_tail = (ldata->read_tail + c) & (N_TTY_BUF_SIZE - 1);
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ldata->read_tail += c;
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ldata->read_cnt -= c;
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if (found) {
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__clear_bit(eol, ldata->read_flags);
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@ -2230,19 +2239,19 @@ static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
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static unsigned long inq_canon(struct n_tty_data *ldata)
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{
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int nr, head, tail;
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size_t nr, head, tail;
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if (!ldata->canon_data)
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return 0;
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head = ldata->canon_head;
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tail = ldata->read_tail;
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nr = (head - tail) & (N_TTY_BUF_SIZE-1);
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nr = head - tail;
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/* Skip EOF-chars.. */
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while (head != tail) {
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if (test_bit(tail, ldata->read_flags) &&
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ldata->read_buf[tail] == __DISABLED_CHAR)
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if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
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read_buf(ldata, tail) == __DISABLED_CHAR)
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nr--;
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tail = (tail+1) & (N_TTY_BUF_SIZE-1);
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tail++;
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}
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return nr;
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}
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