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    Subject[PATCH v3 6/7] printk: insert newline in devkmsg_read()
    Date
    If a log record has LOG_PREFIX set, its predecessor record should be
    terminated if it was marked LOG_CONT.

    In devkmsg_read(), this condition was being ignored, which would
    lead to such records showing up combined when reading /dev/kmsg.
    Fix this oversight.

    We should similarly insert a newline in msg_print_text() in this
    case, to avoid formatted records getting merged.

    Suggested-by: Petr Mládek <pmladek@suse.cz>
    Signed-off-by: Alex Elder <elder@linaro.org>
    ---
    kernel/printk/printk.c | 18 +++++++++++++++---
    1 file changed, 15 insertions(+), 3 deletions(-)

    diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
    index a5c6427..abb129c 100644
    --- a/kernel/printk/printk.c
    +++ b/kernel/printk/printk.c
    @@ -575,6 +575,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
    char cont;
    size_t len;
    ssize_t ret;
    + bool insert_newline;

    if (!user)
    return -EBADF;
    @@ -626,7 +627,10 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
    else
    cont = '-';

    - len = sprintf(user->buf, "%u,%llu,%llu,%c;",
    + /* Insert a newline if the previous line was not terminated properly */
    + insert_newline = (user->prev & LOG_CONT) && (msg->flags & LOG_PREFIX);
    + len = sprintf(user->buf, "%s%u,%llu,%llu,%c;",
    + insert_newline ? "\n" : "",
    (msg->facility << 3) | msg->level,
    user->seq, ts_usec, cont);
    user->prev = msg->flags;
    @@ -999,10 +1003,12 @@ static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
    {
    const char *text = log_text(msg);
    size_t text_size = msg->text_len;
    + size_t len = 0;
    + bool insert_newline;
    bool prefix = true;
    bool newline = true;
    - size_t len = 0;

    + insert_newline = (prev & LOG_CONT) && (msg->flags & LOG_PREFIX);
    if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
    prefix = false;

    @@ -1023,9 +1029,13 @@ static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,

    if (buf) {
    if (print_prefix(msg, syslog, NULL) +
    - text_len + 1 >= size - len)
    + text_len + 2 >= size - len)
    break;

    + if (insert_newline) {
    + insert_newline = false;
    + buf[len++] = '\n';
    + }
    if (prefix)
    len += print_prefix(msg, syslog, buf + len);
    memcpy(buf + len, text, text_len);
    @@ -1034,6 +1044,8 @@ static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
    buf[len++] = '\n';
    } else {
    /* SYSLOG_ACTION_* buffer size only calculation */
    + if (insert_newline)
    + len++;
    if (prefix)
    len += print_prefix(msg, syslog, NULL);
    len += text_len;
    --
    1.9.1
    --
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