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kmsg - export "continuation record" flag to /dev/kmsg

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In some cases we are forced to store individual records for a continuation
line print.

Export a flag to allow the external re-construction of the line. The flag
allows us to apply a similar logic externally which is used internally when
the console, /proc/kmsg or the syslog() output is printed.

  $ cat /dev/kmsg
  4,165,0,-;Free swap  = 0kB
  4,166,0,-;Total swap = 0kB
  6,167,0,c;[
  4,168,0,+;0
  4,169,0,+;1
  4,170,0,+;2
  4,171,0,+;3
  4,172,0,+;]
  6,173,0,-;[0 1 2 3 ]
  6,174,0,-;Console: colour VGA+ 80x25
  6,175,0,-;console [tty0] enabled

Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kay Sievers
2012-07-16 18:35:30 -07:00
committed by Greg Kroah-Hartman
parent 96efedf149
commit d39f3d77c9
2 changed files with 41 additions and 11 deletions
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23
kernel/printk.c
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@@ -361,6 +361,7 @@ static void log_store(int facility, int level,
struct devkmsg_user {
u64 seq;
u32 idx;
enum log_flags prev;
struct mutex lock;
char buf[8192];
};
@@ -426,6 +427,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
struct log *msg;
u64 ts_usec;
size_t i;
char cont = '-';
size_t len;
ssize_t ret;
@@ -463,8 +465,25 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
msg = log_from_idx(user->idx);
ts_usec = msg->ts_nsec;
do_div(ts_usec, 1000);
len = sprintf(user->buf, "%u,%llu,%llu;",
(msg->facility << 3) | msg->level, user->seq, ts_usec);
/*
* If we couldn't merge continuation line fragments during the print,
* export the stored flags to allow an optional external merge of the
* records. Merging the records isn't always neccessarily correct, like
* when we hit a race during printing. In most cases though, it produces
* better readable output. 'c' in the record flags mark the first
* fragment of a line, '+' the following.
*/
if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
cont = 'c';
else if ((msg->flags & LOG_CONT) ||
((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
cont = '+';
len = sprintf(user->buf, "%u,%llu,%llu,%c;",
(msg->facility << 3) | msg->level,
user->seq, ts_usec, cont);
user->prev = msg->flags;
/* escape non-printable characters */
for (i = 0; i < msg->text_len; i++) {