|
HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | NOTES | COLOPHON |
|
|
|
LIBTRACEEVENT(3) libtraceevent Manual LIBTRACEEVENT(3)
kbuffer_timestamp, kbuffer_subbuf_timestamp - Functions that read
various data of a kbuffer descriptor
#include <kbuffer.h>
unsigned long long kbuffer_timestamp(struct kbuffer *kbuf);
unsigned long long kbuffer_subbuf_timestamp(struct kbuffer *kbuf, void *subbuf);
The function kbuffer_timestamp() returns the timestamp of the
current event of kbuf.
The function kbuffer_subbuf_timestamp() returns the timestamp for
the sub-buffer that was loaded in kbuf. This usually is (but not
guaranteed to be) the timestamp of the first event on the
sub-buffer.
The function kbuffer_start_of_data() returns the offset of where
the delta
kbuffer_read_event() returns the event that the kbuf descriptor
is currently at, or NULL if the last event was passed (by
kbuffer_next_event()).
kbuffer_next_event() returns the next event after the current
event or NULL if there are no more events.
kbuffer_read_at_offset() returns the event at a given offset from
the start of the sub-buffer stored in kbuf, or NULL if there
exists no event. Note, offset only needs to be an offset that
lands on the record, or is at the start of it. It does not need
to be exactly at the beginning of the record.
kbuffer_missed_events() returns 0 if there were no missed events
before loaded sub-buffer. Returns -1 if there were an unknown
number of missed events, or if the number of missed events is
known, that number will be returned.
kbuffer_event_size() returns the size of the data payload of the
current event of kbuf.
kbuffer_curr_size() returns the size of the entire record of the
current event of kbuf. This includes the size of the meta data
for that record.
kbuf_curr_offset() returns the offset of the current record from
the beginning of the kbuf sub-buffer.
kbuf_curr_index() returns the index of the current record from
the beginning of the kbuf data section.
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <kbuffer.h>
int main (int argc, char **argv)
{
unsigned long long ts;
struct kbuffer *kbuf;
struct stat st;
char *buf;
void *event;
int save_offset = -1;
int record_size;
int offset;
int index;
int size;
int ret;
int fd;
int i = 0;
if (argc < 2) {
printf("usage: %s raw-subbuffer-page\n", argv[0]);
printf(" Try: dd count=1 bs=4096 if=/sys/kernel/tracing/per_cpu/cpu0/trace_pipe_raw of=/tmp/file\n");
exit(0);
}
if (stat(argv[1], &st) < 0) {
perror("stat");
exit(-1);
}
buf = malloc(st.st_size);
if (!buf) {
perror("Allocating buffer");
exit(-1);
}
fd = open(argv[1], O_RDONLY);
if (fd < 0) {
perror(argv[1]);
exit(-1);
}
ret = read(fd, buf, st.st_size);
if (ret < 0) {
perror("Reading buffer");
exit(-1);
}
close(fd);
kbuf = kbuffer_alloc(KBUFFER_ENDIAN_SAME_AS_HOST,
KBUFFER_LSIZE_SAME_AS_HOST);
if (!kbuf) {
perror("Creating kbuffer");
exit(-1);
}
ret = kbuffer_load_subbuffer(kbuf, buf);
if (ret < 0) {
perror("Loading sub bufer");
exit(-1);
}
if (kbuffer_subbuffer_size(kbuf) > st.st_size) {
fprintf(stderr, "kbuffer is bigger than raw size %d > %ld\n",
kbuffer_subbuffer_size(kbuf), st.st_size);
exit(-1);
}
ret = kbuffer_missed_events(kbuf);
if (ret) {
if (ret > 0)
printf("Missed %d events before this buffer\n", ret);
else
printf("Missed unknown number of events before this buffer\n");
}
do {
event = kbuffer_read_event(kbuf, &ts);
if (event) {
record_size = kbuffer_curr_size(kbuf);
offset = kbuffer_curr_offset(kbuf);
index = kbuffer_curr_index(kbuf);
size = kbuffer_event_size(kbuf);
if (i == 20)
save_offset = offset;
printf(" event %3d ts:%lld\trecord_size:%d size:%d\tindex:%d offset:%d\n",
i++, ts, record_size, size, index, offset);
event = kbuffer_next_event(kbuf, NULL);
}
} while (event);
if (!event)
printf("Finished sub buffer\n");
if (save_offset > 0) {
event = kbuffer_read_at_offset(kbuf, save_offset, &ts);
if (!event) {
fprintf(stderr, "Funny, can't find event 20 at offset %d\n", save_offset);
exit(-1);
}
record_size = kbuffer_curr_size(kbuf);
offset = kbuffer_curr_offset(kbuf);
index = kbuffer_curr_index(kbuf);
size = kbuffer_event_size(kbuf);
printf("\n saved event 20 ts:%lld\trecord_size:%d size:%d\tindex:%d offset:%d\n\n",
ts, record_size, size, index, offset);
}
kbuffer_free(kbuf);
return 0;
}
event-parse.h
Header file to include in order to have access to the library APIs.
-ltraceevent
Linker switch to add when building a program that uses the library.
libtraceevent(3), trace-cmd(1)
Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent.
Report bugs to <linux-trace-devel@vger.kernel.org[2]>
libtraceevent is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/
1. rostedt@goodmis.org
mailto:rostedt@goodmis.org
2. linux-trace-devel@vger.kernel.org
mailto:linux-trace-devel@vger.kernel.org
This page is part of the libtraceevent (Linux kernel trace event
library) project. Information about the project can be found at
⟨https://www.trace-cmd.org/⟩. If you have a bug report for this
manual page, see ⟨https://www.trace-cmd.org/⟩. This page was
obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git⟩
on 2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-05-17.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
libtraceevent 1.7.3 09/24/2023 LIBTRACEEVENT(3)
|
HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|