dmesg: read /dev/kmsg (since kernel 3.5.0)
kmsg advantages: - extendible format - tags for messages - one read() returns one complete record See kernel Documentation/ABI/testing/dev-kmsg. Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak
parent
ed61acc254
commit
ddca870aa9
1 changed files with 202 additions and 28 deletions
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@ -31,6 +31,7 @@
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#include "bitops.h"
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#include "closestream.h"
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#include "optutils.h"
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#include "mangle.h"
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/* Close the log. Currently a NOP. */
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#define SYSLOG_ACTION_CLOSE 0
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@ -156,6 +157,18 @@ struct dmesg_record {
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size_t next_size; /* size of the next buffer */
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};
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#define INIT_DMESG_RECORD(_r) do { \
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(_r)->mesg = NULL; \
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(_r)->mesg_size = 0; \
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(_r)->facility = -1; \
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(_r)->level = -1; \
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(_r)->tv.tv_sec = 0; \
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(_r)->tv.tv_usec = 0; \
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} while (0)
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static int read_kmsg(struct dmesg_control *ctl);
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static void __attribute__((__noreturn__)) usage(FILE *out)
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{
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size_t i;
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@ -288,7 +301,7 @@ static int parse_facility(const char *str, size_t len)
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* bottom 3 bits are the priority (0-7) and the top 28 bits are the facility
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* (0-big number).
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*
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* Note that the number has to end with '>' char.
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* Note that the number has to end with '>' or ',' char.
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*/
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static const char *parse_faclev(const char *str, int *fac, int *lev)
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{
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@ -309,13 +322,20 @@ static const char *parse_faclev(const char *str, int *fac, int *lev)
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*lev = -1;
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if (*fac < 0 || (size_t) *fac > ARRAY_SIZE(facility_names))
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*fac = -1;
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return end + 1; /* skip '<' */
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return end + 1; /* skip '<' or ',' */
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}
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return str;
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}
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static const char *parse_timestamp(const char *str0, struct timeval *tv)
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/*
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* Parses timestamp from syslog message prefix, expected format:
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*
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* seconds.microseconds]
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*
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* the ']' is the timestamp field terminator.
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*/
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static const char *parse_syslog_timestamp(const char *str0, struct timeval *tv)
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{
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const char *str = str0;
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char *end = NULL;
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@ -337,6 +357,35 @@ static const char *parse_timestamp(const char *str0, struct timeval *tv)
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return end + 1; /* skip ']' */
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}
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/*
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* Parses timestamp from /dev/kmsg, expected formats:
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*
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* microseconds,
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* microseconds;
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*
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* the ',' is fields separators and ';' items terminator (for the last item)
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*/
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static const char *parse_kmsg_timestamp(const char *str0, struct timeval *tv)
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{
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const char *str = str0;
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char *end = NULL;
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uint64_t usec;
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if (!str0)
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return str0;
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errno = 0;
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usec = strtoumax(str, &end, 10);
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if (!errno && end && (*end == ';' || *end == ',')) {
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tv->tv_usec = usec % 1000000;
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tv->tv_sec = usec / 1000000;
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} else
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return str0;
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return end + 1; /* skip separator */
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}
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static double time_diff(struct timeval *a, struct timeval *b)
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{
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@ -441,6 +490,12 @@ static ssize_t read_buffer(struct dmesg_control *ctl, char **buf)
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n = read_syslog_buffer(ctl, buf);
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break;
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case DMESG_METHOD_KMSG:
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/*
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* Since kernel 3.5.0
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*/
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n = read_kmsg(ctl);
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break;
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}
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return n;
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@ -471,7 +526,7 @@ static void safe_fwrite(const char *buf, size_t size, FILE *out)
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for (i = 0; i < size; i++) {
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const char *p = buf + i;
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int rc, hex = 0;
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size_t len = 1;
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size_t len = 1;
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#ifdef HAVE_WIDECHAR
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wchar_t wc;
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@ -501,6 +556,18 @@ static void safe_fwrite(const char *buf, size_t size, FILE *out)
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}
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}
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static const char *skip_item(const char *begin, const char *end, const char *sep)
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{
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while (begin < end) {
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int c = *begin++;
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if (c == '\0' || strchr(sep, c))
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break;
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}
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return begin;
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}
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static int get_next_syslog_record(struct dmesg_control *ctl,
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struct dmesg_record *rec)
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{
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@ -514,12 +581,7 @@ static int get_next_syslog_record(struct dmesg_control *ctl,
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if (!rec->next || !rec->next_size)
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return 1;
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rec->mesg = NULL;
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rec->mesg_size = 0;
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rec->facility = -1;
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rec->level = -1;
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rec->tv.tv_sec = 0;
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rec->tv.tv_usec = 0;
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INIT_DMESG_RECORD(rec);
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/*
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* Unmap already printed file data from memory
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@ -551,30 +613,20 @@ static int get_next_syslog_record(struct dmesg_control *ctl,
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continue; /* error or empty line? */
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if (*begin == '<') {
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if (ctl->fltr_lev || ctl->fltr_fac || ctl->decode) {
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if (ctl->fltr_lev || ctl->fltr_fac || ctl->decode)
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begin = parse_faclev(begin + 1, &rec->facility,
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&rec->level);
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} else {
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/* ignore facility and level */
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while (begin < end) {
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begin++;
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if (*(begin - 1) == '>')
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break;
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}
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}
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else
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begin = skip_item(begin, end, ">");
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}
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if (*begin == '[' && (*(begin + 1) == ' ' ||
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isdigit(*(begin + 1)))) {
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if (ctl->delta || ctl->ctime) {
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begin = parse_timestamp(begin + 1, &rec->tv);
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} else if (ctl->notime) {
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while (begin < end) {
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begin++;
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if (*(begin - 1) == ']')
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break;
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}
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}
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if (ctl->delta || ctl->ctime)
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begin = parse_syslog_timestamp(begin + 1, &rec->tv);
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else if (ctl->notime)
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begin = skip_item(begin, end, "]");
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if (begin < end && *begin == ' ')
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begin++;
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}
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@ -678,6 +730,18 @@ static void print_record(struct dmesg_control *ctl, struct dmesg_record *rec)
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printf("[%s] ", tbuf);
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}
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/*
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* In syslog output the timestamp is part of the message and we don't
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* parse the timestamp by default. We parse the timestamp only if
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* --show-delta or --ctime is specified.
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*
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* In kmsg output we always parse the timesptamp, so we have to compose
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* the [sec.usec] string.
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*/
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if (ctl->method == DMESG_METHOD_KMSG &&
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!ctl->notime && !ctl->delta && !ctl->ctime)
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printf("[%5d.%06d] ", (int) rec->tv.tv_sec, (int) rec->tv.tv_usec);
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safe_fwrite(rec->mesg, rec->mesg_size, stdout);
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if (*(rec->mesg + rec->mesg_size - 1) != '\n')
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@ -708,6 +772,116 @@ static int init_kmsg(struct dmesg_control *ctl)
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return ctl->kmsg < 0 ? -1 : 0;
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}
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/*
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* /dev/kmsg record format:
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*
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* faclev,seqnum,timestamp[optional, ...];messgage\n
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* TAGNAME=value
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* ...
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*
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* - fields are separated by ','
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* - last field is terminated by ';'
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*
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*/
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#define LAST_KMSG_FIELD(s) (!s || !*s || *(s - 1) == ';')
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static int parse_kmsg_record(struct dmesg_control *ctl,
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struct dmesg_record *rec,
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char *buf,
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size_t sz)
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{
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const char *p = buf, *end;
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if (sz == 0 || !buf || !*buf)
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return -1;
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end = buf + (sz - 1);
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INIT_DMESG_RECORD(rec);
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while (p < end && isspace(*p))
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p++;
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/* A) priority and facility */
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if (ctl->fltr_lev || ctl->fltr_fac || ctl->decode || ctl->raw)
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p = parse_faclev(p, &rec->facility, &rec->level);
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else
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p = skip_item(p, end, ",");
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if (LAST_KMSG_FIELD(p))
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goto mesg;
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/* B) sequence number */
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p = skip_item(p, end, ",;");
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if (LAST_KMSG_FIELD(p))
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goto mesg;
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/* C) timestamp */
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if (ctl->notime)
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p = skip_item(p, end, ",;");
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else
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p = parse_kmsg_timestamp(p, &rec->tv);
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if (LAST_KMSG_FIELD(p))
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goto mesg;
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/* D) optional fields (ignore) */
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p = skip_item(p, end, ";");
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if (LAST_KMSG_FIELD(p))
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goto mesg;
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mesg:
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/* E) message text */
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rec->mesg = p;
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p = skip_item(p, end, "\n");
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if (!p)
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return -1;
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rec->mesg_size = p - rec->mesg;
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/*
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* Kernel escapes non-printable characters, unfortuately kernel
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* definition of "non-printable" is too strict. On UTF8 console we can
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* print many chars, so let's decode from kernel.
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*/
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unhexmangle_to_buffer(rec->mesg, (char *) rec->mesg, rec->mesg_size + 1);
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/* F) message tags (ignore) */
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return 0;
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}
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/*
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* Note that each read() call for /dev/kmsg returns always one record. It means
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* that we don't have to read whole message buffer before the records parsing.
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*
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* So this function does not compose one huge buffer (like read_syslog_buffer())
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* and print_buffer() is unnecessary. All is done in this function.
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*
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* Returns 0 on success, -1 on error.
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*/
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static int read_kmsg(struct dmesg_control *ctl)
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{
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char buf[BUFSIZ];
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struct dmesg_record rec;
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if (ctl->method != DMESG_METHOD_KMSG || ctl->kmsg < 0)
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return -1;
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do {
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ssize_t sz = read(ctl->kmsg, buf, sizeof(buf) - 1);
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if (sz <= 0)
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break;
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*(buf + sz) = '\0'; /* for debug messages */
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if (parse_kmsg_record(ctl, &rec, buf, (size_t) sz) != 0)
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continue;
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print_record(ctl, &rec);
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} while (1);
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return 0;
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}
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int main(int argc, char *argv[])
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{
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char *buf = NULL;
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