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log: Correct formatting of timestamps

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logtime_fmt_and_arg() is a rather odd macro, producing both a format
string and an argument, which can only be used in quite specific printf()
like formulations.  It also has a significant bug: it tries to display 4
digits after the decimal point (so down to tenths of milliseconds) using
%04i.  But the field width in printf() is always a *minimum* not maximum
field width, so this will not truncate the given value, but will redisplay
the entire tenth-of-milliseconds difference again after the decimal point.

Replace the macro with an snprintf() like function which will format the
timestamp, and use an explicit % to correct the display.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Make logtime_fmt() static]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2024-08-06 16:18:37 +10:00 committed by Stefano Brivio
parent 95569e4aa4
commit b91bae1ded
1 changed files with 24 additions and 12 deletions
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36
log.c
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@ -46,14 +46,24 @@ int log_trace; /* --trace mode enabled */
bool log_conf_parsed; /* Logging options already parsed */ bool log_conf_parsed; /* Logging options already parsed */
bool log_stderr = true; /* Not daemonised, no shell spawned */ bool log_stderr = true; /* Not daemonised, no shell spawned */
#define LL_STRLEN (sizeof("-9223372036854775808"))
#define LOGTIME_STRLEN (LL_STRLEN + 5)
/** /**
* logtime_fmt_and_arg() - Build format and arguments to print relative log time * logtime_fmt() - Format timestamp into a string for the log
* @x: Current timestamp * @buf: Buffer into which to format the time
* @size: Size of @buf
* @ts: Time to format
*
* Return: number of characters written to @buf (excluding \0)
*/ */
#define logtime_fmt_and_arg(x) \ static int logtime_fmt(char *buf, size_t size, const struct timespec *ts)
"%lli.%04lli", \ {
(timespec_diff_us((x), &log_start) / 1000000LL), \ int64_t delta = timespec_diff_us(ts, &log_start);
(timespec_diff_us((x), &log_start) / 100LL)
return snprintf(buf, size, "%lli.%04lli", delta / 1000000LL,
(delta / 100LL) % 10000);
}
/* Prefixes for log file messages, indexed by priority */ /* Prefixes for log file messages, indexed by priority */
const char *logfile_prefix[] = { const char *logfile_prefix[] = {
@ -85,7 +95,7 @@ static void logfile_rotate_fallocate(int fd, const struct timespec *now)
return; return;
n = snprintf(buf, BUFSIZ, "%s - log truncated at ", log_header); n = snprintf(buf, BUFSIZ, "%s - log truncated at ", log_header);
n += snprintf(buf + n, BUFSIZ - n, logtime_fmt_and_arg(now)); n += logtime_fmt(buf + n, BUFSIZ - n, now);
/* Avoid partial lines by padding the header with spaces */ /* Avoid partial lines by padding the header with spaces */
nl = memchr(buf + n + 1, '\n', BUFSIZ - n - 1); nl = memchr(buf + n + 1, '\n', BUFSIZ - n - 1);
@ -117,8 +127,7 @@ static void logfile_rotate_move(int fd, const struct timespec *now)
header_len = snprintf(buf, BUFSIZ, "%s - log truncated at ", header_len = snprintf(buf, BUFSIZ, "%s - log truncated at ",
log_header); log_header);
header_len += snprintf(buf + header_len, BUFSIZ - header_len, header_len += logtime_fmt(buf + header_len, BUFSIZ - header_len, now);
logtime_fmt_and_arg(now));
if (lseek(fd, 0, SEEK_SET) == -1) if (lseek(fd, 0, SEEK_SET) == -1)
return; return;
@ -211,7 +220,7 @@ static void logfile_write(bool newline, int pri, const char *format, va_list ap)
if (clock_gettime(CLOCK_MONOTONIC, &now)) if (clock_gettime(CLOCK_MONOTONIC, &now))
return; return;
n = snprintf(buf, BUFSIZ, logtime_fmt_and_arg(&now)); n = logtime_fmt(buf, BUFSIZ, &now);
n += snprintf(buf + n, BUFSIZ - n, ": %s", logfile_prefix[pri]); n += snprintf(buf + n, BUFSIZ - n, ": %s", logfile_prefix[pri]);
n += vsnprintf(buf + n, BUFSIZ - n, format, ap); n += vsnprintf(buf + n, BUFSIZ - n, format, ap);
@ -239,9 +248,12 @@ void vlogmsg(bool newline, int pri, const char *format, va_list ap)
struct timespec tp; struct timespec tp;
if (debug_print) { if (debug_print) {
char logtime[LOGTIME_STRLEN];
clock_gettime(CLOCK_MONOTONIC, &tp); clock_gettime(CLOCK_MONOTONIC, &tp);
fprintf(stderr, logtime_fmt_and_arg(&tp));
fprintf(stderr, ": "); logtime_fmt(logtime, sizeof(logtime), &tp);
fprintf(stderr, "%s: ", logtime);
} }
if ((log_mask & LOG_MASK(LOG_PRI(pri))) || !log_conf_parsed) { if ((log_mask & LOG_MASK(LOG_PRI(pri))) || !log_conf_parsed) {