util-linux/sys-utils/dmesg.c

/*
 * dmesg.c -- Print out the contents of the kernel ring buffer
 *
 * Copyright (C) 1993 Theodore Ts'o <tytso@athena.mit.edu>
 * Copyright (C) 2011 Karel Zak <kzak@redhat.com>
 *
 * This program comes with ABSOLUTELY NO WARRANTY.
 */
#include <linux/unistd.h>
#include <stdio.h>
#include <getopt.h>
#include <stdlib.h>
#include <sys/klog.h>
#include <sys/syslog.h>
#include <sys/time.h>
#include <sys/sysinfo.h>
#include <ctype.h>
#include <time.h>

#include "c.h"
#include "nls.h"
#include "strutils.h"
#include "xalloc.h"
#include "widechar.h"
#include "writeall.h"
#include "bitops.h"

/* Close the log.  Currently a NOP. */
#define SYSLOG_ACTION_CLOSE          0
/* Open the log. Currently a NOP. */
#define SYSLOG_ACTION_OPEN           1
/* Read from the log. */
#define SYSLOG_ACTION_READ           2
/* Read all messages remaining in the ring buffer. (allowed for non-root) */
#define SYSLOG_ACTION_READ_ALL       3
/* Read and clear all messages remaining in the ring buffer */
#define SYSLOG_ACTION_READ_CLEAR     4
/* Clear ring buffer. */
#define SYSLOG_ACTION_CLEAR          5
/* Disable printk's to console */
#define SYSLOG_ACTION_CONSOLE_OFF    6
/* Enable printk's to console */
#define SYSLOG_ACTION_CONSOLE_ON     7
/* Set level of messages printed to console */
#define SYSLOG_ACTION_CONSOLE_LEVEL  8
/* Return number of unread characters in the log buffer */
#define SYSLOG_ACTION_SIZE_UNREAD    9
/* Return size of the log buffer */
#define SYSLOG_ACTION_SIZE_BUFFER   10

/*
 * Priority and facility names
 */
struct dmesg_name {
	const char *name;
	const char *help;
};

/*
 * Priority names -- based on sys/syslog.h
 */
static const struct dmesg_name level_names[] =
{
	[LOG_EMERG]   = { "emerg", N_("system is unusable") },
	[LOG_ALERT]   = { "alert", N_("action must be taken immediately") },
	[LOG_CRIT]    = { "crit",  N_("critical conditions") },
	[LOG_ERR]     = { "err",   N_("error conditions") },
	[LOG_WARNING] = { "warn",  N_("warning conditions") },
	[LOG_NOTICE]  = { "notice",N_("normal but significant condition") },
	[LOG_INFO]    = { "info",  N_("informational") },
	[LOG_DEBUG]   = { "debug", N_("debug-level messages") }
};

/*
 * sys/syslog.h uses (f << 3) for all facility codes.
 * We want to use the codes as array idexes, so shift back...
 *
 * Note that libc LOG_FAC() macro returns the base codes, not the
 * shifted code :-)
 */
#define FAC_BASE(f)	((f) >> 3)

static const struct dmesg_name facility_names[] =
{
	[FAC_BASE(LOG_KERN)]     = { "kern",     N_("kernel messages") },
	[FAC_BASE(LOG_USER)]     = { "user",     N_("random user-level messages") },
	[FAC_BASE(LOG_MAIL)]     = { "mail",     N_("mail system") },
	[FAC_BASE(LOG_DAEMON)]   = { "daemon",   N_("system daemons") },
	[FAC_BASE(LOG_AUTH)]     = { "auth",     N_("security/authorization messages") },
	[FAC_BASE(LOG_SYSLOG)]   = { "syslog",   N_("messages generated internally by syslogd") },
	[FAC_BASE(LOG_LPR)]      = { "lpr",      N_("line printer subsystem") },
	[FAC_BASE(LOG_NEWS)]     = { "news",     N_("network news subsystem") },
	[FAC_BASE(LOG_UUCP)]     = { "uucp",     N_("UUCP subsystem") },
	[FAC_BASE(LOG_CRON)]     = { "cron",     N_("clock daemon") },
	[FAC_BASE(LOG_AUTHPRIV)] = { "authpriv", N_("security/authorization messages (private)") },
	[FAC_BASE(LOG_FTP)]      = { "ftp",      N_("ftp daemon") },
};

struct dmesg_control {
	/* bit arrays -- see include/bitops.h */
	char levels[ARRAY_SIZE(level_names) / NBBY + 1];
	char facilities[ARRAY_SIZE(facility_names) / NBBY + 1];

	struct timeval	lasttime;	/* last printed timestamp */
	time_t		boot_time;	/* system boot time */

	unsigned int	raw:1,		/* raw mode */
			fltr_lev:1,	/* filter out by levels[] */
			fltr_fac:1,	/* filter out by facilities[] */
			decode:1,	/* use "facility: level: " prefix */
			notime:1,	/* don't print timestamp */
			delta:1,	/* show time deltas */
			ctime:1;	/* show human readable time */
};

struct dmesg_record {
	const char	*mesg;
	size_t		mesg_size;

	int		level;
	int		facility;
	struct timeval  tv;

	const char	*next;		/* buffer with next unparsed record */
	size_t		next_size;	/* size of the next buffer */
};

static void __attribute__((__noreturn__)) usage(FILE *out)
{
	size_t i;

	fputs(_("\nUsage:\n"), out);
	fprintf(out,
	      _(" %s [options]\n"), program_invocation_short_name);

	fputs(_("\nOptions:\n"), out);
	fputs(_(" -C, --clear                 clear the kernel ring buffer\n"
		" -c, --read-clear            read and clear all messages\n"
		" -D, --console-off           disable printing messages to console\n"
		" -d, --show-delta            show time delta between printed messages\n"
		" -E, --console-on            enable printing messages to console\n"
		" -f, --facility <list>       restrict output to defined facilities\n"
		" -h, --help                  display this help and exit\n"
		" -k, --kernel                display kernel messages\n"
		" -l, --level <list>          restrict output to defined levels\n"
		" -n, --console-level <level> set level of messages printed to console\n"
		" -r, --raw                   print the raw message buffer\n"
		" -s, --buffer-size <size>    buffer size to query the kernel ring buffer\n"
		" -T, --ctime                 show human readable timestamp (could be \n"
		"                             inaccurate if you have used SUSPEND/RESUME)\n"
		" -t, --notime                don't print messages timestamp\n"
		" -u, --userspace             display userspace messages\n"
		" -V, --version               output version information and exit\n"
		" -x, --decode                decode facility and level to readable string\n"), out);

	fputs(_("\nSupported log facilities:\n"), out);
	for (i = 0; i < ARRAY_SIZE(level_names); i++) {
		fprintf(stderr, " %7s - %s\n",
				facility_names[i].name,
				_(facility_names[i].help));
	}

	fputs(_("\nSupported log levels (priorities):\n"), out);
	for (i = 0; i < ARRAY_SIZE(level_names); i++) {
		fprintf(stderr, " %7s - %s\n",
				level_names[i].name,
				_(level_names[i].help));
	}

	fputc('\n', out);

	exit(out == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
}

/*
 * LEVEL     ::= <number> | <name>
 *  <number> ::= number in range <0..N>, where N < ARRAY_SIZE(level_names)
 *  <name>   ::= case-insensitive text
 */
static int parse_level(const char *str, size_t len)
{
	if (!str)
		return -1;
	if (!len)
		len = strlen(str);
	errno = 0;

	if (isdigit(*str)) {
		char *end = NULL;
		long x = strtol(str, &end, 10);

		if (!errno && end && end > str && (size_t) (end - str) == len &&
		    x >= 0 && (size_t) x < ARRAY_SIZE(level_names))
			return x;
	} else {
		size_t i;

		for (i = 0; i < ARRAY_SIZE(level_names); i++) {
			const char *n = level_names[i].name;

			if (strncasecmp(str, n, len) == 0 && *(n + len) == '\0')
				return i;
		}
	}

	if (errno)
		err(EXIT_FAILURE, _("failed to parse level '%s'"), str);

	errx(EXIT_FAILURE, _("unknown level '%s'"), str);
	return -1;
}

/*
 * FACILITY  ::= <number> | <name>
 *  <number> ::= number in range <0..N>, where N < ARRAY_SIZE(facility_names)
 *  <name>   ::= case-insensitive text
 */
static int parse_facility(const char *str, size_t len)
{
	if (!str)
		return -1;
	if (!len)
		len = strlen(str);
	errno = 0;

	if (isdigit(*str)) {
		char *end = NULL;
		long x = strtol(str, &end, 10);

		if (!errno && end && end > str && (size_t) (end - str) == len &&
		    x >= 0 && (size_t) x < ARRAY_SIZE(facility_names))
			return x;
	} else {
		size_t i;

		for (i = 0; i < ARRAY_SIZE(facility_names); i++) {
			const char *n = facility_names[i].name;

			if (strncasecmp(str, n, len) == 0 && *(n + len) == '\0')
				return i;
		}
	}

	if (errno)
		err(EXIT_FAILURE, _("failed to parse facility '%s'"), str);

	errx(EXIT_FAILURE, _("unknown facility '%s'"), str);
	return -1;
}

/*
 * Parses numerical prefix used for all messages in kernel ring buffer.
 *
 * Priorities/facilities are encoded into a single 32-bit quantity, where the
 * bottom 3 bits are the priority (0-7) and the top 28 bits are the facility
 * (0-big number).
 *
 * Note that the number has to end with '>' char.
 */
static const char *parse_faclev(const char *str, int *fac, int *lev)
{
	long num;
	char *end = NULL;

	if (!str)
		return str;

	errno = 0;
	num = strtol(str, &end, 10);

	if (!errno && end && end > str) {
		*fac = LOG_FAC(num);
		*lev = LOG_PRI(num);

		if (*lev < 0 || (size_t) *lev > ARRAY_SIZE(level_names))
			*lev = -1;
		if (*fac < 0 || (size_t) *fac > ARRAY_SIZE(facility_names))
			*fac = -1;
		return end + 1;		/* skip '<' */
	}

	return str;
}

static const char *parse_timestamp(const char *str0, struct timeval *tv)
{
	const char *str = str0;
	char *end = NULL;

	if (!str0)
		return str0;

	errno = 0;
	tv->tv_sec = strtol(str, &end, 10);

	if (!errno && end && *end == '.' && *(end + 1)) {
		str = end + 1;
		end = NULL;
		tv->tv_usec = strtol(str, &end, 10);
	}
	if (errno || !end || end == str || *end != ']')
		return str0;

	return end + 1;	/* skip ']' */
}


static double time_diff(struct timeval *a, struct timeval *b)
{
	return (a->tv_sec - b->tv_sec) + (a->tv_usec - b->tv_usec) / 1E6;
}

static int get_buffer_size()
{
	int n = klogctl(SYSLOG_ACTION_SIZE_BUFFER, NULL, 0);

	return n > 0 ? n : 0;
}

static time_t get_boot_time(void)
{
	struct sysinfo info;
	struct timeval tv;

	if (sysinfo(&info) != 0)
		warn(_("sysinfo failed"));
	else if (gettimeofday(&tv, NULL) != 0)
		warn(_("gettimeofday failed"));
	else
		return tv.tv_sec -= info.uptime;
	return 0;
}

/*
 * Reads messages from kernel ring buffer
 */
static int read_buffer(char **buf, size_t bufsize, int clear)
{
	size_t sz;
	int rc = -1;
	int cmd = clear ? SYSLOG_ACTION_READ_CLEAR :
			  SYSLOG_ACTION_READ_ALL;

	if (bufsize) {
		sz = bufsize + 8;
		*buf = xmalloc(sz * sizeof(char));
		rc = klogctl(cmd, *buf, sz);
	} else {
		sz = 16392;
		while (1) {
			*buf = xmalloc(sz * sizeof(char));
			rc = klogctl(SYSLOG_ACTION_READ_ALL, *buf, sz);
			if (rc < 0)
				break;
			if ((size_t) rc != sz || sz > (1 << 28))
				break;
			free(*buf);
			*buf = NULL;
			sz *= 4;
		}

		if (rc > 0 && clear)
			rc = klogctl(SYSLOG_ACTION_READ_CLEAR, *buf, sz);
	}

	return rc;
}

static int fwrite_hex(const char *buf, size_t size, FILE *out)
{
	size_t i;

	for (i = 0; i < size; i++) {
		int rc = fprintf(out, "\\x%02x", buf[i]);
		if (rc < 0)
			return rc;
	}
	return 0;
}

/*
 * Prints to 'out' and non-printable chars are replaced with \x<hex> sequences.
 */
static void safe_fwrite(const char *buf, size_t size, FILE *out)
{
	size_t i;
#ifdef HAVE_WIDECHAR
	mbstate_t s;
	memset(&s, 0, sizeof (s));
#endif
	for (i = 0; i < size; i++) {
		const char *p = buf + i;
		int rc, hex = 0;

#ifdef HAVE_WIDECHAR
		wchar_t wc;
		size_t len = mbrtowc(&wc, p, size - i, &s);

		if (len == 0)				/* L'\0' */
			return;

		if (len == (size_t)-1 || len == (size_t)-2) {		/* invalid sequence */
			memset(&s, 0, sizeof (s));
			len = hex = 1;

		} else if (len > 1 && !iswprint(wc)) {	/* non-printable multibyte */
			hex = 1;
		} else
#endif
		{
			if (!isprint((unsigned int) *p) &&
			    !isspace((unsigned int) *p))		/* non-printable */
				hex = 1;
		}
		if (hex)
			rc = fwrite_hex(p, len, out);
		else
			rc = fwrite(p, 1, len, out) != len;
		if (rc != 0)
			err(EXIT_FAILURE, _("write failed"));
	}
}

static int get_next_record(struct dmesg_control *ctl, struct dmesg_record *rec)
{
	size_t i;
	const char *begin = NULL;

	if (!rec->next || !rec->next_size)
		return 1;

	rec->mesg = NULL;
	rec->mesg_size = 0;
	rec->facility = -1;
	rec->level = -1;
	rec->tv.tv_sec = 0;
	rec->tv.tv_usec = 0;

	for (i = 0; i < rec->next_size; i++) {
		const char *p = rec->next + i;
		const char *end = NULL;

		if (!begin)
			begin = p;
		if (*p == '\n')
			end = p;
		if (i + 1 == rec->next_size) {
			end = p + 1;
			i++;
		}
		if (begin && !*begin)
			begin = NULL;	/* zero(s) at the end of the buffer? */
		if (!begin || !end)
			continue;
		if (end <= begin)
			continue;	/* error or empty line? */

		if (*begin == '<') {
			if (ctl->fltr_lev || ctl->fltr_fac || ctl->decode) {
				begin = parse_faclev(begin + 1, &rec->facility,
						     &rec->level);
			} else {
				/* ignore facility and level */
				while (begin < end) {
					begin++;
					if (*(begin - 1) == '>')
						break;
				}
			}
		}

		if (end <= begin)
			return -1;	/* error */

		if (*begin == '[' && (*(begin + 1) == ' ' ||
				      isdigit(*(begin + 1)))) {
			if (ctl->delta || ctl->ctime) {
				begin = parse_timestamp(begin + 1, &rec->tv);
			} else if (ctl->notime) {
				while (begin < end) {
					begin++;
					if (*(begin - 1) == ']')
						break;
				}
			}
		}

		if (begin < end && *begin == ' ')
			begin++;

		rec->mesg = begin;
		rec->mesg_size = end - begin;

		rec->next_size -= end - rec->next;
		rec->next = rec->next_size > 0 ? end + 1 : NULL;
		if (rec->next_size > 0)
			rec->next_size--;

		return 0;
	}

	return 1;
}

static int accept_record(struct dmesg_control *ctl, struct dmesg_record *rec)
{
	if (ctl->fltr_lev && (rec->facility < 0 ||
			      !isset(ctl->levels, rec->level)))
		return 0;

	if (ctl->fltr_fac && (rec->facility < 0 ||
			      !isset(ctl->facilities, rec->facility)))
		return 0;

	return 1;
}

/*
 * Prints the 'buf' kernel ring buffer; the messages are filtered out according
 * to 'levels' and 'facilities' bitarrays.
 */
static void print_buffer(const char *buf, size_t size,
			 struct dmesg_control *ctl)
{
	struct dmesg_record rec = { .next = buf, .next_size = size };
	char tbuf[256];

	if (ctl->raw) {
		/* print whole buffer */
		safe_fwrite(buf, size, stdout);
		if (buf[size - 1] != '\n')
			putchar('\n');
		return;
	}

	while (get_next_record(ctl, &rec) == 0) {
		if (!rec.mesg_size)
			continue;

		if (!accept_record(ctl, &rec))
			continue;

		if (ctl->decode && rec.level >= 0 && rec.facility >= 0)
			printf("%-6s:%-6s: ", facility_names[rec.facility].name,
					      level_names[rec.level].name);

		*tbuf = '\0';
		if (ctl->ctime) {
			time_t t = ctl->boot_time + rec.tv.tv_sec;
			if (strftime(tbuf, sizeof(tbuf), "%a %b %e %H:%M:%S %Y",
				     localtime(&t)) == 0)
				*tbuf = '\0';
		}
		if (ctl->delta) {
			double delta = 0;

			if (timerisset(&ctl->lasttime))
				delta = time_diff(&rec.tv, &ctl->lasttime);
			ctl->lasttime = rec.tv;

			if (ctl->ctime && *tbuf)
				printf("[%s ", tbuf);
			else if (ctl->notime)
				putchar('[');
			else
				printf("[%5d.%06d ", (int) rec.tv.tv_sec,
						     (int) rec.tv.tv_usec);
			printf("<%12.06f>] ", delta);
		} else if (ctl->ctime && *tbuf) {
			printf("[%s] ", tbuf);
		}

		safe_fwrite(rec.mesg, rec.mesg_size, stdout);

		if (*(rec.mesg + rec.mesg_size - 1) != '\n')
			putchar('\n');
	}
}

int main(int argc, char *argv[])
{
	char *buf = NULL;
	int  bufsize = 0;
	int  n;
	int  c;
	int  console_level = 0;
	int  cmd = -1;
	static struct dmesg_control ctl;

	static const struct option longopts[] = {
		{ "buffer-size",   required_argument, NULL, 's' },
		{ "clear",         no_argument,	      NULL, 'C' },
		{ "console-level", required_argument, NULL, 'n' },
		{ "console-off",   no_argument,       NULL, 'D' },
		{ "console-on",    no_argument,       NULL, 'E' },
		{ "decode",        no_argument,	      NULL, 'x' },
		{ "facility",      required_argument, NULL, 'f' },
		{ "help",          no_argument,	      NULL, 'h' },
		{ "kernel",        no_argument,       NULL, 'k' },
		{ "level",         required_argument, NULL, 'l' },
		{ "raw",           no_argument,       NULL, 'r' },
		{ "read-clear",    no_argument,	      NULL, 'c' },
		{ "show-delta",    no_argument,	      NULL, 'd' },
		{ "ctime",         no_argument,       NULL, 'T' },
		{ "notime",        no_argument,       NULL, 't' },
		{ "userspace",     no_argument,       NULL, 'u' },
		{ "version",       no_argument,	      NULL, 'V' },
		{ NULL,	           0, NULL, 0 }
	};

	setlocale(LC_ALL, "");
	bindtextdomain(PACKAGE, LOCALEDIR);
	textdomain(PACKAGE);

	while ((c = getopt_long(argc, argv, "CcDdEf:hkl:n:rs:TtuVx",
				longopts, NULL)) != -1) {

		if (cmd != -1 && strchr("CcnDE", c))
			errx(EXIT_FAILURE, _("clear, read-clear, console-level, "
			     "console-on, and console-off options are mutually "
			     "exclusive"));

		switch (c) {
		case 'C':
			cmd = SYSLOG_ACTION_CLEAR;
			break;
		case 'c':
			cmd = SYSLOG_ACTION_READ_CLEAR;
			break;
		case 'D':
			cmd = SYSLOG_ACTION_CONSOLE_OFF;
			break;
		case 'd':
			ctl.delta = 1;
			break;
		case 'E':
			cmd = SYSLOG_ACTION_CONSOLE_ON;
			break;
		case 'f':
			ctl.fltr_fac = 1;
			if (string_to_bitarray(optarg,
					     ctl.facilities, parse_facility) < 0)
				return EXIT_FAILURE;
			break;
		case 'h':
			usage(stdout);
			break;
		case 'k':
			ctl.fltr_fac = 1;
			setbit(ctl.facilities, FAC_BASE(LOG_KERN));
			break;
		case 'l':
			ctl.fltr_lev= 1;
			if (string_to_bitarray(optarg,
					     ctl.levels, parse_level) < 0)
				return EXIT_FAILURE;
			break;
		case 'n':
			cmd = SYSLOG_ACTION_CONSOLE_LEVEL;
			console_level = parse_level(optarg, 0);
			break;
		case 'r':
			ctl.raw = 1;
			break;
		case 's':
			bufsize = strtol_or_err(optarg,
					_("failed to parse buffer size"));
			if (bufsize < 4096)
				bufsize = 4096;
			break;
		case 'T':
			ctl.boot_time = get_boot_time();
			if (ctl.boot_time)
				ctl.ctime = 1;
			break;
		case 't':
			ctl.notime = 1;
			break;
		case 'u':
			ctl.fltr_fac = 1;
			for (n = 1; (size_t) n < ARRAY_SIZE(facility_names); n++)
				setbit(ctl.facilities, n);
			break;
		case 'V':
			printf(_("%s from %s\n"), program_invocation_short_name,
						  PACKAGE_STRING);
			return EXIT_SUCCESS;
		case 'x':
			ctl.decode = 1;
			break;
		case '?':
		default:
			usage(stderr);
		}
	}
	argc -= optind;
	argv += optind;
	n = 0;

	if (argc > 1)
		usage(stderr);

	if (cmd == -1)
		cmd = SYSLOG_ACTION_READ_ALL;	/* default */

	if (ctl.raw && (ctl.fltr_lev || ctl.fltr_fac || ctl.delta ||
			ctl.notime || ctl.ctime || ctl.decode))
		errx(EXIT_FAILURE, _("--raw can't be used together with level, "
		     "facility, decode, delta, ctime or notime options"));

	if (ctl.notime && ctl.ctime)
		errx(EXIT_FAILURE, _("--notime can't be used together with ctime "));

	switch (cmd) {
	case SYSLOG_ACTION_READ_ALL:
	case SYSLOG_ACTION_READ_CLEAR:
		if (!bufsize)
			bufsize = get_buffer_size();
		n = read_buffer(&buf, bufsize, cmd == SYSLOG_ACTION_READ_CLEAR);
		if (n > 0)
			print_buffer(buf, n, &ctl);
		free(buf);
		break;
	case SYSLOG_ACTION_CLEAR:
	case SYSLOG_ACTION_CONSOLE_OFF:
	case SYSLOG_ACTION_CONSOLE_ON:
		n = klogctl(cmd, NULL, 0);
		break;
	case SYSLOG_ACTION_CONSOLE_LEVEL:
		n = klogctl(cmd, NULL, console_level);
		break;
	default:
		errx(EXIT_FAILURE, _("unsupported command"));
		break;
	}

	if (n < 0)
		err(EXIT_FAILURE, _("klogctl failed"));

	return EXIT_SUCCESS;
}