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Merged
merged 2 commits into from
Jan 23, 2024
Merged

dmesg: add PRINTK_CALLER support #2647

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b90a0a1
build-sys: fix po-man clean
karelzak Jan 23, 2024
467a5b3
dmesg: add caller_id support
echron-arista Jan 4, 2024
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3 changes: 3 additions & 0 deletions include/pathnames.h
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Original file line number Diff line number Diff line change
Expand Up @@ -230,4 +230,7 @@
/* cgroup path */
#define _PATH_SYS_CGROUP "/sys/fs/cgroup"

/* Maximum number of PIDs system supports */
#define _PATH_PROC_PIDMAX "/proc/sys/kernel/pid_max"

#endif /* PATHNAMES_H */
2 changes: 0 additions & 2 deletions po-man/Makefile.am
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Original file line number Diff line number Diff line change
Expand Up @@ -63,8 +63,6 @@ all: gen-mans

clean-local:
rm -f *~ *.bak

distclean-local:
rm -rf $(PO_LANGS) *.stamp

install-data-local: gen-mans
Expand Down
128 changes: 125 additions & 3 deletions sys-utils/dmesg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,9 @@
*/
#include <stdio.h>
#include <getopt.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <sys/klog.h>
#include <sys/syslog.h>
#include <sys/time.h>
Expand Down Expand Up @@ -41,6 +43,7 @@
#include "mangle.h"
#include "pager.h"
#include "jsonwrt.h"
#include "pathnames.h"

/* Close the log. Currently a NOP. */
#define SYSLOG_ACTION_CLOSE 0
Expand All @@ -65,6 +68,12 @@
/* Return size of the log buffer */
#define SYSLOG_ACTION_SIZE_BUFFER 10

#define PID_CHARS_MAX sizeof(stringify_value(LONG_MAX))
#define PID_CHARS_DEFAULT sizeof(stringify_value(INT_MAX))
#define SYSLOG_DEFAULT_CALLER_ID_CHARS sizeof(stringify_value(SHRT_MAX))-1
#define DMESG_CALLER_PREFIX "caller="
#define DMESG_CALLER_PREFIXSZ (sizeof(DMESG_CALLER_PREFIX)-1)

/*
* Color scheme
*/
Expand Down Expand Up @@ -237,6 +246,7 @@ struct dmesg_control {
force_prefix:1; /* force timestamp and decode prefix
on each line */
int indent; /* due to timestamps if newline */
size_t caller_id_size; /* PRINTK_CALLERID max field size */
};

struct dmesg_record {
Expand All @@ -246,6 +256,7 @@ struct dmesg_record {
int level;
int facility;
struct timeval tv;
char caller_id[PID_CHARS_MAX];

const char *next; /* buffer with next unparsed record */
size_t next_size; /* size of the next buffer */
Expand All @@ -258,6 +269,7 @@ struct dmesg_record {
(_r)->level = -1; \
(_r)->tv.tv_sec = 0; \
(_r)->tv.tv_usec = 0; \
(_r)->caller_id[0] = 0; \
} while (0)

static int process_kmsg(struct dmesg_control *ctl);
Expand Down Expand Up @@ -602,6 +614,45 @@ static int get_syslog_buffer_size(void)
return n > 0 ? n : 0;
}

/*
* Get the number of characters needed to hold the maximum number
* of tasks this system supports. This size of string could hold
* a thread id large enough for the highest thread id.
* This is needed to determine the number of characters reserved for
* the PRINTK_CALLER field if it has been configured in the Linux Kernel.
*
* The number of digits sets the max value since the value can't exceed
* a value of that size. The /proc field defined by _PATH_PROC_PIDMAX
* holds the maximum number of PID values that may be ussed by the system,
* so 0 to that value minus one.
*
* For determining the size of the PRINTK_CALLER field, we make the safe
* assumption that the number of threads >= number of cpus. This because
* the PRINTK_CALLER field can hold either a thread id or a CPU id value.
*
* If we can't access the pid max kernel proc entry we assign a default
* field size of 5 characters as that is what the old syslog interface
* uses as the reserved field size. This is justified because 32-bit Linux
* systems are limited to PID values between (0-32767).
*
*/
static size_t max_threads_id_size(void)
{
char taskmax[PID_CHARS_MAX] = {'\0'};
ssize_t rdsize;
int fd;

fd = open(_PATH_PROC_PIDMAX, O_RDONLY);
if (fd == -1)
return PID_CHARS_DEFAULT;

rdsize = read(fd, taskmax, sizeof(taskmax));
if (rdsize == -1)
return PID_CHARS_DEFAULT;

return strnlen(taskmax, sizeof(taskmax));
}

/*
* Reads messages from regular file by mmap
*/
Expand Down Expand Up @@ -675,6 +726,8 @@ static ssize_t process_buffer(struct dmesg_control *ctl, char **buf)
ctl->bufsize = get_syslog_buffer_size();

n = read_syslog_buffer(ctl, buf);
/* Set number of PID characters for caller_id spacing */
ctl->caller_id_size = SYSLOG_DEFAULT_CALLER_ID_CHARS;
break;
case DMESG_METHOD_KMSG:
if (ctl->filename)
Expand Down Expand Up @@ -779,6 +832,39 @@ static const char *skip_item(const char *begin, const char *end, const char *sep
return begin;
}

/*
* Checks to see if the caller (caller id) field is present in the kmsg record.
* This is true if the PRINTK_CALLER config option has been set in the kernel.
*
* If the caller_id is found in the kmsg buffer then return the id and id type
* to the caller in dmesg caller_id. Returns string pointer to next value.
*
*/
static const char *parse_callerid(const char *p_str, const char *end,
struct dmesg_record *p_drec)
{
const char *p_after;
const char *p_next;
size_t cid_size;
char *p_scn;
char *p_cid;

/* Check for PRINTK_CALLER prefix, must be before msg text */
p_cid = strstr(p_str, DMESG_CALLER_PREFIX);
p_scn = strchr(p_str, ';');
if (p_cid != NULL && p_drec != NULL && p_scn != NULL && p_cid < p_scn) {
p_next = p_cid + DMESG_CALLER_PREFIXSZ;
p_after = skip_item(p_next, end, ",;");
cid_size = p_after - p_next;
if (cid_size < sizeof(p_drec->caller_id))
xstrncpy(p_drec->caller_id, p_next, cid_size);
else
return p_str;
return p_after;
}
return p_str;
}

/*
* Parses one record from syslog(2) buffer
*/
Expand Down Expand Up @@ -846,8 +932,22 @@ static int get_next_syslog_record(struct dmesg_control *ctl,
begin++;
}

rec->mesg = begin;
rec->mesg_size = end - begin;
if (*begin == '[' && (*(begin + 1) == ' ' ||
(*(begin + 1) == 'T' || *(begin + 1) == 'C'))) {
const char *start = begin + 1;
size_t id_size;

start = start + strspn(start, " ");
begin = skip_item(begin, end, "]");
id_size = begin - start;
if (id_size < sizeof(rec->caller_id))
xstrncpy(rec->caller_id, start, id_size);
rec->mesg = begin + 1;
rec->mesg_size = end - begin - 1;
} else {
rec->mesg = begin;
rec->mesg_size = end - begin;
}

/* Don't count \n from the last message to the message size */
if (*end != '\n' && *(end - 1) == '\n')
Expand Down Expand Up @@ -1165,6 +1265,19 @@ static void print_record(struct dmesg_control *ctl,
color_disable();
}

if (*rec->caller_id) {
if (ctl->json) {
ul_jsonwrt_value_s(&ctl->jfmt, "caller", rec->caller_id);
} else {
char cidbuf[PID_CHARS_MAX+3] = {'\0'};

sprintf(cidbuf, "[%*s] ",
(char)ctl->caller_id_size, rec->caller_id);
ctl->indent += strnlen(cidbuf, sizeof(cidbuf));
fputs(cidbuf, stdout);
}
}

/*
* A kernel message may contain several lines of output, separated
* by '\n'. If the timestamp and decode outputs are forced then each
Expand Down Expand Up @@ -1348,7 +1461,10 @@ static int parse_kmsg_record(struct dmesg_control *ctl,
goto mesg;

/* D) optional fields (ignore) */
p = skip_item(p, end, ";");
p = skip_item(p, end, ",;");

/* Include optional PRINTK_CALLER field if it is present */
p = parse_callerid(p, end, rec);

mesg:
/* E) message text */
Expand Down Expand Up @@ -1400,6 +1516,9 @@ static int process_kmsg(struct dmesg_control *ctl)
if (ctl->method != DMESG_METHOD_KMSG || ctl->kmsg < 0)
return -1;

/* Determine number of PID characters for caller_id spacing */
ctl->caller_id_size = max_threads_id_size();

/*
* The very first read() call is done in kmsg_init() where we test
* /dev/kmsg usability. The return code from the initial read() is
Expand Down Expand Up @@ -1512,6 +1631,7 @@ int main(int argc, char *argv[])
.kmsg = -1,
.ntime_fmts = 0,
.indent = 0,
.caller_id_size = 0,
};
int colormode = UL_COLORMODE_UNDEF;
enum {
Expand Down Expand Up @@ -1606,10 +1726,12 @@ int main(int argc, char *argv[])
case 'F':
ctl.filename = optarg;
ctl.method = DMESG_METHOD_MMAP;
ctl.caller_id_size = SYSLOG_DEFAULT_CALLER_ID_CHARS;
break;
case 'K':
ctl.filename = optarg;
ctl.method = DMESG_METHOD_KMSG;
ctl.caller_id_size = max_threads_id_size();
break;
case 'f':
ctl.fltr_fac = 1;
Expand Down
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