NAME
kprintf, ksprintf,
ksnprintf, kvprintf,
kvsprintf, kvsnprintf,
krateprintf, tprintf,
uprintf, log —
formatted output conversion
SYNOPSIS
#include
<sys/types.h>
#include <sys/systm.h>
int
kprintf(const
char *format,
...);
int
ksprintf(char
*str, const char
*format, ...);
int
ksnprintf(char
*str, size_t size,
const char *format,
...);
int
kvprintf(const
char *format, __va_list
ap);
int
kvsprintf(char
*str, const char
*format, __va_list
ap);
int
kvsnprintf(char
*str, size_t size,
const char *format,
__va_list ap);
int
krateprintf(struct
krate *rate, const char
*format, ...);
int
uprintf(const
char *format,
...);
#include
<sys/tprintf.h>
int
tprintf(struct
proc *p, int pri,
const char *format,
...);
#include
<sys/syslog.h>
int
log(int
pri, const char
*format, ...);
DESCRIPTION
The kprintf family of functions are
similar to the
printf(3) family of functions. The different functions each use a
different output stream. The
uprintf()
function outputs to the current process' controlling tty, while
kprintf(),
ksprintf(),
ksnprintf(),
kvprintf(),
kvsprintf()
and
kvsnprintf()
write to the console as well as to the logging facility. The
tprintf()
function outputs to the tty associated with the process
p and the logging facility if
pri is not -1. The log()
function sends the message to the kernel logging facility, using the log
level as indicated by pri.
Each of these related functions use the
format, str,
size and va parameters in the
same manner as
printf(3). However, the kprintf functions add
another conversion specifier to format:
The %pb%i identifier expects two
arguments: an char * and a int.
These are used as a register value and a print mask for decoding bitmasks.
The print mask is made up of two parts: the base and the arguments. The base
value is the output base expressed as an integer value; for example, \10
gives octal and \20 gives hexadecimal. The arguments are made up of a
sequence of bit identifiers. Each bit identifier begins with an integer
value which is the number of the bit (starting from 1) this identifier
describes. The rest of the identifier is a string of characters containing
the name of the bit. The string is terminated by either the bit number at
the start of the next bit identifier or NUL for the
last bit identifier.
The
log() function
uses syslog(3) level values LOG_DEBUG
through LOG_EMERG for its pri
parameter (mistakenly called ‘priority’ here). Alternatively,
if a pri of -1 is given, the message will be appended
to the last log message started by a previous call to
log(). As these messages are generated by the kernel
itself, the facility will always be LOG_KERN.
The
krateprintf()
function is a rate controlled version of kprintf().
The freq member of the struct
krate pointed to by rate must be initialized
with the desired reporting frequency. A freq of 0 will
result in no output. Initializing count to a negative
value allows an initial burst.
RETURN VALUES
The kprintf(),
ksprintf(), ksnprintf(),
kvprintf(), kvsprintf(),
kvsnprintf(), tprintf(),
uprintf(), and log()
functions return the number of characters displayed.
The krateprintf() function returns 1 or 0,
depending on whether anything was printed or not, allowing code to issue
additional kprintf()s if desired.
LOADER TUNABLES
Tunables can be set at the loader(8) prompt before booting the kernel or stored in loader.conf(5).
- kern.kprintf_logging
- A bit mask that specifies the targets of
kprintf(). Supported targets are the console (0x1) and the dmesg buffer (0x4). The default value is 5 (print to both). - kern.log_console_output
- Specifies whether console output is duplicated to the syslog. The default value is 1.
- security.ptr_restrict
- Specifying 1 masks out the upper bits of pointers printed with %p, and specifying 2 masks out pointer values altogether. The default value is 0.
- security.unprivileged_read_msgbuf
- Specifies if unprivileged processes may read the kernel buffer. The default value is 1.
SYSCTL VARIABLES
The loader tunables described in LOADER TUNABLES are also available as sysctl(8) variables of the same names.
EXAMPLES
This example demonstrates the use of the
%pb%i conversion specifier. The function
void
kprintf_test(void)
{
kprintf("reg=%pb%i\n", "\10\2BITTWO\1BITONE\n", 3);
}
will produce the following output:
reg=3<BITTWO,BITONE>
The call
log(LOG_DEBUG, "%s%d: been there.\n", sc->sc_name, sc->sc_unit);
will add the appropriate debug message at priority
“kern.debug” to the system log.