DragonFly On-Line Manual Pages
KPRINTF(9) DragonFly Kernel Developer's Manual KPRINTF(9)
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 ap
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.
SEE ALSO
printf(3), syslog(3)
DragonFly 6.1-DEVELOPMENT March 13, 2020 DragonFly 6.1-DEVELOPMENT