cmn_err(9F) Kernel Functions for Drivers cmn_err(9F)
NAME
cmn_err, vcmn_err, zcmn_err - display an error message or panic the system
SYNOPSIS
#include <sys/cmn_err.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
void cmn_err(int level, char *format...
#include <sys/varargs.h>
void vcmn_err(int level, char *format, va_list ap);
#include <sys/types.h>
void zcmn_err(zoneid_t zoneid, int level, char *format...);
INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI).
PARAMETERS
cmn_err()
level A constant indicating the severity of the error condition.
format Message to be displayed.
vcmn_err()
The vcmn_err() function takes level and format as described for cmn_err(), but its third argument is different:
ap Variable argument list passed to the function.
zcmn_err()
The zcmn_err() function works exactly like cmn_err(), but includes an additional argument:
zoneid Zone to which log messages should be directed. See zones(5).
DESCRIPTION
cmn_err()
The cmn_err() function displays a specified message on the console. cmn_err() can also panic the system. When the system panics, it
attempts to save recent changes to data, display a "panic message" on the console, attempt to write a core file, and halt system process-
ing. See the CE_PANIC level below.
level is a constant indicating the severity of the error condition. The four severity levels are:
CE_CONT Used to continue another message or to display an informative message not associated with an error. Note that multiple CE_CONT
messages without a newline may or may not appear on the system console or in the system log as a single line message. A single
line message may be produced by constructing the message with sprintf(9F) or vsprintf(9F) before calling cmn_err().
CE_NOTE Used to display a message preceded with NOTICE. This message is used to report system events that do not necessarily require
user action, but may interest the system administrator. For example, a message saying that a sector on a disk needs to be
accessed repeatedly before it can be accessed correctly might be noteworthy.
CE_WARN Used to display a message preceded with WARNING. This message is used to report system events that require immediate attention,
such as those where if an action is not taken, the system may panic. For example, when a peripheral device does not initialize
correctly, this level should be used.
CE_PANIC Used to display a message preceded with "panic", and to panic the system. Drivers should specify this level only under the most
severe conditions or when debugging a driver. A valid use of this level is when the system cannot continue to function. If the
error is recoverable, or not essential to continued system operation, do not panic the system.
format is the message to be displayed. It is a character string which may contain plain characters and conversion specifications. By
default, the message is sent both to the system console and to the system log.
Each conversion specification in format is introduced by the % character, after which the following appear in sequence:
An optional decimal digit specifying a minimum field width for numeric conversion. The converted value will be right-justified and padded
with leading zeroes if it has fewer characters than the minimum.
An optional l (ll) specifying that a following d, D, o, O, x, X, or u conversion character applies to a long (long long) integer argument.
An l (ll) before any other conversion character is ignored.
A character indicating the type of conversion to be applied:
d,D,o,O,x,X,u The integer argument is converted to signed decimal (d, D), unsigned octal (o, O), unsigned hexadecimal (x, X), or
unsigned decimal (u), respectively, and displayed. The letters abcdef are used for x and X conversion.
c The character value of the argument is displayed.
b The %b conversion specification allows bit values to be displayed meaningfully. Each %b takes an integer value and a for-
mat string from the argument list. The first character of the format string should be the output base encoded as a control
character. This base is used to display the integer argument. The remaining groups of characters in the format string con-
sist of a bit number (between 1 and 32, also encoded as a control character) and the next characters (up to the next con-
trol character or ' ') give the name of the bit field. The string corresponding to the bit fields set in the integer
argument is displayed after the numerical value. See EXAMPLE section.
p The argument is taken to be a pointer; the value of the pointer is displayed in unsigned hexadecimal. The display format
is equivalent to %lx. To avoid lint warnings, cast pointers to type void * when using the %p format specifier.
s The argument is taken to be a string (character pointer), and characters from the string are displayed until a null char-
acter is encountered. If the character pointer is NULL, the string <null string> is used in its place.
% Copy a %; no argument is converted.
The first character in format affects where the message will be written:
! The message goes only to the system log.
^ The message goes only to the console.
? If level is also CE_CONT, the message is always sent to the system log, but is only written to the console when the system has been
booted in verbose mode. See kernel(1M). If neither condition is met, the '?' character has no effect and is simply ignored.
Refer to syslogd(1M) to determine where the system log is written.
The cmn_err() function sends log messages to the log of the global zone. cmn_err() appends a
to each format, except when level is
CE_CONT.
vcmn_err()
The vcmn_err() function is identical to cmn_err() except that its last argument, ap, is a pointer to a variable list of arguments. ap con-
tains the list of arguments used by the conversion specifications in format. ap must be initialized by calling va_start(9F). va_end(9F) is
used to clean up and must be called after each traversal of the list. Multiple traversals of the argument list, each bracketed by
va_start(9F) and va_end(9F), are possible.
zcmn_err()
With the exception of its first argument (zoneid), zcmn_err() is identical to cmn_err(). zoneid is the numeric ID of the zone to which the
message should be directed. Note that zoneid only has an effect if the message is sent to the system log. Using zoneid will cause messages
to be sent to the log associated with the specified local zone rather than the log in the global zone. This is accomplished by the message
being received and processed by the syslogd(1M) process running in the specified zone instead of the one running in the global zone. You
can retrieve a process zone ID from its credential structure using crgetzoneid(9F).
RETURN VALUES
None. However, if an unknown level is passed to cmn_err(), the following panic error message is displayed:
panic: unknown level in cmn_err (level=level, msg=format)
CONTEXT
The cmn_err() function can be called from user, kernel, interrupt, or high-level interrupt context.
EXAMPLES
Example 1 Using cmn_err()
This first example shows how cmn_err() can record tracing and debugging information only in the system log (lines 17); display problems
with a device only on the system console (line 23); or display problems with the device on both the system console and in the system log
(line 28).
1 struct reg {
2 uchar_t data;
3 uchar_t csr;
4 };
5
6 struct xxstate {
7 ...
8 dev_info_t *dip;
9 struct reg *regp;
10 ...
11 };
12
13 dev_t dev;
14 struct xxstate *xsp;
15 ...
16 #ifdef DEBUG /* in debugging mode, log function call */
17 cmn_err(CE_CONT, "!%s%d: xxopen function called.",
18 ddi_binding_name(xsp->dip), getminor(dev));
19 #endif /* end DEBUG */
20 ...
21 /* display device power failure on system console */
22 if ((xsp->regp->csr & POWER) == OFF)
23 cmn_err(CE_NOTE, "^OFF.",
24 ddi_binding_name(xsp->dip), getminor(dev));
25 ...
26 /* display warning if device has bad VTOC */
27 if (xsp->regp->csr & BADVTOC)
28 cmn_err(CE_WARN, "%s%d: xxopen: Bad VTOC.",
29 ddi_binding_name(xsp->dip), getminor(dev));
Example 2 Using the %b conversion specification
This example shows how to use the %b conversion specification. Because of the leading '?' character in the format string, this message will
always be logged, but it will only be displayed when the kernel is booted in verbose mode.
cmn_err(CE_CONT, "?reg=0x%b
", regval, " 203Intr2Err1Enable");
Example 3 Using regval
When regval is set to (decimal) 13, the following message would be displayed:
reg=0xd<Intr,,Enable>
Example 4 Error Routine
This example shows an error reporting routine which accepts a variable number of arguments and displays a single line error message both in
the system log and on the system console. Note the use of vsprintf() to construct the error message before calling cmn_err().
#include <sys/varargs.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#define MAX_MSG 256;
void
xxerror(dev_info_t *dip, int level, const char *fmt, ...)
{
va_list ap;
int instance;
char buf[MAX_MSG], *name;
instance = ddi_get_instance(dip);
name = ddi_binding_name(dip);
/* format buf using fmt and arguments contained in ap */
va_start(ap, fmt);
vsprintf(buf, fmt, ap);
va_end(ap);
/* pass formatted string to cmn_err(9F) */
cmn_err(level, "%s%d: %s", name, instance, buf);
}
Example 5 Log to Current Zone
This example shows how messages can be sent to the log of the zone in which a thread is currently running, when applicable. Note that most
hardware-related messages should instead be sent to the global zone using cmn_err().
zcmn_err(crgetzoneid(ddi_get_cred()), CE_NOTE, "out of processes0);
SEE ALSO
dmesg(1M), kernel(1M), printf(3C), zones(5), ddi_binding_name(9F), ddi_cred(9F), sprintf(9F), va_arg(9F), va_end(9F), va_start(9F),
vsprintf(9F)
Writing Device Drivers
WARNINGS
The cmn_err() function with the CE_CONT argument can be used by driver developers as a driver code debugging tool. However, using cmn_err()
in this capacity can change system timing characteristics.
NOTES
Messages of arbitrary length can be generated using cmn_err(), but if the call to cmn_err() is made from high-level interrupt context and
insufficient memory is available to create a buffer of the specified size, the message will be truncated to LOG_MSGSIZE bytes (see
<sys/log.h>). For this reason, callers of cmn_err() that require complete and accurate message generation should post down from high-level
interrupt context before calling cmn_err().
SunOS 5.11 16 Jan 2006 cmn_err(9F)