man/man9f/cmn_err.9f

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.Dd Dec 1, 2016
.Dt CMN_ERR 9F
.Os
.Sh NAME
.Nm cmn_err, dev_err, vcmn_err, zcmn_err, vzcmn_err
.Nd display an error message or panic the system
.Sh SYNOPSIS
.In sys/cmn_err.h
.In sys/ddi.h
.In sys/sunddi.h
.Ft void
.Fo cmn_err
.Fa "int level"
.Fa "char *format"
.Fa ...
.Fc
.Ft void
.Fo dev_err
.Fa "dev_info_t *dip"
.Fa "int level"
.Fa "char *format"
.Fa ...
.Fc
.In sys/varargs.h
.Ft void
.Fo vcmn_err
.Fa "int level"
.Fa "char *format"
.Fa "va_list ap"
.Fc
.In sys/types.h
.Ft void
.Fo zcmn_err
.Fa "zoneid_t zoneid"
.Fa "int level"
.Fa "char *format"
.Fa  ...
.Fc
.Ft void
.Fo vzcmn_err
.Fa "zoneid_t zoneid"
.Fa "int level"
.Fa "char *format"
.Fa "va_list ap"
.Fc
.Sh INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI).
.Sh PARAMETERS
.Ss Fn cmn_err
.Bl -tag -width Ds
.It Fa level
A constant indicating the severity of the error condition.
.It Fa format
Message to be displayed.
.El
.Ss Fn dev_err
The
.Fn dev_err
function works exactly like
.Fn cmn_err ,
but includes an additional argument:
.Bl -tag -width Ds
.It Fa dip
A pointer to the device's
.Ft dev_info
structure.
.El
.Ss Fn vcmn_err
The
.Fn vcmn_err
function takes
.Fa level
and
.Fa format
as described for
.Fn cmn_err ,
but its third argument is different:
.Bl -tag -width Ds
.It Fa ap
Variable argument list passed to the function.
.El
.Ss Fn zcmn_err
The
.Fn zcmn_err
function works exactly like
.Fn cmn_err ,
but includes an additional argument:
.Bl -tag -width Ds
.It Fa zoneid
Zone to which log messages should be directed.
See
.Xr zones 5 .
.El
.Ss Fn vzcmn_err
The
.Fn vzcmn_err
function works exactly like
.Fn vcmn_err ,
but includes an additional argument:
.Bl -tag -width Ds
.It Fa zoneid
Zone to which log messages should be directed.
See
.Xr zones 5 .
.El
.Sh DESCRIPTION
.Ss Fn cmn_err
The
.Fn cmn_err
function displays a specified message on the console.
.Fn cmn_err
can also panic the system.
When the system panics, it attempts to save recent changes to data, display a
.Qq panic message
on the console, attempt to write a core file, and halt system processing.
See the
.Sy CE_PANIC
.Fa level
below.
.Pp
.Fa level
is a constant indicating the severity of the error condition.
The four severity levels are:
.Bl -tag -width "CE_PANIC"
.It Sy CE_CONT
Used to continue another message or to display an informative message not
associated with an error.
Note that multiple
.Sy 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
.Xr sprintf 9F
or
.Xr vsprintf 9F
before calling
.Fn cmn_err .
.It Sy CE_NOTE
Used to display a message preceded with
.Sy 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.
.It Sy CE_WARN
Used to display a message preceded with
.Sy 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.
.It Sy CE_PANIC
Used to display a message preceded with
.Qq Sy 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.
.El
.Pp
The
.Fa format
is identical to the one described in
.Xr sprintf 9F
with additional meaning of the first character affecting where the message will
be written:
.Bl -tag -width Ds
.It Sy \!
The message goes only to the system log.
.It Sy ^
The message goes only to the console.
.It Sy \?
If
.Fa level
is also
.Sy 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
.Xr kernel 1M .
If neither condition is met, the
.Qq Sy \?
character has no effect and is simply ignored.
.El
.Pp
Refer to
.Xr syslogd 1M
to determine where the system log is written.
.Pp
The
.Fn cmn_err
function sends log messages to the log of the global zone.
.Fn cmn_err
appends a
.Sy \en
to each
.Fa format ,
except when
.Fa level
is
.Sy CE_CONT .
.Ss Fn dev_err
With the exception of its first argument
.Pq Fa dip ,
.Fn dev_err
is identical to
.Fn cmn_err .
.Fa dip
is a pointer to a device's
.Ft dev_info
structure, which is used to prepend the driver name and instance number to the
message.
The driver name and instance number are retrieved using
.Xr ddi_driver_name 9F
and
.Xr ddi_get_instance 9F .
.Ss Fn vcmn_err
The
.Fn vcmn_err
function is identical to
.Fn cmn_err
except that its last argument,
.Fa ap ,
is a pointer to a variable list of arguments.
.Fa ap
contains the list of arguments used by the conversion specifications in
.Fa format .
.Fa ap
must be initialized by calling
.Xr va_start 9F .
.Xr 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
.Xr va_start 9F
and
.Xr va_end 9F ,
are possible.
.Ss Fn zcmn_err
With the exception of its first argument
.Pq Fa zoneid ,
.Fn zcmn_err
is identical to
.Fn cmn_err .
.Fa zoneid
is the numeric ID of the zone to which the message should be directed.
Note that
.Fa zoneid
only has an effect if the message is sent to the system log.
Using
.Fa 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
.Xr 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
.Xr crgetzoneid 9F .
.Ss Fn vzcmn_err
With the exception of its first argument
.Pq Fa zoneid ,
.Fn vzcmn_err
is identical to
.Fn vcmn_err .
See the description of
.Fn zcmn_err
above for an explanation on how the
.Fa zoneid
argument is handled.
.Sh CONTEXT
The
.Fn cmn_err
function can be called from user, kernel, interrupt, or high-level interrupt
context.
.Sh RETURN VALUES
None.
However, if an unknown
.Fa level
is passed to
.Fn cmn_err ,
the following panic error message is displayed:
.Bd -literal
panic: unknown level in cmn_err (level=level, msg=format)
.Ed
.Sh EXAMPLES
.Bl -tag -width Ds
.It Sy Example 1 No Using Fn cmn_err
This first example shows how
.Fn cmn_err
can record tracing and debugging information only in the system log
.Pq lines 17 ;
display problems with a device only on the system console
.Pq line 23 ;
or display problems with the device on both the system console and in the system
log
.Pq line 28 .
.Bd -literal
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));
.Ed
.It Sy Example 2 No Using the %b conversion specification
This example shows how to use the
.Sy %b
conversion specification.
Because of the leading
.Qq Sy \?
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.
.Bd -literal
cmn_err(CE_CONT, "?reg=0x%b\en", regval, "\e020\e3Intr\e2Err\e1Enable");
.Ed
.It Sy Example 3 No Using Fa regval
When
.Fa regval
is set to
.Pq decimal
13, the following message would be displayed:
.Bd -literal
reg=0xd<Intr,,Enable>
.Ed
.It Sy Example 4 No 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
.Fn vsprintf
to construct the error message before calling
.Fn cmn_err .
.Bd -literal
#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);

}
.Ed
.It Sy Example 5 No 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
.Fn cmn_err .
.Bd -literal
zcmn_err(crgetzoneid(ddi_get_cred()), CE_NOTE, "out of processes");
.Ed
.El
.Sh SEE ALSO
.Xr dmesg 1M ,
.Xr kernel 1M ,
.Xr zones 5 ,
.Xr ddi_binding_name 9F ,
.Xr ddi_cred 9F ,
.Xr ddi_driver_name 9F ,
.Xr ddi_get_instance 9F ,
.Xr sprintf 9F ,
.Xr va_arg 9F ,
.Xr va_end 9F ,
.Xr va_start 9F
.Pp
Writing Device Drivers
.Sh WARNINGS
The
.Fn cmn_err
function with the
.Sy CE_CONT
argument can be used by driver developers as a driver code debugging tool.
However, using
.Fn cmn_err
in this capacity can change system timing characteristics.
.Sh NOTES
Messages of arbitrary length can be generated using
.Fn cmn_err ,
but if the call to
.Fn 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
.Pq see Pa sys/log.h .
For this reason, callers of
.Fn cmn_err
that require complete and accurate message generation should post down from
high-level interrupt context before calling
.Fn cmn_err .