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NAME

siginfo.h, siginfo - signal generation information
 

SYNOPSIS

#include <siginfo.h> 

DESCRIPTION

If a process is catching a signal, it might request information that tells why the system generated that signal. See sigaction(2). If a process is monitoring its children, it might receive information that tells why a child changed state. See waitid(2). In either case, the system returns the information in a structure of type siginfo_t, which includes the following information:

int            si_signo        /* signal number */
int            si_errno        /* error number */
int            si_code         /* signal code */
union sigval   si_value        /* signal value */

si_signo contains the system-generated signal number. For the waitid(2) function, si_signo is always SIGCHLD.

If si_errno is non-zero, it contains an error number associated with this signal, as defined in <errno.h>.

si_code contains a code identifying the cause of the signal.

If the value of the si_code member is SI_NOINFO, only the si_signo member of siginfo_t is meaningful, and the value of all other members is unspecified.  

User Signals

If the value of si_code is less than or equal to 0, then the signal was generated by a user process (see kill(2), _lwp_kill(2), sigqueue(3C), sigsend(2), abort(3C), and raise(3C)) and the siginfo structure contains the following additional information:

pid_t        si_pid      /* sending process ID */
uid_t        si_uid      /* sending user ID */
ctid_t       si_ctid     /* sending contract ID */
zoneid_t     si_zoneid   /* sending zone ID */S

If the signal was generated by a user process, the following values are defined for si_code:

SI_USER

The implementation sets si_code to SI_USER if the signal was sent by kill(2), sigsend(2), raise(3C) or abort(3C).

SI_LWP

The signal was sent by _lwp_kill(2).

SI_QUEUE

The signal was sent by sigqueue(3C).

SI_TIMER

The signal was generated by the expiration of a timer created by timer_settime(3C).

SI_ASYNCIO

The signal was generated by the completion of an asynchronous I/O request.

SI_MESGQ

The signal was generated by the arrival of a message on an empty message queue. See mq_notify(3C).

si_value contains the application specified value, which is passed to the application's signal-catching function at the time of the signal delivery if si_code is any of SI_QUEUE, SI_TIMER, SI_ASYNCHIO, or SI_MESGQ.  

System Signals

Non-user generated signals can arise for a number of reasons. For all of these cases, si_code contains a positive value reflecting the reason why the system generated the signal:

Signal	Code	Reason
SIGILL	ILL_ILLOPC	illegal opcode
SIGFPE
SIGSEGV
SIGBUS
SIGTRAP
SIGCHLD
SIGPOLL

Signals can also be generated from the resource control subsystem. Where these signals do not already possess kernel-level siginfo codes, the siginfo si_code will be filled with SI_RCTL to indicate a kernel-generated signal from an established resource control value.

Signal	Code	Reason
SIGXRES	SI_RCTL	resource-control generated signal
SIGHUP
SIGTERM

The uncatchable signals SIGSTOP and SIGKILL have undefined siginfo codes.

Signals sent with a siginfo code of SI_RCTL contain code-dependent information for kernel-generated signals:

Code	Field	Value
SI_RCTL	hr_time si_entity	process-model entity of control

In addition, the following signal-dependent information is available for kernel-generated signals:

Signal	Field	Value
SIGILL	caddr_t si_addr	address of faulting instruction
SIGFPE
SIGSEGV
SIGBUS
SIGCHLD
SIGPOLL

SEE ALSO

_lwp_kill(2), kill(2), setrctl(2), sigaction(2), sigsend(2), waitid(2), abort(3C), aio_read(3C), mq_notify(3C), raise(3C), signal.h(3HEAD), sigqueue(3C), timer_create(3C), timer_settime(3C)  

NOTES

For SIGCHLD signals, if si_code is equal to CLD_EXITED, then si_status is equal to the exit value of the process; otherwise, it is equal to the signal that caused the process to change state. For some implementations, the exact value of si_addr might not be available; in that case, si_addr is guaranteed to be on the same page as the faulting instruction or memory reference.

Index

NAME

SYNOPSIS

DESCRIPTION

User Signals

System Signals

SEE ALSO

NOTES

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