NAME

siginfo - signal generation information

SYNOPSIS

#include <siginfo.h>

DESCRIPTION

If a process is catching a signal, it may request information that tells why the system generated that signal (see sigaction(2)). If a process is monitoring its children, it may 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(3R), sigsend(2), abort(3C), and raise(3C)) and the siginfo structure contains the following additional information:

typedef long pid_t    si_pid     /* sending process ID * /
typedef long uid_t    si_uid     /* sending user ID * /

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(3R).

SI_TIMER

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

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(3R)).

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

Otherwise, si_code contains a positive value reflecting the reason why the system generated the signal:

Signal      Code                  Reason
SIGILL      ILL_ILLOPC            illegal opcode
            ILL_ILLOPN           illegal operand
            ILL_ILLADR           illegal addressing mode
            ILL_ILLTRP           illegal trap
            ILL_PRVOPC           privileged opcode
            ILL_PRVREG           privileged register
            ILL_COPROC           co-processor error
            ILL_BADSTK           internal stack error

SIGFPE

FPE_INTDIV

integer divide by zero

            FPE_INTOVF           integer overflow
            FPE_FLTDIV           floating point divide by zero
            FPE_FLTOVF           floating point overflow
            FPE_FLTUND           floating point underflow
            FPE_FLTRES           floating point inexact result
            FPE_FLTINV           invalid floating point operation
            FPE_FLTSUB           subscript out of range

SIGSEGV

SEGV_MAPERR

address not mapped to object

            SEGV_ACCERR          invalid permissions for mapped object

SIGBUS

BUS_ADRALN

invalid address alignment

            BUS_ADRERR           non-existent physical address
            BUS_OBJERR           object specific hardware error

SIGTRAP

TRAP_BRKPT

process breakpoint

            TRAP_TRACE           process trace trap

SIGCHLD

CLD_EXITED

child has exited

            CLD_KILLED           child was killed
            CLD_DUMPED           child terminated abnormally
            CLD_TRAPPED          traced child has trapped
            CLD_STOPPED          child has stopped
            CLD_CONTINUED        stopped child had continued

SIGPOLL

POLL_IN

data input available

            POLL_OUT             output buffers available
            POLL_MSG             input message available
            POLL_ERR             I/O error
            POLL_PRI             high priority input available
            POLL_HUP             device disconnected

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     caddr_t si_addr  address of faulting memory reference
SIGBUS
SIGCHLD     pid_t si_pid     child process ID
            int si_status    exit value or signal
SIGPOLL     long si_band     band event for POLL_IN ,POLL_OUT ,or
                             POLL_MSG

SEE ALSO

_lwp_kill(2), kill(2), sigaction(2), sigsend(2), waitid(2), abort(3C), raise(3C), aio_read(3R), mq_notify(3R), sigqueue(3R), timer_create(3R), timer_settime(3R), signal(5)

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 may not be available; in that case, si_addr is guaranteed to be on the same page as the faulting instruction or memory reference.