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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.

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