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SIGINFO(3)             FreeBSD Library Functions Manual             SIGINFO(3)

     siginfo - signal generation information

     #include <signal.h>

     A process may request signal information when it is catching a signal.
     The information specifies why the system generated that signal.  To
     request signal information in a signal handler, the user can set
     SA_SIGINFO in sa_flags before sigaction(2) is called, otherwise the user
     can use sigwaitinfo(2) and sigtimedwait(2) to get signal information.  In
     either case, the system returns the information in a structure of type
     siginfo_t, which includes the following information:

     Type                Member            Description
     int                 si_signo          signal number
     int                 si_errno          error number
     int                 si_code           signal code
     union sigval        si_value          signal value
     pid_t               si_pid            sending process ID
     uid_t               si_uid            sending process's real user ID
     void                *si_addr          address of faulting instruction
     int                 si_status         exit value or signal
     long                si_band           band event for SIGPOLL
     int                 si_trapno         machine trap code
     int                 si_timerid        POSIX timer ID
     int                 si_overrun        POSIX timer overrun count
     int                 si_mqd            POSIX message queue ID

     The si_signo member contains the signal number.

     The si_errno member contains an error number defined in the file

     The si_code member contains a code which describes the cause of the
     signal.  The macros specified in the Code column of the following table
     are defined for use as values of si_code that are signal-specific or non-
     signal-specific reasons why the signal was generated:

     Signal         Code                 Reason
     SIGILL         ILL_ILLOPC           illegal opcode
                    ILL_ILLOPN           illegal operand
                    ILL_ILLADR           illegal addressing mode
                    ILL_ILLTRP           illegal trap
                    ILL_PRVOPC           illegal privileged opcode
                    ILL_PRVREG           illegal privileged register
                    ILL_COPROC           coprocessor 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           nonexistent physical address
                    BUS_OBJERR           object-specific hardware error
     SIGTRAP        TRAP_BRKPT           process breakpoint
                    TRAP_TRACE           process trace trap
                    TRAP_DTRACE          DTrace induced trap
     SIGCHLD        CLD_EXITED           child has exited
                    CLD_KILLED           child has terminated abnormally and
                                         did not create a core file
                    CLD_DUMPED           child has terminated abnormally and
                                         created a core file
                    CLD_TRAPPED          traced child has trapped
                    CLD_STOPPED          child has stopped
                    CLD_CONTINUED        stopped child has 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
     Any            SI_NOINFO            Only the si_signo member is
                                         meaningful; the value of all other
                                         members is unspecified.
                    SI_USER              signal sent by kill(2)
                    SI_QUEUE             signal sent by sigqueue(2)
                    SI_TIMER             signal generated by expiration of a
                                         timer set by timer_settime(2)
                    SI_ASYNCIO           signal generated by completion of an
                                         asynchronous I/O request
                    SI_MESGQ             signal generated by arrival of a
                                         message on an empty message queue
                    SI_KERNEL            signal generated by miscellaneous
                                         parts of the kernel
                    SI_LWP               signal sent by pthread_kill(3)

     In addition, the following signal-specific information is available:

     Signal         Member               Value
     SIGILL         si_addr              address of faulting instruction
                    si_trapno            machine dependent of trap code
     SIGFPE         si_addr              address of faulting instruction
                    si_trapno            machine dependent of trap code
     SIGSEGV        si_addr              address of faulting memory reference
                    si_trapno            machine dependent of trap code
     SIGBUS         si_addr              address of faulting instruction
                    si_trapno            machine dependent of trap code
     SIGCHLD        si_pid               child process ID
                    si_status            exit value or signal; if si_code is
                                         equal to CLD_EXITED, then it is equal
                                         to the exit value of the child
                                         process, otherwise, it is equal to a
                                         signal that caused the child process
                                         to change state.
                    si_uid               real user ID of the process that sent
                                         the signal
     SIGPOLL        si_band              band event for POLL_IN, POLL_OUT, or

     Finally, the following code-specific information is available:

     Code              Member            Value
     SI_USER           si_pid            the process ID that sent the signal
                       si_uid            real user ID of the process that sent
                                         the signal
     SI_QUEUE          si_value          the value passed to sigqueue(2)
                                         system call
                       si_pid            the process ID that sent the signal
                       si_uid            real user ID of the process that sent
                                         the signal
     SI_TIMER          si_value          the value passed to timer_create(2)
                                         system call
                       si_timerid        the timer ID returned by
                                         timer_create(2) system call
                       si_overrun        timer overrun count corresponding to
                                         the signal
                       si_errno          If timer overrun will be
                                         {DELAYTIMER_MAX}, an error code
                                         defined in <errno.h> is set
     SI_ASYNCIO        si_value          the value passed to aio system calls
     SI_MESGQ          si_value          the value passed to mq_notify(2)
                                         system call
                       si_mqd            the ID of the message queue which
                                         generated the signal
     SI_LWP            si_pid            the process ID that sent the signal
                       si_uid            real user ID of the process that sent
                                         the signal

     Currently, the kernel never generates the SIGPOLL signal.  SIGCHLD signal
     is queued when a process changed its status or exited.  POSIX Realtime
     Extensions like aio, timer, and message queue also queue signals.
     Signals with code SI_USER, SI_KERNEL or SI_LWP are only queued if there
     are sufficient resources; otherwise, SI_NOINFO results.  For some
     hardware architectures, the exact value of si_addr might not be

     aio_read(2), kill(2), mq_notify(2), sigaction(2), sigqueue(2),
     sigwaitinfo(2), timer_create(2), timer_settime(2), waitpid(2),

     The siginfo_t type conforms to IEEE Std 1003.1-2004 (``POSIX.1'').

     Full support for POSIX signal information first appeared in FreeBSD 7.0.
     The codes SI_USER and SI_KERNEL can be generated as of FreeBSD 8.1.  The
     code SI_LWP can be generated as of FreeBSD 9.0.

     This manual page was written by David Xu <[email protected]>.

FreeBSD 11.1-RELEASE-p4          July 14, 2016         FreeBSD 11.1-RELEASE-p4
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