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SIGINFO(3) Library Functions Manual SIGINFO(3) NAME siginfo -- signal generation information SYNOPSIS #include <signal.h> DESCRIPTION A process may request signal information when it is catching a signal. The information specifies why the system generated that signal. To re- quest 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 informa- tion. In either case, the system returns the information in a struc- ture 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 virtual address 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 int si_syscall system-call number for system calls blocked by Capsicum The si_signo member contains the signal number. The si_errno member contains an error number defined in the file <errno.h>. 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 BUS_OOMERR cannot alloc a page to map at fault SIGTRAP TRAP_BRKPT process breakpoint TRAP_TRACE process trace trap TRAP_DTRACE DTrace induced trap TRAP_CAP capabilities protective 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 asyn- chronous 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) For synchronous signals, si_addr is generally set to the address of the faulting instruction. However, synchronous signals raised by a fault- ing memory access such as SIGSEGV and SIGBUS may report the address of the faulting memory access (if available) in si_addr instead. Addi- tionally SIGTRAP raised by a hardware watchpoint exception may report the data address that triggered the watchpoint in si_addr. Sychronous signals set si_trapno to a machine-dependent trap number. In addition, the following signal-specific information is available: Signal Member Value 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 POLL_MSG 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 NOTES Currently, the kernel never generates the SIGPOLL signal. SIGCHLD sig- nal is queued when a process changed its status or exited. POSIX Real- time 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 hard- ware architectures, the exact value of si_addr might not be available. SEE ALSO aio_read(2), kill(2), mq_notify(2), sigaction(2), sigqueue(2), sigwaitinfo(2), timer_create(2), timer_settime(2), waitpid(2), pthread_kill(3) STANDARDS The siginfo_t type conforms to IEEE Std 1003.1-2004 ("POSIX.1"). HISTORY 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. AUTHORS This manual page was written by David Xu <davidxu@FreeBSD.org>. FreeBSD 15.0 February 17, 2021 SIGINFO(3)
NAME | SYNOPSIS | DESCRIPTION | NOTES | SEE ALSO | STANDARDS | HISTORY | AUTHORS
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