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Annotation of 43BSDTahoe/man/man2/sigvec.2, revision 1.1

1.1     ! root        1: .\" Copyright (c) 1980 Regents of the University of California.
        !             2: .\" All rights reserved.  The Berkeley software License Agreement
        !             3: .\" specifies the terms and conditions for redistribution.
        !             4: .\"
        !             5: .\"    @(#)sigvec.2    6.3 (Berkeley) 1/8/86
        !             6: .\"
        !             7: .TH SIGVEC 2 "January 8, 1986"
        !             8: .UC 4
        !             9: .ie t .ds d \(dg
        !            10: .el .ds d \z'|+'
        !            11: .ie t .ds b \(bu
        !            12: .el .ds b @
        !            13: .SH NAME
        !            14: sigvec \- software signal facilities
        !            15: .SH SYNOPSIS
        !            16: .nf
        !            17: .B #include <signal.h>
        !            18: .PP
        !            19: .B struct sigvec {
        !            20: .B     int     (*sv_handler)();
        !            21: .B     int     sv_mask;
        !            22: .B     int     sv_flags;
        !            23: .B };
        !            24: .PP
        !            25: .B sigvec(sig, vec, ovec)
        !            26: .B int sig;
        !            27: .B struct sigvec *vec, *ovec;
        !            28: .fi
        !            29: .SH DESCRIPTION
        !            30: The system defines a set of signals that may be delivered to a process.
        !            31: Signal delivery resembles the occurence of a hardware interrupt:
        !            32: the signal is blocked from further occurrence, the current process 
        !            33: context is saved, and a new one is built.  A process may specify a
        !            34: .I handler
        !            35: to which a signal is delivered, or specify that a signal is to be 
        !            36: .I blocked
        !            37: or
        !            38: .IR ignored .
        !            39: A process may also specify that a default action is to be taken
        !            40: by the system when a signal occurs.
        !            41: Normally, signal handlers execute on the current stack
        !            42: of the process.  This may be changed, on a per-handler basis,
        !            43: so that signals are taken on a special
        !            44: .IR "signal stack" .
        !            45: .PP
        !            46: All signals have the same
        !            47: .IR priority .
        !            48: Signal routines execute with the signal that caused their
        !            49: invocation
        !            50: .IR blocked ,
        !            51: but other signals may yet occur.
        !            52: A global 
        !            53: .I "signal mask"
        !            54: defines the set of signals currently blocked from delivery
        !            55: to a process.  The signal mask for a process is initialized
        !            56: from that of its parent (normally 0).  It
        !            57: may be changed with a
        !            58: .IR sigblock (2)
        !            59: or
        !            60: .IR sigsetmask (2)
        !            61: call, or when a signal is delivered to the process.
        !            62: .PP
        !            63: When a signal
        !            64: condition arises for a process, the signal is added to a set of
        !            65: signals pending for the process.  If the signal is not currently
        !            66: .I blocked
        !            67: by the process then it is delivered to the process.  When a signal
        !            68: is delivered, the current state of the process is saved,
        !            69: a new signal mask is calculated (as described below), 
        !            70: and the signal handler is invoked.  The call to the handler
        !            71: is arranged so that if the signal handling routine returns
        !            72: normally the process will resume execution in the context
        !            73: from before the signal's delivery.
        !            74: If the process wishes to resume in a different context, then it
        !            75: must arrange to restore the previous context itself.
        !            76: .PP
        !            77: When a signal is delivered to a process a new signal mask is
        !            78: installed for the duration of the process' signal handler
        !            79: (or until a
        !            80: .I sigblock
        !            81: or
        !            82: .I sigsetmask
        !            83: call is made).
        !            84: This mask is formed by taking the current signal mask,
        !            85: adding the signal to be delivered, and 
        !            86: .IR or 'ing
        !            87: in the signal mask associated with the handler to be invoked.
        !            88: .PP
        !            89: .I Sigvec
        !            90: assigns a handler for a specific signal.  If
        !            91: .I vec
        !            92: is non-zero, it
        !            93: specifies a handler routine and mask
        !            94: to be used when delivering the specified signal.
        !            95: Further, if the SV_ONSTACK bit is set in
        !            96: .I sv_flags,
        !            97: the system will deliver the signal to the process on a
        !            98: .IR "signal stack" ,
        !            99: specified with
        !           100: .IR sigstack (2).
        !           101: If 
        !           102: .I ovec
        !           103: is non-zero, the previous handling information for the signal
        !           104: is returned to the user.
        !           105: .PP
        !           106: The following is a list of all signals
        !           107: with names as in the include file
        !           108: .RI < signal.h >:
        !           109: .LP
        !           110: .nf
        !           111: .ta \w'SIGVTALRM 'u +\w'15*  'u
        !           112: SIGHUP 1       hangup
        !           113: SIGINT 2       interrupt
        !           114: SIGQUIT        3*      quit
        !           115: SIGILL 4*      illegal instruction
        !           116: SIGTRAP        5*      trace trap
        !           117: SIGIOT 6*      IOT instruction
        !           118: SIGEMT 7*      EMT instruction
        !           119: SIGFPE 8*      floating point exception
        !           120: SIGKILL        9       kill (cannot be caught, blocked, or ignored)
        !           121: SIGBUS 10*     bus error
        !           122: SIGSEGV        11*     segmentation violation
        !           123: SIGSYS 12*     bad argument to system call
        !           124: SIGPIPE        13      write on a pipe with no one to read it
        !           125: SIGALRM        14      alarm clock
        !           126: SIGTERM        15      software termination signal
        !           127: SIGURG 16\*b   urgent condition present on socket
        !           128: SIGSTOP        17\*d   stop (cannot be caught, blocked, or ignored)
        !           129: SIGTSTP        18\*d   stop signal generated from keyboard
        !           130: SIGCONT        19\*b   continue after stop (cannot be blocked)
        !           131: SIGCHLD        20\*b   child status has changed
        !           132: SIGTTIN        21\*d   background read attempted from control terminal
        !           133: SIGTTOU        22\*d   background write attempted to control terminal
        !           134: SIGIO  23\*b   i/o is possible on a descriptor (see \fIfcntl\fP(2))
        !           135: SIGXCPU        24      cpu time limit exceeded (see \fIsetrlimit\fP(2))
        !           136: SIGXFSZ        25      file size limit exceeded (see \fIsetrlimit\fP(2))
        !           137: SIGVTALRM      26      virtual time alarm (see \fIsetitimer\fP(2))
        !           138: SIGPROF        27      profiling timer alarm (see \fIsetitimer\fP(2))
        !           139: SIGWINCH       28\*b   window size change
        !           140: SIGUSR1        30      user defined signal 1
        !           141: SIGUSR2        31      user defined signal 2
        !           142: .fi
        !           143: .PP
        !           144: The starred signals in the list above cause a core image
        !           145: if not caught or ignored.
        !           146: .PP
        !           147: Once a signal handler is installed, it remains installed
        !           148: until another
        !           149: .I sigvec
        !           150: call is made, or an 
        !           151: .IR execve (2)
        !           152: is performed.
        !           153: The default action for a signal may be reinstated by setting
        !           154: .I sv_handler
        !           155: to SIG_DFL; this default is termination
        !           156: (with a core image for starred signals)
        !           157: except for signals marked with \*b or \*d.
        !           158: Signals marked with \*b are discarded if the action
        !           159: is SIG_DFL; signals marked
        !           160: with \*d cause the process to stop.
        !           161: If
        !           162: .I sv_handler
        !           163: is SIG_IGN the signal is subsequently ignored,
        !           164: and pending instances of the signal are discarded.
        !           165: .PP
        !           166: If a caught signal occurs during certain system calls,
        !           167: the call is normally restarted.
        !           168: The call can be forced to terminate prematurely with an
        !           169: EINTR error return by setting the SV_INTERRUPT bit in
        !           170: .I sv_flags.
        !           171: The affected system calls are
        !           172: .IR read (2)
        !           173: or
        !           174: .IR write (2)
        !           175: on a slow device (such as a terminal; but not a file)
        !           176: and during a
        !           177: .IR wait (2).
        !           178: .PP
        !           179: After a
        !           180: .IR fork (2)
        !           181: or
        !           182: .IR vfork (2)
        !           183: the child inherits
        !           184: all signals, the signal mask, the signal stack,
        !           185: and the restart/interrupt flags.
        !           186: .PP
        !           187: .IR  Execve (2)
        !           188: resets all
        !           189: caught signals to default action and
        !           190: resets all signals to be caught on the user stack.
        !           191: Ignored signals remain ignored;
        !           192: the signal mask remains the same;
        !           193: signals that interrupt system calls continue to do so.
        !           194: .SH NOTES
        !           195: The mask specified in 
        !           196: .I vec
        !           197: is not allowed to block SIGKILL, SIGSTOP, or SIGCONT.  This
        !           198: is done silently by the system.
        !           199: .PP
        !           200: The SV_INTERRUPT flag is not available in 4.2BSD,
        !           201: hence it should not be used if backward compatibility is needed.
        !           202: .SH "RETURN VALUE
        !           203: A 0 value indicated that the call succeeded.  A \-1 return value
        !           204: indicates an error occurred and
        !           205: .I errno
        !           206: is set to indicated the reason.
        !           207: .SH ERRORS
        !           208: .I Sigvec
        !           209: will fail and no new signal handler will be installed if one
        !           210: of the following occurs:
        !           211: .TP 15
        !           212: [EFAULT]
        !           213: Either
        !           214: .I vec
        !           215: or 
        !           216: .I ovec
        !           217: points to memory that is not a valid part of the process
        !           218: address space.
        !           219: .TP 15
        !           220: [EINVAL]
        !           221: .I Sig
        !           222: is not a valid signal number.
        !           223: .TP 15
        !           224: [EINVAL]
        !           225: An attempt is made to ignore or supply a handler for SIGKILL
        !           226: or SIGSTOP.
        !           227: .TP 15
        !           228: [EINVAL]
        !           229: An attempt is made to ignore SIGCONT (by default SIGCONT
        !           230: is ignored).
        !           231: .SH "SEE ALSO"
        !           232: kill(1),
        !           233: ptrace(2), kill(2),
        !           234: sigblock(2), sigsetmask(2), sigpause(2),
        !           235: sigstack(2), sigvec(2), setjmp(3), siginterrupt(3), tty(4)
        !           236: .SH "NOTES  (VAX-11)"
        !           237: The handler routine can be declared:
        !           238: .PP
        !           239:     handler(sig, code, scp)
        !           240:     int sig, code;
        !           241:     struct sigcontext *scp;
        !           242: .PP
        !           243: Here
        !           244: .I sig
        !           245: is the signal number, into which the hardware faults and traps are
        !           246: mapped as defined below. 
        !           247: .I Code
        !           248: is a parameter that is either a constant
        !           249: as given below or, for compatibility mode faults, the code provided by
        !           250: the hardware (Compatibility mode faults are distinguished from the
        !           251: other SIGILL traps by having PSL_CM set in the psl).
        !           252: .I Scp
        !           253: is a pointer to the
        !           254: .I sigcontext
        !           255: structure (defined in
        !           256: .RI < signal.h >),
        !           257: used to restore the context from before the signal.
        !           258: .PP
        !           259: The following defines the mapping of hardware traps to signals
        !           260: and codes.  All of these symbols are defined in
        !           261: .RI < signal.h >:
        !           262: .LP
        !           263: .ta \w'     Floating/decimal divide by zero   'u +\w'15*  'u +8n
        !           264: .nf
        !           265:    Hardware condition  Signal  Code
        !           266: 
        !           267: Arithmetic traps:
        !           268:    Integer overflow    SIGFPE  FPE_INTOVF_TRAP
        !           269:    Integer division by zero    SIGFPE  FPE_INTDIV_TRAP
        !           270:    Floating overflow trap      SIGFPE  FPE_FLTOVF_TRAP
        !           271:    Floating/decimal division by zero   SIGFPE  FPE_FLTDIV_TRAP
        !           272:    Floating underflow trap     SIGFPE  FPE_FLTUND_TRAP
        !           273:    Decimal overflow trap       SIGFPE  FPE_DECOVF_TRAP
        !           274:    Subscript-range     SIGFPE  FPE_SUBRNG_TRAP
        !           275:    Floating overflow fault     SIGFPE  FPE_FLTOVF_FAULT
        !           276:    Floating divide by zero fault       SIGFPE  FPE_FLTDIV_FAULT
        !           277:    Floating underflow fault    SIGFPE  FPE_FLTUND_FAULT
        !           278: Length access control  SIGSEGV
        !           279: Protection violation   SIGBUS
        !           280: Reserved instruction   SIGILL  ILL_RESAD_FAULT
        !           281: Customer-reserved instr.       SIGEMT
        !           282: Reserved operand       SIGILL  ILL_PRIVIN_FAULT
        !           283: Reserved addressing    SIGILL  ILL_RESOP_FAULT
        !           284: Trace pending  SIGTRAP
        !           285: Bpt instruction        SIGTRAP
        !           286: Compatibility-mode     SIGILL  hardware supplied code
        !           287: Chme   SIGSEGV
        !           288: Chms   SIGSEGV
        !           289: Chmu   SIGSEGV
        !           290: .fi
        !           291: .SH BUGS
        !           292: This manual page is still confusing.

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