compat-43/sigvec.2

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  32 .\"     @(#)sigvec.2    8.2 (Berkeley) 4/19/94
  33 .\" $FreeBSD: src/lib/libc/compat-43/sigvec.2,v 1.9.2.7 2001/12/14 18:33:49 ru Exp $
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  35 .Dd April 19, 1994
  36 .Dt SIGVEC 2
  37 .Os
  38 .Sh NAME
  39 .Nm sigvec
  40 .Nd software signal facilities
  41 .Sh LIBRARY
  42 .Lb libc
  43 .Sh SYNOPSIS
  44 .In signal.h
  45 .Bd -literal
  46 struct sigvec {
  47         void     (*sv_handler)();
  48         int      sv_mask;
  49         int      sv_flags;
  50 };
  51 .Ed
  52 .Ft int
  53 .Fn sigvec "int sig" "struct sigvec *vec" "struct sigvec *ovec"
  54 .Sh DESCRIPTION
  55 .Bf -symbolic
  56 This interface is made obsolete by
  57 .Xr sigaction 2 .
  58 .Ef
  59 .Pp
  60 The system defines a set of signals that may be delivered to a process.
  61 Signal delivery resembles the occurrence of a hardware interrupt:
  62 the signal is blocked from further occurrence, the current process
  63 context is saved, and a new one is built.  A process may specify a
  64 .Em handler
  65 to which a signal is delivered, or specify that a signal is to be
  66 .Em blocked
  67 or
  68 .Em ignored .
  69 A process may also specify that a default action is to be taken
  70 by the system when a signal occurs.
  71 Normally, signal handlers execute on the current stack
  72 of the process.  This may be changed, on a per-handler basis,
  73 so that signals are taken on a special
  74 .Em "signal stack" .
  75 .Pp
  76 All signals have the same
  77 .Em priority .
  78 Signal routines execute with the signal that caused their
  79 invocation
  80 .Em blocked ,
  81 but other signals may yet occur.
  82 A global
  83 .Em "signal mask"
  84 defines the set of signals currently blocked from delivery
  85 to a process.  The signal mask for a process is initialized
  86 from that of its parent (normally 0).  It
  87 may be changed with a
  88 .Xr sigblock 2
  89 or
  90 .Xr sigsetmask 2
  91 call, or when a signal is delivered to the process.
  92 .Pp
  93 When a signal
  94 condition arises for a process, the signal is added to a set of
  95 signals pending for the process.  If the signal is not currently
  96 .Em blocked
  97 by the process then it is delivered to the process.  When a signal
  98 is delivered, the current state of the process is saved,
  99 a new signal mask is calculated (as described below),
 100 and the signal handler is invoked.  The call to the handler
 101 is arranged so that if the signal handling routine returns
 102 normally the process will resume execution in the context
 103 from before the signal's delivery.
 104 If the process wishes to resume in a different context, then it
 105 must arrange to restore the previous context itself.
 106 .Pp
 107 When a signal is delivered to a process a new signal mask is
 108 installed for the duration of the process' signal handler
 109 (or until a
 110 .Xr sigblock 2
 111 or
 112 .Xr sigsetmask 2
 113 call is made).
 114 This mask is formed by taking the current signal mask,
 115 adding the signal to be delivered, and
 116 .Em or Ns 'ing
 117 in the signal mask associated with the handler to be invoked.
 118 .Pp
 119 .Fn Sigvec
 120 assigns a handler for a specific signal.  If
 121 .Fa vec
 122 is non-zero, it
 123 specifies a handler routine and mask
 124 to be used when delivering the specified signal.
 125 Further, if the
 126 .Dv SV_ONSTACK
 127 bit is set in
 128 .Fa sv_flags ,
 129 the system will deliver the signal to the process on a
 130 .Em "signal stack" ,
 131 specified with
 132 .Xr sigaltstack 2 .
 133 If
 134 .Fa ovec
 135 is non-zero, the previous handling information for the signal
 136 is returned to the user.
 137 .Pp
 138 The following is a list of all signals
 139 with names as in the include file
 140 .Aq Pa signal.h :
 141 .Bl -column SIGVTALARMXX "create core imagexxx"
 142 .It Sy "NAME    Default Action  Description"
 143 .It Dv SIGHUP No "      terminate process" "    terminal line hangup"
 144 .It Dv SIGINT No "      terminate process" "    interrupt program"
 145 .It Dv SIGQUIT No "     create core image" "    quit program"
 146 .It Dv SIGILL No "      create core image" "    illegal instruction"
 147 .It Dv SIGTRAP No "     create core image" "    trace trap"
 148 .It Dv SIGABRT No "     create core image" Ta Xr abort 3
 149 call (formerly
 150 .Dv SIGIOT )
 151 .It Dv SIGEMT No "      create core image" "    emulate instruction executed"
 152 .It Dv SIGFPE No "      create core image" "    floating-point exception"
 153 .It Dv SIGKILL No "     terminate process" "    kill program"
 154 .It Dv SIGBUS No "      create core image" "    bus error"
 155 .It Dv SIGSEGV No "     create core image" "    segmentation violation"
 156 .It Dv SIGSYS No "      create core image" "    non-existent system call invoked"
 157 .It Dv SIGPIPE No "     terminate process" "    write on a pipe with no reader"
 158 .It Dv SIGALRM No "     terminate process" "    real-time timer expired"
 159 .It Dv SIGTERM No "     terminate process" "    software termination signal"
 160 .It Dv SIGURG No "      discard signal" "       urgent condition present on socket"
 161 .It Dv SIGSTOP No "     stop process" " stop (cannot be caught or ignored)"
 162 .It Dv SIGTSTP No "     stop process" " stop signal generated from keyboard"
 163 .It Dv SIGCONT No "     discard signal" "       continue after stop"
 164 .It Dv SIGCHLD No "     discard signal" "       child status has changed"
 165 .It Dv SIGTTIN No "     stop process" " background read attempted from control terminal"
 166 .It Dv SIGTTOU No "     stop process" " background write attempted to control terminal"
 167 .It Dv SIGIO No "       discard signal" Tn "    I/O"
 168 is possible on a descriptor (see
 169 .Xr fcntl 2 )
 170 .It Dv SIGXCPU No "     terminate process" "    cpu time limit exceeded (see"
 171 .Xr setrlimit 2 )
 172 .It Dv SIGXFSZ No "     terminate process" "    file size limit exceeded (see"
 173 .Xr setrlimit 2 )
 174 .It Dv SIGVTALRM No "   terminate process" "    virtual time alarm (see"
 175 .Xr setitimer 2 )
 176 .It Dv SIGPROF No "     terminate process" "    profiling timer alarm (see"
 177 .Xr setitimer 2 )
 178 .It Dv SIGWINCH No "    discard signal" "       Window size change"
 179 .It Dv SIGINFO No "     discard signal" "       status request from keyboard"
 180 .It Dv SIGUSR1 No "     terminate process" "    User defined signal 1"
 181 .It Dv SIGUSR2 No "     terminate process" "    User defined signal 2"
 182 .El
 183 .Pp
 184 Once a signal handler is installed, it remains installed
 185 until another
 186 .Fn sigvec
 187 call is made, or an
 188 .Xr execve 2
 189 is performed.
 190 A signal-specific default action may be reset by
 191 setting
 192 .Fa sv_handler
 193 to
 194 .Dv SIG_DFL .
 195 The defaults are process termination, possibly with core dump;
 196 no action; stopping the process; or continuing the process.
 197 See the above signal list for each signal's default action.
 198 If
 199 .Fa sv_handler
 200 is
 201 .Dv SIG_IGN
 202 current and pending instances
 203 of the signal are ignored and discarded.
 204 .Pp
 205 If a signal is caught during the system calls listed below,
 206 the call is normally restarted.
 207 The call can be forced to terminate prematurely with an
 208 .Er EINTR
 209 error return by setting the
 210 .Dv SV_INTERRUPT
 211 bit in
 212 .Fa sv_flags .
 213 The affected system calls include
 214 .Xr read 2 ,
 215 .Xr write 2 ,
 216 .Xr sendto 2 ,
 217 .Xr recvfrom 2 ,
 218 .Xr sendmsg 2
 219 and
 220 .Xr recvmsg 2
 221 on a communications channel or a slow device (such as a terminal,
 222 but not a regular file)
 223 and during a
 224 .Xr wait 2
 225 or
 226 .Xr ioctl 2 .
 227 However, calls that have already committed are not restarted,
 228 but instead return a partial success (for example, a short read count).
 229 .Pp
 230 After a
 231 .Xr fork 2
 232 or
 233 .Xr vfork 2
 234 all signals, the signal mask, the signal stack,
 235 and the restart/interrupt flags are inherited by the child.
 236 .Pp
 237 .Xr Execve 2
 238 reinstates the default
 239 action for all signals which were caught and
 240 resets all signals to be caught on the user stack.
 241 Ignored signals remain ignored;
 242 the signal mask remains the same;
 243 signals that interrupt system calls continue to do so.
 244 .Sh NOTES
 245 The mask specified in
 246 .Fa vec
 247 is not allowed to block
 248 .Dv SIGKILL
 249 or
 250 .Dv SIGSTOP .
 251 This is done silently by the system.
 252 .Pp
 253 The
 254 .Dv SV_INTERRUPT
 255 flag is not available in
 256 .Bx 4.2 ,
 257 hence it should not be used if backward compatibility is needed.
 258 .Sh RETURN VALUES
 259 .Rv -std sigvec
 260 .Sh ERRORS
 261 .Fn Sigvec
 262 will fail and no new signal handler will be installed if one
 263 of the following occurs:
 264 .Bl -tag -width Er
 265 .It Bq Er EFAULT
 266 Either
 267 .Fa vec
 268 or
 269 .Fa ovec
 270 points to memory that is not a valid part of the process
 271 address space.
 272 .It Bq Er EINVAL
 273 .Fa Sig
 274 is not a valid signal number.
 275 .It Bq Er EINVAL
 276 An attempt is made to ignore or supply a handler for
 277 .Dv SIGKILL
 278 or
 279 .Dv SIGSTOP .
 280 .El
 281 .Sh SEE ALSO
 282 .Xr kill 1 ,
 283 .Xr kill 2 ,
 284 .Xr ptrace 2 ,
 285 .Xr sigaction 2 ,
 286 .Xr sigaltstack 2 ,
 287 .Xr sigblock 2 ,
 288 .Xr sigpause 2 ,
 289 .Xr sigprocmask 2 ,
 290 .Xr sigsetmask 2 ,
 291 .Xr sigsuspend 2 ,
 292 .Xr setjmp 3 ,
 293 .Xr siginterrupt 3 ,
 294 .Xr signal 3 ,
 295 .Xr sigsetops 3 ,
 296 .Xr tty 4
 297 .Sh EXAMPLES
 298 On the
 299 .Tn VAX\-11
 300 The handler routine can be declared:
 301 .Bd -literal -offset indent
 302 void handler(sig, code, scp)
 303 int sig, code;
 304 struct sigcontext *scp;
 305 .Ed
 306 .Pp
 307 Here
 308 .Fa sig
 309 is the signal number, into which the hardware faults and traps are
 310 mapped as defined below.
 311 .Fa Code
 312 is a parameter that is either a constant
 313 as given below or, for compatibility mode faults, the code provided by
 314 the hardware (Compatibility mode faults are distinguished from the
 315 other
 316 .Dv SIGILL
 317 traps by having
 318 .Dv PSL_CM
 319 set in the psl).
 320 .Fa Scp
 321 is a pointer to the
 322 .Fa sigcontext
 323 structure (defined in
 324 .Aq Pa signal.h ) ,
 325 used to restore the context from before the signal.
 326 .Sh BUGS
 327 This manual page is still confusing.