SIGVEC(2) COMMAND REFERENCE SIGVEC(2)
NAME
sigvec - software signal facilities
SYNOPSIS
#include <signal.h>
sigvec(sig, vec, ovec)
int sig;
struct sigvec *vec, *ovec;
DESCRIPTION
Sigvec assigns a handler for a specific signal sig, using
the following structure, defined in <signal.h>:
struct sigvec {
int (*sv_handler)();
int sv_mask;
int sv_onstack;
};
If vec is non-zero, it specifies a handler routine
sv_handler() and mask sv_mask to be used when delivering
sig. Further, if sv_onstack is 1, the system will deliver
the signal to the process on a signal stack, specified with
sigstack(2). If ovec is non-zero, the previous handling
information for the signal is returned to the user. For an
explanation of these terms, see below.
The system defines a set of signals that may be delivered to
a process. Signal delivery resembles the occurrence of a
hardware interrupt: the signal is blocked from further
occurrence, the current process context is saved, and a new
one is built. A process may specify a handler to which a
signal is delivered, may reinstate the default action for a
signal, or may specify that a signal is to be ignored. A
process may also specify that a default action is to be
taken by the system when a signal occurs. Normally, signal
handlers execute on the current stack of the process. This
may be changed, on a per-handler basis, so that signals are
taken on a special signal stack.
All signals have the same priority. Signal routines execute
with the signal that caused their invocation blocked, but
other signals may yet occur. A global signal mask defines
the set of signals currently blocked from delivery to a
process. The signal mask for a process is initilized from
that of its parent (normally 0). It may be changed with a
sigblock(2) or sigsetmask(2) call, or when a signal is
delivered to the process.
When a signal condition arises for a process, the signal is
added to a set of signals pending for the process. If the
Printed 10/17/86 1
SIGVEC(2) COMMAND REFERENCE SIGVEC(2)
signal is not currently blocked by the process then it is
delivered to the process. When a signal is delivered, the
current state of the process is saved, a new signal mask is
calculated (as described below), and the signal handler is
invoked. The call to the handler is arranged so that if the
signal handling routine returns normally the process will
resume execution in the context from before the signal's
delivery. If the process wishes to resume in a different
context, then it must arrange to restore the previous
context itself.
When a signal is delivered to a process a new signal mask is
installed for the duration of the process' signal handler
(or until a sigblock or sigsetmask call is made). This mask
is formed by taking the current signal mask, adding the
signal to be delivered, and or'ing in the signal mask
associated with the handler to be invoked.
The following is a list of all signals with names as in the
include file <signal.h>:
SIGHUP 1 hangup
SIGINT 2 interrupt
SIGQUIT 3* quit
SIGILL 4* illegal instruction (not reset when caught)
SIGTRAP 5* trace trap (not reset when caught)
SIGIOT 6* FLAG instruction when F condition set
SIGEMT 7* (unused)
SIGFPE 8* floating point exception
SIGKILL 9 kill (cannot be caught or ignored)
SIGBUS 10* bus error
SIGSEGV 11* segmentation violation
SIGSYS 12* bad argument to system call
SIGPIPE 13 write on a pipe with no one to read it
SIGALRM 14 alarm clock
SIGTERM 15 software termination signal from kill
SIGURG 16• urgent condition present on socket,
exception condition present on a device
SIGSTOP 17† stop (cannot be caught or ignored)
SIGTSTP 18† stop signal generated from keyboard
SIGCONT 19• continue after stop (cannot be blocked)
SIGCHLD 20• to parent on child stop or exit
SIGTTIN 21† background read attempted from control terminal
SIGTTOU 22† background write attempted to control terminal
SIGIO 23• I/O is possible on a descriptor (see fcntl(2))
SIGXCPU 24 cpu time limit exceeded (see setrlimit(2))
SIGXFSZ 25 file size limit exceeded (see setrlimit(2))
SIGVTALRM 26 virtual time alarm (see setitimer(2))
SIGPROF 27 profiling timer alarm (see setitimer(2))
SIGUSR1 28 user-defined signal 1
SIGUSR2 29 user-defined signal 2
SIGPWR 31 power fail
Printed 10/17/86 2
SIGVEC(2) COMMAND REFERENCE SIGVEC(2)
The starred signals in the list above cause a core image if
not caught or ignored.
Once a signal handler is installed, it remains installed
until another sigvec call is made, or an execve(2) is
performed. The default action for a signal may be
reinstated by setting sv_handler to SIG_DFL; this default is
termination (with a core image for starred signals) except
for signals marked with • or †. Signals marked with • are
discarded if the action is SIG_DFL; signals marked with †
cause the process to stop. If sv_handler is SIG_IGN the
signal is subsequently ignored, and pending instances of the
signal are discarded.
If a caught signal occurs during certain system calls,
causing the call to terminate prematurely, the call is
automatically restarted. In particular this can occur
during a read or write(2) on a slow device (such as a
terminal; but not a file) and during a wait(2).
After a fork(2) or vfork(2) the child inherits all signals,
the signal mask, and the signal stack.
The system call execve(2) resets all caught signals to
default action; ignored signals remain ignored; the signal
mask remains the same; the signal stack state is reset.
The mask specified in vec is not allowed to block SIGKILL,
SIGSTOP, or SIGCONT. This is done silently by the system.
The handler routine can be declared:
handler(sig, code, scp)
int sig, code;
struct sigcontext *scp;
Here sig is the signal number, into which the hardware
faults and traps are mapped as defined below. Code is a
parameter, a constant as given below. Scp is a pointer to
the sigcontext structure (defined in <signal.h>), used to
restore the context from before the signal.
The following defines the mapping of hardware traps to
signals and codes. All of these symbols are defined in
<signal.h>:
Hardware condition Signal Code
Arithmetic traps:
Integer division by zero SIGFPE FPE_INTDIV_TRAP
Floating overflow trap SIGFPE FPE_FLTOVF_TRAP
Floating/decimal division by zero SIGFPE FPE_FLTDIV_TRAP
Printed 10/17/86 3
SIGVEC(2) COMMAND REFERENCE SIGVEC(2)
Floating underflow trap SIGFPE FPE_FLTUND_TRAP
Floating inexact result SIGFPE FPE_INEXCT_TRAP
Length access control SIGSEGV
Protection violation SIGBUS
Undefined instruction trap SIGILL ILL_UNDEF_TRAP
Privileged instruction trap SIGILL ILL_PRIVIN_TRAP
Floating reserved operand trap SIGILL ILL_RESOP_TRAP
Floating illegal instruction trap SIGILL ILL_FLOAT_TRAP
Customer-reserved instr. SIGEMT
Trace pending SIGTRAP
Bpt instruction SIGTRAP
DIAGNOSTICS
Sigvec will fail and no new signal handler will be installed
if one of the following occurs:
[EFAULT]
Either vec or ovec points to memory which is not a valid
part of the process address space.
[EINVAL]
Sig is not a valid signal number.
[EINVAL]
An attempt is made to ignore or supply a handler for
SIGKILL or SIGSTOP.
[EINVAL]
An attempt is made to ignore SIGCONT (by default SIGCONT
is ignored).
RETURN VALUE
If ovec is non-zero, upon successful completion the previous
handling information is returned in ovec. If ovec is NULL,
upon successful completion a 0 is returned. If an error
occurs, a value of -1 is returned and errno is set to
indicate the error.
SEE ALSO
kill(1), kill(2), ptrace(2), sigblock(2), sigpause(2)
sigsetmask(2), sigstack(2), sigvec(2), setjmp(3c),
setjmp(3f), tty(4).
Printed 10/17/86 4
%%index%%
na:72,71;
sy:143,566;
de:709,2428;3281,2801;6226,2525;8895,694;
di:9589,630;
rv:10219,390;
se:10609,365;
%%index%%000000000138