sigvec.2

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 2 代码 · 共 286 行

.\" SCCSID: @(#)sigvec.2	2.3	6/8/87
.TH sigvec 2 VAX
.ie t .ds d \(dg
.el .ds d \z'|+'
.ie t .ds b \(bu
.el .ds b @
.SH Name
sigvec \- software signal facilities
.SH Syntax
.nf
#include <signal.h>
.PP
struct sigvec {
void		(*\fIsv_handler\fP)\^(\^);
sigset_t	sv_mask;
int		sv_flags;
};
.PP
sigvec\^(\fIsig, vec, ovec\fP)
int \fIsig\fP;
struct sigvec *\fIvec, *ovec\fP;
.fi
.SH Description
.NXR "sigvec system call"
.NXR "signal handler" "assigning"
The system defines a set of signals that can 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 can specify a handler
to which a signal is delivered, or specify that a signal is to be 
blocked or ignored.
A process can 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 can be changed on a per-handler basis
so that signals are taken on a special signal stack.
.PP
All signals have the same priority.  Signal routines execute with the
signal that caused their invocation to be blocked , but other signals can occur.
A global signal mask defines the set of signals currently blocked from delivery
to a process.  The signal mask for a process is initialized
from that of its parent (normally 0).  It may be changed with a
.PN sigblock 
or
.PN sigsetmask 
call, or when a signal is delivered to the process.
.PP
When a signal condition arises for a process, the signal is added to a set of
signals pending for the process.  If the signal is not currently
blocked by the process, 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 later), 
and the signal handler is invoked.  The call to the handler
is arranged so that, if the signal handling routine returns
normally, the process resumes execution in the context
from before the signal's delivery.
If the process wishes to resume in a different context, it
must arrange to restore the previous context itself.
.PP
When a signal is delivered to a process, a new signal mask is
installed for the duration of the process's signal handler
(or until a
.PN sigblock
or
.PN sigsetmask
call is made).
This mask is formed by taking the current signal mask,
adding the signal to be delivered, and ORing
in the signal mask associated with the handler to be invoked.
.PP
The
.PN sigvec
system call assigns a handler for a specific signal.  If
.I vec
is nonzero, it specifies a handler routine and mask
to be used when delivering the specified signal.  Further, if the SV_ONSTACK
bit is set in
.I sv_flags,
the system delivers the signal to the process on a signal stack,
specified with 
.PN sigstack .
If 
.I ovec
is nonzero, the previous handling information for the signal
is returned to the user.
.PP
The following is a list of all signals
with names as in the include file
.PN <signal.h> :
.NXR "sigvec system call" "signal list"
.PP
.nf
.ta \w'SIGVTALRM 'u +\w'15*  'u
SIGHUP	1	hangup
SIGINT	2	interrupt
SIGQUIT	3*	quit
SIGILL	4*	illegal instruction
SIGTRAP	5*	trace trap
SIGIOT	6*	IOT instruction
SIGEMT	7*	EMT instruction
SIGFPE	8*	floating point exception
SIGKILL	9	kill (cannot be caught, blocked, 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
SIGURG	16.	urgent condition present on socket
SIGSTOP	17+	stop (cannot be caught, blocked, or ignored)
SIGTSTP	18+	stop signal generated from keyboard
SIGCONT	19.	continue after stop 
SIGCHLD	20.	child status has changed
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))
SIGWINCH	28.  window size change
SIGLOST	29	lock not reclaimed after server recovery
SIGUSR1	30	user defined signal 1
SIGUSR2	31	user defined signal 2
SIGCLD		System V name for SIGCHLD
SIGABRT		X/OPEN name for SIGIOT
.fi
.PP
The signals marked with asterisks (*) in this list cause a core image
if not caught or ignored.  Explanations of the meaning of the periods (.)
and plus signs (+) are included in the following paragraph.
.PP
Once a signal handler is installed, it remains installed
until another
.PN sigvec
call is made or an 
.PN execve 
is performed.
The default action for a signal can be reinstated by setting
.I sv_handler
to SIG_DFL. This default is termination (with a core image for signals
marked with asterisks (*)),
except for signals marked with periods (.) or plus signs (+).
Signals marked with periods (.) are
discarded if the action is SIG_DFL. 
Signals marked with plus signs (+) cause the
process to stop.  If
.I sv_handler
is SIG_IGN the signal is subsequently ignored, and pending instances of the
signal are discarded.
.PP
If a caught signal occurs during certain system calls,
the call is normally restarted.
The call can be forced to terminate prematurely with an
EINTR error return, by setting the SV_INTERRUPT bit in
.I sv_flags.
The affected system calls are
.PN read ,
.PN write ,
or
.PN ioctl
on a slow device (such as a terminal; but not a file),
.PN flock ,
and
.PN wait .
.PP
After a 
.PN fork
or
.PN vfork ,
the child inherits
all signals, the signal mask, the signal stack,
and the restart/interrupt flags.
.PP
The
.PN execve
system call resets all caught signals to default action and
resets all signals to be caught on the user stack.
Ignored signals remain ignored, the signal mask remains the same;
signals that interrupt system calls continue to do so.
.PP
The mask specified in 
.I vec
is not allowed to block SIGKILL or SIGSTOP.  This is done silently
by the system.
.PP
The SV_INTERRUPT flag is not available in ULTRIX 2.0 or earlier versions.
Therefore, it should not be used if backward compatibility is needed.
.PP
.B Notes 
.PP
.NXR "sigvec system call" "VAX notes"
The handler routine can be declared:
.EX
void handler(sig, code, scp)
int sig, code;
struct sigcontext *scp;
.EE
Here
.I sig
is the signal number into which the hardware faults and traps are
mapped as defined in the following table. 
The
.I code
is a parameter that is either a constant
or, for compatibility mode faults, the code provided by
the hardware.  Compatibility mode faults are distinguished from the
other SIGILL traps by having PSL_CM set in the psl.
The
.I scp
is a pointer to the
.I sigcontext
structure (defined in
.PN <signal.h>
), used to restore the context from before the signal.
.PP
The following defines the mapping of hardware traps to signals
and codes.  All of these symbols are defined in
.PN <signal.h> :
.PP
.ta \w'     Floating/decimal divide by zero   'u +\w'15*  'u +8n
.nf
   \fBHardware condition	Signal	Code\fR

Arithmetic traps:
   Integer overflow	SIGFPE	FPE_INTOVF_TRAP
   Integer division by zero	SIGFPE	FPE_INTDIV_TRAP
   Floating overflow trap	SIGFPE	FPE_FLTOVF_TRAP
   Floating/decimal division by zero	SIGFPE	FPE_FLTDIV_TRAP
   Floating underflow trap	SIGFPE	FPE_FLTUND_TRAP
   Decimal overflow trap	SIGFPE	FPE_DECOVF_TRAP
   Subscript-range	SIGFPE	FPE_SUBRNG_TRAP
   Floating overflow fault	SIGFPE	FPE_FLTOVF_FAULT
   Floating divide by zero fault	SIGFPE	FPE_FLTDIV_FAULT
   Floating underflow fault	SIGFPE	FPE_FLTUND_FAULT
Length access control	SIGSEGV	faulting virtual addr
Protection violation	SIGBUS	faulting virtual addr
Reserved instruction	SIGILL	ILL_PRIVIN_FAULT
Customer-reserved instr.	SIGEMT
Reserved operand	SIGILL	ILL_RESOP_FAULT
Reserved addressing	SIGILL	ILL_RESAD_FAULT
Trace pending	SIGTRAP
Bpt instruction	SIGTRAP
Compatibility-mode	SIGILL	hardware-supplied code
Chme	SIGSEGV
Chms	SIGSEGV
Chmu	SIGSEGV
.fi
.SH Return Values
A zero (0) value indicates that the call succeeded.  A \-1 return value
indicates an error occurred, and
.I errno
is set to indicate the reason.
.SH Diagnostics
.NXR "sigvec system call" "diagnostics"
The
.PN sigvec
system call fails and no new signal handler is installed, if one
of the following occurs:
.TP 15
[EFAULT]
Either
.I vec
or 
.I ovec
points to memory that is not a valid part of the process
address space.
.TP 15
[EINVAL]
The
.I sig
argument is not a valid signal number.
.TP 15
[EINVAL]
An attempt is made to ignore or supply a handler for SIGKILL
or SIGSTOP.
.SH Environment
.TP
SYSTEM_FIVE
You can not use the
.PN sigvec
call in your program under SYSTEM_FIVE environment.
.SH See Also
kill(1), kill(2), ptrace(2), sigblock(2), sigpause(2), sigsetmask(2),
sigstack(2), setjmp(3), siginterrupt(3), tty(4)