4.3BSD-UWisc/man/cat2/sigvec.2
SIGVEC(2) UNIX Programmer's Manual SIGVEC(2)
NAME
sigvec - software signal facilities
SYNOPSIS
#include <signal.h>
struct sigvec {
int (*sv_handler)();
int sv_mask;
int sv_flags;
};
sigvec(sig, vec, ovec)
int sig;
struct sigvec *vec, *ovec;
DESCRIPTION
The system defines a set of signals that may be delivered to
a process. Signal delivery resembles the occurence 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 _h_a_n_d_l_e_r to which a
signal is delivered, or specify that a signal is to be
_b_l_o_c_k_e_d or _i_g_n_o_r_e_d. 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 _s_i_g_n_a_l _s_t_a_c_k.
All signals have the same _p_r_i_o_r_i_t_y. Signal routines execute
with the signal that caused their invocation _b_l_o_c_k_e_d, but
other signals may yet occur. A global _s_i_g_n_a_l _m_a_s_k defines
the set of signals currently blocked from delivery to a pro-
cess. The signal mask for a process is initialized from
that of its parent (normally 0). It may be changed with a
_s_i_g_b_l_o_c_k(2) or _s_i_g_s_e_t_m_a_s_k(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
signal is not currently _b_l_o_c_k_e_d 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 con-
text itself.
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SIGVEC(2) UNIX Programmer's Manual SIGVEC(2)
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 _s_i_g_b_l_o_c_k or _s_i_g_s_e_t_m_a_s_k call is made). This mask
is formed by taking the current signal mask, adding the sig-
nal to be delivered, and _o_r'ing in the signal mask associ-
ated with the handler to be invoked.
_S_i_g_v_e_c assigns a handler for a specific signal. If _v_e_c is
non-zero, it specifies a handler routine and mask to be used
when delivering the specified signal. Further, if the
SV_ONSTACK bit is set in _s_v__f_l_a_g_s, the system will deliver
the signal to the process on a _s_i_g_n_a_l _s_t_a_c_k, specified with
_s_i_g_s_t_a_c_k(2). If _o_v_e_c is non-zero, the previous handling
information for the signal is returned to the user.
The following is a list of all signals with names as in the
include file <_s_i_g_n_a_l._h>:
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 (cannot be blocked)
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 _f_c_n_t_l(2))
SIGXCPU 24 cpu time limit exceeded (see _s_e_t_r_l_i_m_i_t(2))
SIGXFSZ 25 file size limit exceeded (see _s_e_t_r_l_i_m_i_t(2))
SIGVTALRM 26 virtual time alarm (see _s_e_t_i_t_i_m_e_r(2))
SIGPROF 27 profiling timer alarm (see _s_e_t_i_t_i_m_e_r(2))
SIGWINCH 28@ window size change
SIGUSR1 30 user defined signal 1
SIGUSR2 31 user defined signal 2
The starred signals in the list above cause a core image if
not caught or ignored.
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Once a signal handler is installed, it remains installed
until another _s_i_g_v_e_c call is made, or an _e_x_e_c_v_e(2) is per-
formed. The default action for a signal may be reinstated
by setting _s_v__h_a_n_d_l_e_r to SIG_DFL; this default is termina-
tion (with a core image for starred signals) except for sig-
nals marked with @ or '|+'. Signals marked with @ are dis-
carded if the action is SIG_DFL; signals marked with '|+'
cause the process to stop. If _s_v__h_a_n_d_l_e_r 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, the
call is normally restarted. The call can be forced to ter-
minate prematurely with an EINTR error return by setting the
SV_INTERRUPT bit in _s_v__f_l_a_g_s. The affected system calls are
_r_e_a_d(2) or _w_r_i_t_e(2) on a slow device (such as a terminal;
but not a file) and during a _w_a_i_t(2).
After a _f_o_r_k(2) or _v_f_o_r_k(2) the child inherits all signals,
the signal mask, the signal stack, and the restart/interrupt
flags.
_E_x_e_c_v_e(2) 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.
NOTES
The mask specified in _v_e_c is not allowed to block SIGKILL,
SIGSTOP, or SIGCONT. This is done silently by the system.
The SV_INTERRUPT flag is not available in 4.2BSD, hence it
should not be used if backward compatibility is needed.
RETURN VALUE
A 0 value indicated that the call succeeded. A -1 return
value indicates an error occurred and _e_r_r_n_o is set to indi-
cated the reason.
ERRORS
_S_i_g_v_e_c will fail and no new signal handler will be installed
if one of the following occurs:
[EFAULT] Either _v_e_c or _o_v_e_c points to memory that is
not a valid part of the process address
space.
[EINVAL] _S_i_g is not a valid signal number.
[EINVAL] An attempt is made to ignore or supply a
handler for SIGKILL or SIGSTOP.
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SIGVEC(2) UNIX Programmer's Manual SIGVEC(2)
[EINVAL] An attempt is made to ignore SIGCONT (by
default SIGCONT is ignored).
SEE ALSO
kill(1), ptrace(2), kill(2), sigblock(2), sigsetmask(2),
sigpause(2), sigstack(2), sigvec(2), setjmp(3), siginter-
rupt(3), tty(4)
NOTES (VAX-11)
The handler routine can be declared:
handler(sig, code, scp)
int sig, code;
struct sigcontext *scp;
Here _s_i_g is the signal number, into which the hardware
faults and traps are mapped as defined below. _C_o_d_e is a
parameter that is either a constant as given below 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). _S_c_p is a
pointer to the _s_i_g_c_o_n_t_e_x_t structure (defined in <_s_i_g_n_a_l._h>),
used to restore the context from before the signal.
The following defines the mapping of hardware traps to sig-
nals and codes. All of these symbols are defined in
<_s_i_g_n_a_l._h>:
Hardware condition Signal Code
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
Protection violation SIGBUS
Reserved instruction SIGILL ILL_RESAD_FAULT
Customer-reserved instr. SIGEMT
Reserved operand SIGILL ILL_PRIVIN_FAULT
Reserved addressing SIGILL ILL_RESOP_FAULT
Trace pending SIGTRAP
Bpt instruction SIGTRAP
Compatibility-mode SIGILL hardware supplied code
Chme SIGSEGV
Chms SIGSEGV
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SIGVEC(2) UNIX Programmer's Manual SIGVEC(2)
Chmu SIGSEGV
BUGS
This manual page is still confusing.
Printed 12/27/86 January 8, 1986 5