1SIGVEC(2) System Calls Manual SIGVEC(2)
2
6 sigvec - software signal facilities
7
9 #include <signal.h>
10 struct sigvec {
12 int (*sv_handler)();
13 long sv_mask;
14 int sv_flags;
15 };
16 sigvec(sig, vec, ovec)
18 int sig;
19 struct sigvec *vec, *ovec;
20
22 This interface has been made obsolete by: [22msigaction(2).
23 The system defines a set of signals that may be delivered to a process.
25 Signal delivery resembles the occurence of a hardware interrupt: the
26 signal is blocked from further occurrence, the current process context
27 is saved, and a new one is built. A process may specify a handler to
28 which a signal is delivered, or specify that a signal is to be blocked
29 or ignored. A process may also specify that a default action is to be
30 taken by the system when a signal occurs. Normally, signal handlers
31 execute on the current stack of the process. This may be changed, on a
32 per-handler basis, so that signals are taken on a special signal stack.
33 All signals have the same priority. Signal routines execute with the
35 signal that caused their invocation blocked, but other signals may yet
36 occur. A global signal mask defines the set of signals currently
37 blocked from delivery to a process. The signal mask for a process is
38 initialized from that of its parent (normally 0). It may be changed
39 with a sigblock(2) or sigsetmask(2) call, or when a signal is delivered
40 to the process.
41 When a signal condition arises for a process, the signal is added to a
43 set of signals pending for the process. If the signal is not currently
44 blocked by the process then it is delivered to the process. When a
45 signal is delivered, the current state of the process is saved, a new
46 signal mask is calculated (as described below), and the signal handler
47 is invoked. The call to the handler is arranged so that if the signal
48 handling routine returns normally the process will resume execution in
49 the context from before the signal's delivery. If the process wishes
50 to resume in a different context, then it must arrange to restore the
51 previous context itself.
52 When a signal is delivered to a process a new signal mask is installed
54 for the duration of the process' signal handler (or until a sigblock or
55 sigsetmask call is made). This mask is formed by taking the current
56 signal mask, adding the signal to be delivered, and or'ing in the sig‐
57 nal mask associated with the handler to be invoked.
58 Sigvec assigns a handler for a specific signal. If vec is non-zero, it
60 specifies a handler routine and mask to be used when delivering the
61 specified signal. Further, if the SV_ONSTACK bit is set in sv_flags,
62 the system will deliver the signal to the process on a signal stack,
63 specified with sigstack(2). If ovec is non-zero, the previous handling
64 information for the signal is returned to the user.
65 The following is a list of all signals with names as in the include
67 file <signal.h>:
68 SIGHUP 1 hangup
70 SIGINT 2 interrupt
71 SIGQUIT 3* quit
72 SIGILL 4* illegal instruction
73 SIGTRAP 5* trace trap
74 SIGIOT 6* IOT instruction
75 SIGEMT 7* EMT instruction
76 SIGFPE 8* floating point exception
77 SIGKILL 9 kill (cannot be caught, blocked, or ignored)
78 SIGBUS 10* bus error
79 SIGSEGV 11* segmentation violation
80 SIGSYS 12* bad argument to system call
81 SIGPIPE 13 write on a pipe with no one to read it
82 SIGALRM 14 alarm clock
83 SIGTERM 15 software termination signal
84 SIGURG 16@ urgent condition present on socket
85 SIGSTOP 17'|+'stop (cannot be caught, blocked, or ignored)
86 SIGTSTP 18'|+'stop signal generated from keyboard
87 SIGCONT 19@ continue after stop (cannot be blocked)
88 SIGCHLD 20@ child status has changed
89 SIGTTIN 21'|+'background read attempted from control terminal
90 SIGTTOU 22'|+'background write attempted to control terminal
91 SIGIO 23@ i/o is possible on a descriptor (see fcntl(2))
92 SIGXCPU 24 cpu time limit exceeded (see setrlimit(2))
93 SIGXFSZ 25 file size limit exceeded (see setrlimit(2))
94 SIGVTALRM 26 virtual time alarm (see setitimer(2))
95 SIGPROF 27 profiling timer alarm (see setitimer(2))
96 SIGWINCH 28@ window size change
97 SIGUSR1 30 user defined signal 1
98 SIGUSR2 31 user defined signal 2
99 The starred signals in the list above cause a core image if not caught
101 or ignored.
102 Once a signal handler is installed, it remains installed until another
104 sigvec call is made, or an execve(2) is performed. The default action
105 for a signal may be reinstated by setting sv_handler to SIG_DFL; this
106 default is termination (with a core image for starred signals) except
107 for signals marked with @ or '|+'. Signals marked with @ are discarded
108 if the action is SIG_DFL; signals marked with '|+' cause the process to
109 stop. If sv_handler is SIG_IGN the signal is subsequently ignored, and
110 pending instances of the signal are discarded.
111 If a caught signal occurs during certain system calls, the call is nor‐
113 mally restarted. The call can be forced to terminate prematurely with
114 an EINTR error return by setting the SV_INTERRUPT bit in sv_flags. The
115 affected system calls are read(2) or write(2) on a slow device (such as
116 a terminal; but not a file) and during a wait(2).
117 After a fork(2) or vfork(2) the child inherits all signals, the signal
119 mask, the signal stack, and the restart/interrupt flags.
120 Execve(2) resets all caught signals to default action and resets all
122 signals to be caught on the user stack. Ignored signals remain
123 ignored; the signal mask remains the same; signals that interrupt sys‐
124 tem calls continue to do so.
125
127 The mask specified in vec is not allowed to block SIGKILL, SIGSTOP, or
128 SIGCONT. This is done silently by the system.
129 The SV_INTERRUPT flag is not available in 4.2BSD, hence it should not
131 be used if backward compatibility is needed.
132
134 A 0 value indicated that the call succeeded. A -1 return value indi‐
135 cates an error occurred and errno is set to indicated the reason.
136
138 Sigvec will fail and no new signal handler will be installed if one of
139 the following occurs:
140 [EFAULT] Either vec or ovec points to memory that is not a valid
142 part of the process address space.
143 [EINVAL] Sig is not a valid signal number.
145 [EINVAL] An attempt is made to ignore or supply a handler for
147 SIGKILL or SIGSTOP.
148 [EINVAL] An attempt is made to ignore SIGCONT (by default SIGCONT
150 is ignored).
151
153 kill(1), ptrace(2), kill(2), sigblock(2), sigsetmask(2), sigpause(2),
154 sigstack(2), sigvec(2), setjmp(3), siginterrupt(3), tty(4)
155
157 The handler routine can be declared:
158 handler(sig, code, scp)
160 int sig, code;
161 struct sigcontext *scp;
162 Here sig is the signal number, into which the hardware faults and traps
164 are mapped as defined below. Code is a parameter that is either a con‐
165 stant as given below or, for compatibility mode faults, the code pro‐
166 vided by the hardware (Compatibility mode faults are distinguished from
167 the other SIGILL traps by having PSL_CM set in the psl). Scp is a
168 pointer to the sigcontext structure (defined in <signal.h>), used to
169 restore the context from before the signal.
170 The following defines the mapping of hardware traps to signals and
172 codes. All of these symbols are defined in <signal.h>:
173 Hardware condition Signal Code
175 Arithmetic traps:
177 Integer overflow SIGFPE FPE_INTOVF_TRAP
178 Integer division by zero SIGFPE FPE_INTDIV_TRAP
179 Floating overflow trap SIGFPE FPE_FLTOVF_TRAP
180 Floating/decimal division by zero SIGFPE FPE_FLTDIV_TRAP
181 Floating underflow trap SIGFPE FPE_FLTUND_TRAP
182 Decimal overflow trap SIGFPE FPE_DECOVF_TRAP
183 Subscript-range SIGFPE FPE_SUBRNG_TRAP
184 Floating overflow fault SIGFPE FPE_FLTOVF_FAULT
185 Floating divide by zero fault SIGFPE FPE_FLTDIV_FAULT
186 Floating underflow fault SIGFPE FPE_FLTUND_FAULT
187 Length access control SIGSEGV
188 Protection violation SIGBUS
189 Reserved instruction SIGILL ILL_RESAD_FAULT
190 Customer-reserved instr. SIGEMT
191 Reserved operand SIGILL ILL_PRIVIN_FAULT
192 Reserved addressing SIGILL ILL_RESOP_FAULT
193 Trace pending SIGTRAP
194 Bpt instruction SIGTRAP
195 Compatibility-mode SIGILL hardware supplied code
196 Chme SIGSEGV
197 Chms SIGSEGV
198 Chmu SIGSEGV
199
201 The handler routine can be declared:
202 handler(sig, code, scp)
204 int sig, code;
205 struct sigcontext *scp;
206 Here sig is the signal number, into which the hardware faults and traps
208 are mapped as defined below. Code is a parameter that is a constant as
209 given below. Scp is a pointer to the sigcontext structure (defined in
210 <signal.h>), used to restore the context from before the signal.
211 The following defines the mapping of hardware traps to signals and
213 codes. All of these symbols are defined in <signal.h>:
214 Hardware condition Signal Code
216 Arithmetic traps:
218 Floating overflow trap SIGFPE FPE_FLTOVF_TRAP
219 Floating/decimal division by zero SIGFPE FPE_FLTDIV_TRAP
220 Floating underflow trap SIGFPE FPE_FLTUND_TRAP
221 Decimal overflow trap SIGFPE FPE_DECOVF_TRAP
222 Illegal return code SIGFPE FPE_CRAZY
223 Bad op code SIGFPE FPE_OPCODE_TRAP
224 Bad operand SIGFPE FPE_OPERAND_TRAP
225 Maintenance trap SIGFPE FPE_MAINT_TRAP
226 Length access control SIGSEGV
227 Protection violation (odd address) SIGBUS
228 Reserved instruction SIGILL ILL_RESAD_FAULT
229 Customer-reserved instr. SIGEMT
230 Trace pending SIGTRAP
231 Bpt instruction SIGTRAP
232 The handler routine must save any registers it uses and restore them
234 before returning. On the PDP-11, the kernel saves r0 and r1 before
235 calling the handler routine, but expect the handler to save any other
236 registers it uses. The standard entry code generated by the C compiler
237 for handler routines written in C automatically saves the remaining
238 general registers, but floating point registers are not saved. As a
239 result there is currently no [standard] method for a handler routine
240 written in C to perform floating point operations without blowing the
241 interrupted program out of the water.
242
244 This manual page is still confusing.
2454th Berkeley Distribution September 3, 1997 SIGVEC(2)