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Diffstat (limited to 'lib/libc/sys/sigaltstack.2')
-rw-r--r-- | lib/libc/sys/sigaltstack.2 | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/lib/libc/sys/sigaltstack.2 b/lib/libc/sys/sigaltstack.2 new file mode 100644 index 0000000..f1ed718 --- /dev/null +++ b/lib/libc/sys/sigaltstack.2 @@ -0,0 +1,165 @@ +.\" Copyright (c) 1983, 1991, 1992, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)sigaltstack.2 8.1 (Berkeley) 6/4/93 +.\" +.Dd June 4, 1993 +.Dt SIGALTSTACK 2 +.Os BSD 4.2 +.Sh NAME +.Nm sigaltstack +.Nd set and/or get signal stack context +.Sh SYNOPSIS +.Fd #include <sys/types.h> +.Fd #include <signal.h> +.Bd -literal +struct sigaltstack { + caddr_t ss_sp; + long ss_size; + int ss_flags; +}; +.Ed +.Ft int +.Fn sigaltstack "const struct sigaltstack *ss" "struct sigaltstack *oss" +.Sh DESCRIPTION +.Fn Sigaltstack +allows users to define an alternate stack on which signals +are to be processed. +If +.Fa ss +is non-zero, +it specifies a pointer to and the size of a +.Em "signal stack" +on which to deliver signals, +and tells the system if the process is currently executing +on that stack. +When a signal's action indicates its handler +should execute on the signal stack (specified with a +.Xr sigaction 2 +call), the system checks to see +if the process is currently executing on that stack. +If the process is not currently executing on the signal stack, +the system arranges a switch to the signal stack for the +duration of the signal handler's execution. +.Pp +If +.Dv SA_DISABLE +is set in +.Fa ss_flags , +.Fa ss_sp +and +.Fa ss_size +are ignored and the signal stack will be disabled. +Trying to disable an active stack will cause +.Nm +to return -1 with +.Va errno +set to +.Dv EINVAL . +A disabled stack will cause all signals to be +taken on the regular user stack. +If the stack is later re-enabled then all signals that were specified +to be processed on an alternate stack will resume doing so. +.Pp +If +.Fa oss +is non-zero, the current signal stack state is returned. +The +.Fa ss_flags +field will contain the value +.Dv SA_ONSTACK +if the process is currently on a signal stack and +.Dv SA_DISABLE +if the signal stack is currently disabled. +.Sh NOTES +The value +.Dv SIGSTKSZ +is defined to be the number of bytes/chars that would be used to cover +the usual case when allocating an alternate stack area. +The following code fragment is typically used to allocate an alternate stack. +.Bd -literal -offset indent +if ((sigstk.ss_sp = malloc(SIGSTKSZ)) == NULL) + /* error return */ +sigstk.ss_size = SIGSTKSZ; +sigstk.ss_flags = 0; +if (sigaltstack(&sigstk,0) < 0) + perror("sigaltstack"); +.Ed +An alternative approach is provided for programs with signal handlers +that require a specific amount of stack space other than the default size. +The value +.Dv MINSIGSTKSZ +is defined to be the number of bytes/chars that is required by +the operating system to implement the alternate stack feature. +In computing an alternate stack size, +programs should add +.Dv MINSIGSTKSZ +to their stack requirements to allow for the operating system overhead. +.Pp +Signal stacks are automatically adjusted for the direction of stack +growth and alignment requirements. +Signal stacks may or may not be protected by the hardware and +are not ``grown'' automatically as is done for the normal stack. +If the stack overflows and this space is not protected +unpredictable results may occur. +.Sh RETURN VALUES +Upon successful completion, a value of 0 is returned. +Otherwise, a value of -1 is returned and +.Va errno +is set to indicate the error. +.Sh ERRORS +.Fn Sigstack +will fail and the signal stack context will remain unchanged +if one of the following occurs. +.Bl -tag -width [ENOMEM] +.It Bq Er EFAULT +Either +.Fa ss +or +.Fa oss +points to memory that is not a valid part of the process +address space. +.It Bq Er EINVAL +An attempt was made to disable an active stack. +.It Bq Er ENOMEM +Size of alternate stack area is less than or equal to +.Dv MINSIGSTKSZ . +.El +.Sh SEE ALSO +.Xr sigaction 2 , +.Xr setjmp 3 +.Sh HISTORY +The predecessor to +.Nm sigaltstack , +the +.Fn sigstack +system call, appeared in +.Bx 4.2 . |