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123 lines
4.5 KiB
Plaintext
123 lines
4.5 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "PTHREAD_ATTR_GETGUARDSIZE" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" pthread_attr_getguardsize
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.SH NAME
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pthread_attr_getguardsize, pthread_attr_setguardsize \- get and set
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the thread guardsize attribute
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.SH SYNOPSIS
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.LP
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\fB#include <pthread.h>
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.br
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.sp
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int pthread_attr_getguardsize(const pthread_attr_t *restrict\fP \fIattr\fP\fB,
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.br
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\ \ \ \ \ \ size_t *restrict\fP \fIguardsize\fP\fB);
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.br
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int pthread_attr_setguardsize(pthread_attr_t\fP \fI*attr\fP\fB,
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.br
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\ \ \ \ \ \ size_t\fP \fIguardsize\fP\fB); \fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIpthread_attr_getguardsize\fP() function shall get the \fIguardsize\fP
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attribute in the \fIattr\fP object. This
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attribute shall be returned in the \fIguardsize\fP parameter.
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.LP
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The \fIpthread_attr_setguardsize\fP() function shall set the \fIguardsize\fP
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attribute in the \fIattr\fP object. The new
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value of this attribute shall be obtained from the \fIguardsize\fP
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parameter. If \fIguardsize\fP is zero, a guard area shall not
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be provided for threads created with \fIattr\fP. If \fIguardsize\fP
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is greater than zero, a guard area of at least size
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\fIguardsize\fP bytes shall be provided for each thread created with
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\fIattr\fP.
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.LP
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The \fIguardsize\fP attribute controls the size of the guard area
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for the created thread's stack. The \fIguardsize\fP
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attribute provides protection against overflow of the stack pointer.
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If a thread's stack is created with guard protection, the
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implementation allocates extra memory at the overflow end of the stack
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as a buffer against stack overflow of the stack pointer. If
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an application overflows into this buffer an error shall result (possibly
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in a SIGSEGV signal being delivered to the thread).
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.LP
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A conforming implementation may round up the value contained in \fIguardsize\fP
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to a multiple of the configurable system
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variable {PAGESIZE} (see \fI<sys/mman.h>\fP). If an implementation
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rounds up the
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value of \fIguardsize\fP to a multiple of {PAGESIZE}, a call to \fIpthread_attr_getguardsize\fP()
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specifying \fIattr\fP shall
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store in the \fIguardsize\fP parameter the guard size specified by
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the previous \fIpthread_attr_setguardsize\fP() function
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call.
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.LP
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The default value of the \fIguardsize\fP attribute is {PAGESIZE} bytes.
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The actual value of {PAGESIZE} is
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implementation-defined.
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.LP
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If the \fIstackaddr\fP or \fIstack\fP attribute has been set (that
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is, the caller is allocating and managing its own thread
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stacks), the \fIguardsize\fP attribute shall be ignored and no protection
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shall be provided by the implementation. It is the
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responsibility of the application to manage stack overflow along with
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stack allocation and management in this case.
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.SH RETURN VALUE
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.LP
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If successful, the \fIpthread_attr_getguardsize\fP() and \fIpthread_attr_setguardsize\fP()
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functions shall return zero;
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otherwise, an error number shall be returned to indicate the error.
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.SH ERRORS
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.LP
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The \fIpthread_attr_getguardsize\fP() and \fIpthread_attr_setguardsize\fP()
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functions shall fail if:
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.TP 7
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.B EINVAL
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The attribute \fIattr\fP is invalid.
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.TP 7
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.B EINVAL
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The parameter \fIguardsize\fP is invalid.
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.sp
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.LP
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These functions shall not return an error code of [EINTR].
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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None.
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.SH RATIONALE
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.LP
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The \fIguardsize\fP attribute is provided to the application for two
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reasons:
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.IP " 1." 4
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Overflow protection can potentially result in wasted system resources.
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An application that creates a large number of threads,
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and which knows its threads never overflow their stack, can save system
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resources by turning off guard areas.
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.LP
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.IP " 2." 4
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When threads allocate large data structures on the stack, large guard
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areas may be needed to detect stack overflow.
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.LP
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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The Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<pthread.h>\fP,
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\fI<sys/mman.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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