1MPROTECT(3P)               POSIX Programmer's Manual              MPROTECT(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       mprotect — set protection of memory mapping
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SYNOPSIS

15       #include <sys/mman.h>
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17       int mprotect(void *addr, size_t len, int prot);
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DESCRIPTION

20       The mprotect() function shall change the access protections to be  that
21       specified  by  prot  for  those  whole pages containing any part of the
22       address space of the process starting at address  addr  and  continuing
23       for  len bytes. The parameter prot determines whether read, write, exe‐
24       cute, or some combination of accesses are permitted to the  data  being
25       mapped.  The  prot  argument should be either PROT_NONE or the bitwise-
26       inclusive OR of one or more of PROT_READ, PROT_WRITE, and PROT_EXEC.
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28       If an implementation cannot support the  combination  of  access  types
29       specified by prot, the call to mprotect() shall fail.
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31       An  implementation  may  permit  accesses other than those specified by
32       prot; however, no implementation shall permit a write to succeed  where
33       PROT_WRITE  has not been set or shall permit any access where PROT_NONE
34       alone has been set. Implementations shall support at least the  follow‐
35       ing  values of prot: PROT_NONE, PROT_READ, PROT_WRITE, and the bitwise-
36       inclusive OR of PROT_READ and PROT_WRITE. If PROT_WRITE  is  specified,
37       the  application  shall ensure that it has opened the mapped objects in
38       the specified address range with write permission,  unless  MAP_PRIVATE
39       was  specified  in the original mapping, regardless of whether the file
40       descriptors used to map the objects have since been closed.
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42       The implementation may require that addr be a multiple of the page size
43       as returned by sysconf().
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45       The  behavior  of  this  function is unspecified if the mapping was not
46       established by a call to mmap().
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48       When mprotect() fails for reasons other than [EINVAL], the  protections
49       on  some  of  the  pages  in  the  range  [addr,addr+len) may have been
50       changed.
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RETURN VALUE

53       Upon successful completion, mprotect() shall return  0;  otherwise,  it
54       shall return -1 and set errno to indicate the error.
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ERRORS

57       The mprotect() function shall fail if:
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59       EACCES The  prot  argument  specifies  a  protection  that violates the
60              access permission the  process  has  to  the  underlying  memory
61              object.
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63       EAGAIN The  prot  argument specifies PROT_WRITE over a MAP_PRIVATE map‐
64              ping and there are insufficient memory resources to reserve  for
65              locking the private page.
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67       ENOMEM Addresses  in  the  range  [addr,addr+len)  are  invalid for the
68              address space of a process, or specify one or more  pages  which
69              are not mapped.
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71       ENOMEM The prot argument specifies PROT_WRITE on a MAP_PRIVATE mapping,
72              and it would require more space than the system is able to  sup‐
73              ply for locking the private pages, if required.
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75       ENOTSUP
76              The  implementation does not support the combination of accesses
77              requested in the prot argument.
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79       The mprotect() function may fail if:
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81       EINVAL The addr argument is not a multiple of the page size as returned
82              by sysconf().
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84       The following sections are informative.
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EXAMPLES

87       None.
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APPLICATION USAGE

90       Most  implementations  require that addr is a multiple of the page size
91       as returned by sysconf().
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RATIONALE

94       None.
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FUTURE DIRECTIONS

97       None.
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SEE ALSO

100       mmap(), sysconf()
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102       The Base Definitions volume of POSIX.1‐2017, <sys_mman.h>
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105       Portions of this text are reprinted and reproduced in  electronic  form
106       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
107       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
108       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
109       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
110       event of any discrepancy between this version and the original IEEE and
111       The Open Group Standard, the original IEEE and The Open Group  Standard
112       is  the  referee document. The original Standard can be obtained online
113       at http://www.opengroup.org/unix/online.html .
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115       Any typographical or formatting errors that appear  in  this  page  are
116       most likely to have been introduced during the conversion of the source
117       files to man page format. To report such errors,  see  https://www.ker‐
118       nel.org/doc/man-pages/reporting_bugs.html .
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122IEEE/The Open Group                  2017                         MPROTECT(3P)
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