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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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MPROTECT(3P) POSIX Programmer's Manual MPROTECT(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
mprotect — set protection of memory mapping
#include <sys/mman.h>
int mprotect(void *addr, size_t len, int prot);
The mprotect() function shall change the access protections to be
that specified by prot for those whole pages containing any part
of the address space of the process starting at address addr and
continuing for len bytes. The parameter prot determines whether
read, write, execute, or some combination of accesses are
permitted to the data being mapped. The prot argument should be
either PROT_NONE or the bitwise-inclusive OR of one or more of
PROT_READ, PROT_WRITE, and PROT_EXEC.
If an implementation cannot support the combination of access
types specified by prot, the call to mprotect() shall fail.
An implementation may permit accesses other than those specified
by prot; however, no implementation shall permit a write to
succeed where PROT_WRITE has not been set or shall permit any
access where PROT_NONE alone has been set. Implementations shall
support at least the following values of prot: PROT_NONE,
PROT_READ, PROT_WRITE, and the bitwise-inclusive OR of PROT_READ
and PROT_WRITE. If PROT_WRITE is specified, the application shall
ensure that it has opened the mapped objects in the specified
address range with write permission, unless MAP_PRIVATE was
specified in the original mapping, regardless of whether the file
descriptors used to map the objects have since been closed.
The implementation may require that addr be a multiple of the page
size as returned by sysconf().
The behavior of this function is unspecified if the mapping was
not established by a call to mmap().
When mprotect() fails for reasons other than [EINVAL], the
protections on some of the pages in the range [addr,addr+len) may
have been changed.
Upon successful completion, mprotect() shall return 0; otherwise,
it shall return -1 and set errno to indicate the error.
The mprotect() function shall fail if:
EACCES The prot argument specifies a protection that violates the
access permission the process has to the underlying memory
object.
EAGAIN The prot argument specifies PROT_WRITE over a MAP_PRIVATE
mapping and there are insufficient memory resources to
reserve for locking the private page.
ENOMEM Addresses in the range [addr,addr+len) are invalid for the
address space of a process, or specify one or more pages
which are not mapped.
ENOMEM The prot argument specifies PROT_WRITE on a MAP_PRIVATE
mapping, and it would require more space than the system is
able to supply for locking the private pages, if required.
ENOTSUP
The implementation does not support the combination of
accesses requested in the prot argument.
The mprotect() function may fail if:
EINVAL The addr argument is not a multiple of the page size as
returned by sysconf().
The following sections are informative.
None.
Most implementations require that addr is a multiple of the page
size as returned by sysconf().
None.
None.
mmap(3p), sysconf(3p)
The Base Definitions volume of POSIX.1‐2017, sys_mman.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 MPROTECT(3P)
Pages that refer to this page: sys_mman.h(0p), mmap(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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