mprotect - Modify access protections of memory mapping
#include <sys/mman.h>
int mprotect(
void *addr,
size_t len,
int prot );
The following definitions of the addr parameter do not
conform to current industry standards and are supported
only for backward compatibility:
caddr_t addr,
const void addr );
Interfaces documented on this reference page conform to
industry standards as follows:
mprotect(): XSH4.2, XSH5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Points to the address of the region to be modified. Specifies
the length in bytes of the region to be modified.
Specifies access permissions as PROT_NONE or any combination
of PROT_READ, PROT_WRITE, and PROT_EXEC ORed
together.
The mprotect() function modifies the access protection of
a mapped file or shared memory region. The addr and len
parameters specify the address and length in bytes of the
region to be modified. The len parameter must be a multiple
of the page size as returned by
sysconf(_SC_PAGE_SIZE). If len is not a multiple of the
page size as returned by sysconf(_SC_PAGE_SIZE), the
length of the region will be rounded up to the next multiple
of the page size.
The prot parameter specifies the new access protection for
the region. The <sys/mman.h> header file defines the following
access options: The mapped region can be read. The
mapped region can be written. The mapped region can be
executed. The mapped region cannot be accessed.
The prot parameter can be PROT_NONE or any combination of
PROT_READ, PROT_WRITE, and PROT_EXEC ORed together. If
PROT_NONE is not specified, access permissions may be
granted to the region in addition to those explicitly
requested, except that write access will not be granted
unless PROT_WRITE is specified.
If the region is a mapped file which was mapped with
MAP_SHARED, the mprotect() function grants read or execute
access permission only if the file descriptor used to map
the file is open for reading, and grants write access permission
only if the file descriptor used to map the file
is open for writing. If the region is a mapped file which
was mapped with MAP_PRIVATE, the mprotect() function
grants read, write, or execute access permission only if
the file descriptor used to map the file is open for reading.
If the region is a shared memory region which was
mapped with MAP_ANONYMOUS, the mprotect() function grants
all requested access permissions.
The mprotect() function does not modify the access permission
of any region which lies outside of the specified
region, except that the effect on addresses between the
end of the region and the end of the page containing the
end of the region is unspecified.
If the mprotect() function fails under a condition other
than that specified by [EINVAL], the access protection of
some of the pages in the range [addr, addr + len) may have
been changed. For example, if the error occurs on some
page at addr2, mprotect() may have modified the protections
of all whole pages in the range [addr, addr2).
Upon successful completion, the mprotect() function
returns 0 (zero). Otherwise, mprotect() returns -1 and
sets errno to indicate the error.
The mprotect() function sets errno to the specified values
for the following conditions:
The prot parameter specifies a protection that conflicts
with the access permission set for the underlying file.
The prot parameter specifies PROT_WRITE over a MAP_PRIVATE
mapping and there are insufficient memory resources to
reserve for locking the private page. [Tru64 UNIX] Some
or all of the addresses in the range starting at addr and
continuing for len bytes are locked. [Tru64 UNIX] The
range [addr, addr + len) includes an invalid address. One
of the following conditions was encountered: The addr
parameter is not a multiple of the page size as returned
by sysconf(_SC_PAGE_SIZE). [Tru64 UNIX] The prot parameter
is invalid. [Tru64 UNIX] Addresses in the range
[addr, addr + len) are invalid for the address space of a
process, or they specify one or more unmapped pages.
Functions: getpagesize(2), mmap(2), msync(2), sysconf(3)
Standards: standards(5)
mprotect(2)
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