NAME
mprotect — set protection of memory mapping
SYNOPSIS
#include <sys/mman.h>
int mprotect(void *addr, size_t len, int prot);
DESCRIPTION
The
mprotect()
function changes the access protections on the mappings
specified by the range
[addr,
addr+len],
rounding
len
up to the next multiple of the page size as returned by
sysconf(),
to be that specified by
prot.
Legitimate values for
prot
are the same as those permitted for
mmap()
and are defined in
<sys/mman.h>:
- PROT_READ
Page can be read.
- PROT_WRITE
Page can be written.
- PROT_EXEC
Page can be executed.
- PROT_NONE
Page cannot be accessed.
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.
RETURN VALUE
Upon successful completion,
mprotect()
returns 0. Otherwise, it returns -1 and sets
errno
to indicate the error.
ERRORS
The
mprotect()
function will fail if:
- [EACCES]
The
prot
argument specifies a protection that violates the access
permission the process has to the underlying memory object.
- [EINVAL]
The
addr
argument is not a multiple of the page size as returned by
sysconf().
- [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.
The
mprotect()
function may fail if:
- [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.
CHANGE HISTORY
First released in Issue 4, Version 2.
mprotect HP-UX EXTENSIONS
SYNOPSIS (HP-UX)
int mprotect(
caddr_t addr,
size_t len,
int prot );
DESCRIPTION
If the address range does not correspond to one created by a
successful call to
mmap(),
mprotect()
returns an error.
prot
determines whether read, write, execute,
or some combination of accesses are permitted
to the data being mapped.
If the address range being modified
corresponds to a mapped file that was mapped with
MAP_SHARED,
mprotect()
grants write access permission
only if the file descriptor used to map the file
was opened for writing.
If the address range corresponds to a mapped file
that was mapped with the
MAP_PRIVATE
or the
MAP_ANONYMOUS
flag,
mprotect()
grants all requested access permissions.
For example, suppose an error occurs on some page at an
addr2;
mprotect()
may have modified the protections of all whole pages in the range
[addr,addr2].
ERRORS
- [EINVAL]
prot
is invalid, or
addr
is not a multiple of the page size as returned by
sysconf(_SC_PAGE_SIZE).
- [EFAULT]
The range specified by
[addr,
addr+len]
(from, and including,
addr
to, but not including,
addr+len)
is invalid for a process' address space,
or the range specifies one or more unmapped pages.
AUTHOR
mprotect()
was developed by HP, AT&T, and OSF.
STANDARDS CONFORMANCE
mprotect():
AES, SVID3
