NAME
mprotect() — set or check 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.
- PROT_CHECK
Check page effective permissions
If
PROT_CHECK
flag is specified,
mprotect()
checks the access protections on the mappings specified with the rest of
prot
value to see if the requested permissions are set.
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.
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.
For example, if an error occurs on some page at an
addr2,
then
mprotect()
may have modified the protections of all whole pages in the range
[addr,addr2].
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, or is different than
(in the case where flag
PROT_CHECK
is present), the access permission the process has to the underlying memory
object.
- 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 the address space of a process,
or the range specifies one or more unmapped pages.
- 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.
- 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.
AUTHOR
mprotect()
was developed by HP, AT&T, and OSF.
STANDARDS CONFORMANCE
mprotect(): AES, SVID3
Printable version
