mprotect(2) [ultrix man page]

mprotect(2) System Calls Manual mprotect(2)

Name
mprotect - memory protection control

Syntax
#include <sys/mman.h>
#include <sys/types.h>

int mprotect (addr, len, prot)
caddr_t addr;
int len, prot;

Description
The system call changes the protection of portions of an application program's data memory. Protection is performed on page cluster bound-
aries. The default protection for data memory on process invocation is user READ/WRITE. The addr argument is the beginning address of the
data block and must fall on a page cluster boundary.

The len argument is the length of the data block, in bytes. The length of the block is rounded up to a cluster boundary, and the size of
the block to be protected is returned.

The prot argument is the requested protection for the block of memory. Protection values affect only the user process. Protection values
are defined in <mman.h> as:
/* protections are chosen from these bits, ORed together */
#define PROT_READ 0x1 /* pages can be read */
#define PROT_WRITE 0x2 /* pages can be written */
#define PROT_EXEC 0x4 /* pages can be executed */
Setting the prot argument to zero (0) indicates that the process cannot reference the memory block, without causing a fault.

A protected page faults if the protection is violated, and a SIGBUS signal is issued. If the process has a handler defined for the SIGBUS
signal, the code parameter, described in and is used to pass in the virtual address that faulted.

Restrictions
The page cluster size may change in future versions of ULTRIX. As a result, should be used to determine the correct len argument, and or
should be used to determine the correct addr argument.

If the user handles a SIGBUS signal, the signal handler must either abort the process or correct the condition that caused the protection
fault (SIGBUS). If some corrective action is not taken, an infinite loop results because the faulting instruction is restarted. If the
user permits the default SIGBUS handler to be used, the process aborts if a referenced page causes a fault.

The VAX architecture makes the following implications; PROT_WRITE implies (PROT_WRITE | PROT_READ | PROT_EXEC), and PROT_READ implies
(PROT_READ | PROT_EXEC).

Only the application can change the call's private data space. This means that attempts to change text, shared memory, or stack space
causes a EACCES failure.

Return Values
Upon successful completion, the size of the protected memory block, in bytes, is returned. Otherwise, a value of -1 is returned and errno
is set to indicate the error.

Diagnostics
The call fails under the following conditions:

[EALIGN] The addr argument is not on a cluster boundary.

[EINVAL] The prot argument is not a valid protection mask.

[EACCES] The memory block is not fully contained within private data space.

See Also
getpagesize(2), sbrk(2), sigvec(2), malloc(3), signal(3)

mprotect(2)

Check Out this Related Man Page

mprotect(2)							   System Calls 						       mprotect(2)

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(3C), to be that specified by prot. Legitimate values for prot are the same  as  those
       permitted for mmap(2) and are defined in <sys/mman.h> as:

       PROT_READ       /* page can be read */

       PROT_WRITE      /* page can be written */

       PROT_EXEC       /* page can be executed */

       PROT_NONE       /* page can not 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. If the error occurs on some page at addr2, then the protections of all whole pages in the range [addr, addr2] will have been modi-
       fied.

RETURN VALUES

       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 len argument has a value equal to 0, or addr is not a multiple of the page size as returned by sysconf(3C).

       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  address  range  [addr,  addr  +  len)  includes one or more pages that have been locked in memory and that were mapped
		       MAP_PRIVATE; prot includes PROT_WRITE; and the system has insufficient resources to reserve memory for  the  private  pages
		       that may be created. These private pages may be created by store operations in the now-writable address range.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       mmap(2), plock(3C), mlock(3C), mlockall(3C), sysconf(3C), attributes(5), standards(5)

SunOS 5.10							    12 Jan 1998 						       mprotect(2)

Linux and UNIX Man Pages

mprotect(2) [ultrix man page]

Check Out this Related Man Page