mprotect(2) — SYSTEM CALLS

NAME

mprotect − set protection of memory mapping

SYNOPSIS

#include <sys/types.h>
#include <sys/mman.h>
int mprotect(caddr_t addr, size_t len, int prot);

DESCRIPTION

The function mprotect changes the access protections on the mappings specified by the range [addr, addr + len) 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 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 ∗/

See the System V Application Binary Interface for further information concerning combinations of the PROT_READ, PROT_WRITE, and PROT_EXEC flags.

RETURN VALUE

Upon successful completion, the function mprotect returns a value of 0; otherwise, it returns a value of −1 and sets errno to indicate an error.

ERRORS

Under the following conditions, the function mprotect fails and sets errno to:

EACCES
if prot specifies a protection that violates the access permission the process has to the underlying memory object.

EAGAIN if prot specifies PROT_WRITE over a MAP_PRIVATE mapping and there are insufficient memory resources to reserve for locking the private page.

EINVAL if addr is not a multiple of the page size as returned by sysconf.

EINVAL The argument len has a value less than or equal to 0.

ENOMEM
if 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.

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 modified.

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