MPROTECT(2) System Calls Manual MPROTECT(2)

mprotect — control the protection of pages

Standard C Library (libc, -lc)

#include <sys/mman.h>

int
mprotect(void *addr, size_t len, int prot);

The mprotect system call changes the specified pages to have protection prot. Not all implementations will guarantee protection on a page basis; the granularity of protection changes may be as large as an entire region.

The protections (region accessibility) are specified in the prot argument by OR'ing the following values:

Pages may be executed.
Pages may be read.
Pages may be written.
Placeholder when requesting no access permission.

Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

[]
A memory protection violation occurred.

The PROT_EXEC flag was attempted on pages which belong to a file system mounted with the NOEXEC flag.

The new protection is less restrictive than the protection originally set with mmap(2).

PaX mprotect restrictions prohibit the requested protection.

[]
An invalid memory range, or invalid parameters were provided.
[]
A resource shortage occurred while internally calling uvm_map_protect(9).

madvise(2), mincore(2), msync(2), munmap(2)

The mprotect function first appeared in SunOS 4.0 and subsequently 4.4BSD.

September 8, 2019 NetBSD 11.0