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MPROTECT(2) FreeBSD System Calls Manual MPROTECT(2) NAME mprotect - control the protection of pages LIBRARY Standard C Library (libc, -lc) SYNOPSIS #include <sys/mman.h> int mprotect(void *addr, size_t len, int prot); DESCRIPTION The mprotect() system call changes the specified pages to have protection prot. The prot argument shall be PROT_NONE (no permissions at all) or the bitwise or of one or more of the following values: PROT_READ The pages can be read. PROT_WRITE The pages can be written. PROT_EXEC The pages can be executed. In addition to these standard protection flags, the FreeBSD implementation of mprotect() provides the ability to set the maximum protection of a region (which prevents mprotect from adding to the permissions later). This is accomplished by bitwise or'ing one or more PROT_ values wrapped in the PROT_MAX() macro into the prot argument. RETURN VALUES The mprotect() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error. ERRORS The mprotect() system call will fail if: [EACCES] The calling process was not allowed to change the protection to the value specified by the prot argument. [EINVAL] The virtual address range specified by the addr and len arguments is not valid. [EINVAL] The prot argument contains unhandled bits. [ENOTSUP] The prot argument contains permissions which are not a subset of the specified maximum permissions. SEE ALSO madvise(2), mincore(2), msync(2), munmap(2) HISTORY The mprotect() system call was first documented in 4.2BSD and first appeared in 4.4BSD. The PROT_MAX functionality was introduced in FreeBSD 13. FreeBSD 14.1-RELEASE-p8 September 7, 2021 FreeBSD 14.1-RELEASE-p8