int mprotect(void *addr, size_t len, int
The mprotect() function shall change the access protections to be that specified by prot for those whole pages containing any part of the address space of the process starting at address addr and continuing for len bytes. The parameter prot determines whether read, write, execute, or some combination of accesses are permitted to the data being mapped. The prot argument should be either PROT_NONE or the bitwise-inclusive OR of one or more of PROT_READ, PROT_WRITE, and PROT_EXEC.
If an implementation cannot support the combination of access types specified by prot, the call to mprotect() shall fail.
An implementation may permit accesses other than those specified by prot; however, no implementation shall permit a write to succeed where PROT_WRITE has not been set or shall permit any access where PROT_NONE alone has been set. Implementations shall support at least the following values of prot: PROT_NONE, PROT_READ, PROT_WRITE, and the bitwise-inclusive OR of PROT_READ and PROT_WRITE. If PROT_WRITE is specified, the application shall ensure that it has opened the mapped objects in the specified address range with write permission, unless MAP_PRIVATE was specified in the original mapping, regardless of whether the file descriptors used to map the objects have since been closed.
The implementation shall require that addr be a multiple of the page size as returned by sysconf().
The behavior of this function is unspecified if the mapping was not established by a call to mmap().
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.
Upon successful completion, mprotect() shall return 0; otherwise, it shall return -1 and set errno to indicate the error.
The mprotect() function shall fail if:
The following sections are informative.
The [EINVAL] error above is marked EX because it is defined as an optional error in the POSIX Realtime Extension.
mmap() , sysconf() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/mman.h>