subpage_prot - define a subpage protection for an address range
#include <sys/syscall.h> /* Definition of SYS_* constants */
#include <unistd.h>
int syscall(SYS_subpage_prot, unsigned long addr, unsigned long len,
uint32_t *map);Note: glibc provides no wrapper for
subpage_prot(), necessitating the use of
syscall(2).
The PowerPC-specific subpage_prot() system call provides the facility to control the access permissions on individual 4 kB subpages on systems configured with a page size of 64 kB.
The protection map is applied to the memory pages in the region
starting at addr and continuing for len bytes. Both of
these arguments must be aligned to a 64-kB boundary.
The protection map is specified in the buffer pointed to by
map. The map has 2 bits per 4 kB subpage; thus each 32-bit word
specifies the protections of 16 4 kB subpages inside a 64 kB page (so,
the number of 32-bit words pointed to by map should equate to
the number of 64-kB pages specified by len). Each 2-bit field
in the protection map is either 0 to allow any access, 1 to prevent
writes, or 2 or 3 to prevent all accesses.
On success, subpage_prot() returns 0. Otherwise, one of the error codes specified below is returned.