Name
subpage_prot - define a subpage protection for an address rangeLibrary
Standard C library ( libc ", " -lc )Synopsis
"#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).
Description
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.
Return Value
On success, subpage_prot() returns 0. Otherwise, one of the error codes specified below is returned.Errors
EFAULT The buffer referred to by map is not accessible.
EINVAL The addr or len arguments are incorrect. Both of these arguments must be aligned to a multiple of the system page size, and they must not refer to a region outside of the address space of the process or to a region that consists of huge pages.
ENOMEM Out of memory.
Standards
Linux.History
Linux 2.6.25 (PowerPC).The system call is provided only if the kernel is configured with CONFIG_PPC_64K_PAGES .