|SUBPAGE_PROT(2)||Linux Programmer's Manual||SUBPAGE_PROT(2)|
NAMEsubpage_prot - define a subpage protection for an address range
long subpage_prot(unsigned long addr , unsigned long len ,
uint32_t * map );
DESCRIPTIONThe PowerPC-specific subpage_prot() system call provides the facility to control the access permissions on individual 4kB subpages on systems configured with a page size of 64kB.
RETURN VALUEOn success, subpage_prot() returns 0. Otherwise, one of the error codes specified below is returned.
- The buffer referred to by map is not accessible.
- 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.
- Out of memory.
VERSIONSThis system call is provided on the PowerPC architecture since Linux 2.6.25. The system call is provided only if the kernel is configured with CONFIG_PPC_64K_PAGES. No library support is provided.
CONFORMING TOThis system call is Linux-specific.
NOTESGlibc does not provide a wrapper for this system call; call it using syscall(2).
RationaleThis system call is provided to assist writing emulators that operate using 64-kB pages on PowerPC systems. When emulating systems such as x86, which uses a smaller page size, the emulator can no longer use the memory-management unit (MMU) and normal system calls for controlling page protections. (The emulator could emulate the MMU by checking and possibly remapping the address for each memory access in software, but that is slow.) The idea is that the emulator supplies an array of protection masks to apply to a specified range of virtual addresses. These masks are applied at the level where hardware page-table entries (PTEs) are inserted into the hardware page table based on the Linux PTEs, so the Linux PTEs are not affected. Implicit in this is that the regions of the address space that are protected are switched to use 4-kB hardware pages rather than 64-kB hardware pages (on machines with hardware 64-kB page support).
SEE ALSOmprotect(2), syscall(2)
COLOPHONThis page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.