/* * FILE NAME fs/pramfs/wprotect.c * * BRIEF DESCRIPTION * * Write protection for the filesystem pages. * * Author: Steve Longerbeam <stevel@mvista.com, or source@mvista.com> * * Copyright 2003 Sony Corporation * Copyright 2003 Matsushita Electric Industrial Co., Ltd. * 2003-2004 (c) MontaVista Software, Inc. This file is licensed under * the terms of the GNU General Public License version 2. This program * is licensed "as is" without any warranty of any kind, whether express * or implied. */#include <linux/module.h>#include <linux/fs.h>#include <linux/pram_fs.h>#include <linux/mm.h>#include <asm/pgtable.h>#include <asm/pgalloc.h>#include <asm/tlbflush.h>// init_mm.page_table_lock must be held before calling!static void pram_page_writeable(unsigned long addr, int rw){	pgd_t *pgdp = pgd_offset_k(addr);	if (!pgd_none(*pgdp)) {		pud_t *pudp = pud_offset(pgdp, addr);		if (!pud_none(*pudp)) {			pmd_t *pmdp = pmd_offset(pudp, addr);			if (!pmd_none(*pmdp)) {				pte_t pte;				pte_t *ptep = pte_offset_kernel(pmdp, addr);				pte = *ptep;				if (pte_present(pte)) {					pte = rw ? pte_mkwrite(pte) :						pte_wrprotect(pte);					set_pte_ext(ptep, pte, 0);				}			}		}	}}// init_mm.page_table_lock must be held before calling!void pram_writeable(void * vaddr, unsigned long size, int rw){        unsigned long addr = (unsigned long)vaddr & PAGE_MASK;	unsigned long end = (unsigned long)vaddr + size;	unsigned long start = addr;	do {		pram_page_writeable(addr, rw);		addr += PAGE_SIZE;	} while (addr && (addr < end));	/*	 * NOTE: we will always flush just one page (one TLB	 * entry) except possibly in one case: when a new	 * filesystem is initialized at mount time, when pram_read_super	 * calls pram_lock_range to make the super block, inode	 * table, and bitmap writeable.	 */#if defined(__arm__) || defined(__mc68000__) || defined(CONFIG_H8300)	/*	 * FIXME: so far only these archs have flush_tlb_kernel_page(),	 * for the rest just use flush_tlb_kernel_range(). Not ideal	 * to use _range() because many archs just flush the whole TLB.	 */	if (end <= start + PAGE_SIZE)		flush_tlb_kernel_page(start);	else#endif		flush_tlb_kernel_range(start, end);}