1/* 2 * linux/mm/fremap.c 3 * 4 * Explicit pagetable population and nonlinear (random) mappings support. 5 * 6 * started by Ingo Molnar, Copyright (C) 2002, 2003 7 */ 8 9#include <linux/mm.h> 10#include <linux/swap.h> 11#include <linux/file.h> 12#include <linux/mman.h> 13#include <linux/pagemap.h> 14#include <linux/swapops.h> 15#include <linux/rmap.h> 16#include <linux/module.h> 17#include <linux/syscalls.h> 18 19#include <asm/mmu_context.h> 20#include <asm/cacheflush.h> 21#include <asm/tlbflush.h> 22 23static int zap_pte(struct mm_struct *mm, struct vm_area_struct *vma, 24 unsigned long addr, pte_t *ptep) 25{ 26 pte_t pte = *ptep; 27 struct page *page = NULL; 28 29 if (pte_present(pte)) { 30 flush_cache_page(vma, addr, pte_pfn(pte)); 31 pte = ptep_clear_flush(vma, addr, ptep); 32 page = vm_normal_page(vma, addr, pte); 33 if (page) { 34 if (pte_dirty(pte)) 35 set_page_dirty(page); 36 page_remove_rmap(page, vma); 37 page_cache_release(page); 38 } 39 } else { 40 if (!pte_file(pte)) 41 free_swap_and_cache(pte_to_swp_entry(pte)); 42 pte_clear_not_present_full(mm, addr, ptep, 0); 43 } 44 return !!page; 45} 46 47/* 48 * Install a file page to a given virtual memory address, release any 49 * previously existing mapping. 50 */ 51int install_page(struct mm_struct *mm, struct vm_area_struct *vma, 52 unsigned long addr, struct page *page, pgprot_t prot) 53{ 54 struct inode *inode; 55 pgoff_t size; 56 int err = -ENOMEM; 57 pte_t *pte; 58 pte_t pte_val; 59 spinlock_t *ptl; 60 61 pte = get_locked_pte(mm, addr, &ptl); 62 if (!pte) 63 goto out; 64 65 /* 66 * This page may have been truncated. Tell the 67 * caller about it. 68 */ 69 err = -EINVAL; 70 inode = vma->vm_file->f_mapping->host; 71 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 72 if (!page->mapping || page->index >= size) 73 goto unlock; 74 err = -ENOMEM; 75 if (page_mapcount(page) > INT_MAX/2) 76 goto unlock; 77 78 if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte)) 79 inc_mm_counter(mm, file_rss); 80 81 flush_icache_page(vma, page); 82 pte_val = mk_pte(page, prot); 83 set_pte_at(mm, addr, pte, pte_val); 84 page_add_file_rmap(page); 85 update_mmu_cache(vma, addr, pte_val); 86 lazy_mmu_prot_update(pte_val); 87 err = 0; 88unlock: 89 pte_unmap_unlock(pte, ptl); 90out: 91 return err; 92} 93EXPORT_SYMBOL(install_page); 94 95/* 96 * Install a file pte to a given virtual memory address, release any 97 * previously existing mapping. 98 */ 99int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, 100 unsigned long addr, unsigned long pgoff, pgprot_t prot) 101{ 102 int err = -ENOMEM; 103 pte_t *pte; 104 spinlock_t *ptl; 105 106 pte = get_locked_pte(mm, addr, &ptl); 107 if (!pte) 108 goto out; 109 110 if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) { 111 update_hiwater_rss(mm); 112 dec_mm_counter(mm, file_rss); 113 } 114 115 set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff)); 116 /* 117 * We don't need to run update_mmu_cache() here because the "file pte" 118 * being installed by install_file_pte() is not a real pte - it's a 119 * non-present entry (like a swap entry), noting what file offset should 120 * be mapped there when there's a fault (in a non-linear vma where 121 * that's not obvious). 122 */ 123 pte_unmap_unlock(pte, ptl); 124 err = 0; 125out: 126 return err; 127} 128 129/*** 130 * sys_remap_file_pages - remap arbitrary pages of a shared backing store 131 * file within an existing vma. 132 * @start: start of the remapped virtual memory range 133 * @size: size of the remapped virtual memory range 134 * @prot: new protection bits of the range 135 * @pgoff: to be mapped page of the backing store file 136 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO. 137 * 138 * this syscall works purely via pagetables, so it's the most efficient 139 * way to map the same (large) file into a given virtual window. Unlike 140 * mmap()/mremap() it does not create any new vmas. The new mappings are 141 * also safe across swapout. 142 * 143 * NOTE: the 'prot' parameter right now is ignored, and the vma's default 144 * protection is used. Arbitrary protections might be implemented in the 145 * future. 146 */ 147asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, 148 unsigned long __prot, unsigned long pgoff, unsigned long flags) 149{ 150 struct mm_struct *mm = current->mm; 151 struct address_space *mapping; 152 unsigned long end = start + size; 153 struct vm_area_struct *vma; 154 int err = -EINVAL; 155 int has_write_lock = 0; 156 157 if (__prot) 158 return err; 159 /* 160 * Sanitize the syscall parameters: 161 */ 162 start = start & PAGE_MASK; 163 size = size & PAGE_MASK; 164 165 /* Does the address range wrap, or is the span zero-sized? */ 166 if (start + size <= start) 167 return err; 168 169 /* Can we represent this offset inside this architecture's pte's? */ 170#if PTE_FILE_MAX_BITS < BITS_PER_LONG 171 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS)) 172 return err; 173#endif 174 175 /* We need down_write() to change vma->vm_flags. */ 176 down_read(&mm->mmap_sem); 177 retry: 178 vma = find_vma(mm, start); 179 180 /* 181 * Make sure the vma is shared, that it supports prefaulting, 182 * and that the remapped range is valid and fully within 183 * the single existing vma. vm_private_data is used as a 184 * swapout cursor in a VM_NONLINEAR vma. 185 */ 186 if (vma && (vma->vm_flags & VM_SHARED) && 187 (!vma->vm_private_data || (vma->vm_flags & VM_NONLINEAR)) && 188 vma->vm_ops && vma->vm_ops->populate && 189 end > start && start >= vma->vm_start && 190 end <= vma->vm_end) { 191 192 /* Must set VM_NONLINEAR before any pages are populated. */ 193 if (pgoff != linear_page_index(vma, start) && 194 !(vma->vm_flags & VM_NONLINEAR)) { 195 if (!has_write_lock) { 196 up_read(&mm->mmap_sem); 197 down_write(&mm->mmap_sem); 198 has_write_lock = 1; 199 goto retry; 200 } 201 mapping = vma->vm_file->f_mapping; 202 spin_lock(&mapping->i_mmap_lock); 203 flush_dcache_mmap_lock(mapping); 204 vma->vm_flags |= VM_NONLINEAR; 205 vma_prio_tree_remove(vma, &mapping->i_mmap); 206 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear); 207 flush_dcache_mmap_unlock(mapping); 208 spin_unlock(&mapping->i_mmap_lock); 209 } 210 211 err = vma->vm_ops->populate(vma, start, size, 212 vma->vm_page_prot, 213 pgoff, flags & MAP_NONBLOCK); 214 215 /* 216 * We can't clear VM_NONLINEAR because we'd have to do 217 * it after ->populate completes, and that would prevent 218 * downgrading the lock. (Locks can't be upgraded). 219 */ 220 } 221 if (likely(!has_write_lock)) 222 up_read(&mm->mmap_sem); 223 else 224 up_write(&mm->mmap_sem); 225 226 return err; 227} 228