/* * linux/mm/fremap.c * * Explicit pagetable population and nonlinear (random) mappings support. * * started by Ingo Molnar, Copyright (C) 2002, 2003 */ #include <linux/mm.h> #include <linux/swap.h> #include <linux/file.h> #include <linux/mman.h> #include <linux/pagemap.h> #include <linux/swapops.h> #include <linux/rmap.h> #include <linux/module.h> #include <linux/syscalls.h> #include <asm/mmu_context.h> #include <asm/cacheflush.h> #include <asm/tlbflush.h> static int zap_pte(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) { pte_t pte = *ptep; struct page *page = NULL; if (pte_present(pte)) { flush_cache_page(vma, addr, pte_pfn(pte)); pte = ptep_clear_flush(vma, addr, ptep); page = vm_normal_page(vma, addr, pte); if (page) { if (pte_dirty(pte)) set_page_dirty(page); page_remove_rmap(page); page_cache_release(page); } } else { if (!pte_file(pte)) free_swap_and_cache(pte_to_swp_entry(pte)); pte_clear(mm, addr, ptep); } return !!page; } /* * Install a file page to a given virtual memory address, release any * previously existing mapping. */ int install_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, struct page *page, pgprot_t prot) { struct inode *inode; pgoff_t size; int err = -ENOMEM; pte_t *pte; pte_t pte_val; spinlock_t *ptl; pte = get_locked_pte(mm, addr, &ptl); if (!pte) goto out; /* * This page may have been truncated. Tell the * caller about it. */ err = -EINVAL; inode = vma->vm_file->f_mapping->host; size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; if (!page->mapping || page->index >= size) goto unlock; err = -ENOMEM; if (page_mapcount(page) > INT_MAX/2) goto unlock; if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte)) inc_mm_counter(mm, file_rss); flush_icache_page(vma, page); pte_val = mk_pte(page, prot); set_pte_at(mm, addr, pte, pte_val); page_add_file_rmap(page); update_mmu_cache(vma, addr, pte_val); lazy_mmu_prot_update(pte_val); err = 0; unlock: pte_unmap_unlock(pte, ptl); out: return err; } EXPORT_SYMBOL(install_page); /* * Install a file pte to a given virtual memory address, release any * previously existing mapping. */ int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, unsigned long pgoff, pgprot_t prot) { int err = -ENOMEM; pte_t *pte; pte_t pte_val; spinlock_t *ptl; pte = get_locked_pte(mm, addr, &ptl); if (!pte) goto out; if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) { update_hiwater_rss(mm); dec_mm_counter(mm, file_rss); } set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff)); pte_val = *pte; /* * We don't need to run update_mmu_cache() here because the "file pte" * being installed by install_file_pte() is not a real pte - it's a * non-present entry (like a swap entry), noting what file offset should * be mapped there when there's a fault (in a non-linear vma where * that's not obvious). */ pte_unmap_unlock(pte, ptl); err = 0; out: return err; } /*** * sys_remap_file_pages - remap arbitrary pages of a shared backing store * file within an existing vma. * @start: start of the remapped virtual memory range * @size: size of the remapped virtual memory range * @prot: new protection bits of the range * @pgoff: to be mapped page of the backing store file * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO. * * this syscall works purely via pagetables, so it's the most efficient * way to map the same (large) file into a given virtual window. Unlike * mmap()/mremap() it does not create any new vmas. The new mappings are * also safe across swapout. * * NOTE: the 'prot' parameter right now is ignored, and the vma's default * protection is used. Arbitrary protections might be implemented in the * future. */ asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, unsigned long __prot, unsigned long pgoff, unsigned long flags) { struct mm_struct *mm = current->mm; struct address_space *mapping; unsigned long end = start + size; struct vm_area_struct *vma; int err = -EINVAL; int has_write_lock = 0; if (__prot) return err; /* * Sanitize the syscall parameters: */ start = start & PAGE_MASK; size = size & PAGE_MASK; /* Does the address range wrap, or is the span zero-sized? */ if (start + size <= start) return err; /* Can we represent this offset inside this architecture's pte's? */ #if PTE_FILE_MAX_BITS < BITS_PER_LONG if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS)) return err; #endif /* We need down_write() to change vma->vm_flags. */ down_read(&mm->mmap_sem); retry: vma = find_vma(mm, start); /* * Make sure the vma is shared, that it supports prefaulting, * and that the remapped range is valid and fully within * the single existing vma. vm_private_data is used as a * swapout cursor in a VM_NONLINEAR vma. */ if (vma && (vma->vm_flags & VM_SHARED) && (!vma->vm_private_data || (vma->vm_flags & VM_NONLINEAR)) && vma->vm_ops && vma->vm_ops->populate && end > start && start >= vma->vm_start && end <= vma->vm_end) { /* Must set VM_NONLINEAR before any pages are populated. */ if (pgoff != linear_page_index(vma, start) && !(vma->vm_flags & VM_NONLINEAR)) { if (!has_write_lock) { up_read(&mm->mmap_sem); down_write(&mm->mmap_sem); has_write_lock = 1; goto retry; } mapping = vma->vm_file->f_mapping; spin_lock(&mapping->i_mmap_lock); flush_dcache_mmap_lock(mapping); vma->vm_flags |= VM_NONLINEAR; vma_prio_tree_remove(vma, &mapping->i_mmap); vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear); flush_dcache_mmap_unlock(mapping); spin_unlock(&mapping->i_mmap_lock); } err = vma->vm_ops->populate(vma, start, size, vma->vm_page_prot, pgoff, flags & MAP_NONBLOCK); /* * We can't clear VM_NONLINEAR because we'd have to do * it after ->populate completes, and that would prevent * downgrading the lock. (Locks can't be upgraded). */ } if (likely(!has_write_lock)) up_read(&mm->mmap_sem); else up_write(&mm->mmap_sem); return err; }