/* * linux/mm/filemap_xip.c * * Copyright (C) 2005 IBM Corporation * Author: Carsten Otte * * derived from linux/mm/filemap.c - Copyright (C) Linus Torvalds * */ #include #include #include #include #include #include #include #include /* * We do use our own empty page to avoid interference with other users * of ZERO_PAGE(), such as /dev/zero */ static struct page *__xip_sparse_page; static struct page *xip_sparse_page(void) { if (!__xip_sparse_page) { struct page *page = alloc_page(GFP_HIGHUSER | __GFP_ZERO); if (page) { static DEFINE_SPINLOCK(xip_alloc_lock); spin_lock(&xip_alloc_lock); if (!__xip_sparse_page) __xip_sparse_page = page; else __free_page(page); spin_unlock(&xip_alloc_lock); } } return __xip_sparse_page; } /* * This is a file read routine for execute in place files, and uses * the mapping->a_ops->get_xip_mem() function for the actual low-level * stuff. * * Note the struct file* is not used at all. It may be NULL. */ static ssize_t do_xip_mapping_read(struct address_space *mapping, struct file_ra_state *_ra, struct file *filp, char __user *buf, size_t len, loff_t *ppos) { struct inode *inode = mapping->host; pgoff_t index, end_index; unsigned long offset; loff_t isize, pos; size_t copied = 0, error = 0; BUG_ON(!mapping->a_ops->get_xip_mem); pos = *ppos; index = pos >> PAGE_CACHE_SHIFT; offset = pos & ~PAGE_CACHE_MASK; isize = i_size_read(inode); if (!isize) goto out; end_index = (isize - 1) >> PAGE_CACHE_SHIFT; do { unsigned long nr, left; void *xip_mem; unsigned long xip_pfn; int zero = 0; /* nr is the maximum number of bytes to copy from this page */ nr = PAGE_CACHE_SIZE; if (index >= end_index) { if (index > end_index) goto out; nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; if (nr <= offset) { goto out; } } nr = nr - offset; if (nr > len) nr = len; error = mapping->a_ops->get_xip_mem(mapping, index, 0, &xip_mem, &xip_pfn); if (unlikely(error)) { if (error == -ENODATA) { /* sparse */ zero = 1; } else goto out; } /* If users can be writing to this page using arbitrary * virtual addresses, take care about potential aliasing * before reading the page on the kernel side. */ if (mapping_writably_mapped(mapping)) /* address based flush */ ; /* * Ok, we have the mem, so now we can copy it to user space... * * The actor routine returns how many bytes were actually used.. * NOTE! This may not be the same as how much of a user buffer * we filled up (we may be padding etc), so we can only update * "pos" here (the actor routine has to update the user buffer * pointers and the remaining count). */ if (!zero) left = __copy_to_user(buf+copied, xip_mem+offset, nr); else left = __clear_user(buf + copied, nr); if (left) { error = -EFAULT; goto out; } copied += (nr - left); offset += (nr - left); index += offset >> PAGE_CACHE_SHIFT; offset &= ~PAGE_CACHE_MASK; } while (copied < len); out: *ppos = pos + copied; if (filp) file_accessed(filp); return (copied ? copied : error); } ssize_t xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos) { if (!access_ok(VERIFY_WRITE, buf, len)) return -EFAULT; return do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp, buf, len, ppos); } EXPORT_SYMBOL_GPL(xip_file_read); /* * __xip_unmap is invoked from xip_unmap and * xip_write * * This function walks all vmas of the address_space and unmaps the * __xip_sparse_page when found at pgoff. */ static void __xip_unmap (struct address_space * mapping, unsigned long pgoff) { struct vm_area_struct *vma; struct mm_struct *mm; struct prio_tree_iter iter; unsigned long address; pte_t *pte; pte_t pteval; spinlock_t *ptl; struct page *page; page = __xip_sparse_page; if (!page) return; spin_lock(&mapping->i_mmap_lock); vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { mm = vma->vm_mm; address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); BUG_ON(address < vma->vm_start || address >= vma->vm_end); pte = page_check_address(page, mm, address, &ptl, 1); if (pte) { /* Nuke the page table entry. */ flush_cache_page(vma, address, pte_pfn(*pte)); pteval = ptep_clear_flush(vma, address, pte); page_remove_rmap(page, vma); dec_mm_counter(mm, file_rss); BUG_ON(pte_dirty(pteval)); pte_unmap_unlock(pte, ptl); page_cache_release(page); } } spin_unlock(&mapping->i_mmap_lock); } /* * xip_fault() is invoked via the vma operations vector for a * mapped memory region to read in file data during a page fault. * * This function is derived from filemap_fault, but used for execute in place */ static int xip_file_fault(struct vm_area_struct *vma, struct vm_fault *vmf) { struct file *file = vma->vm_file; struct address_space *mapping = file->f_mapping; struct inode *inode = mapping->host; pgoff_t size; void *xip_mem; unsigned long xip_pfn; struct page *page; int error; /* XXX: are VM_FAULT_ codes OK? */ size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; if (vmf->pgoff >= size) return VM_FAULT_SIGBUS; error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0, &xip_mem, &xip_pfn); if (likely(!error)) goto found; if (error != -ENODATA) return VM_FAULT_OOM; /* sparse block */ if ((vma->vm_flags & (VM_WRITE | VM_MAYWRITE)) && (vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) && (!(mapping->host->i_sb->s_flags & MS_RDONLY))) { int err; /* maybe shared writable, allocate new block */ error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 1, &xip_mem, &xip_pfn); if (error) return VM_FAULT_SIGBUS; /* unmap sparse mappings at pgoff from all other vmas */ __xip_unmap(mapping, vmf->pgoff); found: err = vm_insert_mixed(vma, (unsigned long)vmf->virtual_address, xip_pfn); if (err == -ENOMEM) return VM_FAULT_OOM; BUG_ON(err); return VM_FAULT_NOPAGE; } else { /* not shared and writable, use xip_sparse_page() */ page = xip_sparse_page(); if (!page) return VM_FAULT_OOM; page_cache_get(page); vmf->page = page; return 0; } } static struct vm_operations_struct xip_file_vm_ops = { .fault = xip_file_fault, }; int xip_file_mmap(struct file * file, struct vm_area_struct * vma) { BUG_ON(!file->f_mapping->a_ops->get_xip_mem); file_accessed(file); vma->vm_ops = &xip_file_vm_ops; vma->vm_flags |= VM_CAN_NONLINEAR | VM_MIXEDMAP; return 0; } EXPORT_SYMBOL_GPL(xip_file_mmap); static ssize_t __xip_file_write(struct file *filp, const char __user *buf, size_t count, loff_t pos, loff_t *ppos) { struct address_space * mapping = filp->f_mapping; const struct address_space_operations *a_ops = mapping->a_ops; struct inode *inode = mapping->host; long status = 0; size_t bytes; ssize_t written = 0; BUG_ON(!mapping->a_ops->get_xip_mem); do { unsigned long index; unsigned long offset; size_t copied; void *xip_mem; unsigned long xip_pfn; offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */ index = pos >> PAGE_CACHE_SHIFT; bytes = PAGE_CACHE_SIZE - offset; if (bytes > count) bytes = count; status = a_ops->get_xip_mem(mapping, index, 0, &xip_mem, &xip_pfn); if (status == -ENODATA) { /* we allocate a new page unmap it */ status = a_ops->get_xip_mem(mapping, index, 1, &xip_mem, &xip_pfn); if (!status) /* unmap page at pgoff from all other vmas */ __xip_unmap(mapping, index); } if (status) break; copied = bytes - __copy_from_user_nocache(xip_mem + offset, buf, bytes); if (likely(copied > 0)) { status = copied; if (status >= 0) { written += status; count -= status; pos += status; buf += status; } } if (unlikely(copied != bytes)) if (status >= 0) status = -EFAULT; if (status < 0) break; } while (count); *ppos = pos; /* * No need to use i_size_read() here, the i_size * cannot change under us because we hold i_mutex. */ if (pos > inode->i_size) { i_size_write(inode, pos); mark_inode_dirty(inode); } return written ? written : status; } ssize_t xip_file_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos) { struct address_space *mapping = filp->f_mapping; struct inode *inode = mapping->host; size_t count; loff_t pos; ssize_t ret; mutex_lock(&inode->i_mutex); if (!access_ok(VERIFY_READ, buf, len)) { ret=-EFAULT; goto out_up; } pos = *ppos; count = len; vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); /* We can write back this queue in page reclaim */ current->backing_dev_info = mapping->backing_dev_info; ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode)); if (ret) goto out_backing; if (count == 0) goto out_backing; ret = remove_suid(filp->f_path.dentry); if (ret) goto out_backing; file_update_time(filp); ret = __xip_file_write (filp, buf, count, pos, ppos); out_backing: current->backing_dev_info = NULL; out_up: mutex_unlock(&inode->i_mutex); return ret; } EXPORT_SYMBOL_GPL(xip_file_write); /* * truncate a page used for execute in place * functionality is analog to block_truncate_page but does use get_xip_mem * to get the page instead of page cache */ int xip_truncate_page(struct address_space *mapping, loff_t from) { pgoff_t index = from >> PAGE_CACHE_SHIFT; unsigned offset = from & (PAGE_CACHE_SIZE-1); unsigned blocksize; unsigned length; void *xip_mem; unsigned long xip_pfn; int err; BUG_ON(!mapping->a_ops->get_xip_mem); blocksize = 1 << mapping->host->i_blkbits; length = offset & (blocksize - 1); /* Block boundary? Nothing to do */ if (!length) return 0; length = blocksize - length; err = mapping->a_ops->get_xip_mem(mapping, index, 0, &xip_mem, &xip_pfn); if (unlikely(err)) { if (err == -ENODATA) /* Hole? No need to truncate */ return 0; else return err; } memset(xip_mem + offset, 0, length); return 0; } EXPORT_SYMBOL_GPL(xip_truncate_page);