1 files changed, 480 insertions, 0 deletions

diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
new file mode 100644
index 00000000..a4eb3113
--- /dev/null
+++ b/mm/filemap_xip.c
@@ -0,0 +1,480 @@
+/*
+ *	linux/mm/filemap_xip.c
+ *
+ * Copyright (C) 2005 IBM Corporation
+ * Author: Carsten Otte <cotte@de.ibm.com>
+ *
+ * derived from linux/mm/filemap.c - Copyright (C) Linus Torvalds
+ *
+ */
+
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/export.h>
+#include <linux/uio.h>
+#include <linux/rmap.h>
+#include <linux/mmu_notifier.h>
+#include <linux/sched.h>
+#include <linux/seqlock.h>
+#include <linux/mutex.h>
+#include <linux/gfp.h>
+#include <asm/tlbflush.h>
+#include <asm/io.h>
+
+/*
+ * We do use our own empty page to avoid interference with other users
+ * of ZERO_PAGE(), such as /dev/zero
+ */
+static DEFINE_MUTEX(xip_sparse_mutex);
+static seqcount_t xip_sparse_seq = SEQCNT_ZERO;
+static struct page *__xip_sparse_page;
+
+/* called under xip_sparse_mutex */
+static struct page *xip_sparse_page(void)
+{
+	if (!__xip_sparse_page) {
+		struct page *page = alloc_page(GFP_HIGHUSER | __GFP_ZERO);
+
+		if (page)
+			__xip_sparse_page = page;
+	}
+	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 - copied)
+			nr = len - copied;
+
+		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;
+	unsigned count;
+	int locked = 0;
+
+	count = read_seqcount_begin(&xip_sparse_seq);
+
+	page = __xip_sparse_page;
+	if (!page)
+		return;
+
+retry:
+	mutex_lock(&mapping->i_mmap_mutex);
+	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_notify(vma, address, pte);
+			page_remove_rmap(page);
+			dec_mm_counter(mm, MM_FILEPAGES);
+			BUG_ON(pte_dirty(pteval));
+			pte_unmap_unlock(pte, ptl);
+			page_cache_release(page);
+		}
+	}
+	mutex_unlock(&mapping->i_mmap_mutex);
+
+	if (locked) {
+		mutex_unlock(&xip_sparse_mutex);
+	} else if (read_seqcount_retry(&xip_sparse_seq, count)) {
+		mutex_lock(&xip_sparse_mutex);
+		locked = 1;
+		goto retry;
+	}
+}
+
+/*
+ * 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? */
+again:
+	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 */
+		mutex_lock(&xip_sparse_mutex);
+		error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 1,
+							&xip_mem, &xip_pfn);
+		mutex_unlock(&xip_sparse_mutex);
+		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;
+		/*
+		 * err == -EBUSY is fine, we've raced against another thread
+		 * that faulted-in the same page
+		 */
+		if (err != -EBUSY)
+			BUG_ON(err);
+		return VM_FAULT_NOPAGE;
+	} else {
+		int err, ret = VM_FAULT_OOM;
+
+		mutex_lock(&xip_sparse_mutex);
+		write_seqcount_begin(&xip_sparse_seq);
+		error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
+							&xip_mem, &xip_pfn);
+		if (unlikely(!error)) {
+			write_seqcount_end(&xip_sparse_seq);
+			mutex_unlock(&xip_sparse_mutex);
+			goto again;
+		}
+		if (error != -ENODATA)
+			goto out;
+		/* not shared and writable, use xip_sparse_page() */
+		page = xip_sparse_page();
+		if (!page)
+			goto out;
+		err = vm_insert_page(vma, (unsigned long)vmf->virtual_address,
+							page);
+		if (err == -ENOMEM)
+			goto out;
+
+		ret = VM_FAULT_NOPAGE;
+out:
+		write_seqcount_end(&xip_sparse_seq);
+		mutex_unlock(&xip_sparse_mutex);
+
+		return ret;
+	}
+}
+
+static const 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 */
+			mutex_lock(&xip_sparse_mutex);
+			status = a_ops->get_xip_mem(mapping, index, 1,
+							&xip_mem, &xip_pfn);
+			mutex_unlock(&xip_sparse_mutex);
+			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 = file_remove_suid(filp);
+	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);