linux/mm/filemap_xip.c
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   1/*
   2 *      linux/mm/filemap_xip.c
   3 *
   4 * Copyright (C) 2005 IBM Corporation
   5 * Author: Carsten Otte <cotte@de.ibm.com>
   6 *
   7 * derived from linux/mm/filemap.c - Copyright (C) Linus Torvalds
   8 *
   9 */
  10
  11#include <linux/fs.h>
  12#include <linux/pagemap.h>
  13#include <linux/export.h>
  14#include <linux/uio.h>
  15#include <linux/rmap.h>
  16#include <linux/mmu_notifier.h>
  17#include <linux/sched.h>
  18#include <linux/seqlock.h>
  19#include <linux/mutex.h>
  20#include <linux/gfp.h>
  21#include <asm/tlbflush.h>
  22#include <asm/io.h>
  23
  24/*
  25 * We do use our own empty page to avoid interference with other users
  26 * of ZERO_PAGE(), such as /dev/zero
  27 */
  28static DEFINE_MUTEX(xip_sparse_mutex);
  29static seqcount_t xip_sparse_seq = SEQCNT_ZERO;
  30static struct page *__xip_sparse_page;
  31
  32/* called under xip_sparse_mutex */
  33static struct page *xip_sparse_page(void)
  34{
  35        if (!__xip_sparse_page) {
  36                struct page *page = alloc_page(GFP_HIGHUSER | __GFP_ZERO);
  37
  38                if (page)
  39                        __xip_sparse_page = page;
  40        }
  41        return __xip_sparse_page;
  42}
  43
  44/*
  45 * This is a file read routine for execute in place files, and uses
  46 * the mapping->a_ops->get_xip_mem() function for the actual low-level
  47 * stuff.
  48 *
  49 * Note the struct file* is not used at all.  It may be NULL.
  50 */
  51static ssize_t
  52do_xip_mapping_read(struct address_space *mapping,
  53                    struct file_ra_state *_ra,
  54                    struct file *filp,
  55                    char __user *buf,
  56                    size_t len,
  57                    loff_t *ppos)
  58{
  59        struct inode *inode = mapping->host;
  60        pgoff_t index, end_index;
  61        unsigned long offset;
  62        loff_t isize, pos;
  63        size_t copied = 0, error = 0;
  64
  65        BUG_ON(!mapping->a_ops->get_xip_mem);
  66
  67        pos = *ppos;
  68        index = pos >> PAGE_CACHE_SHIFT;
  69        offset = pos & ~PAGE_CACHE_MASK;
  70
  71        isize = i_size_read(inode);
  72        if (!isize)
  73                goto out;
  74
  75        end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
  76        do {
  77                unsigned long nr, left;
  78                void *xip_mem;
  79                unsigned long xip_pfn;
  80                int zero = 0;
  81
  82                /* nr is the maximum number of bytes to copy from this page */
  83                nr = PAGE_CACHE_SIZE;
  84                if (index >= end_index) {
  85                        if (index > end_index)
  86                                goto out;
  87                        nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
  88                        if (nr <= offset) {
  89                                goto out;
  90                        }
  91                }
  92                nr = nr - offset;
  93                if (nr > len - copied)
  94                        nr = len - copied;
  95
  96                error = mapping->a_ops->get_xip_mem(mapping, index, 0,
  97                                                        &xip_mem, &xip_pfn);
  98                if (unlikely(error)) {
  99                        if (error == -ENODATA) {
 100                                /* sparse */
 101                                zero = 1;
 102                        } else
 103                                goto out;
 104                }
 105
 106                /* If users can be writing to this page using arbitrary
 107                 * virtual addresses, take care about potential aliasing
 108                 * before reading the page on the kernel side.
 109                 */
 110                if (mapping_writably_mapped(mapping))
 111                        /* address based flush */ ;
 112
 113                /*
 114                 * Ok, we have the mem, so now we can copy it to user space...
 115                 *
 116                 * The actor routine returns how many bytes were actually used..
 117                 * NOTE! This may not be the same as how much of a user buffer
 118                 * we filled up (we may be padding etc), so we can only update
 119                 * "pos" here (the actor routine has to update the user buffer
 120                 * pointers and the remaining count).
 121                 */
 122                if (!zero)
 123                        left = __copy_to_user(buf+copied, xip_mem+offset, nr);
 124                else
 125                        left = __clear_user(buf + copied, nr);
 126
 127                if (left) {
 128                        error = -EFAULT;
 129                        goto out;
 130                }
 131
 132                copied += (nr - left);
 133                offset += (nr - left);
 134                index += offset >> PAGE_CACHE_SHIFT;
 135                offset &= ~PAGE_CACHE_MASK;
 136        } while (copied < len);
 137
 138out:
 139        *ppos = pos + copied;
 140        if (filp)
 141                file_accessed(filp);
 142
 143        return (copied ? copied : error);
 144}
 145
 146ssize_t
 147xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
 148{
 149        if (!access_ok(VERIFY_WRITE, buf, len))
 150                return -EFAULT;
 151
 152        return do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp,
 153                            buf, len, ppos);
 154}
 155EXPORT_SYMBOL_GPL(xip_file_read);
 156
 157/*
 158 * __xip_unmap is invoked from xip_unmap and
 159 * xip_write
 160 *
 161 * This function walks all vmas of the address_space and unmaps the
 162 * __xip_sparse_page when found at pgoff.
 163 */
 164static void
 165__xip_unmap (struct address_space * mapping,
 166                     unsigned long pgoff)
 167{
 168        struct vm_area_struct *vma;
 169        struct mm_struct *mm;
 170        unsigned long address;
 171        pte_t *pte;
 172        pte_t pteval;
 173        spinlock_t *ptl;
 174        struct page *page;
 175        unsigned count;
 176        int locked = 0;
 177
 178        count = read_seqcount_begin(&xip_sparse_seq);
 179
 180        page = __xip_sparse_page;
 181        if (!page)
 182                return;
 183
 184retry:
 185        mutex_lock(&mapping->i_mmap_mutex);
 186        vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
 187                mm = vma->vm_mm;
 188                address = vma->vm_start +
 189                        ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
 190                BUG_ON(address < vma->vm_start || address >= vma->vm_end);
 191                pte = page_check_address(page, mm, address, &ptl, 1);
 192                if (pte) {
 193                        /* Nuke the page table entry. */
 194                        flush_cache_page(vma, address, pte_pfn(*pte));
 195                        pteval = ptep_clear_flush(vma, address, pte);
 196                        page_remove_rmap(page);
 197                        dec_mm_counter(mm, MM_FILEPAGES);
 198                        BUG_ON(pte_dirty(pteval));
 199                        pte_unmap_unlock(pte, ptl);
 200                        /* must invalidate_page _before_ freeing the page */
 201                        mmu_notifier_invalidate_page(mm, address);
 202                        page_cache_release(page);
 203                }
 204        }
 205        mutex_unlock(&mapping->i_mmap_mutex);
 206
 207        if (locked) {
 208                mutex_unlock(&xip_sparse_mutex);
 209        } else if (read_seqcount_retry(&xip_sparse_seq, count)) {
 210                mutex_lock(&xip_sparse_mutex);
 211                locked = 1;
 212                goto retry;
 213        }
 214}
 215
 216/*
 217 * xip_fault() is invoked via the vma operations vector for a
 218 * mapped memory region to read in file data during a page fault.
 219 *
 220 * This function is derived from filemap_fault, but used for execute in place
 221 */
 222static int xip_file_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 223{
 224        struct file *file = vma->vm_file;
 225        struct address_space *mapping = file->f_mapping;
 226        struct inode *inode = mapping->host;
 227        pgoff_t size;
 228        void *xip_mem;
 229        unsigned long xip_pfn;
 230        struct page *page;
 231        int error;
 232
 233        /* XXX: are VM_FAULT_ codes OK? */
 234again:
 235        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 236        if (vmf->pgoff >= size)
 237                return VM_FAULT_SIGBUS;
 238
 239        error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
 240                                                &xip_mem, &xip_pfn);
 241        if (likely(!error))
 242                goto found;
 243        if (error != -ENODATA)
 244                return VM_FAULT_OOM;
 245
 246        /* sparse block */
 247        if ((vma->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
 248            (vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) &&
 249            (!(mapping->host->i_sb->s_flags & MS_RDONLY))) {
 250                int err;
 251
 252                /* maybe shared writable, allocate new block */
 253                mutex_lock(&xip_sparse_mutex);
 254                error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 1,
 255                                                        &xip_mem, &xip_pfn);
 256                mutex_unlock(&xip_sparse_mutex);
 257                if (error)
 258                        return VM_FAULT_SIGBUS;
 259                /* unmap sparse mappings at pgoff from all other vmas */
 260                __xip_unmap(mapping, vmf->pgoff);
 261
 262found:
 263                err = vm_insert_mixed(vma, (unsigned long)vmf->virtual_address,
 264                                                        xip_pfn);
 265                if (err == -ENOMEM)
 266                        return VM_FAULT_OOM;
 267                /*
 268                 * err == -EBUSY is fine, we've raced against another thread
 269                 * that faulted-in the same page
 270                 */
 271                if (err != -EBUSY)
 272                        BUG_ON(err);
 273                return VM_FAULT_NOPAGE;
 274        } else {
 275                int err, ret = VM_FAULT_OOM;
 276
 277                mutex_lock(&xip_sparse_mutex);
 278                write_seqcount_begin(&xip_sparse_seq);
 279                error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 0,
 280                                                        &xip_mem, &xip_pfn);
 281                if (unlikely(!error)) {
 282                        write_seqcount_end(&xip_sparse_seq);
 283                        mutex_unlock(&xip_sparse_mutex);
 284                        goto again;
 285                }
 286                if (error != -ENODATA)
 287                        goto out;
 288                /* not shared and writable, use xip_sparse_page() */
 289                page = xip_sparse_page();
 290                if (!page)
 291                        goto out;
 292                err = vm_insert_page(vma, (unsigned long)vmf->virtual_address,
 293                                                        page);
 294                if (err == -ENOMEM)
 295                        goto out;
 296
 297                ret = VM_FAULT_NOPAGE;
 298out:
 299                write_seqcount_end(&xip_sparse_seq);
 300                mutex_unlock(&xip_sparse_mutex);
 301
 302                return ret;
 303        }
 304}
 305
 306static const struct vm_operations_struct xip_file_vm_ops = {
 307        .fault  = xip_file_fault,
 308        .page_mkwrite   = filemap_page_mkwrite,
 309        .remap_pages = generic_file_remap_pages,
 310};
 311
 312int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
 313{
 314        BUG_ON(!file->f_mapping->a_ops->get_xip_mem);
 315
 316        file_accessed(file);
 317        vma->vm_ops = &xip_file_vm_ops;
 318        vma->vm_flags |= VM_MIXEDMAP;
 319        return 0;
 320}
 321EXPORT_SYMBOL_GPL(xip_file_mmap);
 322
 323static ssize_t
 324__xip_file_write(struct file *filp, const char __user *buf,
 325                  size_t count, loff_t pos, loff_t *ppos)
 326{
 327        struct address_space * mapping = filp->f_mapping;
 328        const struct address_space_operations *a_ops = mapping->a_ops;
 329        struct inode    *inode = mapping->host;
 330        long            status = 0;
 331        size_t          bytes;
 332        ssize_t         written = 0;
 333
 334        BUG_ON(!mapping->a_ops->get_xip_mem);
 335
 336        do {
 337                unsigned long index;
 338                unsigned long offset;
 339                size_t copied;
 340                void *xip_mem;
 341                unsigned long xip_pfn;
 342
 343                offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
 344                index = pos >> PAGE_CACHE_SHIFT;
 345                bytes = PAGE_CACHE_SIZE - offset;
 346                if (bytes > count)
 347                        bytes = count;
 348
 349                status = a_ops->get_xip_mem(mapping, index, 0,
 350                                                &xip_mem, &xip_pfn);
 351                if (status == -ENODATA) {
 352                        /* we allocate a new page unmap it */
 353                        mutex_lock(&xip_sparse_mutex);
 354                        status = a_ops->get_xip_mem(mapping, index, 1,
 355                                                        &xip_mem, &xip_pfn);
 356                        mutex_unlock(&xip_sparse_mutex);
 357                        if (!status)
 358                                /* unmap page at pgoff from all other vmas */
 359                                __xip_unmap(mapping, index);
 360                }
 361
 362                if (status)
 363                        break;
 364
 365                copied = bytes -
 366                        __copy_from_user_nocache(xip_mem + offset, buf, bytes);
 367
 368                if (likely(copied > 0)) {
 369                        status = copied;
 370
 371                        if (status >= 0) {
 372                                written += status;
 373                                count -= status;
 374                                pos += status;
 375                                buf += status;
 376                        }
 377                }
 378                if (unlikely(copied != bytes))
 379                        if (status >= 0)
 380                                status = -EFAULT;
 381                if (status < 0)
 382                        break;
 383        } while (count);
 384        *ppos = pos;
 385        /*
 386         * No need to use i_size_read() here, the i_size
 387         * cannot change under us because we hold i_mutex.
 388         */
 389        if (pos > inode->i_size) {
 390                i_size_write(inode, pos);
 391                mark_inode_dirty(inode);
 392        }
 393
 394        return written ? written : status;
 395}
 396
 397ssize_t
 398xip_file_write(struct file *filp, const char __user *buf, size_t len,
 399               loff_t *ppos)
 400{
 401        struct address_space *mapping = filp->f_mapping;
 402        struct inode *inode = mapping->host;
 403        size_t count;
 404        loff_t pos;
 405        ssize_t ret;
 406
 407        sb_start_write(inode->i_sb);
 408
 409        mutex_lock(&inode->i_mutex);
 410
 411        if (!access_ok(VERIFY_READ, buf, len)) {
 412                ret=-EFAULT;
 413                goto out_up;
 414        }
 415
 416        pos = *ppos;
 417        count = len;
 418
 419        /* We can write back this queue in page reclaim */
 420        current->backing_dev_info = mapping->backing_dev_info;
 421
 422        ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
 423        if (ret)
 424                goto out_backing;
 425        if (count == 0)
 426                goto out_backing;
 427
 428        ret = file_remove_suid(filp);
 429        if (ret)
 430                goto out_backing;
 431
 432        ret = file_update_time(filp);
 433        if (ret)
 434                goto out_backing;
 435
 436        ret = __xip_file_write (filp, buf, count, pos, ppos);
 437
 438 out_backing:
 439        current->backing_dev_info = NULL;
 440 out_up:
 441        mutex_unlock(&inode->i_mutex);
 442        sb_end_write(inode->i_sb);
 443        return ret;
 444}
 445EXPORT_SYMBOL_GPL(xip_file_write);
 446
 447/*
 448 * truncate a page used for execute in place
 449 * functionality is analog to block_truncate_page but does use get_xip_mem
 450 * to get the page instead of page cache
 451 */
 452int
 453xip_truncate_page(struct address_space *mapping, loff_t from)
 454{
 455        pgoff_t index = from >> PAGE_CACHE_SHIFT;
 456        unsigned offset = from & (PAGE_CACHE_SIZE-1);
 457        unsigned blocksize;
 458        unsigned length;
 459        void *xip_mem;
 460        unsigned long xip_pfn;
 461        int err;
 462
 463        BUG_ON(!mapping->a_ops->get_xip_mem);
 464
 465        blocksize = 1 << mapping->host->i_blkbits;
 466        length = offset & (blocksize - 1);
 467
 468        /* Block boundary? Nothing to do */
 469        if (!length)
 470                return 0;
 471
 472        length = blocksize - length;
 473
 474        err = mapping->a_ops->get_xip_mem(mapping, index, 0,
 475                                                &xip_mem, &xip_pfn);
 476        if (unlikely(err)) {
 477                if (err == -ENODATA)
 478                        /* Hole? No need to truncate */
 479                        return 0;
 480                else
 481                        return err;
 482        }
 483        memset(xip_mem + offset, 0, length);
 484        return 0;
 485}
 486EXPORT_SYMBOL_GPL(xip_truncate_page);
 487
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