linux/fs/jffs2/read.c
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   1/*
   2 * JFFS2 -- Journalling Flash File System, Version 2.
   3 *
   4 * Copyright © 2001-2007 Red Hat, Inc.
   5 *
   6 * Created by David Woodhouse <dwmw2@infradead.org>
   7 *
   8 * For licensing information, see the file 'LICENCE' in this directory.
   9 *
  10 */
  11
  12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14#include <linux/kernel.h>
  15#include <linux/slab.h>
  16#include <linux/crc32.h>
  17#include <linux/pagemap.h>
  18#include <linux/mtd/mtd.h>
  19#include <linux/compiler.h>
  20#include "nodelist.h"
  21#include "compr.h"
  22
  23int jffs2_read_dnode(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
  24                     struct jffs2_full_dnode *fd, unsigned char *buf,
  25                     int ofs, int len)
  26{
  27        struct jffs2_raw_inode *ri;
  28        size_t readlen;
  29        uint32_t crc;
  30        unsigned char *decomprbuf = NULL;
  31        unsigned char *readbuf = NULL;
  32        int ret = 0;
  33
  34        ri = jffs2_alloc_raw_inode();
  35        if (!ri)
  36                return -ENOMEM;
  37
  38        ret = jffs2_flash_read(c, ref_offset(fd->raw), sizeof(*ri), &readlen, (char *)ri);
  39        if (ret) {
  40                jffs2_free_raw_inode(ri);
  41                pr_warn("Error reading node from 0x%08x: %d\n",
  42                        ref_offset(fd->raw), ret);
  43                return ret;
  44        }
  45        if (readlen != sizeof(*ri)) {
  46                jffs2_free_raw_inode(ri);
  47                pr_warn("Short read from 0x%08x: wanted 0x%zx bytes, got 0x%zx\n",
  48                        ref_offset(fd->raw), sizeof(*ri), readlen);
  49                return -EIO;
  50        }
  51        crc = crc32(0, ri, sizeof(*ri)-8);
  52
  53        jffs2_dbg(1, "Node read from %08x: node_crc %08x, calculated CRC %08x. dsize %x, csize %x, offset %x, buf %p\n",
  54                  ref_offset(fd->raw), je32_to_cpu(ri->node_crc),
  55                  crc, je32_to_cpu(ri->dsize), je32_to_cpu(ri->csize),
  56                  je32_to_cpu(ri->offset), buf);
  57        if (crc != je32_to_cpu(ri->node_crc)) {
  58                pr_warn("Node CRC %08x != calculated CRC %08x for node at %08x\n",
  59                        je32_to_cpu(ri->node_crc), crc, ref_offset(fd->raw));
  60                ret = -EIO;
  61                goto out_ri;
  62        }
  63        /* There was a bug where we wrote hole nodes out with csize/dsize
  64           swapped. Deal with it */
  65        if (ri->compr == JFFS2_COMPR_ZERO && !je32_to_cpu(ri->dsize) &&
  66            je32_to_cpu(ri->csize)) {
  67                ri->dsize = ri->csize;
  68                ri->csize = cpu_to_je32(0);
  69        }
  70
  71        D1(if(ofs + len > je32_to_cpu(ri->dsize)) {
  72                        pr_warn("jffs2_read_dnode() asked for %d bytes at %d from %d-byte node\n",
  73                                len, ofs, je32_to_cpu(ri->dsize));
  74                ret = -EINVAL;
  75                goto out_ri;
  76        });
  77
  78
  79        if (ri->compr == JFFS2_COMPR_ZERO) {
  80                memset(buf, 0, len);
  81                goto out_ri;
  82        }
  83
  84        /* Cases:
  85           Reading whole node and it's uncompressed - read directly to buffer provided, check CRC.
  86           Reading whole node and it's compressed - read into comprbuf, check CRC and decompress to buffer provided
  87           Reading partial node and it's uncompressed - read into readbuf, check CRC, and copy
  88           Reading partial node and it's compressed - read into readbuf, check checksum, decompress to decomprbuf and copy
  89        */
  90        if (ri->compr == JFFS2_COMPR_NONE && len == je32_to_cpu(ri->dsize)) {
  91                readbuf = buf;
  92        } else {
  93                readbuf = kmalloc(je32_to_cpu(ri->csize), GFP_KERNEL);
  94                if (!readbuf) {
  95                        ret = -ENOMEM;
  96                        goto out_ri;
  97                }
  98        }
  99        if (ri->compr != JFFS2_COMPR_NONE) {
 100                if (len < je32_to_cpu(ri->dsize)) {
 101                        decomprbuf = kmalloc(je32_to_cpu(ri->dsize), GFP_KERNEL);
 102                        if (!decomprbuf) {
 103                                ret = -ENOMEM;
 104                                goto out_readbuf;
 105                        }
 106                } else {
 107                        decomprbuf = buf;
 108                }
 109        } else {
 110                decomprbuf = readbuf;
 111        }
 112
 113        jffs2_dbg(2, "Read %d bytes to %p\n", je32_to_cpu(ri->csize),
 114                  readbuf);
 115        ret = jffs2_flash_read(c, (ref_offset(fd->raw)) + sizeof(*ri),
 116                               je32_to_cpu(ri->csize), &readlen, readbuf);
 117
 118        if (!ret && readlen != je32_to_cpu(ri->csize))
 119                ret = -EIO;
 120        if (ret)
 121                goto out_decomprbuf;
 122
 123        crc = crc32(0, readbuf, je32_to_cpu(ri->csize));
 124        if (crc != je32_to_cpu(ri->data_crc)) {
 125                pr_warn("Data CRC %08x != calculated CRC %08x for node at %08x\n",
 126                        je32_to_cpu(ri->data_crc), crc, ref_offset(fd->raw));
 127                ret = -EIO;
 128                goto out_decomprbuf;
 129        }
 130        jffs2_dbg(2, "Data CRC matches calculated CRC %08x\n", crc);
 131        if (ri->compr != JFFS2_COMPR_NONE) {
 132                jffs2_dbg(2, "Decompress %d bytes from %p to %d bytes at %p\n",
 133                          je32_to_cpu(ri->csize), readbuf,
 134                          je32_to_cpu(ri->dsize), decomprbuf);
 135                ret = jffs2_decompress(c, f, ri->compr | (ri->usercompr << 8), readbuf, decomprbuf, je32_to_cpu(ri->csize), je32_to_cpu(ri->dsize));
 136                if (ret) {
 137                        pr_warn("Error: jffs2_decompress returned %d\n", ret);
 138                        goto out_decomprbuf;
 139                }
 140        }
 141
 142        if (len < je32_to_cpu(ri->dsize)) {
 143                memcpy(buf, decomprbuf+ofs, len);
 144        }
 145 out_decomprbuf:
 146        if(decomprbuf != buf && decomprbuf != readbuf)
 147                kfree(decomprbuf);
 148 out_readbuf:
 149        if(readbuf != buf)
 150                kfree(readbuf);
 151 out_ri:
 152        jffs2_free_raw_inode(ri);
 153
 154        return ret;
 155}
 156
 157int jffs2_read_inode_range(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
 158                           unsigned char *buf, uint32_t offset, uint32_t len)
 159{
 160        uint32_t end = offset + len;
 161        struct jffs2_node_frag *frag;
 162        int ret;
 163
 164        jffs2_dbg(1, "%s(): ino #%u, range 0x%08x-0x%08x\n",
 165                  __func__, f->inocache->ino, offset, offset + len);
 166
 167        frag = jffs2_lookup_node_frag(&f->fragtree, offset);
 168
 169        /* XXX FIXME: Where a single physical node actually shows up in two
 170           frags, we read it twice. Don't do that. */
 171        /* Now we're pointing at the first frag which overlaps our page
 172         * (or perhaps is before it, if we've been asked to read off the
 173         * end of the file). */
 174        while(offset < end) {
 175                jffs2_dbg(2, "%s(): offset %d, end %d\n",
 176                          __func__, offset, end);
 177                if (unlikely(!frag || frag->ofs > offset ||
 178                             frag->ofs + frag->size <= offset)) {
 179                        uint32_t holesize = end - offset;
 180                        if (frag && frag->ofs > offset) {
 181                                jffs2_dbg(1, "Eep. Hole in ino #%u fraglist. frag->ofs = 0x%08x, offset = 0x%08x\n",
 182                                          f->inocache->ino, frag->ofs, offset);
 183                                holesize = min(holesize, frag->ofs - offset);
 184                        }
 185                        jffs2_dbg(1, "Filling non-frag hole from %d-%d\n",
 186                                  offset, offset + holesize);
 187                        memset(buf, 0, holesize);
 188                        buf += holesize;
 189                        offset += holesize;
 190                        continue;
 191                } else if (unlikely(!frag->node)) {
 192                        uint32_t holeend = min(end, frag->ofs + frag->size);
 193                        jffs2_dbg(1, "Filling frag hole from %d-%d (frag 0x%x 0x%x)\n",
 194                                  offset, holeend, frag->ofs,
 195                                  frag->ofs + frag->size);
 196                        memset(buf, 0, holeend - offset);
 197                        buf += holeend - offset;
 198                        offset = holeend;
 199                        frag = frag_next(frag);
 200                        continue;
 201                } else {
 202                        uint32_t readlen;
 203                        uint32_t fragofs; /* offset within the frag to start reading */
 204
 205                        fragofs = offset - frag->ofs;
 206                        readlen = min(frag->size - fragofs, end - offset);
 207                        jffs2_dbg(1, "Reading %d-%d from node at 0x%08x (%d)\n",
 208                                  frag->ofs+fragofs,
 209                                  frag->ofs + fragofs+readlen,
 210                                  ref_offset(frag->node->raw),
 211                                  ref_flags(frag->node->raw));
 212                        ret = jffs2_read_dnode(c, f, frag->node, buf, fragofs + frag->ofs - frag->node->ofs, readlen);
 213                        jffs2_dbg(2, "node read done\n");
 214                        if (ret) {
 215                                jffs2_dbg(1, "%s(): error %d\n",
 216                                          __func__, ret);
 217                                memset(buf, 0, readlen);
 218                                return ret;
 219                        }
 220                        buf += readlen;
 221                        offset += readlen;
 222                        frag = frag_next(frag);
 223                        jffs2_dbg(2, "node read was OK. Looping\n");
 224                }
 225        }
 226        return 0;
 227}
 228
 229
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