read.c

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/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright © 2001-2007 Red Hat, Inc.
 *
 * Created by David Woodhouse <[email protected]>
 *
 * For licensing information, see the file 'LICENCE' in this directory.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/crc32.h>
#include <linux/pagemap.h>
#include <linux/mtd/mtd.h>
#include <linux/compiler.h>
#include "nodelist.h"
#include "compr.h"

int jffs2_read_dnode(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
             struct jffs2_full_dnode *fd, unsigned char *buf,
             int ofs, int len)
{
    struct jffs2_raw_inode *ri;
    size_t readlen;
    uint32_t crc;
    unsigned char *decomprbuf = NULL;
    unsigned char *readbuf = NULL;
    int ret = 0;

    ri = jffs2_alloc_raw_inode();
    if (!ri)
        return -ENOMEM;

    ret = jffs2_flash_read(c, ref_offset(fd->raw), sizeof(*ri), &readlen, (char *)ri);
    if (ret) {
        jffs2_free_raw_inode(ri);
        pr_warn("Error reading node from 0x%08x: %d\n",
            ref_offset(fd->raw), ret);
        return ret;
    }
    if (readlen != sizeof(*ri)) {
        jffs2_free_raw_inode(ri);
        pr_warn("Short read from 0x%08x: wanted 0x%zx bytes, got 0x%zx\n",
            ref_offset(fd->raw), sizeof(*ri), readlen);
        return -EIO;
    }
    crc = crc32(0, ri, sizeof(*ri)-8);

    jffs2_dbg(1, "Node read from %08x: node_crc %08x, calculated CRC %08x. dsize %x, csize %x, offset %x, buf %p\n",
          ref_offset(fd->raw), je32_to_cpu(ri->node_crc),
          crc, je32_to_cpu(ri->dsize), je32_to_cpu(ri->csize),
          je32_to_cpu(ri->offset), buf);
    if (crc != je32_to_cpu(ri->node_crc)) {
        pr_warn("Node CRC %08x != calculated CRC %08x for node at %08x\n",
            je32_to_cpu(ri->node_crc), crc, ref_offset(fd->raw));
        ret = -EIO;
        goto out_ri;
    }
    /* There was a bug where we wrote hole nodes out with csize/dsize
       swapped. Deal with it */
    if (ri->compr == JFFS2_COMPR_ZERO && !je32_to_cpu(ri->dsize) &&
        je32_to_cpu(ri->csize)) {
        ri->dsize = ri->csize;
        ri->csize = cpu_to_je32(0);
    }

    D1(if(ofs + len > je32_to_cpu(ri->dsize)) {
            pr_warn("jffs2_read_dnode() asked for %d bytes at %d from %d-byte node\n",
                len, ofs, je32_to_cpu(ri->dsize));
        ret = -EINVAL;
        goto out_ri;
    });


    if (ri->compr == JFFS2_COMPR_ZERO) {
        memset(buf, 0, len);
        goto out_ri;
    }

    /* Cases:
       Reading whole node and it's uncompressed - read directly to buffer provided, check CRC.
       Reading whole node and it's compressed - read into comprbuf, check CRC and decompress to buffer provided
       Reading partial node and it's uncompressed - read into readbuf, check CRC, and copy
       Reading partial node and it's compressed - read into readbuf, check checksum, decompress to decomprbuf and copy
    */
    if (ri->compr == JFFS2_COMPR_NONE && len == je32_to_cpu(ri->dsize)) {
        readbuf = buf;
    } else {
        readbuf = kmalloc(je32_to_cpu(ri->csize), GFP_KERNEL);
        if (!readbuf) {
            ret = -ENOMEM;
            goto out_ri;
        }
    }
    if (ri->compr != JFFS2_COMPR_NONE) {
        if (len < je32_to_cpu(ri->dsize)) {
            decomprbuf = kmalloc(je32_to_cpu(ri->dsize), GFP_KERNEL);
            if (!decomprbuf) {
                ret = -ENOMEM;
                goto out_readbuf;
            }
        } else {
            decomprbuf = buf;
        }
    } else {
        decomprbuf = readbuf;
    }

    jffs2_dbg(2, "Read %d bytes to %p\n", je32_to_cpu(ri->csize),
          readbuf);
    ret = jffs2_flash_read(c, (ref_offset(fd->raw)) + sizeof(*ri),
                   je32_to_cpu(ri->csize), &readlen, readbuf);

    if (!ret && readlen != je32_to_cpu(ri->csize))
        ret = -EIO;
    if (ret)
        goto out_decomprbuf;

    crc = crc32(0, readbuf, je32_to_cpu(ri->csize));
    if (crc != je32_to_cpu(ri->data_crc)) {
        pr_warn("Data CRC %08x != calculated CRC %08x for node at %08x\n",
            je32_to_cpu(ri->data_crc), crc, ref_offset(fd->raw));
        ret = -EIO;
        goto out_decomprbuf;
    }
    jffs2_dbg(2, "Data CRC matches calculated CRC %08x\n", crc);
    if (ri->compr != JFFS2_COMPR_NONE) {
        jffs2_dbg(2, "Decompress %d bytes from %p to %d bytes at %p\n",
              je32_to_cpu(ri->csize), readbuf,
              je32_to_cpu(ri->dsize), decomprbuf);
        ret = jffs2_decompress(c, f, ri->compr | (ri->usercompr << 8), readbuf, decomprbuf, je32_to_cpu(ri->csize), je32_to_cpu(ri->dsize));
        if (ret) {
            pr_warn("Error: jffs2_decompress returned %d\n", ret);
            goto out_decomprbuf;
        }
    }

    if (len < je32_to_cpu(ri->dsize)) {
        memcpy(buf, decomprbuf+ofs, len);
    }
 out_decomprbuf:
    if(decomprbuf != buf && decomprbuf != readbuf)
        kfree(decomprbuf);
 out_readbuf:
    if(readbuf != buf)
        kfree(readbuf);
 out_ri:
    jffs2_free_raw_inode(ri);

    return ret;
}

int jffs2_read_inode_range(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
               unsigned char *buf, uint32_t offset, uint32_t len)
{
    uint32_t end = offset + len;
    struct jffs2_node_frag *frag;
    int ret;

    jffs2_dbg(1, "%s(): ino #%u, range 0x%08x-0x%08x\n",
          __func__, f->inocache->ino, offset, offset + len);

    frag = jffs2_lookup_node_frag(&f->fragtree, offset);

    /* XXX FIXME: Where a single physical node actually shows up in two
       frags, we read it twice. Don't do that. */
    /* Now we're pointing at the first frag which overlaps our page
     * (or perhaps is before it, if we've been asked to read off the
     * end of the file). */
    while(offset < end) {
        jffs2_dbg(2, "%s(): offset %d, end %d\n",
              __func__, offset, end);
        if (unlikely(!frag || frag->ofs > offset ||
                 frag->ofs + frag->size <= offset)) {
            uint32_t holesize = end - offset;
            if (frag && frag->ofs > offset) {
                jffs2_dbg(1, "Eep. Hole in ino #%u fraglist. frag->ofs = 0x%08x, offset = 0x%08x\n",
                      f->inocache->ino, frag->ofs, offset);
                holesize = min(holesize, frag->ofs - offset);
            }
            jffs2_dbg(1, "Filling non-frag hole from %d-%d\n",
                  offset, offset + holesize);
            memset(buf, 0, holesize);
            buf += holesize;
            offset += holesize;
            continue;
        } else if (unlikely(!frag->node)) {
            uint32_t holeend = min(end, frag->ofs + frag->size);
            jffs2_dbg(1, "Filling frag hole from %d-%d (frag 0x%x 0x%x)\n",
                  offset, holeend, frag->ofs,
                  frag->ofs + frag->size);
            memset(buf, 0, holeend - offset);
            buf += holeend - offset;
            offset = holeend;
            frag = frag_next(frag);
            continue;
        } else {
            uint32_t readlen;
            uint32_t fragofs; /* offset within the frag to start reading */

            fragofs = offset - frag->ofs;
            readlen = min(frag->size - fragofs, end - offset);
            jffs2_dbg(1, "Reading %d-%d from node at 0x%08x (%d)\n",
                  frag->ofs+fragofs,
                  frag->ofs + fragofs+readlen,
                  ref_offset(frag->node->raw),
                  ref_flags(frag->node->raw));
            ret = jffs2_read_dnode(c, f, frag->node, buf, fragofs + frag->ofs - frag->node->ofs, readlen);
            jffs2_dbg(2, "node read done\n");
            if (ret) {
                jffs2_dbg(1, "%s(): error %d\n",
                      __func__, ret);
                memset(buf, 0, readlen);
                return ret;
            }
            buf += readlen;
            offset += readlen;
            frag = frag_next(frag);
            jffs2_dbg(2, "node read was OK. Looping\n");
        }
    }
    return 0;
}