libdex/DexOptData.cpp

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Functions to parse and manipulate the additional data tables added
 * to optimized .dex files.
 */

#include <zlib.h>

#include "DexOptData.h"

/*
 * Check to see if a given data pointer is a valid double-word-aligned
 * pointer into the given memory range (from start inclusive to end
 * exclusive). Returns true if valid.
 */
static bool isValidPointer(const void* ptr, const void* start, const void* end)
{
    return (ptr >= start) && (ptr < end) && (((uintptr_t) ptr & 7) == 0);
}

/* (documented in header file) */
u4 dexComputeOptChecksum(const DexOptHeader* pOptHeader)
{
    const u1* start = (const u1*) pOptHeader + pOptHeader->depsOffset;
    const u1* end = (const u1*) pOptHeader +
        pOptHeader->optOffset + pOptHeader->optLength;

    uLong adler = adler32(0L, Z_NULL, 0);

    return (u4) adler32(adler, start, end - start);
}

/* (documented in header file) */
bool dexParseOptData(const u1* data, size_t length, DexFile* pDexFile)
{
    const void* pOptStart = data + pDexFile->pOptHeader->optOffset;
    const void* pOptEnd = data + length;
    const u4* pOpt = (const u4*) pOptStart;
    u4 optLength = (const u1*) pOptEnd - (const u1*) pOptStart;

    /*
     * Make sure the opt data start is in range and aligned. This may
     * seem like a superfluous check, but (a) if the file got
     * truncated, it might turn out that pOpt >= pOptEnd; and (b)
     * if the opt data header got corrupted, pOpt might not be
     * properly aligned. This test will catch both of these cases.
     */
    if (!isValidPointer(pOpt, pOptStart, pOptEnd)) {
        ALOGE("Bogus opt data start pointer");
        return false;
    }

    /* Make sure that the opt data length is a whole number of words. */
    if ((optLength & 3) != 0) {
        ALOGE("Unaligned opt data area end");
        return false;
    }

    /*
     * Make sure that the opt data area is large enough to have at least
     * one chunk header.
     */
    if (optLength < 8) {
        ALOGE("Undersized opt data area (%u)", optLength);
        return false;
    }

    /* Process chunks until we see the end marker. */
    while (*pOpt != kDexChunkEnd) {
        if (!isValidPointer(pOpt + 2, pOptStart, pOptEnd)) {
            ALOGE("Bogus opt data content pointer at offset %u",
                    ((const u1*) pOpt) - data);
            return false;
        }

        u4 size = *(pOpt + 1);
        const u1* pOptData = (const u1*) (pOpt + 2);

        /*
         * The rounded size is 64-bit aligned and includes +8 for the
         * type/size header (which was extracted immediately above).
         */
        u4 roundedSize = (size + 8 + 7) & ~7;
        const u4* pNextOpt = pOpt + (roundedSize / sizeof(u4));

        if (!isValidPointer(pNextOpt, pOptStart, pOptEnd)) {
            ALOGE("Opt data area problem for chunk of size %u at offset %u",
                    size, ((const u1*) pOpt) - data);
            return false;
        }

        switch (*pOpt) {
        case kDexChunkClassLookup:
            pDexFile->pClassLookup = (const DexClassLookup*) pOptData;
            break;
        case kDexChunkRegisterMaps:
            ALOGV("+++ found register maps, size=%u", size);
            pDexFile->pRegisterMapPool = pOptData;
            break;
        default:
            ALOGI("Unknown chunk 0x%08x (%c%c%c%c), size=%d in opt data area",
                *pOpt,
                (char) ((*pOpt) >> 24), (char) ((*pOpt) >> 16),
                (char) ((*pOpt) >> 8),  (char)  (*pOpt),
                size);
            break;
        }

        pOpt = pNextOpt;
    }

    return true;
}