packer.cpp

UPX 源代码

void Packer::checkPatch(void *b, int blen, int boff, int size)
{
    if (b == NULL && blen == 0 && boff == 0 && size == 0)
    {
        // reset
        last_patch = NULL;
        last_patch_len = 0;
        last_patch_off = 0;
        return;
    }
    if (b == NULL || blen <= 0 || boff < 0 || size <= 0)
        throwBadLoader();
    if (boff + size <= 0 || boff + size > blen)
        throwBadLoader();
    //printf("checkPatch: %p %5d %5d %2d\n", b, blen, boff, size);
    if (b == last_patch)
    {
        if (boff + size > last_patch_off)
            throwInternalError("invalid patch order");
        // The next check is not strictly necessary, but the buffer
        // length should better not increase...
        if (blen > last_patch_len)
            throwInternalError("invalid patch order (length)");
    }
    else
        last_patch = b;
    last_patch_len = blen;
    last_patch_off = boff;
}


int Packer::patch_be16(void *b, int blen, unsigned old, unsigned new_)
{
    int boff = find_be16(b, blen, old);
    checkPatch(b, blen, boff, 2);

    unsigned char *p = (unsigned char *)b + boff;
    set_be16(p, new_);

    return boff;
}


int Packer::patch_be16(void *b, int blen, const void *old, unsigned new_)
{
    int boff = find(b, blen, old, 2);
    checkPatch(b, blen, boff, 2);

    unsigned char *p = (unsigned char *)b + boff;
    set_be16(p, new_);

    return boff;
}


int Packer::patch_be32(void *b, int blen, unsigned old, unsigned new_)
{
    int boff = find_be32(b, blen, old);
    checkPatch(b, blen, boff, 4);

    unsigned char *p = (unsigned char *)b + boff;
    set_be32(p, new_);

    return boff;
}


int Packer::patch_be32(void *b, int blen, const void *old, unsigned new_)
{
    int boff = find(b, blen, old, 4);
    checkPatch(b, blen, boff, 4);

    unsigned char *p = (unsigned char *)b + boff;
    set_be32(p, new_);

    return boff;
}


int Packer::patch_le16(void *b, int blen, unsigned old, unsigned new_)
{
    int boff = find_le16(b, blen, old);
    checkPatch(b, blen, boff, 2);

    unsigned char *p = (unsigned char *)b + boff;
    set_le16(p, new_);

    return boff;
}


int Packer::patch_le16(void *b, int blen, const void *old, unsigned new_)
{
    int boff = find(b, blen, old, 2);
    checkPatch(b, blen, boff, 2);

    unsigned char *p = (unsigned char *)b + boff;
    set_le16(p, new_);

    return boff;
}


int Packer::patch_le32(void *b, int blen, unsigned old, unsigned new_)
{
    int boff = find_le32(b, blen, old);
    checkPatch(b, blen, boff, 4);

    unsigned char *p = (unsigned char *)b + boff;
    set_le32(p, new_);

    return boff;
}


int Packer::patch_le32(void *b, int blen, const void *old, unsigned new_)
{
    int boff = find(b, blen, old, 4);
    checkPatch(b, blen, boff, 4);

    unsigned char *p = (unsigned char *)b + boff;
    set_le32(p, new_);

    return boff;
}


/*************************************************************************
// relocation util
**************************************************************************/

upx_byte *Packer::optimizeReloc32(upx_byte *in, unsigned relocnum,
                                  upx_byte *out, upx_byte *image,
                                  int bswap, int *big)
{
    if (opt->exact)
        throwCantPackExact();

    *big = 0;
    if (relocnum == 0)
        return out;
    qsort(in,relocnum,4,le32_compare);

    unsigned jc,pc,oc;
    upx_byte *fix = out;

    pc = (unsigned) -4;
    for (jc = 0; jc<relocnum; jc++)
    {
        oc = get_le32(in+jc*4) - pc;
        if (oc == 0)
            continue;
        else if ((int)oc < 4)
            throwCantPack("overlapping fixups");
        else if (oc < 0xF0)
            *fix++ = (unsigned char) oc;
        else if (oc < 0x100000)
        {
            *fix++ = (unsigned char) (0xF0+(oc>>16));
            *fix++ = (unsigned char) oc;
            *fix++ = (unsigned char) (oc>>8);
        }
        else
        {
            *big = 1;
            *fix++ = 0xf0;
            *fix++ = 0;
            *fix++ = 0;
            set_le32(fix,oc);
            fix += 4;
        }
        pc += oc;
        if (bswap)
            acc_ua_swab32s(image + pc);
    }
    *fix++ = 0;
    return fix;
}


unsigned Packer::unoptimizeReloc32(upx_byte **in, upx_byte *image,
                                   MemBuffer *out, int bswap)
{
    upx_byte *p;
    unsigned relocn = 0;
    for (p = *in; *p; p++, relocn++)
        if (*p >= 0xF0)
        {
            if (*p == 0xF0 && get_le16(p+1) == 0)
                p += 4;
            p += 2;
        }
    //fprintf(stderr,"relocnum=%x\n",relocn);
    out->alloc(4*relocn+4); // one extra data
    LE32 *outp = (LE32*) (unsigned char *) *out;
    LE32 *relocs = outp;
    unsigned jc = (unsigned) -4;
    for (p = *in; *p; p++)
    {
        if (*p < 0xF0)
            jc += *p;
        else
        {
            unsigned dif = (*p & 0x0F)*0x10000 + get_le16(p+1);
            p += 2;
            if (dif == 0)
            {
                dif = get_le32(p+1);
                p += 4;
            }
            jc += dif;
        }
        *relocs++ = jc;
        if (bswap && image)
            acc_ua_swab32s(image + jc);
    }
    //fprintf(stderr,"relocnum=%x\n",relocn);
    *in = p+1;
    return (unsigned) (relocs - outp);
}


/*************************************************************************
// loader util (interface to linker)
**************************************************************************/

static const char *getIdentstr(unsigned *size, int small)
{
    static char identbig[] =
        "\n\0"
        "$Info: "
        "This file is packed with the UPX executable packer http://upx.sf.net $"
        "\n\0"
        "$Id: UPX "
        UPX_VERSION_STRING4
        " Copyright (C) 1996-" UPX_VERSION_YEAR " the UPX Team. All Rights Reserved. $"
        "\n";
    static char identsmall[] =
        "\n"
        "$Id: UPX "
        "(C) 1996-" UPX_VERSION_YEAR " the UPX Team. All Rights Reserved. http://upx.sf.net $"
        "\n";
    static char identtiny[] = UPX_VERSION_STRING4;

    static int done;
    if (!done && (opt->debug.fake_stub_version[0] || opt->debug.fake_stub_year[0]))
    {
        struct strinfo_t { char *s; int size; };
        static const strinfo_t strlist[] = {
            { identbig,   (int)sizeof(identbig) },
            { identsmall, (int)sizeof(identsmall) },
            { identtiny,  (int)sizeof(identtiny) },
        { NULL, 0 } };
        const strinfo_t* iter;

        for (iter = strlist; iter->s; ++iter)
        {
            if (opt->debug.fake_stub_version[0])
                mem_replace(iter->s, iter->size, UPX_VERSION_STRING4, 4, opt->debug.fake_stub_version);
            if (opt->debug.fake_stub_year[0])
                mem_replace(iter->s, iter->size, UPX_VERSION_YEAR, 4, opt->debug.fake_stub_year);
        }
        done = 1;
    }


    if (small < 0)
        small = opt->small;
    if (small >= 2)
    {
        *size = sizeof(identtiny);
        return identtiny;
    }
    else if (small >= 1)
    {
        *size = sizeof(identsmall);
        return identsmall;
    }
    else
    {
        *size = sizeof(identbig);
        return identbig;
    }
}


void Packer::initLoader(const void *pdata, int plen, int small)
{
    delete linker;
    linker = newLinker();
    assert(bele == linker->bele);
    linker->init(pdata, plen);

    unsigned size;
    char const * const ident = getIdentstr(&size, small);
    linker->addSection("IDENTSTR", ident, size, 0);
}


#define C const char *
void Packer::addLoader(C a)
{ addLoaderVA(a, NULL); }
void Packer::addLoader(C a, C b)
{ addLoaderVA(a, b, NULL); }
void Packer::addLoader(C a, C b, C c)
{ addLoaderVA(a, b, c, NULL); }
void Packer::addLoader(C a, C b, C c, C d)
{ addLoaderVA(a, b, c, d, NULL); }
void Packer::addLoader(C a, C b, C c, C d, C e)
{ addLoaderVA(a, b, c, d, e, NULL); }
void Packer::addLoader(C a, C b, C c, C d, C e, C f)
{ addLoaderVA(a, b, c, d, e, f, NULL); }
void Packer::addLoader(C a, C b, C c, C d, C e, C f, C g)
{ addLoaderVA(a, b, c, d, e, f, g, NULL); }
void Packer::addLoader(C a, C b, C c, C d, C e, C f, C g, C h)
{ addLoaderVA(a, b, c, d, e, f, g, h, NULL); }
void Packer::addLoader(C a, C b, C c, C d, C e, C f, C g, C h, C i)
{ addLoaderVA(a, b, c, d, e, f, g, h, i, NULL); }
void Packer::addLoader(C a, C b, C c, C d, C e, C f, C g, C h, C i, C j)
{ addLoaderVA(a, b, c, d, e, f, g, h, i, j, NULL); }
#undef C

void __acc_cdecl_va Packer::addLoaderVA(const char *s, ...)
{
    va_list ap;
    va_start(ap, s);
    linker->addLoader(s, ap);
    va_end(ap);
}

upx_byte *Packer::getLoader() const
{
    int size = -1;
    upx_byte *oloader = linker->getLoader(&size);
    if (oloader == NULL || size <= 0)
        throwBadLoader();
    return oloader;
}

int Packer::getLoaderSize() const
{
    int size = -1;
    upx_byte *oloader = linker->getLoader(&size);
    if (oloader == NULL || size <= 0)
        throwBadLoader();
    return size;
}


int Packer::getLoaderSection(const char *name, int *slen) const
{
    int size = -1;
    int ostart = linker->getSection(name, &size);
    if (ostart < 0 || size <= 0)
        throwBadLoader();
    if (slen)
        *slen = size;
    return ostart;
}

// same, but the size of the section may be == 0
int Packer::getLoaderSectionStart(const char *name, int *slen) const
{
    int size = -1;
    int ostart = linker->getSection(name, &size);
    if (ostart < 0 || size < 0)
        throwBadLoader();
    if (slen)
        *slen = size;
    return ostart;
}


void Packer::relocateLoader()
{
    linker->relocate();

#if 0
    // "relocate" packheader
    if (linker->findSection("UPX1HEAD", false))
    {
        int lsize = -1;
        int loff = getLoaderSectionStart("UPX1HEAD", &lsize);
        assert(lsize == ph.getPackHeaderSize());
        unsigned char *p = getLoader() + loff;
        assert(get_le32(p) == UPX_MAGIC_LE32);