upx/src/p_vmlinz.cpp

/* p_vmlinz.cpp --

   This file is part of the UPX executable compressor.

   Copyright (C) 1996-2000 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1996-2000 Laszlo Molnar
   All Rights Reserved.

   UPX and the UCL library are free software; you can redistribute them
   and/or modify them under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of
   the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; see the file COPYING.
   If not, write to the Free Software Foundation, Inc.,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   Markus F.X.J. Oberhumer                   Laszlo Molnar
   markus.oberhumer@jk.uni-linz.ac.at        ml1050@cdata.tvnet.hu
 */


#include "conf.h"

#include "file.h"
#include "packer.h"
#include "p_vmlinz.h"
#include <zlib.h>

static const
#include "stub/l_vmlinz.h"

const unsigned kernel_entry = 0x100000;
const unsigned stack_during_uncompression = 0x90000;

// from /usr/src/linux/arch/i386/boot/compressed/Makefile
const unsigned bzimage_offset = 0x100000;
const unsigned zimage_offset = 0x1000;


PackvmlinuzI386::PackvmlinuzI386(InputFile *f) :
    super(f)
{
    assert(sizeof(boot_sect_t) == 0x218);
}


int PackvmlinuzI386::getCompressionMethod() const
{
    if (M_IS_NRV2B(opt->method))
        return M_NRV2B_LE32;
    if (M_IS_NRV2D(opt->method))
        return M_NRV2D_LE32;
    return opt->level > 1 ? M_NRV2D_LE32 : M_NRV2B_LE32;
}


const int *PackvmlinuzI386::getFilters() const
{
    return NULL;
}


bool PackvmlinuzI386::canPack()
{
    boot_sect_t h;
    fi->readx(&h, sizeof(h));
    if (h.boot_flag != 0xAA55)
        return false;

    setup_size = (1 + (h.setup_sects ? h.setup_sects : 4)) * 0x200;
    if (setup_size > file_size)
        return false;

    bzImage = memcmp(h.hdrs, "HdrS", 4) == 0 && (h.load_flags & 1) != 0;

    obuf.alloc(file_size);
    fi->seek(0, SEEK_SET);
    fi->readx(obuf, file_size);

    ibuf.alloc(3 * 1024 * 1024); // 3M should be enough

    upx_bytep gzpos = obuf + setup_size;
    while (1)
    {
        int pos = find(gzpos, file_size - (gzpos - obuf), "\x1F\x8B", 2);
        if (pos < 0)
            return false;
        gzpos += pos;
#if 0
        ulen = ibuf.getSize();
        if (::uncompress(ibuf, &ulen, gzpos, file_size - (gzpos - obuf)) == Z_OK)
            return true;
        gzpos++;
#else
        fi->seek(gzpos - obuf, SEEK_SET);
        gzFile zf = gzdopen(fi->getFd(), "r");
        if (zf == 0)
            return false;
        ulen = gzread(zf, ibuf, ibuf.getSize());
        return ulen > (unsigned) file_size;
#endif
    }
    return false;
}


void PackvmlinuzI386::pack(OutputFile *fo)
{
    MemBuffer setupbuf(setup_size);
    memcpy(setupbuf, obuf, setup_size);

    obuf.free();
    obuf.allocForCompression(ibuf.getSize());

    // FILE *f1 = fopen("kernel.img", "wb"); fwrite(ibuf, 1, ulen, f1); fclose(f1);

    ph.u_len = ulen;
    if (!compress(ibuf, obuf))
        throwNotCompressible();

    initLoader(nrv_loader, sizeof(nrv_loader));

    const unsigned overlapoh = bzImage ? findOverlapOverhead(obuf, 512) : 0;
    unsigned clen = ph.c_len;

    if (bzImage)
    {
        // align everything to dword boundary - it is easier to handle
        memset(obuf + clen, 0, 4);
        clen = ALIGN_UP(clen, 4);

        addLoader("LINUZ000""LBZIMAGE""IDENTSTR",
                  "+40D++++", // align the stuff to 4 byte boundary
                  "UPX1HEAD", // 32 byte
                  "LZCUTPOI""+0000000",
                  getDecompressor(),
                  "LINUZ990",
                  NULL
                 );
    }
    else
        addLoader("LINUZ000""LZIMAGE0",
                  getDecompressor(),
                  "LINUZ990""IDENTSTR""UPX1HEAD",
                  NULL
                 );

    const unsigned lsize = getLoaderSize();
    MemBuffer loader(lsize);
    memcpy(loader, getLoader(), lsize);

    int e_len = bzImage ? getLoaderSection("LZCUTPOI") : lsize;
    patchPackHeader(loader, lsize);

    if (bzImage)
    {
        assert(e_len > 0);

        const unsigned d_len4 = ALIGN_UP(lsize - e_len, 4);
        const unsigned decompr_pos = ALIGN_UP(ulen + overlapoh, 16);
        const unsigned copy_size = clen + d_len4;
        const unsigned edi = decompr_pos + d_len4 - 4; // copy to
        const unsigned esi = ALIGN_UP(clen + lsize, 4) - 4; // copy from

        unsigned jpos = find_le32(loader, e_len, get_le32("JMPD"));
        patch_le32(loader, e_len, "JMPD", decompr_pos - jpos - 4);

        patch_le32(loader, e_len, "ESI1", bzimage_offset + decompr_pos - clen);
        patch_le32(loader, e_len, "ECX0", copy_size / 4);
        patch_le32(loader, e_len, "EDI0", bzimage_offset + edi);
        patch_le32(loader, e_len, "ESI0", bzimage_offset + esi);
    }
    else
        patch_le32(loader, lsize, "ESI1", zimage_offset + lsize);

    patch_le32(loader, e_len, "KEIP", kernel_entry);
    patch_le32(loader, e_len, "STAK", stack_during_uncompression);

    ((boot_sect_t *)((unsigned char *)setupbuf))->sys_size = ALIGN_UP(lsize + clen, 16) / 16;

    fo->write(setupbuf, setupbuf.getSize());
    fo->write(loader, e_len);
    fo->write(obuf, clen);
    fo->write(loader + e_len, lsize - e_len);

    //if (!checkCompressionRatio(file_size, fo->getBytesWritten()))
    //    throwNotCompressible();
}

/*************************************************************************
//
**************************************************************************/

int PackvmlinuzI386::canUnpack()
{
    return false;
}

void PackvmlinuzI386::unpack(OutputFile *)
{
    // no uncompression support for this format, so
    // it is possible to remove the original deflate code (>10KB)
    throwCantUnpack("build a new kernel instead :-)");
}