p_unix.cpp

UPX 源代码

/* p_unix.cpp --

   This file is part of the UPX executable compressor.

   Copyright (C) 1996-2007 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1996-2007 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
   [e-mail]      [e-mail]
 */


#include "conf.h"

#include "file.h"
#include "filter.h"
#include "packer.h"
#include "p_unix.h"
#include "p_elf.h"

// do not change
#define BLOCKSIZE       (512*1024)


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

PackUnix::PackUnix(InputFile *f) :
    super(f), exetype(0), blocksize(0), overlay_offset(0), lsize(0)
{
    COMPILE_TIME_ASSERT(sizeof(Elf32_Ehdr) == 52);
    COMPILE_TIME_ASSERT(sizeof(Elf32_Phdr) == 32);
    COMPILE_TIME_ASSERT(sizeof(b_info) == 12);
    COMPILE_TIME_ASSERT(sizeof(l_info) == 12);
    COMPILE_TIME_ASSERT(sizeof(p_info) == 12);
}


// common part of canPack(), enhanced by subclasses
bool PackUnix::canPack()
{
    if (exetype == 0)
        return false;

#if defined(__unix__)
    // must be executable by owner
    if ((fi->st.st_mode & S_IXUSR) == 0)
        throwCantPack("file not executable; try 'chmod +x'");
#endif
    if (file_size < 4096)
        throwCantPack("file is too small");

    // info: currently the header is 36 (32+4) bytes before EOF
    unsigned char buf[256];
    fi->seek(-(off_t)sizeof(buf), SEEK_END);
    fi->readx(buf, sizeof(buf));
    checkAlreadyPacked(buf, sizeof(buf));

    return true;
}


void PackUnix::writePackHeader(OutputFile *fo)
{
    unsigned char buf[32];
    memset(buf, 0, sizeof(buf));

    const int hsize = ph.getPackHeaderSize();
    assert((unsigned)hsize <= sizeof(buf));

    // note: magic constants are always le32
    set_le32(buf+0, UPX_MAGIC_LE32);
    set_le32(buf+4, UPX_MAGIC2_LE32);

    checkPatch(NULL, 0, 0, 0);  // reset
    patchPackHeader(buf, hsize);
    checkPatch(NULL, 0, 0, 0);  // reset

    fo->write(buf, hsize);
}


/*************************************************************************
// Generic Unix pack(). Subclasses must provide patchLoader().
//
// A typical compressed Unix executable looks like this:
//   - loader stub
//   - 12 bytes header info
//   - the compressed blocks, each with a 8 byte header for block sizes
//   - 4 bytes block end marker (uncompressed size 0)
//   - 32 bytes UPX packheader
//   - 4 bytes overlay offset (needed for decompression)
**************************************************************************/

// see note below and Packer::compress()
bool PackUnix::checkCompressionRatio(unsigned, unsigned) const
{
    return true;
}

void PackUnix::pack1(OutputFile * /*fo*/, Filter & /*ft*/)
{
    // derived class usually provides this
}

int PackUnix::getStrategy(Filter &/*ft*/)
{
    // Called just before reading and compressing each block.
    // Might want to adjust blocksize, etc.

    // If user specified the filter, then use it (-2==filter_strategy).
    // Else try the first two filters, and pick the better (2==filter_strategy).
    return (opt->no_filter ? -3 : ((opt->filter > 0) ? -2 : 2));
}

void PackUnix::pack2(OutputFile *fo, Filter &ft)
{
    // compress blocks
    unsigned total_in = 0;
    unsigned total_out = 0;

// FIXME: ui_total_passes is not correct with multiple blocks...
//    ui_total_passes = (file_size + blocksize - 1) / blocksize;
//    if (ui_total_passes == 1)
//        ui_total_passes = 0;

    unsigned remaining = file_size;
    while (remaining > 0)
    {
        // FIXME: disable filters if we have more than one block.
        // FIXME: There is only 1 un-filter in the stub [as of 2002-11-10].
        // So the next block really has no choice!
        // This merely prevents an assert() in compressWithFilters(),
        // which assumes it has free choice on each call [block].
        // And if the choices aren't the same on each block,
        // then un-filtering will give incorrect results.
        int filter_strategy = getStrategy(ft);
        if (file_size > (off_t)blocksize)
            filter_strategy = -3;      // no filters

        int l = fi->readx(ibuf, UPX_MIN(blocksize, remaining));
        remaining -= l;

        // Note: compression for a block can fail if the
        //       file is e.g. blocksize + 1 bytes long

        // compress
        ph.overlap_overhead = 0;
        ph.c_len = ph.u_len = l;
        ft.buf_len = l;

        // compressWithFilters() updates u_adler _inside_ compress();
        // that is, AFTER filtering.  We want BEFORE filtering,
        // so that decompression checks the end-to-end checksum.
        unsigned const end_u_adler = upx_adler32(ibuf, ph.u_len, ph.u_adler);
        compressWithFilters(&ft, OVERHEAD, NULL_cconf, filter_strategy);

        if (ph.c_len < ph.u_len) {
            const upx_bytep tbuf = NULL;
            if (ft.id == 0) tbuf = ibuf;
            ph.overlap_overhead = OVERHEAD;
            if (!testOverlappingDecompression(obuf, tbuf, ph.overlap_overhead)) {
                // not in-place compressible
                ph.c_len = ph.u_len;
            }
        }
        if (ph.c_len >= ph.u_len) {
            // block is not compressible
            ph.c_len = ph.u_len;
            // must manually update checksum of compressed data
            ph.c_adler = upx_adler32(ibuf, ph.u_len, ph.saved_c_adler);
        }

        // write block header
        b_info blk_info;
        memset(&blk_info, 0, sizeof(blk_info));
        set_native32(&blk_info.sz_unc, ph.u_len);
        set_native32(&blk_info.sz_cpr, ph.c_len);
        if (ph.c_len < ph.u_len) {
            blk_info.b_method = (unsigned char) ph.method;
            blk_info.b_ftid = (unsigned char) ph.filter;
            blk_info.b_cto8 = (unsigned char) ph.filter_cto;
        }
        fo->write(&blk_info, sizeof(blk_info));
        b_len += sizeof(b_info);

        // write compressed data
        if (ph.c_len < ph.u_len) {
            fo->write(obuf, ph.c_len);
            verifyOverlappingDecompression();  // uses ph.u_adler
        }
        else {
            fo->write(ibuf, ph.u_len);
        }
        ph.u_adler = end_u_adler;

        total_in += ph.u_len;
        total_out += ph.c_len;
    }

    // update header with totals
    ph.u_len = total_in;
    ph.c_len = total_out;

    if ((off_t)total_in != file_size) {
        throwEOFException();
    }
}

void
PackUnix::patchLoaderChecksum()
{
    unsigned char *const ptr = getLoader();
    l_info *const lp = &linfo;
    // checksum for loader; also some PackHeader info
    lp->l_magic = UPX_MAGIC_LE32;  // LE32 always
    lp->l_lsize = (unsigned short) lsize;
    lp->l_version = (unsigned char) ph.version;
    lp->l_format  = (unsigned char) ph.format;
    // INFO: lp->l_checksum is currently unused
    lp->l_checksum = upx_adler32(ptr, lsize);
}

void PackUnix::pack3(OutputFile *fo, Filter &/*ft*/)
{
    upx_byte *p = getLoader();
    lsize = getLoaderSize();
    updateLoader(fo);
    patchLoaderChecksum();
    fo->write(p, lsize);
}

void PackUnix::pack4(OutputFile *fo, Filter &)
{
    writePackHeader(fo);

    unsigned tmp;
    set_native32(&tmp, overlay_offset);
    fo->write(&tmp, sizeof(tmp));
}

void PackUnix::pack(OutputFile *fo)
{
    Filter ft(ph.level);
    ft.addvalue = 0;
    b_len = 0;
    progid = 0;

    // set options
    blocksize = opt->o_unix.blocksize;
    if (blocksize <= 0)
        blocksize = BLOCKSIZE;
    if ((off_t)blocksize > file_size)
        blocksize = file_size;

    // init compression buffers
    ibuf.alloc(blocksize);
    obuf.allocForCompression(blocksize);

    fi->seek(0, SEEK_SET);
    pack1(fo, ft);  // generate Elf header, etc.

    p_info hbuf;
    set_native32(&hbuf.p_progid, progid);
    set_native32(&hbuf.p_filesize, file_size);
    set_native32(&hbuf.p_blocksize, blocksize);
    fo->write(&hbuf, sizeof(hbuf));

    pack2(fo, ft);  // append the compressed body

    // write block end marker (uncompressed size 0)
    b_info hdr; memset(&hdr, 0, sizeof(hdr));
    set_le32(&hdr.sz_cpr, UPX_MAGIC_LE32);
    fo->write(&hdr, sizeof(hdr));

    pack3(fo, ft);  // append loader

    pack4(fo, ft);  // append PackHeader and overlay_offset; update Elf header

    // finally check the compression ratio
    if (!checkFinalCompressionRatio(fo))
        throwNotCompressible();
}


void PackUnix::packExtent(
    const Extent &x,
    unsigned &total_in,
    unsigned &total_out,
    Filter *ft,
    OutputFile *fo,
    unsigned hdr_u_len
)
{
    unsigned const init_u_adler = ph.u_adler;
    unsigned const init_c_adler = ph.c_adler;
    MemBuffer hdr_ibuf;
    if (hdr_u_len) {
        hdr_ibuf.alloc(hdr_u_len);
        fi->seek(0, SEEK_SET);
        int l = fi->readx(hdr_ibuf, hdr_u_len);
        (void)l;
    }
    fi->seek(x.offset, SEEK_SET);
    for (off_t rest = x.size; 0 != rest; ) {
        int const filter_strategy = getStrategy(*ft);