i386-linux.elf-main.c

UPX 源代码

/* i386-linux.elf-main.c -- stub loader for Linux x86 ELF executable

   This file is part of the UPX executable compressor.

   Copyright (C) 1996-2007 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1996-2007 Laszlo Molnar
   Copyright (C) 2000-2007 John F. Reiser
   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]>

   John F. Reiser
   <[e-mail]>
 */


#include "include/linux.h"
void *mmap(void *, size_t, int, int, int, off_t);
ssize_t write(int, void const *, size_t);


/*************************************************************************
// configuration section
**************************************************************************/

// In order to make it much easier to move this code at runtime and execute
// it at an address different from it load address:  there must be no
// static data, and no string constants.

#if 1  /*{*/
#define DPRINTF(a) /* empty: no debug drivel */
#else  /*}{*/
#if 0
#include "stdarg.h"
#else
#define va_arg      __builtin_va_arg
#define va_end      __builtin_va_end
#define va_list     __builtin_va_list
#define va_start    __builtin_va_start
#endif

static int
unsimal(unsigned x, char *ptr, int n)
{
    if (10<=x) {
        n = unsimal(x/10, ptr, n);
        x %= 10;
    }
    ptr[n] = '0' + x;
    return 1+ n;
}

static int
decimal(int x, char *ptr, int n)
{
    if (x < 0) {
        *ptr++ = '-'; ++n;
        x = -x;
    }
    return unsimal(x, ptr, n);
}

extern char const *STR_hex(void);

static int
heximal(unsigned x, char *ptr, int n)
{
    if (16<=x) {
        n = heximal(x>>4, ptr, n);
        x &= 0xf;
    }
    ptr[n] = STR_hex()[x];
    return 1+ n;
}


#define DPRINTF(a) dprintf a
extern char const *STR_0x(void);
extern char const *STR_xread(void);
extern char const *STR_unpackExtent(void);
extern char const *STR_make_hatch_arm(void);
extern char const *STR_auxv_up(void);
extern char const *STR_xfind_pages(void);
extern char const *STR_do_xmap(void);
extern char const *STR_upx_main(void);


static int
dprintf(char const *fmt, ...)
{
    char c;
    int n= 0;
    char *ptr;
    char buf[20];
    va_list va; va_start(va, fmt);
    ptr= &buf[0];
    while (0!=(c= *fmt++)) if ('%'!=c) goto literal;
    else switch (c= *fmt++) {
    default: {
literal:
        n+= write(2, fmt-1, 1);
    } break;
    case 0: goto done;  /* early */
    case 'u': {
        n+= write(2, buf, unsimal(va_arg(va, unsigned), buf, 0));
    } break;
    case 'd': {
        n+= write(2, buf, decimal(va_arg(va, int), buf, 0));
    } break;
    case 'p':  /* same as 'x'; relies on sizeof(int)==sizeof(void *) */
    case 'x': {
        buf[0] = '0';
        buf[1] = 'x';
        n+= write(2, buf, heximal(va_arg(va, int), buf, 2));
    } break;
    }
done:
    va_end(va);
    return n;
}
#endif  /*}*/

#define MAX_ELF_HDR 512  // Elf32_Ehdr + n*Elf32_Phdr must fit in this


/*************************************************************************
// "file" util
**************************************************************************/

typedef struct {
    size_t size;  // must be first to match size[0] uncompressed size
    char *buf;
} Extent;


static void
#if (ACC_CC_GNUC >= 0x030300) && defined(__i386__)  /*{*/
__attribute__((__noinline__, __used__, regparm(3), stdcall))
#endif  /*}*/
xread(Extent *x, char *buf, size_t count)
{
    char *p=x->buf, *q=buf;
    size_t j;
    DPRINTF((STR_xread(), x, x->size, x->buf, buf, count));
    if (x->size < count) {
        exit(127);
    }
    for (j = count; 0!=j--; ++p, ++q) {
        *q = *p;
    }
    x->buf  += count;
    x->size -= count;
}


/*************************************************************************
// util
**************************************************************************/

#if 1  //{  save space
#define ERR_LAB error: exit(127);
#define err_exit(a) goto error
#else  //}{  save debugging time
#define ERR_LAB
static void __attribute__ ((__noreturn__))
err_exit(int a)
{
    (void)a;  // debugging convenience
    exit(127);
}
#endif  //}

static void *
do_brk(void *addr)
{
    return brk(addr);
}


/*************************************************************************
// UPX & NRV stuff
**************************************************************************/

typedef void f_unfilter(
    nrv_byte *,  // also addvalue
    nrv_uint,
    unsigned cto8, // junk in high 24 bits
    unsigned ftid
);
typedef int f_expand(
    const nrv_byte *, nrv_uint,
          nrv_byte *, nrv_uint *, unsigned );

static void
unpackExtent(
    Extent *const xi,  // input
    Extent *const xo,  // output
    f_expand *const f_decompress,
    f_unfilter *f_unf
)
{
    DPRINTF((STR_unpackExtent(),
        xi, xi->size, xi->buf, xo, xo->size, xo->buf, f_decompress, f_unf));
    while (xo->size) {
        struct b_info h;
        //   Note: if h.sz_unc == h.sz_cpr then the block was not
        //   compressible and is stored in its uncompressed form.

        // Read and check block sizes.
        xread(xi, (char *)&h, sizeof(h));
        if (h.sz_unc == 0) {                     // uncompressed size 0 -> EOF
            if (h.sz_cpr != UPX_MAGIC_LE32)      // h.sz_cpr must be h->magic
                err_exit(2);
            if (xi->size != 0)                 // all bytes must be written
                err_exit(3);
            break;
        }
        if (h.sz_cpr <= 0) {
            err_exit(4);
ERR_LAB
        }
        if (h.sz_cpr > h.sz_unc
        ||  h.sz_unc > xo->size ) {
            err_exit(5);
        }
        // Now we have:
        //   assert(h.sz_cpr <= h.sz_unc);
        //   assert(h.sz_unc > 0 && h.sz_unc <= blocksize);
        //   assert(h.sz_cpr > 0 && h.sz_cpr <= blocksize);

        if (h.sz_cpr < h.sz_unc) { // Decompress block
            nrv_uint out_len = h.sz_unc;  // EOF for lzma
            int const j = (*f_decompress)((unsigned char *)xi->buf, h.sz_cpr,
                (unsigned char *)xo->buf, &out_len, *(int *)(void *)&h.b_method );
            if (j != 0 || out_len != (nrv_uint)h.sz_unc)
                err_exit(7);
            // Skip Ehdr+Phdrs: separate 1st block, not filtered
            if (h.b_ftid!=0 && f_unf  // have filter
            &&  ((512 < out_len)  // this block is longer than Ehdr+Phdrs
              || (xo->size==(unsigned)h.sz_unc) )  // block is last in Extent
            ) {
                (*f_unf)((unsigned char *)xo->buf, out_len, h.b_cto8, h.b_ftid);
            }
            xi->buf  += h.sz_cpr;
            xi->size -= h.sz_cpr;
        }
        else { // copy literal block
            xread(xi, xo->buf, h.sz_cpr);
        }
        xo->buf  += h.sz_unc;
        xo->size -= h.sz_unc;
    }
}

#if defined(__i386__)  /*{*/
// Create (or find) an escape hatch to use when munmapping ourselves the stub.
// Called by do_xmap to create it; remembered in AT_NULL.d_val
static void *
make_hatch_x86(Elf32_Phdr const *const phdr, unsigned const reloc)
{
    unsigned *hatch = 0;
    if (phdr->p_type==PT_LOAD && phdr->p_flags & PF_X) {
        // The format of the 'if' is
        //  if ( ( (hatch = loc1), test_loc1 )
        //  ||   ( (hatch = loc2), test_loc2 ) ) {
        //      action
        //  }
        // which uses the comma to save bytes when test_locj involves locj
        // and the action is the same when either test succeeds.

        // Try page fragmentation just beyond .text .
        if ( ( (hatch = (void *)(phdr->p_memsz + phdr->p_vaddr + reloc)),
                ( phdr->p_memsz==phdr->p_filesz  // don't pollute potential .bss
                &&  4<=(~PAGE_MASK & -(int)hatch) ) ) // space left on page
        // Try Elf32_Ehdr.e_ident[12..15] .  warning: 'const' cast away
        ||   ( (hatch = (void *)(&((Elf32_Ehdr *)phdr->p_vaddr + reloc)->e_ident[12])),
                (phdr->p_offset==0) ) ) {
            // Omitting 'const' saves repeated literal in gcc.
            unsigned /*const*/ escape = 0xc36180cd;  // "int $0x80; popa; ret"
            // Don't store into read-only page if value is already there.
            if (* (volatile unsigned*) hatch != escape) {
                * hatch  = escape;
            }
        }
        else {
            hatch = 0;
        }
    }
    return hatch;
}
#elif defined(__arm__)  /*}{*/
static void *
make_hatch_arm(Elf32_Phdr const *const phdr, unsigned const reloc)
{
    unsigned *hatch = 0;
    DPRINTF((STR_make_hatch_arm(),phdr,reloc));
    if (phdr->p_type==PT_LOAD && phdr->p_flags & PF_X) {
        // The format of the 'if' is
        //  if ( ( (hatch = loc1), test_loc1 )
        //  ||   ( (hatch = loc2), test_loc2 ) ) {
        //      action
        //  }
        // which uses the comma to save bytes when test_locj involves locj
        // and the action is the same when either test succeeds.

        // Try page fragmentation just beyond .text .
        if ( ( (hatch = (void *)(phdr->p_memsz + phdr->p_vaddr + reloc)),
                ( phdr->p_memsz==phdr->p_filesz  // don't pollute potential .bss
                &&  (2*4)<=(~PAGE_MASK & -(int)hatch) ) ) // space left on page
        // Try Elf32_Ehdr.e_ident[8..15] .  warning: 'const' cast away
        ||   ( (hatch = (void *)(&((Elf32_Ehdr *)phdr->p_vaddr + reloc)->e_ident[8])),
                (phdr->p_offset==0) ) )
        {
            hatch[0]= 0xef90005b;  // syscall __NR_unmap
            hatch[1]= 0xe1a0f00e;  // mov pc,lr
        }
        else {
            hatch = 0;
        }
    }
    return hatch;
}
#elif defined(__mips__)  /*}{*/
static void *
make_hatch_mips(
    Elf32_Phdr const *const phdr,
    unsigned const reloc,
    unsigned const frag_mask)
{
    unsigned *hatch = 0;
    DPRINTF((STR_make_hatch_arm(),phdr,reloc));
    if (phdr->p_type==PT_LOAD && phdr->p_flags & PF_X) {