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Sweden-Number/loader/preloader.c

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/*
* Preloader for ld.so
*
* Copyright (C) 1995,96,97,98,99,2000,2001,2002 Free Software Foundation, Inc.
* Copyright (C) 2004 Mike McCormack for Codeweavers
* Copyright (C) 2004 Alexandre Julliard
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Design notes
*
* The goal of this program is to be a workaround for exec-shield, as used
* by the Linux kernel distributed with Fedora Core and other distros.
*
* To do this, we implement our own shared object loader that reserves memory
* that is important to Wine, and then loads the main binary and its ELF
* interpreter.
*
* We will try to set up the stack and memory area so that the program that
* loads after us (eg. the wine binary) never knows we were here, except that
* areas of memory it needs are already magically reserved.
*
* The following memory areas are important to Wine:
* 0x00000000 - 0x00110000 the DOS area
* 0x80000000 - 0x81000000 the shared heap
* ??? - ??? the PE binary load address (usually starting at 0x00400000)
*
* If this program is used as the shared object loader, the only difference
* that the loaded programs should see is that this loader will be mapped
* into memory when it starts.
*/
/*
* References (things I consulted to understand how ELF loading works):
*
* glibc 2.3.2 elf/dl-load.c
* http://www.gnu.org/directory/glibc.html
*
* Linux 2.6.4 fs/binfmt_elf.c
* ftp://ftp.kernel.org/pub/linux/kernel/v2.6/linux-2.6.4.tar.bz2
*
* Userland exec, by <grugq@hcunix.net>
* http://cert.uni-stuttgart.de/archive/bugtraq/2004/01/msg00002.html
*
* The ELF specification:
* http://www.linuxbase.org/spec/booksets/LSB-Embedded/LSB-Embedded/book387.html
*/
#include "config.h"
#include "wine/port.h"
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#ifdef HAVE_SYS_MMAN_H
# include <sys/mman.h>
#endif
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#ifdef HAVE_ELF_H
# include <elf.h>
#endif
#ifdef HAVE_LINK_H
# include <link.h>
#endif
#ifdef HAVE_SYS_LINK_H
# include <sys/link.h>
#endif
#include "main.h"
/* ELF definitions */
#define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) (mapstartpref)
#define ELF_FIXED_ADDRESS(loader, mapstart) ((void) 0)
#define MAP_BASE_ADDR(l) 0
#ifndef MAP_COPY
#define MAP_COPY MAP_PRIVATE
#endif
#ifndef MAP_NORESERVE
#define MAP_NORESERVE 0
#endif
static struct wine_preload_info preload_info[] =
{
{ (void *)0x00000000, 0x00110000 }, /* DOS area */
{ (void *)0x80000000, 0x01000000 }, /* shared heap */
{ (void *)0x00110000, 0x0fef0000 }, /* PE exe range (FIXME) */
{ 0, 0 } /* end of list */
};
/* debugging */
#undef DUMP_SEGMENTS
#undef DUMP_AUX_INFO
#undef DUMP_SYMS
/* older systems may not define these */
#ifndef PT_TLS
#define PT_TLS 7
#endif
static unsigned int page_size, page_mask;
struct wld_link_map {
ElfW(Addr) l_addr;
ElfW(Dyn) *l_ld;
const ElfW(Phdr) *l_phdr;
ElfW(Addr) l_entry;
ElfW(Half) l_ldnum;
ElfW(Half) l_phnum;
ElfW(Addr) l_map_start, l_map_end;
ElfW(Addr) l_interp;
};
/*
* The _start function is the entry and exit point of this program
*
* It calls wld_start, passing a pointer to the args it receives
* then jumps to the address wld_start returns after removing the
* first argv[] value, and decrementing argc
*/
void _start();
extern char _end[];
__ASM_GLOBAL_FUNC(_start,
"\tcall wld_start\n"
"\tpush %eax\n"
"\txor %eax,%eax\n"
"\txor %ecx,%ecx\n"
"\txor %edx,%edx\n"
"\tret\n")
/*
* wld_printf - just the basics
*
* %x prints a hex number
* %s prints a string
*/
static void wld_vsprintf(char *str, char *fmt, va_list args )
{
char *p = fmt;
while( *p )
{
if( *p == '%' )
{
p++;
if( *p == 'x' )
{
int ch, i, x = va_arg( args, int );
for(i=7; i>=0; i--)
{
ch = (x>>(i*4))&0xf;
ch += '0';
if(ch>'9')
ch+=('A'-10-'0');
*str++ = ch;
}
}
else if( *p == 's' )
{
char *s = va_arg( args, char * );
while(*s)
*str++ = *s++;
}
else if( *p == 0 )
break;
p++;
}
*str++ = *p++;
}
*str = 0;
}
static void wld_printf(char *fmt, ... )
{
va_list args;
char buffer[256];
va_start( args, fmt );
wld_vsprintf(buffer, fmt, args );
va_end( args );
write(2, buffer, strlen(buffer));
}
static void fatal_error(char *fmt, ... )
{
va_list args;
char buffer[256];
va_start( args, fmt );
wld_vsprintf(buffer, fmt, args );
va_end( args );
write(2, buffer, strlen(buffer));
_exit(1);
}
#ifdef DUMP_AUX_INFO
/*
* Dump interesting bits of the ELF auxv_t structure that is passed
* as the 4th parameter to the _start function
*/
static void dump_auxiliary( ElfW(auxv_t) *av )
{
for ( ; av->a_type != AT_NULL; av++)
switch (av->a_type)
{
case AT_PAGESZ:
wld_printf("AT_PAGESZ = %x\n",av->a_un.a_val);
break;
case AT_PHDR:
wld_printf("AT_PHDR = %x\n",av->a_un.a_ptr);
break;
case AT_PHNUM:
wld_printf("AT_PHNUM = %x\n",av->a_un.a_val);
break;
case AT_ENTRY:
wld_printf("AT_ENTRY = %x\n",av->a_un.a_val);
break;
case AT_BASE:
wld_printf("AT_BASE = %x\n",av->a_un.a_val);
break;
}
}
#endif
/*
* set_auxiliary
*
* Set a field of the auxiliary structure
*/
static void set_auxiliary( ElfW(auxv_t) *av, int type, long int val )
{
for ( ; av->a_type != AT_NULL; av++)
if( av->a_type == type )
av->a_un.a_val = val;
}
/*
* get_auxiliary
*
* Get a field of the auxiliary structure
*/
static int get_auxiliary( ElfW(auxv_t) *av, int type, int *val )
{
for ( ; av->a_type != AT_NULL; av++)
if( av->a_type == type )
{
*val = av->a_un.a_val;
return 1;
}
return 0;
}
/*
* map_so_lib
*
* modelled after _dl_map_object_from_fd() from glibc-2.3.1/elf/dl-load.c
*
* This function maps the segments from an ELF object, and optionally
* stores information about the mapping into the auxv_t structure.
*/
static void map_so_lib( const char *name, struct wld_link_map *l)
{
int fd;
unsigned char buf[0x800];
ElfW(Ehdr) *header = (ElfW(Ehdr)*)buf;
ElfW(Phdr) *phdr, *ph;
/* Scan the program header table, collecting its load commands. */
struct loadcmd
{
ElfW(Addr) mapstart, mapend, dataend, allocend;
off_t mapoff;
int prot;
} loadcmds[16], *c;
size_t nloadcmds = 0, maplength;
fd = open( name, O_RDONLY );
if (fd == -1) fatal_error("%s: could not open\n", name );
if (read( fd, buf, sizeof(buf) ) != sizeof(buf))
fatal_error("%s: failed to read ELF header\n", name);
phdr = (void*) (((unsigned char*)buf) + header->e_phoff);
if( ( header->e_ident[0] != 0x7f ) ||
( header->e_ident[1] != 'E' ) ||
( header->e_ident[2] != 'L' ) ||
( header->e_ident[3] != 'F' ) )
fatal_error( "%s: not an ELF binary... don't know how to load it\n", name );
if( header->e_machine != EM_386 )
fatal_error("%s: not an i386 ELF binary... don't know how to load it\n", name );
if (header->e_phnum > sizeof(loadcmds)/sizeof(loadcmds[0]))
fatal_error( "%s: oops... not enough space for load commands\n", name );
maplength = header->e_phnum * sizeof (ElfW(Phdr));
if (header->e_phoff + maplength > sizeof(buf))
fatal_error( "%s: oops... not enough space for ELF headers\n", name );
l->l_ld = 0;
l->l_addr = 0;
l->l_phdr = 0;
l->l_phnum = header->e_phnum;
l->l_entry = header->e_entry;
l->l_interp = 0;
for (ph = phdr; ph < &phdr[l->l_phnum]; ++ph)
{
#ifdef DUMP_SEGMENTS
wld_printf( "ph = %x\n", ph );
wld_printf( " p_type = %x\n", ph->p_type );
wld_printf( " p_flags = %x\n", ph->p_flags );
wld_printf( " p_offset = %x\n", ph->p_offset );
wld_printf( " p_vaddr = %x\n", ph->p_vaddr );
wld_printf( " p_paddr = %x\n", ph->p_paddr );
wld_printf( " p_filesz = %x\n", ph->p_filesz );
wld_printf( " p_memsz = %x\n", ph->p_memsz );
wld_printf( " p_align = %x\n", ph->p_align );
#endif
switch (ph->p_type)
{
/* These entries tell us where to find things once the file's
segments are mapped in. We record the addresses it says
verbatim, and later correct for the run-time load address. */
case PT_DYNAMIC:
l->l_ld = (void *) ph->p_vaddr;
l->l_ldnum = ph->p_memsz / sizeof (Elf32_Dyn);
break;
case PT_PHDR:
l->l_phdr = (void *) ph->p_vaddr;
break;
case PT_LOAD:
{
if ((ph->p_align & page_mask) != 0)
fatal_error( "%s: ELF load command alignment not page-aligned\n", name );
if (((ph->p_vaddr - ph->p_offset) & (ph->p_align - 1)) != 0)
fatal_error( "%s: ELF load command address/offset not properly aligned\n", name );
c = &loadcmds[nloadcmds++];
c->mapstart = ph->p_vaddr & ~(ph->p_align - 1);
c->mapend = ((ph->p_vaddr + ph->p_filesz + page_mask) & ~page_mask);
c->dataend = ph->p_vaddr + ph->p_filesz;
c->allocend = ph->p_vaddr + ph->p_memsz;
c->mapoff = ph->p_offset & ~(ph->p_align - 1);
c->prot = 0;
if (ph->p_flags & PF_R)
c->prot |= PROT_READ;
if (ph->p_flags & PF_W)
c->prot |= PROT_WRITE;
if (ph->p_flags & PF_X)
c->prot |= PROT_EXEC;
}
break;
case PT_INTERP:
l->l_interp = ph->p_vaddr;
break;
case PT_TLS:
/*
* We don't need to set anything up because we're
* emulating the kernel, not ld-linux.so.2
* The ELF loader will set up the TLS data itself.
*/
case PT_SHLIB:
case PT_NOTE:
default:
break;
}
}
/* Now process the load commands and map segments into memory. */
c = loadcmds;
/* Length of the sections to be loaded. */
maplength = loadcmds[nloadcmds - 1].allocend - c->mapstart;
if( header->e_type == ET_DYN )
{
ElfW(Addr) mappref;
mappref = (ELF_PREFERRED_ADDRESS (loader, maplength, c->mapstart)
- MAP_BASE_ADDR (l));
/* Remember which part of the address space this object uses. */
l->l_map_start = (ElfW(Addr)) mmap ((void *) mappref, maplength,
c->prot, MAP_COPY | MAP_FILE,
fd, c->mapoff);
/* wld_printf("set : offset = %x\n", c->mapoff); */
/* wld_printf("l->l_map_start = %x\n", l->l_map_start); */
l->l_map_end = l->l_map_start + maplength;
l->l_addr = l->l_map_start - c->mapstart;
mprotect ((caddr_t) (l->l_addr + c->mapend),
loadcmds[nloadcmds - 1].allocend - c->mapend,
PROT_NONE);
goto postmap;
}
else
{
char *preloader_start = (char *)_start - ((unsigned int)_start & page_mask);
char *preloader_end = (char *)((unsigned int)(_end + page_mask) & ~page_mask);
/* sanity check */
if ((char *)c->mapstart + maplength > preloader_start &&
(char *)c->mapstart <= preloader_end)
fatal_error( "%s: binary overlaps preloader (%x-%x)\n",
name, c->mapstart, (char *)c->mapstart + maplength );
ELF_FIXED_ADDRESS (loader, c->mapstart);
}
/* Remember which part of the address space this object uses. */
l->l_map_start = c->mapstart + l->l_addr;
l->l_map_end = l->l_map_start + maplength;
while (c < &loadcmds[nloadcmds])
{
if (c->mapend > c->mapstart)
/* Map the segment contents from the file. */
mmap ((void *) (l->l_addr + c->mapstart),
c->mapend - c->mapstart, c->prot,
MAP_FIXED | MAP_COPY | MAP_FILE, fd, c->mapoff);
postmap:
if (l->l_phdr == 0
&& (ElfW(Off)) c->mapoff <= header->e_phoff
&& ((size_t) (c->mapend - c->mapstart + c->mapoff)
>= header->e_phoff + header->e_phnum * sizeof (ElfW(Phdr))))
/* Found the program header in this segment. */
l->l_phdr = (void *)(unsigned int) (c->mapstart + header->e_phoff - c->mapoff);
if (c->allocend > c->dataend)
{
/* Extra zero pages should appear at the end of this segment,
after the data mapped from the file. */
ElfW(Addr) zero, zeroend, zeropage;
zero = l->l_addr + c->dataend;
zeroend = l->l_addr + c->allocend;
zeropage = (zero + page_mask) & ~page_mask;
/*
* This is different from the dl-load load...
* ld-linux.so.2 relies on the whole page being zero'ed
*/
zeroend = (zeroend + page_mask) & ~page_mask;
if (zeroend < zeropage)
{
/* All the extra data is in the last page of the segment.
We can just zero it. */
zeropage = zeroend;
}
if (zeropage > zero)
{
/* Zero the final part of the last page of the segment. */
if ((c->prot & PROT_WRITE) == 0)
{
/* Dag nab it. */
mprotect ((caddr_t) (zero & ~page_mask), page_size, c->prot|PROT_WRITE);
}
memset ((void *) zero, '\0', zeropage - zero);
if ((c->prot & PROT_WRITE) == 0)
mprotect ((caddr_t) (zero & ~page_mask), page_size, c->prot);
}
if (zeroend > zeropage)
{
/* Map the remaining zero pages in from the zero fill FD. */
caddr_t mapat;
mapat = mmap ((caddr_t) zeropage, zeroend - zeropage,
c->prot, MAP_ANON|MAP_PRIVATE|MAP_FIXED,
-1, 0);
}
}
++c;
}
if (l->l_phdr == NULL) fatal_error("no program header\n");
l->l_phdr = (void *)((ElfW(Addr))l->l_phdr + l->l_addr);
l->l_entry += l->l_addr;
close( fd );
}
/*
* Find a symbol in the symbol table of the executable loaded
*/
static void *find_symbol( const ElfW(Phdr) *phdr, int num, char *var )
{
const ElfW(Dyn) *dyn = NULL;
const ElfW(Phdr) *ph;
const ElfW(Sym) *symtab = NULL;
const char *strings = NULL;
Elf_Symndx i, symtabend = 0;
/* check the values */
#ifdef DUMP_SYMS
wld_printf("%x %x\n", phdr, num );
#endif
if( ( phdr == NULL ) || ( num == 0 ) )
{
wld_printf("could not find PT_DYNAMIC header entry\n");
return NULL;
}
/* parse the (already loaded) ELF executable's header */
for (ph = phdr; ph < &phdr[num]; ++ph)
{
if( PT_DYNAMIC == ph->p_type )
{
dyn = (void *) ph->p_vaddr;
num = ph->p_memsz / sizeof (Elf32_Dyn);
break;
}
}
if( !dyn ) return NULL;
while( dyn->d_tag )
{
if( dyn->d_tag == DT_STRTAB )
strings = (const char*) dyn->d_un.d_ptr;
if( dyn->d_tag == DT_SYMTAB )
symtab = (const ElfW(Sym) *)dyn->d_un.d_ptr;
if( dyn->d_tag == DT_HASH )
symtabend = *((const Elf_Symndx *)dyn->d_un.d_ptr + 1);
#ifdef DUMP_SYMS
wld_printf("%x %x\n", dyn->d_tag, dyn->d_un.d_ptr );
#endif
dyn++;
}
if( (!symtab) || (!strings) ) return NULL;
for (i = 0; i < symtabend; i++)
{
if( ( ELF32_ST_BIND(symtab[i].st_info) == STT_OBJECT ) &&
( 0 == strcmp( strings+symtab[i].st_name, var ) ) )
{
#ifdef DUMP_SYMS
wld_printf("Found %s -> %x\n", strings+symtab[i].st_name, symtab[i].st_value );
#endif
return (void*)symtab[i].st_value;
}
}
return NULL;
}
/*
* wld_start
*
* Repeat the actions the kernel would do when loading a dynamically linked .so
* Load the binary and then its ELF interpreter.
* Note, we assume that the binary is a dynamically linked ELF shared object.
*/
void* wld_start( int argc, ... )
{
int i;
char **argv, **p;
char *interp;
ElfW(auxv_t)* av;
struct wld_link_map main_binary_map, ld_so_map;
struct wine_preload_info **wine_main_preload_info;
argv = (char **)&argc + 1;
/* skip over the parameters */
p = argv + argc + 1;
/* skip over the environment */
while (*p) p++;
av = (ElfW(auxv_t)*) (p+1);
if (!get_auxiliary( av, AT_PAGESZ, &page_size )) page_size = 4096;
page_mask = page_size - 1;
#ifdef DUMP_AUX_INFO
for( i = 0; i<argc; i++ ) wld_printf("argv[%x] = %s\n", i, argv[i]);
dump_auxiliary( av );
#endif
/* reserve memory that Wine needs */
for (i = 0; preload_info[i].size; i++)
mmap( preload_info[i].addr, preload_info[i].size,
PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANON | MAP_NORESERVE, -1, 0 );
/* load the main binary */
map_so_lib( argv[0], &main_binary_map );
/* load the ELF interpreter */
interp = (char *)main_binary_map.l_addr + main_binary_map.l_interp;
map_so_lib( interp, &ld_so_map );
/* store pointer to the preload info into the appropriate main binary variable */
wine_main_preload_info = find_symbol( main_binary_map.l_phdr, main_binary_map.l_phnum,
"wine_main_preload_info" );
if (wine_main_preload_info) *wine_main_preload_info = preload_info;
else wld_printf( "wine_main_preload_info not found\n" );
set_auxiliary( av, AT_PHDR, (unsigned long)main_binary_map.l_phdr );
set_auxiliary( av, AT_PHNUM, main_binary_map.l_phnum );
set_auxiliary( av, AT_BASE, ld_so_map.l_addr );
set_auxiliary( av, AT_ENTRY, main_binary_map.l_entry );
#ifdef DUMP_AUX_INFO
wld_printf("New auxiliary info:\n");
dump_auxiliary( av );
wld_printf("jumping to %x\n", ld_so_map.l_entry);
#endif
return (void *)ld_so_map.l_entry;
}
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