elf.c

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/* $Id: elf.c 21802 2006-05-05 15:31:16Z mbosma $
*/

/*
 * REACTOS ELF LOADER
 *
 * ELF run-time linker, ported from FreeBSD by KJK::Hyperion as part of the ELF
 * support initiative. Original copyright, licensing and disclaimers follow
 */

/*-
 * Copyright 1996, 1997, 1998, 1999, 2000 John D. Polstra.
 * Copyright 2003 Alexander Kabaev <[e-mail]>.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $FreeBSD: src/libexec/rtld-elf/rtld.c,v 1.101 2004/11/02 09:42:21 ssouhlal Exp $
 */

/*
 * Dynamic linker for ELF.
 *
 * John Polstra <[e-mail]>.
 */

#include <ntdll.h>
#define NDEBUG
#include <debug.h>

#if 0

#ifndef __GNUC__
#error "GCC is needed to compile this file"
#endif

#include <sys/param.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include <dlfcn.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "debug.h"
#include "rtld.h"
#include "libmap.h"
#include "rtld_tls.h"

#ifndef COMPAT_32BIT
#define PATH_RTLD	"/libexec/ld-elf.so.1"
#else
#define PATH_RTLD	"/libexec/ld-elf32.so.1"
#endif

/* Types. */
typedef void (*func_ptr_type)();
typedef void * (*path_enum_proc) (const char *path, size_t len, void *arg);

/*
 * This structure provides a reentrant way to keep a list of objects and
 * check which ones have already been processed in some way.
 */
typedef struct Struct_DoneList {
    const Obj_Entry **objs;		/* Array of object pointers */
    unsigned int num_alloc;		/* Allocated size of the array */
    unsigned int num_used;		/* Number of array slots used */
} DoneList;

/*
 * Function declarations.
 */
static const char *basename(const char *);
static void die(void);
static void digest_dynamic(Obj_Entry *, int);
static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *);
static Obj_Entry *dlcheck(void *);
static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *);
static bool donelist_check(DoneList *, const Obj_Entry *);
static void errmsg_restore(char *);
static char *errmsg_save(void);
static void *fill_search_info(const char *, size_t, void *);
static char *find_library(const char *, const Obj_Entry *);
static const char *gethints(void);
static void init_dag(Obj_Entry *);
static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *);
static void init_rtld(caddr_t);
static void initlist_add_neededs(Needed_Entry *needed, Objlist *list);
static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail,
  Objlist *list);
static bool is_exported(const Elf_Sym *);
static void linkmap_add(Obj_Entry *);
static void linkmap_delete(Obj_Entry *);
static int load_needed_objects(Obj_Entry *);
static int load_preload_objects(void);
static Obj_Entry *load_object(char *);
static Obj_Entry *obj_from_addr(const void *);
static void objlist_call_fini(Objlist *);
static void objlist_call_init(Objlist *);
static void objlist_clear(Objlist *);
static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *);
static void objlist_init(Objlist *);
static void objlist_push_head(Objlist *, Obj_Entry *);
static void objlist_push_tail(Objlist *, Obj_Entry *);
static void objlist_remove(Objlist *, Obj_Entry *);
static void objlist_remove_unref(Objlist *);
static void *path_enumerate(const char *, path_enum_proc, void *);
static int relocate_objects(Obj_Entry *, bool, Obj_Entry *);
static int rtld_dirname(const char *, char *);
static void rtld_exit(void);
static char *search_library_path(const char *, const char *);
static const void **get_program_var_addr(const char *name);
static void set_program_var(const char *, const void *);
static const Elf_Sym *symlook_default(const char *, unsigned long hash,
  const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt);
static const Elf_Sym *symlook_list(const char *, unsigned long,
  Objlist *, const Obj_Entry **, bool in_plt, DoneList *);
static void trace_loaded_objects(Obj_Entry *obj);
static void unlink_object(Obj_Entry *);
static void unload_object(Obj_Entry *);
static void unref_dag(Obj_Entry *);
static void ref_dag(Obj_Entry *);

void r_debug_state(struct r_debug*, struct link_map*);

/*
 * Data declarations.
 */
static char *error_message;	/* Message for dlerror(), or NULL */
struct r_debug r_debug;		/* for GDB; */
static bool libmap_disable;	/* Disable libmap */
static bool trust;		/* False for setuid and setgid programs */
static char *ld_bind_now;	/* Environment variable for immediate binding */
static char *ld_debug;		/* Environment variable for debugging */
static char *ld_library_path;	/* Environment variable for search path */
static char *ld_preload;	/* Environment variable for libraries to
				   load first */
static char *ld_tracing;	/* Called from ldd to print libs */
static Obj_Entry *obj_list;	/* Head of linked list of shared objects */
static Obj_Entry **obj_tail;	/* Link field of last object in list */
static Obj_Entry *obj_main;	/* The main program shared object */
static Obj_Entry obj_rtld;	/* The dynamic linker shared object */
static unsigned int obj_count;	/* Number of objects in obj_list */

static Objlist list_global =	/* Objects dlopened with RTLD_GLOBAL */
  STAILQ_HEAD_INITIALIZER(list_global);
static Objlist list_main =	/* Objects loaded at program startup */
  STAILQ_HEAD_INITIALIZER(list_main);
static Objlist list_fini =	/* Objects needing fini() calls */
  STAILQ_HEAD_INITIALIZER(list_fini);

static Elf_Sym sym_zero;	/* For resolving undefined weak refs. */

#define GDB_STATE(s,m)	r_debug.r_state = s; r_debug_state(&r_debug,m);

extern Elf_Dyn _DYNAMIC;
#pragma weak _DYNAMIC
#ifndef RTLD_IS_DYNAMIC
#define	RTLD_IS_DYNAMIC()	(&_DYNAMIC != NULL)
#endif

/*
 * These are the functions the dynamic linker exports to application
 * programs.  They are the only symbols the dynamic linker is willing
 * to export from itself.
 */
static func_ptr_type exports[] = {
    (func_ptr_type) &_rtld_error,
    (func_ptr_type) &dlclose,
    (func_ptr_type) &dlerror,
    (func_ptr_type) &dlopen,
    (func_ptr_type) &dlsym,
    (func_ptr_type) &dladdr,
    (func_ptr_type) &dllockinit,
    (func_ptr_type) &dlinfo,
    (func_ptr_type) &_rtld_thread_init,
#ifdef __i386__
    (func_ptr_type) &___tls_get_addr,
#endif
    (func_ptr_type) &__tls_get_addr,
    (func_ptr_type) &_rtld_allocate_tls,
    (func_ptr_type) &_rtld_free_tls,
    NULL
};

/*
 * Global declarations normally provided by crt1.  The dynamic linker is
 * not built with crt1, so we have to provide them ourselves.
 */
char *__progname;
char **environ;

/*
 * Globals to control TLS allocation.
 */
size_t tls_last_offset;		/* Static TLS offset of last module */
size_t tls_last_size;		/* Static TLS size of last module */
size_t tls_static_space;	/* Static TLS space allocated */
int tls_dtv_generation = 1;	/* Used to detect when dtv size changes  */
int tls_max_index = 1;		/* Largest module index allocated */

/*
 * Fill in a DoneList with an allocation large enough to hold all of
 * the currently-loaded objects.  Keep this as a macro since it calls
 * alloca and we want that to occur within the scope of the caller.
 */
#define donelist_init(dlp)					\
    ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]),	\
    assert((dlp)->objs != NULL),				\
    (dlp)->num_alloc = obj_count,				\
    (dlp)->num_used = 0)

/*
 * Main entry point for dynamic linking.  The first argument is the
 * stack pointer.  The stack is expected to be laid out as described
 * in the SVR4 ABI specification, Intel 386 Processor Supplement.
 * Specifically, the stack pointer points to a word containing
 * ARGC.  Following that in the stack is a null-terminated sequence
 * of pointers to argument strings.  Then comes a null-terminated
 * sequence of pointers to environment strings.  Finally, there is a
 * sequence of "auxiliary vector" entries.
 *
 * The second argument points to a place to store the dynamic linker's
 * exit procedure pointer and the third to a place to store the main
 * program's object.
 *
 * The return value is the main program's entry point.
 */
func_ptr_type
_rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
{
    Elf_Auxinfo *aux_info[AT_COUNT];
    int i;
    int argc;
    char **argv;
    char **env;
    Elf_Auxinfo *aux;
    Elf_Auxinfo *auxp;
    const char *argv0;
    Objlist_Entry *entry;
    Obj_Entry *obj;
    Obj_Entry **preload_tail;
    Objlist initlist;
    int lockstate;

    /*
     * On entry, the dynamic linker itself has not been relocated yet.
     * Be very careful not to reference any global data until after
     * init_rtld has returned.  It is OK to reference file-scope statics
     * and string constants, and to call static and global functions.
     */

    /* Find the auxiliary vector on the stack. */
    argc = *sp++;
    argv = (char **) sp;
    sp += argc + 1;	/* Skip over arguments and NULL terminator */
    env = (char **) sp;
    while (*sp++ != 0)	/* Skip over environment, and NULL terminator */
	;
    aux = (Elf_Auxinfo *) sp;

    /* Digest the auxiliary vector. */
    for (i = 0;  i < AT_COUNT;  i++)
	aux_info[i] = NULL;
    for (auxp = aux;  auxp->a_type != AT_NULL;  auxp++) {
	if (auxp->a_type < AT_COUNT)
	    aux_info[auxp->a_type] = auxp;
    }

    /* Initialize and relocate ourselves. */
    assert(aux_info[AT_BASE] != NULL);
    init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr);

    __progname = obj_rtld.path;
    argv0 = argv[0] != NULL ? argv[0] : "(null)";
    environ = env;

    trust = !issetugid();

    ld_bind_now = getenv(LD_ "BIND_NOW");
    if (trust) {
	ld_debug = getenv(LD_ "DEBUG");
	libmap_disable = getenv(LD_ "LIBMAP_DISABLE") != NULL;
	ld_library_path = getenv(LD_ "LIBRARY_PATH");
	ld_preload = getenv(LD_ "PRELOAD");
    }
    ld_tracing = getenv(LD_ "TRACE_LOADED_OBJECTS");

    if (ld_debug != NULL && *ld_debug != '\0')
	debug = 1;
    dbg("%s is initialized, base address = %p", __progname,
	(caddr_t) aux_info[AT_BASE]->a_un.a_ptr);
    dbg("RTLD dynamic = %p", obj_rtld.dynamic);
    dbg("RTLD pltgot  = %p", obj_rtld.pltgot);

    /*
     * Load the main program, or process its program header if it is
     * already loaded.
     */
    if (aux_info[AT_EXECFD] != NULL) {	/* Load the main program. */
	int fd = aux_info[AT_EXECFD]->a_un.a_val;
	dbg("loading main program");
	obj_main = map_object(fd, argv0, NULL);
	close(fd);
	if (obj_main == NULL)
	    die();
    } else {				/* Main program already loaded. */
	const Elf_Phdr *phdr;
	int phnum;
	caddr_t entry;

	dbg("processing main program's program header");
	assert(aux_info[AT_PHDR] != NULL);
	phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr;
	assert(aux_info[AT_PHNUM] != NULL);
	phnum = aux_info[AT_PHNUM]->a_un.a_val;
	assert(aux_info[AT_PHENT] != NULL);
	assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr));
	assert(aux_info[AT_ENTRY] != NULL);
	entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr;
	if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL)
	    die();
    }

    obj_main->path = xstrdup(argv0);
    obj_main->mainprog = true;

    /*
     * Get the actual dynamic linker pathname from the executable if
     * possible.  (It should always be possible.)  That ensures that
     * gdb will find the right dynamic linker even if a non-standard
     * one is being used.
     */
    if (obj_main->interp != NULL &&
      strcmp(obj_main->interp, obj_rtld.path) != 0) {
	free(obj_rtld.path);
	obj_rtld.path = xstrdup(obj_main->interp);
        __progname = obj_rtld.path;
    }

    digest_dynamic(obj_main, 0);

    linkmap_add(obj_main);
    linkmap_add(&obj_rtld);

    /* Link the main program into the list of objects. */
    *obj_tail = obj_main;
    obj_tail = &obj_main->next;
    obj_count++;
    /* Make sure we don't call the main program's init and fini functions. */
    obj_main->init = obj_main->fini = (Elf_Addr)NULL;

    /* Initialize a fake symbol for resolving undefined weak references. */
    sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE);
    sym_zero.st_shndx = SHN_UNDEF;

    if (!libmap_disable)
        libmap_disable = (bool)lm_init();

    dbg("loading LD_PRELOAD libraries");
    if (load_preload_objects() == -1)
	die();
    preload_tail = obj_tail;

    dbg("loading needed objects");
    if (load_needed_objects(obj_main) == -1)
	die();

    /* Make a list of all objects loaded at startup. */
    for (obj = obj_list;  obj != NULL;  obj = obj->next) {
	objlist_push_tail(&list_main, obj);
    	obj->refcount++;
    }

    if (ld_tracing) {		/* We're done */
	trace_loaded_objects(obj_main);
	exit(0);
    }

    if (getenv(LD_ "DUMP_REL_PRE") != NULL) {
       dump_relocations(obj_main);
       exit (0);
    }

    /* setup TLS for main thread */
    dbg("initializing initial thread local storage");
    STAILQ_FOREACH(entry, &list_main, link) {
	/*
	 * Allocate all the initial objects out of the static TLS
	 * block even if they didn't ask for it.
	 */
	allocate_tls_offset(entry->obj);
    }
    allocate_initial_tls(obj_list);

    if (relocate_objects(obj_main,
	ld_bind_now != NULL && *ld_bind_now != '\0', &obj_rtld) == -1)
	die();

    dbg("doing copy relocations");
    if (do_copy_relocations(obj_main) == -1)
	die();

    if (getenv(LD_ "DUMP_REL_POST") != NULL) {
       dump_relocations(obj_main);
       exit (0);
    }

    dbg("initializing key program variables");
    set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : "");
    set_program_var("environ", env);

    dbg("initializing thread locks");
    lockdflt_init();

    /* Make a list of init functions to call. */
    objlist_init(&initlist);
    initlist_add_objects(obj_list, preload_tail, &initlist);

    r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */

    objlist_call_init(&initlist);
    lockstate = wlock_acquire(rtld_bind_lock);
    objlist_clear(&initlist);
    wlock_release(rtld_bind_lock, lockstate);

    dbg("transferring control to program entry point = %p", obj_main->entry);

    /* Return the exit procedure and the program entry point. */
    *exit_proc = rtld_exit;
    *objp = obj_main;
    return (func_ptr_type) obj_main->entry;
}

#endif /* 0 */

Elf_Addr
_rtld_bind(Obj_Entry *obj, Elf_Word reloff)
{
    const Elf_Rel *rel;
    const Elf_Sym *def;
    const Obj_Entry *defobj;
    Elf_Addr *where;
    Elf_Addr target;
    int lockstate;

    lockstate = rlock_acquire(rtld_bind_lock);
    if (obj->pltrel)
	rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff);
    else
	rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff);

    where = (Elf_Addr *) (obj->relocbase + rel->r_offset);
    def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL);
    if (def == NULL)
	die();