libexec/ld.so/resolve.c

/*	$OpenBSD: resolve.c,v 1.74 2016/08/08 21:59:20 guenther Exp $ */

/*
 * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
 *
 * 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.
 *
 */

#define _DYN_LOADER

#include <sys/types.h>

#include <limits.h>
#include <nlist.h>
#include <link.h>
#include "syscall.h"
#include "archdep.h"
#include "path.h"
#include "resolve.h"

/* substitution types */
typedef enum {
	SUBST_UNKNOWN, SUBST_ORIGIN, SUBST_OSNAME, SUBST_OSREL, SUBST_PLATFORM
} SUBST_TYPES;

elf_object_t *_dl_objects;
elf_object_t *_dl_last_object;
elf_object_t *_dl_loading_object;

/*
 * Add a new dynamic object to the object list.
 */
void
_dl_add_object(elf_object_t *object)
{
	/*
	 * If a .so is marked nodelete, then the entire load group that it's
	 * in needs to be kept around forever, so add a reference there.
	 * XXX It would be better if we tracked inter-object dependencies
	 * from relocations and didn't leave dangling pointers when a load
	 * group was partially unloaded.  That would render this unnecessary.
	 */
	if (object->obj_flags & DF_1_NODELETE &&
	    (object->load_object->status & STAT_NODELETE) == 0) {
		DL_DEB(("objname %s is nodelete\n", object->load_name));
		object->load_object->opencount++;
		object->load_object->status |= STAT_NODELETE;
	}

	/*
	 * if this is a new object, prev will be NULL
	 * != NULL if an object already in the list
	 * prev == NULL for the first item in the list, but that will
	 * be the executable.
	 */
	if (object->prev != NULL)
		return;

	if (_dl_objects == NULL) {			/* First object ? */
		_dl_last_object = _dl_objects = object;
	} else {
		_dl_last_object->next = object;
		object->prev = _dl_last_object;
		_dl_last_object = object;
	}
}

/*
 * Identify substitution sequence name.
 */
static int
_dl_subst_name(const char *name, size_t siz) {
	switch (siz) {
	case 5:
		if (_dl_strncmp(name, "OSREL", 5) == 0)
			return SUBST_OSREL;
		break;
	case 6:
		if (_dl_strncmp(name, "ORIGIN", 6) == 0)
			return SUBST_ORIGIN;
		if (_dl_strncmp(name, "OSNAME", 6) == 0)
			return SUBST_OSNAME;
		break;
	case 8:
		if (_dl_strncmp(name, "PLATFORM", 8) == 0)
			return SUBST_PLATFORM;
		break;
	}

	return (SUBST_UNKNOWN);
}

/*
 * Perform $ORIGIN substitutions on path
 */
static void
_dl_origin_subst_path(elf_object_t *object, const char *origin_path,
    char **path)
{
	char tmp_path[PATH_MAX];
	char *new_path, *tp;
	const char *pp, *name, *value;
	static struct utsname uts;
	size_t value_len;
	int skip_brace;

	if (uts.sysname[0] == '\0') {
		if (_dl_uname(&uts) != 0)
			return;
	}

	tp = tmp_path;
	pp = *path;

	while (*pp != '\0' && (tp - tmp_path) < sizeof(tmp_path)) {

		/* copy over chars up to but not including $ */
		while (*pp != '\0' && *pp != '$' &&
		    (tp - tmp_path) < sizeof(tmp_path))
			*tp++ = *pp++;

		/* substitution sequence detected */
		if (*pp == '$' && (tp - tmp_path) < sizeof(tmp_path)) {
			pp++;

			if ((skip_brace = (*pp == '{')))
				pp++;

			/* skip over name */
			name = pp;
			while (_dl_isalnum((unsigned char)*pp) || *pp == '_')
				pp++;

			switch (_dl_subst_name(name, pp - name)) {
			case SUBST_ORIGIN:
				value = origin_path;
				break;
			case SUBST_OSNAME:
				value = uts.sysname;
				break;
			case SUBST_OSREL:
				value = uts.release;
				break;
			case SUBST_PLATFORM:
				value = uts.machine;
				break;
			default:
				value = "";
			}

			value_len = _dl_strlen(value);
			if (value_len >= sizeof(tmp_path) - (tp - tmp_path))
				return;

			_dl_bcopy(value, tp, value_len);
			tp += value_len;

			if (skip_brace && *pp == '}')
				pp++;
		}
	}

	/* no substitution made if result exceeds sizeof(tmp_path) */
	if (tp - tmp_path >= sizeof(tmp_path))
		return;

	/* NULL terminate tmp_path */
	*tp = '\0';

	if (_dl_strcmp(tmp_path, *path) == 0)
		return;

	new_path = _dl_strdup(tmp_path);
	if (new_path == NULL)
		return;

	DL_DEB(("orig_path %s\n", *path));
	DL_DEB(("new_path  %s\n", new_path));

	_dl_free(*path);
	*path = new_path;
}

/*
 * Determine origin_path from object load_name. The origin_path argument
 * must refer to a buffer capable of storing at least PATH_MAX characters.
 * Returns 0 on success.
 */
static int
_dl_origin_path(elf_object_t *object, char *origin_path)
{
	const char *dirname_path = _dl_dirname(object->load_name);

	if (dirname_path == NULL)
		return -1;

	if (_dl_realpath(dirname_path, origin_path) == NULL)
		return -1;

	return 0;
}

/*
 * Perform $ORIGIN substitutions on rpath
 */
static void
_dl_origin_subst(elf_object_t *object)
{
	char origin_path[PATH_MAX];
	char **pp;

	if (_dl_origin_path(object, origin_path) != 0)
		return;

	/* perform path substitutions on each segment of rpath */
	for (pp = object->rpath; *pp != NULL; pp++) {
		_dl_origin_subst_path(object, origin_path, pp);
	}
}

/*
 * Initialize a new dynamic object.
 */
elf_object_t *
_dl_finalize_object(const char *objname, Elf_Dyn *dynp, Elf_Phdr *phdrp,
    int phdrc, const int objtype, const long lbase, const long obase)
{
	elf_object_t *object;
#if 0
	_dl_printf("objname [%s], dynp %p, objtype %x lbase %lx, obase %lx\n",
	    objname, dynp, objtype, lbase, obase);
#endif
	object = _dl_calloc(1, sizeof(elf_object_t));
	if (object == NULL)
		_dl_exit(7);
	object->prev = object->next = NULL;

	object->load_dyn = dynp;
	while (dynp->d_tag != DT_NULL) {
		if (dynp->d_tag < DT_NUM)
			object->Dyn.info[dynp->d_tag] = dynp->d_un.d_val;
		else if (dynp->d_tag >= DT_LOPROC &&
		    dynp->d_tag < DT_LOPROC + DT_PROCNUM)
			object->Dyn.info[dynp->d_tag + DT_NUM - DT_LOPROC] =
			    dynp->d_un.d_val;
		if (dynp->d_tag == DT_TEXTREL)
			object->dyn.textrel = 1;
		if (dynp->d_tag == DT_SYMBOLIC)
			object->dyn.symbolic = 1;
		if (dynp->d_tag == DT_BIND_NOW)
			object->obj_flags |= DF_1_NOW;
		if (dynp->d_tag == DT_FLAGS_1)
			object->obj_flags |= dynp->d_un.d_val;
		if (dynp->d_tag == DT_RELACOUNT)
			object->relacount = dynp->d_un.d_val;
		if (dynp->d_tag == DT_RELCOUNT)
			object->relcount = dynp->d_un.d_val;
		dynp++;
	}
	DL_DEB((" flags %s = 0x%x\n", objname, object->obj_flags ));
	object->obj_type = objtype;

	if (_dl_loading_object == NULL) {
		/*
		 * no loading object, object is the loading object,
		 * as it is either executable, or dlopened()
		 */
		_dl_loading_object = object;
	}

	if ((object->obj_flags & DF_1_NOOPEN) != 0 &&
	    _dl_loading_object->obj_type == OBJTYPE_DLO &&
	    _dl_traceld == NULL) {
		_dl_free(object);
		_dl_errno = DL_CANT_LOAD_OBJ;
		return(NULL);
	}

	/*
	 *  Now relocate all pointer to dynamic info, but only
	 *  the ones which have pointer values.
	 */
	if (object->Dyn.info[DT_PLTGOT])
		object->Dyn.info[DT_PLTGOT] += obase;
	if (object->Dyn.info[DT_HASH])
		object->Dyn.info[DT_HASH] += obase;
	if (object->Dyn.info[DT_STRTAB])
		object->Dyn.info[DT_STRTAB] += obase;
	if (object->Dyn.info[DT_SYMTAB])
		object->Dyn.info[DT_SYMTAB] += obase;
	if (object->Dyn.info[DT_RELA])
		object->Dyn.info[DT_RELA] += obase;
	if (object->Dyn.info[DT_SONAME])
		object->Dyn.info[DT_SONAME] += object->Dyn.info[DT_STRTAB];
	if (object->Dyn.info[DT_RPATH])
		object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB];
	if (object->Dyn.info[DT_REL])
		object->Dyn.info[DT_REL] += obase;
	if (object->Dyn.info[DT_INIT])
		object->Dyn.info[DT_INIT] += obase;
	if (object->Dyn.info[DT_FINI])
		object->Dyn.info[DT_FINI] += obase;
	if (object->Dyn.info[DT_JMPREL])
		object->Dyn.info[DT_JMPREL] += obase;

	if (object->Dyn.info[DT_HASH] != 0) {
		Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH];

		object->nbuckets = hashtab[0];
		object->nchains = hashtab[1];
		object->buckets = hashtab + 2;
		object->chains = object->buckets + object->nbuckets;
	}

	object->phdrp = phdrp;
	object->phdrc = phdrc;
	object->load_base = lbase;
	object->obj_base = obase;
	object->load_name = _dl_strdup(objname);
	if (object->load_name == NULL)
		_dl_exit(7);
	object->load_object = _dl_loading_object;
	if (object->load_object == object)
		DL_DEB(("head %s\n", object->load_name));
	DL_DEB(("obj %s has %s as head\n", object->load_name,
	    _dl_loading_object->load_name ));
	object->refcount = 0;
	TAILQ_INIT(&object->child_list);
	object->opencount = 0;	/* # dlopen() & exe */
	object->grprefcount = 0;
	/* default dev, inode for dlopen-able objects. */
	object->dev = 0;
	object->inode = 0;
	object->grpsym_gen = 0;
	TAILQ_INIT(&object->grpsym_list);
	TAILQ_INIT(&object->grpref_list);

	if (object->dyn.rpath) {
		object->rpath = _dl_split_path(object->dyn.rpath);
		if ((object->obj_flags & DF_1_ORIGIN) && _dl_trust)
			_dl_origin_subst(object);
	}

	_dl_trace_object_setup(object);

	return (object);
}

static void
_dl_tailq_free(struct dep_node *n)
{
	struct dep_node *next;

	while (n != NULL) {
		next = TAILQ_NEXT(n, next_sib);
		_dl_free(n);
		n = next;
	}
}

elf_object_t *free_objects;

void
_dl_cleanup_objects()
{
	elf_object_t *nobj, *head;
	struct dep_node *n, *next;

	n = TAILQ_FIRST(&_dlopened_child_list);
	while (n != NULL) {
		next = TAILQ_NEXT(n, next_sib);
		if (OBJECT_DLREF_CNT(n->data) == 0) {
			TAILQ_REMOVE(&_dlopened_child_list, n, next_sib);
			_dl_free(n);
		}
		n = next;
	}

	head = free_objects;
	free_objects = NULL;
	while (head != NULL) {
		if (head->load_name)
			_dl_free(head->load_name);
		if (head->sod.sod_name)
			_dl_free((char *)head->sod.sod_name);
		if (head->rpath)
			_dl_free_path(head->rpath);
		_dl_tailq_free(TAILQ_FIRST(&head->grpsym_list));
		_dl_tailq_free(TAILQ_FIRST(&head->child_list));
		_dl_tailq_free(TAILQ_FIRST(&head->grpref_list));
		nobj = head->next;
		_dl_free(head);
		head = nobj;
	}
}

void
_dl_remove_object(elf_object_t *object)
{
	object->prev->next = object->next;
	if (object->next)
		object->next->prev = object->prev;

	if (_dl_last_object == object)
		_dl_last_object = object->prev;

	object->next = free_objects;
	free_objects = object;
}

/*
 * mprotect a segment to the indicated protection.  If 'addr' is non-zero,
 * then it's the start address, else the value of 'start_sym' is the start.
 * The value of 'end_sym' is the end address.  The start is rounded down
 * and the end is rounded up to page boundaries.  Returns 'addr' or the
 * address of the start symbol.
 */
void *
_dl_protect_segment(elf_object_t *object, Elf_Addr addr,
    const char *start_sym, const char *end_sym, int prot)
{
	const Elf_Sym *this;
	Elf_Addr ooff, start, end;

	if (addr == 0 && start_sym[2] == 'g' &&
	    (addr = object->relro_addr) != 0) {
		DL_DEB(("protect start RELRO = 0x%lx in %s\n",
		    addr, object->load_name));
	}
	else if (addr == 0) {
		this = NULL;
		ooff = _dl_find_symbol(start_sym, &this,
		    SYM_SEARCH_OBJ | SYM_NOWARNNOTFOUND | SYM_PLT, NULL,
		    object, NULL);
		/* If not found, nothing to do */
		if (this == NULL) {
			DL_DEB(("protect start \"%s\" not found in %s\n",
			    start_sym, object->load_name));
			return (NULL);
		}
		addr = ooff + this->st_value;
		DL_DEB(("protect start \"%s\" to %x = 0x%lx in %s\n",
		    start_sym, prot, addr, object->load_name));
	}

	if (object->relro_addr != 0 && start_sym[2] == 'g') {
		end = object->relro_addr + object->relro_size;
		DL_DEB(("protect end RELRO = 0x%lx in %s\n",
		    end, object->load_name));
	} else {
		this = NULL;
		ooff = _dl_find_symbol(end_sym, &this,
		    SYM_SEARCH_OBJ | SYM_NOWARNNOTFOUND | SYM_PLT, NULL,
		    object, NULL);
		if (this == NULL) {
			DL_DEB(("protect end \"%s\" not found in %s\n",
			    end_sym, object->load_name));
			addr = 0;
		} else {
			end = ooff + this->st_value;
			DL_DEB(("protect end \"%s\" = 0x%lx in %s\n",
			    end_sym, end, object->load_name));
		}
	}

	if (addr != 0 && addr < end) {
		start = ELF_TRUNC(addr, _dl_pagesz);
		end = ELF_ROUND(end, _dl_pagesz);
		_dl_mprotect((void *)start, end - start, prot);
	}

	return ((void *)addr);
}


sym_cache *_dl_symcache;
int _dl_symcachestat_hits;
int _dl_symcachestat_lookups;


Elf_Addr
_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
    const Elf_Sym **this, int flags, const Elf_Sym *ref_sym, const elf_object_t **pobj)
{
	Elf_Addr ret;
	const Elf_Sym *sym;
	const char *symn;
	const elf_object_t *sobj;

	_dl_symcachestat_lookups ++;
	if (_dl_symcache != NULL &&
	    symidx < req_obj->nchains &&
	    _dl_symcache[symidx].obj != NULL &&
	    _dl_symcache[symidx].sym != NULL &&
	    _dl_symcache[symidx].flags == flags) {

		_dl_symcachestat_hits++;
		sobj = _dl_symcache[symidx].obj;
		*this = _dl_symcache[symidx].sym;
		if (pobj)
			*pobj = sobj;
		return sobj->obj_base;
	}

	sym = req_obj->dyn.symtab;
	sym += symidx;
	symn = req_obj->dyn.strtab + sym->st_name;

	ret = _dl_find_symbol(symn, this, flags, ref_sym, req_obj, &sobj);

	if (pobj)
		*pobj = sobj;

	if (_dl_symcache != NULL && symidx < req_obj->nchains) {
#if 0
		DL_DEB(("cache miss %d %p %p, %p %p %s %s %d %d %s\n",
		    symidx,
		    _dl_symcache[symidx].sym, *this,
		    _dl_symcache[symidx].obj, sobj, sobj->load_name,
		    sobj->dyn.strtab + (*this)->st_name,
		    _dl_symcache[symidx].flags, flags, req_obj->load_name));
#endif

		_dl_symcache[symidx].sym = *this;
		_dl_symcache[symidx].obj = sobj;
		_dl_symcache[symidx].flags = flags;
	}

	return ret;
}

static int
_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
    int flags, const Elf_Sym **this, const Elf_Sym **weak_sym,
    elf_object_t **weak_object)
{
	const Elf_Sym	*symt = object->dyn.symtab;
	const char	*strt = object->dyn.strtab;
	long	si;
	const char *symn;

	for (si = object->buckets[hash % object->nbuckets];
	    si != STN_UNDEF; si = object->chains[si]) {
		const Elf_Sym *sym = symt + si;

		if (sym->st_value == 0)
			continue;

		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
			continue;

		symn = strt + sym->st_name;
		if (sym != *this && _dl_strcmp(symn, name))
			continue;

		/* allow this symbol if we are referring to a function
		 * which has a value, even if section is UNDEF.
		 * this allows &func to refer to PLT as per the
		 * ELF spec. st_value is checked above.
		 * if flags has SYM_PLT set, we must have actual
		 * symbol, so this symbol is skipped.
		 */
		if (sym->st_shndx == SHN_UNDEF) {
			if ((flags & SYM_PLT) || sym->st_value == 0 ||
			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
				continue;
		}

		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
			*this = sym;
			return 1;
		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
			if (!*weak_sym) {
				*weak_sym = sym;
				*weak_object = object;
			}
		}
	}
	return 0;
}

Elf_Addr
_dl_find_symbol(const char *name, const Elf_Sym **this,
    int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj,
    const elf_object_t **pobj)
{
	const Elf_Sym *weak_sym = NULL;
	unsigned long h = 0;
	const char *p = name;
	elf_object_t *object = NULL, *weak_object = NULL;
	int found = 0;
	struct dep_node *n, *m;


	while (*p) {
		unsigned long g;
		h = (h << 4) + *p++;
		if ((g = h & 0xf0000000))
			h ^= g >> 24;
		h &= ~g;
	}

	if (req_obj->dyn.symbolic)
		if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym,
		    &weak_object)) {
			object = req_obj;
			found = 1;
			goto found;
		}

	if (flags & SYM_SEARCH_OBJ) {
		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
		    &weak_sym, &weak_object)) {
			object = req_obj;
			found = 1;
		}
	} else if (flags & SYM_DLSYM) {
		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
		    &weak_sym, &weak_object)) {
			object = req_obj;
			found = 1;
		}
		if (weak_object != NULL && found == 0) {
			object=weak_object;
			*this = weak_sym;
			found = 1;
		}
		/* search dlopened obj and all children */

		if (found == 0) {
			TAILQ_FOREACH(n, &req_obj->load_object->grpsym_list,
			    next_sib) {
				if (_dl_find_symbol_obj(n->data, name, h,
				    flags, this,
				    &weak_sym, &weak_object)) {
					object = n->data;
					found = 1;
					break;
				}
			}
		}
	} else {
		int skip = 0;

		if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT))
			skip = 1;

		/*
		 * search dlopened objects: global or req_obj == dlopened_obj
		 * and and it's children
		 */
		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
			if (((n->data->obj_flags & DF_1_GLOBAL) == 0) &&
			    (n->data != req_obj->load_object))
				continue;

			TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) {
				if (skip == 1) {
					if (m->data == req_obj) {
						skip = 0;
						if (flags & SYM_SEARCH_NEXT)
							continue;
					} else
						continue;
				}
				if ((flags & SYM_SEARCH_OTHER) &&
				    (m->data == req_obj))
					continue;
				if (_dl_find_symbol_obj(m->data, name, h, flags,
				    this, &weak_sym, &weak_object)) {
					object = m->data;
					found = 1;
					goto found;
				}
			}
		}
	}

found:
	if (weak_object != NULL && found == 0) {
		object=weak_object;
		*this = weak_sym;
		found = 1;
	}


	if (found == 0) {
		if ((ref_sym == NULL ||
		    (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) &&
		    (flags & SYM_WARNNOTFOUND))
			_dl_printf("%s:%s: undefined symbol '%s'\n",
			    __progname, req_obj->load_name, name);
		return (0);
	}

	if (ref_sym != NULL && ref_sym->st_size != 0 &&
	    (ref_sym->st_size != (*this)->st_size)  &&
	    (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) {
		_dl_printf("%s:%s: %s : WARNING: "
		    "symbol(%s) size mismatch, relink your program\n",
		    __progname, req_obj->load_name, object->load_name, name);
	}

	if (pobj)
		*pobj = object;

	return (object->obj_base);
}

void
_dl_debug_state(void)
{
	/* Debugger stub */
}