path: root/ldso/libdl/libdl.c

/* vi: set sw=4 ts=4: */
/*
 * Program to load an ELF binary on a linux system, and run it
 * after resolving ELF shared library symbols
 *
 * Copyright (C) 2000-2004 by Erik Andersen <andersen@codpoet.org>
 * Copyright (c) 1994-2000 Eric Youngdale, Peter MacDonald,
 *				David Engel, Hongjiu Lu and Mitch D'Souza
 *
 * 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. The name of the above contributors may not be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``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 CONTRIBUTORS 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.
 */


#include <ldso.h>
#include <stdio.h>


#if defined (__LIBDL_SHARED__)

/* When libdl is loaded as a shared library, we need to load in
 * and use a pile of symbols from ldso... */

extern char *_dl_find_hash(const char *, struct dyn_elf *, int)
	__attribute__ ((__weak__));
extern struct elf_resolve * _dl_load_shared_library(int, struct dyn_elf **,
	struct elf_resolve *, char *, int) __attribute__ ((__weak__));
extern struct elf_resolve * _dl_check_if_named_library_is_loaded(const char *, int)
	__attribute__ ((__weak__));
extern int _dl_fixup(struct dyn_elf *rpnt, int lazy)
	 __attribute__ ((__weak__));
extern int _dl_errno __attribute__ ((__weak__));
extern struct dyn_elf *_dl_symbol_tables __attribute__ ((__weak__));
extern struct dyn_elf *_dl_handles __attribute__ ((__weak__));
extern struct elf_resolve *_dl_loaded_modules __attribute__ ((__weak__));
extern struct r_debug *_dl_debug_addr __attribute__ ((__weak__));
extern unsigned long _dl_error_number __attribute__ ((__weak__));
extern void *(*_dl_malloc_function)(size_t) __attribute__ ((__weak__));
#ifdef USE_CACHE
int _dl_map_cache(void) __attribute__ ((__weak__));
int _dl_unmap_cache(void) __attribute__ ((__weak__));
#endif
#ifdef __mips__
extern void _dl_perform_mips_global_got_relocations(struct elf_resolve *tpnt)
	__attribute__ ((__weak__));
#endif
#ifdef __SUPPORT_LD_DEBUG__
extern char *_dl_debug __attribute__ ((__weak__));
#endif


#else /* __LIBDL_SHARED__ */

/* When libdl is linked as a static library, we need to replace all
 * the symbols that otherwise would have been loaded in from ldso... */

#ifdef __SUPPORT_LD_DEBUG__
char *_dl_debug  = 0;
#endif
char *_dl_library_path         = 0;		    /* Where we look for libraries */
char *_dl_ldsopath             = 0;		    /* Location of the shared lib loader */
int _dl_errno                  = 0;         /* We can't use the real errno in ldso */
size_t _dl_pagesize            = PAGE_SIZE; /* Store the page size for use later */
/* This global variable is also to communicate with debuggers such as gdb. */
struct r_debug *_dl_debug_addr = NULL;
#define _dl_malloc malloc
#include "dl-progname.h"
#include "../ldso/dl-hash.c"
#define _dl_trace_loaded_objects    0
#include "../ldso/dl-elf.c"
#endif

static int do_dlclose(void *, int need_fini);


static const char *dl_error_names[] = {
	"",
	"File not found",
	"Unable to open /dev/zero",
	"Not an ELF file",
#if defined (__i386__)
	"Not i386 binary",
#elif defined (__sparc__)
	"Not sparc binary",
#elif defined (__mc68000__)
	"Not m68k binary",
#else
	"Unrecognized binary type",
#endif
	"Not an ELF shared library",
	"Unable to mmap file",
	"No dynamic section",
#ifdef ELF_USES_RELOCA
	"Unable to process REL relocs",
#else
	"Unable to process RELA relocs",
#endif
	"Bad handle",
	"Unable to resolve symbol"
};

void __attribute__ ((destructor)) dl_cleanup(void)
{
	struct dyn_elf *d;
	for (d = _dl_handles; d; d = d->next_handle) {
		do_dlclose(d, 1);
	}
}

void *dlopen(const char *libname, int flag)
{
	struct elf_resolve *tpnt, *tfrom, *tcurr;
	struct dyn_elf *dyn_chain, *rpnt = NULL, *dyn_ptr;
	struct dyn_elf *dpnt;
	static int dl_init = 0;
	ElfW(Addr) from;
	struct elf_resolve *tpnt1;
	void (*dl_brk) (void);
	int now_flag;

	/* A bit of sanity checking... */
	if (!(flag & (RTLD_LAZY|RTLD_NOW))) {
		_dl_error_number = LD_BAD_HANDLE;
		return NULL;
	}

	from = (ElfW(Addr)) __builtin_return_address(0);

	/* Have the dynamic linker use the regular malloc function now */
	if (!dl_init) {
		dl_init++;
#if defined (__LIBDL_SHARED__)
		_dl_malloc_function = malloc;
#endif
	}

	/* Cover the trivial case first */
	if (!libname)
		return _dl_symbol_tables;

	_dl_map_cache();

	/*
	 * Try and locate the module we were called from - we
	 * need this so that we get the correct RPATH.  Note that
	 * this is the current behavior under Solaris, but the
	 * ABI+ specifies that we should only use the RPATH from
	 * the application.  Thus this may go away at some time
	 * in the future.
	 */
	tfrom = NULL;
	for (dpnt = _dl_symbol_tables; dpnt; dpnt = dpnt->next) {
		tpnt = dpnt->dyn;
		if (tpnt->loadaddr < from
				&& (tfrom == NULL || tfrom->loadaddr < tpnt->loadaddr))
			tfrom = tpnt;
	}
	for(rpnt = _dl_symbol_tables; rpnt->next; rpnt=rpnt->next);
	/* Try to load the specified library */
#ifdef __SUPPORT_LD_DEBUG__
	if(_dl_debug)
		fprintf(stderr, "Trying to dlopen '%s'\n", (char*)libname);
#endif
	tpnt = _dl_check_if_named_library_is_loaded((char *)libname, 0);
	if (!(tpnt))
		tpnt = _dl_load_shared_library(0, &rpnt, tfrom, (char*)libname, 0);
	else
		tpnt->usage_count++;
	if (tpnt == NULL) {
		_dl_unmap_cache();
		return NULL;
	}

	dyn_chain = (struct dyn_elf *) malloc(sizeof(struct dyn_elf));
	_dl_memset(dyn_chain, 0, sizeof(struct dyn_elf));
	dyn_chain->dyn = tpnt;
	tpnt->rtld_flags |= RTLD_GLOBAL;

	dyn_chain->next_handle = _dl_handles;
	_dl_handles = dyn_ptr = dyn_chain;

#ifdef __SUPPORT_LD_DEBUG__
	if(_dl_debug)
		fprintf(stderr, "Looking for needed libraries\n");
#endif

	for (tcurr = tpnt; tcurr; tcurr = tcurr->next)
	{
		Elf32_Dyn *dpnt;
		char *lpntstr;
		for (dpnt = (Elf32_Dyn *) tcurr->dynamic_addr; dpnt->d_tag; dpnt++) {
			if (dpnt->d_tag == DT_NEEDED) {

				char *name;
				lpntstr = (char*) (tcurr->loadaddr + tcurr->dynamic_info[DT_STRTAB] +
						dpnt->d_un.d_val);
				name = _dl_get_last_path_component(lpntstr);
				tpnt1 = _dl_check_if_named_library_is_loaded(name, 0);
#ifdef __SUPPORT_LD_DEBUG__
				if(_dl_debug)
					fprintf(stderr, "Trying to load '%s', needed by '%s'\n",
							lpntstr, tcurr->libname);
#endif
				dyn_ptr->next = (struct dyn_elf *) malloc(sizeof(struct dyn_elf));
				_dl_memset (dyn_ptr->next, 0, sizeof (struct dyn_elf));
				dyn_ptr = dyn_ptr->next;
				dyn_ptr->dyn = tpnt1;
				if (!tpnt1) {
					tpnt1 = _dl_load_shared_library(0, &rpnt, tcurr, lpntstr, 0);
					dyn_ptr->dyn = tpnt1;
					if (!tpnt1)
						goto oops;
					tpnt1->rtld_flags |= RTLD_GLOBAL;
				} else {
					tpnt1->rtld_flags |= RTLD_GLOBAL;
					tpnt1->usage_count++;
				}
			}
		}
	}

	if (dyn_chain->dyn->init_flag & INIT_FUNCS_CALLED) {
		/* If the init and fini stuff has already been run, that means
		 * the dlopen'd library has already been loaded, and nothing
		 * further needs to be done. */
		return (void *) dyn_chain;
	}
#ifdef __mips__
	/*
	 * Relocation of the GOT entries for MIPS have to be done
	 * after all the libraries have been loaded.
	 */
	_dl_perform_mips_global_got_relocations(tpnt);
#endif

#ifdef __SUPPORT_LD_DEBUG__
	if(_dl_debug)
		fprintf(stderr, "Beginning dlopen relocation fixups\n");
#endif
	/*
	 * OK, now all of the kids are tucked into bed in their proper addresses.
	 * Now we go through and look for REL and RELA records that indicate fixups
	 * to the GOT tables.  We need to do this in reverse order so that COPY
	 * directives work correctly */
	now_flag = (flag & RTLD_NOW) ? RTLD_NOW : 0;
	if (getenv("LD_BIND_NOW"))
		now_flag = RTLD_NOW;
	if (_dl_fixup(dyn_chain, now_flag))
		goto oops;

	/* TODO:  Should we set the protections of all pages back to R/O now ? */


	/* Notify the debugger we have added some objects. */
	if (_dl_debug_addr) {
		dl_brk = (void (*)(void)) _dl_debug_addr->r_brk;
		if (dl_brk != NULL) {
			_dl_debug_addr->r_state = RT_ADD;
			(*dl_brk) ();

			_dl_debug_addr->r_state = RT_CONSISTENT;
			(*dl_brk) ();
		}
	}

#if defined (__LIBDL_SHARED__)
	/* Find the last library so we can run things in the right order */
	for (tpnt = dyn_chain->dyn; tpnt->next!=NULL; tpnt = tpnt->next)
		;

	/* Run the ctors and set up the dtors */
	for (; tpnt != dyn_chain->dyn->prev; tpnt=tpnt->prev)
	{
		/* Apparently crt1 for the application is responsible for handling this.
		 * We only need to run the init/fini for shared libraries
		 */
		if (tpnt->libtype == program_interpreter)
			continue;
		if (tpnt->libtype == elf_executable)
			continue;
		if (tpnt->init_flag & INIT_FUNCS_CALLED)
			continue;
		tpnt->init_flag |= INIT_FUNCS_CALLED;

		if (tpnt->dynamic_info[DT_INIT]) {
			void (*dl_elf_func) (void);
			dl_elf_func = (void (*)(void)) (tpnt->loadaddr + tpnt->dynamic_info[DT_INIT]);
			if (dl_elf_func && *dl_elf_func != NULL) {
#ifdef __SUPPORT_LD_DEBUG__
				if(_dl_debug)
					fprintf(stderr, "running ctors for library %s at '%x'\n", tpnt->libname, dl_elf_func);
#endif
				(*dl_elf_func) ();
			}
		}
	}
#endif
	return (void *) dyn_chain;

oops:
	/* Something went wrong.  Clean up and return NULL. */
	_dl_unmap_cache();
	do_dlclose(dyn_chain, 0);
	return NULL;
}

void *dlsym(void *vhandle, const char *name)
{
	struct elf_resolve *tpnt, *tfrom;
	struct dyn_elf *handle;
	ElfW(Addr) from;
	struct dyn_elf *rpnt;
	void *ret;

	handle = (struct dyn_elf *) vhandle;

	/* First of all verify that we have a real handle
	   of some kind.  Return NULL if not a valid handle. */

	if (handle == NULL)
		handle = _dl_symbol_tables;
	else if (handle != RTLD_NEXT && handle != _dl_symbol_tables) {
		for (rpnt = _dl_handles; rpnt; rpnt = rpnt->next_handle)
			if (rpnt == handle)
				break;
		if (!rpnt) {
			_dl_error_number = LD_BAD_HANDLE;
			return NULL;
		}
	} else if (handle == RTLD_NEXT) {
		/*
		 * Try and locate the module we were called from - we
		 * need this so that we know where to start searching
		 * from.  We never pass RTLD_NEXT down into the actual
		 * dynamic loader itself, as it doesn't know
		 * how to properly treat it.
		 */
		from = (ElfW(Addr)) __builtin_return_address(0);

		tfrom = NULL;
		for (rpnt = _dl_symbol_tables; rpnt; rpnt = rpnt->next) {
			tpnt = rpnt->dyn;
			if (tpnt->loadaddr < from
					&& (tfrom == NULL || tfrom->loadaddr < tpnt->loadaddr)) {
				tfrom = tpnt;
				handle = rpnt->next;
			}
		}
	}

	ret = _dl_find_hash((char*)name, handle, 0);

	/*
	 * Nothing found.
	 */
	if (!ret)
		_dl_error_number = LD_NO_SYMBOL;
	return ret;
}

static int do_dlclose(void *vhandle, int need_fini)
{
	struct dyn_elf *rpnt, *rpnt1;
	ElfW(Phdr) *ppnt;
	struct elf_resolve *tpnt;
	int (*dl_elf_fini) (void);
	void (*dl_brk) (void);
	struct dyn_elf *handle;
	unsigned int end;
	int i = 0;

	handle = (struct dyn_elf *) vhandle;
	rpnt1 = NULL;
	for (rpnt = _dl_handles; rpnt; rpnt = rpnt->next_handle) {
		if (rpnt == handle)
			break;
		rpnt1 = rpnt;
	}

	if (!rpnt) {
		_dl_error_number = LD_BAD_HANDLE;
		return 1;
	}
	if (rpnt1)
		rpnt1->next_handle = rpnt->next_handle;
	else
		_dl_handles = rpnt->next_handle;
	/* OK, this is a valid handle - now close out the file */
	for (rpnt = handle; rpnt; rpnt = rpnt->next) {
		tpnt = rpnt->dyn;
		if (--tpnt->usage_count == 0) {
			if (need_fini && tpnt->dynamic_info[DT_FINI]) {
				dl_elf_fini = (int (*)(void)) (tpnt->loadaddr + tpnt->dynamic_info[DT_FINI]);
				(*dl_elf_fini) ();
			}

			end = 0;
			for (i = 0, ppnt = tpnt->ppnt;
					i < tpnt->n_phent; ppnt++, i++) {
				if (ppnt->p_type != PT_LOAD)
					continue;
				if (end < ppnt->p_vaddr + ppnt->p_memsz)
					end = ppnt->p_vaddr + ppnt->p_memsz;
			}
			_dl_munmap((void*)tpnt->loadaddr, end);
			/* Next, remove tpnt from the loaded_module list */
			if (_dl_loaded_modules == tpnt) {
				_dl_loaded_modules = tpnt->next;
				if (_dl_loaded_modules)
					_dl_loaded_modules->prev = 0;
			} else
				for (tpnt = _dl_loaded_modules; tpnt; tpnt = tpnt->next)
					if (tpnt->next == rpnt->dyn) {
						tpnt->next = tpnt->next->next;
						if (tpnt->next)
							tpnt->next->prev = tpnt;
						break;
					}

			/* Next, remove tpnt from the global symbol table list */
			if (_dl_symbol_tables->dyn == rpnt->dyn) {
				_dl_symbol_tables = rpnt->next;
				if (_dl_symbol_tables)
					_dl_symbol_tables->prev = 0;
			} else
				for (rpnt1 = _dl_symbol_tables; rpnt1->next; rpnt1 = rpnt1->next) {
					if (rpnt1->next->dyn == rpnt->dyn) {
						free(rpnt1->next);
						rpnt1->next = rpnt1->next->next;
						if (rpnt1->next)
							rpnt1->next->prev = rpnt1;
						break;
					}
				}
			free(rpnt->dyn->libname);
			free(rpnt->dyn);
		}
		free(rpnt);
	}


	if (_dl_debug_addr) {
		dl_brk = (void (*)(void)) _dl_debug_addr->r_brk;
		if (dl_brk != NULL) {
			_dl_debug_addr->r_state = RT_DELETE;
			(*dl_brk) ();

			_dl_debug_addr->r_state = RT_CONSISTENT;
			(*dl_brk) ();
		}
	}

	return 0;
}

int dlclose(void *vhandle)
{
	return do_dlclose(vhandle, 1);
}

const char *dlerror(void)
{
	const char *retval;

	if (!_dl_error_number)
		return NULL;
	retval = dl_error_names[_dl_error_number];
	_dl_error_number = 0;
	return retval;
}

/*
 * Dump information to stderrr about the current loaded modules
 */
static char *type[] = { "Lib", "Exe", "Int", "Mod" };

void dlinfo(void)
{
	struct elf_resolve *tpnt;
	struct dyn_elf *rpnt, *hpnt;

	fprintf(stderr, "List of loaded modules\n");
	/* First start with a complete list of all of the loaded files. */
	for (tpnt = _dl_loaded_modules; tpnt; tpnt = tpnt->next) {
		fprintf(stderr, "\t%x %x %x %s %d %s\n",
				(unsigned) tpnt->loadaddr, (unsigned) tpnt,
				(unsigned) tpnt->symbol_scope,
				type[tpnt->libtype],
				tpnt->usage_count, tpnt->libname);
	}

	/* Next dump the module list for the application itself */
	fprintf(stderr, "\nModules for application (%x):\n",
			(unsigned) _dl_symbol_tables);
	for (rpnt = _dl_symbol_tables; rpnt; rpnt = rpnt->next)
		fprintf(stderr, "\t%x %s\n", (unsigned) rpnt->dyn, rpnt->dyn->libname);

	for (hpnt = _dl_handles; hpnt; hpnt = hpnt->next_handle) {
		fprintf(stderr, "Modules for handle %x\n", (unsigned) hpnt);
		for (rpnt = hpnt; rpnt; rpnt = rpnt->next)
			fprintf(stderr, "\t%x %s\n", (unsigned) rpnt->dyn,
					rpnt->dyn->libname);
	}
}

int dladdr(void *__address, Dl_info * __dlip)
{
	struct elf_resolve *pelf;
	struct elf_resolve *rpnt;

	_dl_map_cache();

	/*
	 * Try and locate the module address is in
	 */
	pelf = NULL;

#if 0
	fprintf(stderr, "dladdr( %x, %x )\n", __address, __dlip);
#endif

	for (rpnt = _dl_loaded_modules; rpnt; rpnt = rpnt->next) {
		struct elf_resolve *tpnt;

		tpnt = rpnt;
#if 0
		fprintf(stderr, "Module \"%s\" at %x\n",
				tpnt->libname, tpnt->loadaddr);
#endif
		if (tpnt->loadaddr < (ElfW(Addr)) __address
				&& (pelf == NULL || pelf->loadaddr < tpnt->loadaddr)) {
			pelf = tpnt;
		}
	}

	if (!pelf) {
		return 0;
	}

	/*
	 * Try and locate the symbol of address
	 */

	{
		char *strtab;
		Elf32_Sym *symtab;
		int hn, si;
		int sf;
		int sn = 0;
		ElfW(Addr) sa;

		sa = 0;
		symtab = (Elf32_Sym *) (pelf->dynamic_info[DT_SYMTAB] + pelf->loadaddr);
		strtab = (char *) (pelf->dynamic_info[DT_STRTAB] + pelf->loadaddr);

		sf = 0;
		for (hn = 0; hn < pelf->nbucket; hn++) {
			for (si = pelf->elf_buckets[hn]; si; si = pelf->chains[si]) {
				ElfW(Addr) symbol_addr;

				symbol_addr = pelf->loadaddr + symtab[si].st_value;
				if (symbol_addr <= (ElfW(Addr))__address && (!sf || sa < symbol_addr)) {
					sa = symbol_addr;
					sn = si;
					sf = 1;
				}
#if 0
				fprintf(stderr, "Symbol \"%s\" at %x\n",
						strtab + symtab[si].st_name, symbol_addr);
#endif
			}
		}

		if (sf) {
			__dlip->dli_fname = pelf->libname;
			__dlip->dli_fbase = (void *)pelf->loadaddr;
			__dlip->dli_sname = strtab + symtab[sn].st_name;
			__dlip->dli_saddr = (void *)sa;
		}
		return 1;
	}
}