dlib.c

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/*
 * libdl.c
 * 
 * Functions required for dlopen et. al.
 */

#include <stdlib.h>
#include <features.h>
#include "dlfcn.h"
#include "sysdep.h"
#include "syscall.h"
#include "hash.h"
#include "string.h"
#include "linuxelf.h"

extern int _dl_error_number;
extern struct r_debug *_dl_debug_addr;

extern void *(*_dl_malloc_function) (size_t size);

static int do_fixup(struct elf_resolve *tpnt, int flag);
static int do_dlclose(void *, int need_fini);

void *_dlopen(char *filename, int flag);
const char *_dlerror(void);
void *_dlsym(void *, char *);
int _dlclose(void *);
int _dladdr(void *__address, Dl_info * __dlip);

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"
};

static void dl_cleanup(void) __attribute__ ((destructor));

static void dl_cleanup(void)
{
	struct dyn_elf *d;

	for (d = _dl_handles; d; d = d->next_handle)
		if (d->dyn->libtype == loaded_file && d->dyn->dynamic_info[DT_FINI]) {
			(* ((int (*)(void)) (d->dyn->loadaddr + d->dyn->dynamic_info[DT_FINI]))) ();
			d->dyn->dynamic_info[DT_FINI] = 0;
		}
}

void *_dlopen(char *libname, int flag)
{
	struct elf_resolve *tpnt, *tfrom;
	struct dyn_elf *rpnt;
	struct dyn_elf *dyn_chain;
	struct dyn_elf *dpnt;
	static int dl_init = 0;
	char *from;
	void (*dl_brk) (void);
	int (*dl_elf_init) (void);

	from = __builtin_return_address(0);

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

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

#ifdef USE_CACHE
	_dl_map_cache();
#endif

	/*
	 * 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;
	}

	if (!(tpnt = _dl_load_shared_library(0, tfrom, libname))) {
#ifdef USE_CACHE
		_dl_unmap_cache();
#endif
		return NULL;
	}

	tpnt->usage_count++;
	dyn_chain = rpnt = (struct dyn_elf *) malloc(sizeof(struct dyn_elf));
	_dl_memset(rpnt, 0, sizeof(*rpnt));
	rpnt->dyn = tpnt;
	rpnt->flags = flag;
	if (!tpnt->symbol_scope)
		tpnt->symbol_scope = dyn_chain;

	rpnt->next_handle = _dl_handles;
	_dl_handles = rpnt;

	/*
	 * OK, we have the requested file in memory.  Now check for
	 * any other requested files that may also be required.
	 */
	  {
	    struct elf_resolve *tcurr;
	    struct elf_resolve * tpnt1;
	    Elf32_Dyn * dpnt;
	    char * lpnt;

	    tcurr = tpnt;
	    do{
	      for(dpnt = (Elf32_Dyn *) tcurr->dynamic_addr; dpnt->d_tag; dpnt++)
		{
	  
		  if(dpnt->d_tag == DT_NEEDED)
		    {
		      lpnt = tcurr->loadaddr + tcurr->dynamic_info[DT_STRTAB] + 
			dpnt->d_un.d_val;
		      if(!(tpnt1 = _dl_load_shared_library(0, tcurr, lpnt)))
			goto oops;

		      rpnt->next = (struct dyn_elf *) malloc(sizeof(struct dyn_elf));
		      _dl_memset (rpnt->next, 0, sizeof (*(rpnt->next)));
		      rpnt = rpnt->next;
		      tpnt1->usage_count++;
		      if (!tpnt1->symbol_scope) tpnt1->symbol_scope = dyn_chain;
		      rpnt->dyn = tpnt1;
		    };
		}
	      
	      tcurr = tcurr->next;
	    } while(tcurr);
	  }
	 
	/*
	 * OK, now attach the entire chain at the end
	 */

	rpnt->next = _dl_symbol_tables;

	if (do_fixup(tpnt, flag)) {
		_dl_error_number = DL_NO_SYMBOL;
		goto oops;
	}

	dl_brk = (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) ();
	}

	for (rpnt = dyn_chain; rpnt; rpnt = rpnt->next) {
		tpnt = rpnt->dyn;
		/* Apparently crt1 for the application is responsible for handling this.
		 * We only need to run the init/fini for shared libraries
		 */
		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]) {
			dl_elf_init = (int (*)(void)) (tpnt->loadaddr + tpnt->dynamic_info[DT_INIT]);
			(*dl_elf_init) ();
		}
	}

#ifdef USE_CACHE
	_dl_unmap_cache();
#endif
	return (void *) dyn_chain;

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

static int do_fixup(struct elf_resolve *tpnt, int flag)
{
	int goof = 0;

	if (tpnt->next)
		goof += do_fixup(tpnt->next, flag);

	if (tpnt->dynamic_info[DT_REL]) {
#ifdef ELF_USES_RELOCA
		goof++;
#else
		if (tpnt->init_flag & RELOCS_DONE)
			return goof;
		tpnt->init_flag |= RELOCS_DONE;

		goof += _dl_parse_relocation_information(tpnt, 
			tpnt->dynamic_info[DT_REL], tpnt->dynamic_info[DT_RELSZ], 0);
#endif
	}
	if (tpnt->dynamic_info[DT_RELA]) {
#ifdef ELF_USES_RELOCA
		if (tpnt->init_flag & RELOCS_DONE)
			return goof;
		tpnt->init_flag |= RELOCS_DONE;

		goof += _dl_parse_relocation_information(tpnt, 
			tpnt->dynamic_info[DT_RELA], tpnt->dynamic_info[DT_RELASZ], 0);
#else
		goof++;
#endif
	}
	if (tpnt->dynamic_info[DT_JMPREL]) {
		if (tpnt->init_flag & JMP_RELOCS_DONE)
			return goof;
		tpnt->init_flag |= JMP_RELOCS_DONE;

		if (flag == RTLD_LAZY)
			_dl_parse_lazy_relocation_information(tpnt, 
				tpnt->dynamic_info[DT_JMPREL], 
				tpnt->dynamic_info[DT_PLTRELSZ], 0);
		else
			goof += _dl_parse_relocation_information(tpnt, 
				tpnt->dynamic_info[DT_JMPREL], 
				tpnt->dynamic_info[DT_PLTRELSZ], 0);
	};
	return goof;
}

void *_dlsym(void *vhandle, char *name)
{
	struct elf_resolve *tpnt, *tfrom;
	struct dyn_elf *handle;
	char *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 = DL_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 = __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(name, handle, 1, NULL, 1);

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