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search.c revision 1.1 
      1 /*	$NetBSD: search.c,v 1.1 1996/12/16 20:38:05 cgd Exp $	*/
      2 
      3 /*
      4  * Copyright 1996 Matt Thomas <matt (at) 3am-software.com>
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *      This product includes software developed by John Polstra.
     18  * 4. The name of the author may not be used to endorse or promote products
     19  *    derived from this software without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 /*
     34  * Dynamic linker for ELF.
     35  *
     36  * John Polstra <jdp (at) polstra.com>.
     37  */
     38 
     39 #include <err.h>
     40 #include <errno.h>
     41 #include <fcntl.h>
     42 #include <stdarg.h>
     43 #include <stdio.h>
     44 #include <stdlib.h>
     45 #include <string.h>
     46 #include <unistd.h>
     47 #include <sys/types.h>
     48 #include <sys/mman.h>
     49 #include <sys/stat.h>
     50 #include <dirent.h>
     51 
     52 #include "debug.h"
     53 #include "rtld.h"
     54 
     55 #define CONCAT(x,y)     __CONCAT(x,y)
     56 #define ELFNAME(x)      CONCAT(elf,CONCAT(ELFSIZE,CONCAT(_,x)))
     57 #define ELFNAME2(x,y)   CONCAT(x,CONCAT(_elf,CONCAT(ELFSIZE,CONCAT(_,y))))
     58 #define ELFNAMEEND(x)   CONCAT(x,CONCAT(_elf,ELFSIZE))
     59 #define ELFDEFNNAME(x)  CONCAT(ELF,CONCAT(ELFSIZE,CONCAT(_,x)))
     60 
     61 /*
     62  * Data declarations.
     63  */
     64 
     65 typedef struct {
     66     const char *si_name;
     67     const char *si_best_name;
     68     char *si_best_fullpath;
     69     const Search_Path *si_best_path;
     70     size_t si_namelen;
     71     int si_desired_major;
     72     int si_desired_minor;
     73     int si_best_major;
     74     int si_best_minor;
     75     unsigned si_exact : 1;
     76 } Search_Info;
     77 
     78 typedef enum {
     79     Search_FoundNothing,
     80     Search_FoundLower,
     81     Search_FoundHigher,
     82     Search_FoundExact
     83 } Search_Result;
     84 
     85 static bool
     86 _rtld_check_library(
     87     const Search_Path *sp,
     88     const char *name,
     89     size_t namelen,
     90     char **fullpath_p)
     91 {
     92     struct stat mystat;
     93     char *fullpath;
     94     Elf_Ehdr ehdr;
     95     int fd;
     96 
     97     fullpath = xmalloc(sp->sp_pathlen + 1 + namelen + 1);
     98     strncpy(fullpath, sp->sp_path, sp->sp_pathlen);
     99     fullpath[sp->sp_pathlen] = '/';
    100     strcpy(&fullpath[sp->sp_pathlen + 1], name);
    101 
    102     dbg("  Trying \"%s\"", fullpath);
    103     if (stat(fullpath, &mystat) >= 0 && S_ISREG(mystat.st_mode)) {
    104 	if ((fd = open(fullpath, O_RDONLY)) >= 0) {
    105 	    if (read(fd, &ehdr, sizeof(ehdr)) != sizeof(ehdr))
    106 		goto lose;
    107 
    108 	    /* Elf_e_ident includes class */
    109 	    if (memcmp(Elf_e_ident, ehdr.e_ident, Elf_e_siz) != 0)
    110 		goto lose;
    111 
    112 	    switch (ehdr.e_machine) {
    113 	    ELFDEFNNAME(MACHDEP_ID_CASES)
    114 
    115 	    default:
    116 		goto lose;
    117 	    }
    118 
    119 	    if (ehdr.e_ident[Elf_ei_version] != Elf_ev_current ||
    120 	      ehdr.e_version != Elf_ev_current ||
    121 	      ehdr.e_ident[Elf_ei_data] != ELFDEFNNAME(MACHDEP_ENDIANNESS) ||
    122 	      ehdr.e_type != Elf_et_dyn)
    123 		goto lose;
    124 
    125 	    if (*fullpath_p != NULL)
    126 		free(*fullpath_p);
    127 	    *fullpath_p = fullpath;
    128 	    return true;
    129 
    130 lose:
    131 	    close(fd);
    132 	}
    133     }
    134 
    135     free(fullpath);
    136     return false;
    137 }
    138 
    139 static Search_Result
    140 _rtld_search_directory(
    141     const Search_Path *sp,
    142     Search_Info *si)
    143 {
    144     struct dirent *entry;
    145     DIR *dirp;
    146     Search_Result result = Search_FoundNothing;
    147 
    148 dbg("_rtld_search_directory");
    149     if (sp->sp_path == NULL || sp->sp_path[0] == '\0')
    150 	return result;
    151 
    152 dbg("_rtld_search_directory 2");
    153     if ((dirp = opendir(sp->sp_path)) == NULL) {
    154 	dbg("_rtld_search_directory 2.1");
    155 	return result;
    156     }
    157 
    158 dbg("_rtld_search_directory 3");
    159     while ((entry = readdir(dirp)) != NULL) {
    160 	long major = -1;
    161 	long minor = -1;
    162 	if (strncmp(entry->d_name, si->si_name, si->si_namelen))
    163 	    continue;
    164 	/*
    165 	 * We are matching libfoo.so only (no more info).  Only take
    166 	 * it as a last resort.
    167 	 */
    168 	if (si->si_exact) {
    169 	    if (strcmp(entry->d_name, si->si_name))
    170 		continue;
    171 #ifdef notyet
    172 	} else if (entry->d_namlen == si->si_namelen) {
    173 	    if (si->si_best_path != NULL || si->si_best_major != -1)
    174 		continue;
    175 #endif
    176 	} else {
    177 	    char *cp;
    178 	    /*
    179 	     * We expect (demand!) that it be of the form
    180 	     * "libfoo.so.<something>"
    181 	     */
    182 	    if (entry->d_name[si->si_namelen] != '.')
    183 		continue;
    184 	    /*
    185 	     * This file has a least a major number (well, maybe not if it
    186 	     * has a name of "libfoo.so." but treat that as equivalent to 0.
    187 	     * It had better match what we are looking for.
    188 	     */
    189 	    major = strtol(&entry->d_name[si->si_namelen+1], &cp, 10);
    190 	    if (major < 0 || (cp[0] != '\0' && cp[0] != '.')
    191 		    || &entry->d_name[si->si_namelen+1] == cp)
    192 		continue;
    193 	    if (cp[0] == '.') {
    194 		char *cp2;
    195 		minor = strtol(&cp[1], &cp2, 10);
    196 		if (minor < 0 || cp2[0] != '\0' || cp == cp2)
    197 		    continue;
    198 	    } else {
    199 		minor = 0;
    200 	    }
    201 	    if (major != si->si_desired_major || minor <= si->si_best_minor)
    202 		continue;
    203 	}
    204 	/*
    205 	 * We have a better candidate...
    206 	 */
    207 	if (!_rtld_check_library(sp, entry->d_name, entry->d_namlen,
    208 			   &si->si_best_fullpath))
    209 	    continue;
    210 
    211 	si->si_best_name = &si->si_best_fullpath[sp->sp_pathlen + 1];
    212 	si->si_best_major = major;
    213 	si->si_best_minor = minor;
    214 	si->si_best_path = sp;
    215 
    216 	if (si->si_exact || si->si_best_minor == si->si_desired_minor)
    217 	    result = Search_FoundExact;
    218 	else if (si->si_best_minor > si->si_desired_minor)
    219 	    result = Search_FoundHigher;
    220 	else
    221 	    result = Search_FoundLower;
    222 
    223 	/*
    224 	 * We were looking for, and found, an exact match.  We're done.
    225 	 */
    226 	if (si->si_exact)
    227 	    break;
    228     }
    229 
    230     dbg("found %s (%d.%d) match for %s (%d.%d) -> %s",
    231 	result == Search_FoundNothing ? "no"
    232 	: result == Search_FoundLower ? "lower"
    233 	: result == Search_FoundExact ? "exact" : "higher",
    234 	si->si_best_major, si->si_best_minor,
    235 	si->si_name,
    236 	si->si_desired_major, si->si_desired_minor,
    237 	si->si_best_fullpath ? si->si_best_fullpath : sp->sp_path);
    238 
    239     closedir(dirp);
    240     return result;
    241 }
    242 
    243 static char *
    245 _rtld_search_library_paths(
    246     const char *name,
    247     Search_Path *paths,
    248     const Search_Path *rpaths)
    249 {
    250     Search_Info info;
    251     Search_Path *path;
    252     const char *cp;
    253     Search_Result result = Search_FoundNothing;
    254 
    255     memset(&info, 0, sizeof(info));
    256     info.si_name = name;
    257     info.si_desired_major = -1;
    258     info.si_desired_minor = -1;
    259     info.si_best_major = -1;
    260     info.si_best_minor = -1;
    261 
    262     cp = strstr(name, ".so");
    263     if (cp == NULL) {
    264 	info.si_exact = true;
    265     } else {
    266 	cp += sizeof(".so") - 1;
    267 	info.si_namelen = cp - name;
    268 	if (cp[0] != '.') {
    269 	    info.si_exact = true;
    270 	} else {
    271 	    info.si_desired_major = atoi(&cp[1]);
    272 	    if ((cp = strchr(&cp[1], '.')) != NULL) {
    273 		info.si_desired_minor = atoi(&cp[1]);
    274 	    } else {
    275 		info.si_desired_minor = 0;
    276 	    }
    277 	}
    278     }
    279 
    280     if (rpaths != NULL && result < Search_FoundHigher) {	/* Exact? */
    281 	dbg("  checking rpaths..");
    282 	for (; rpaths != NULL; rpaths = rpaths->sp_next) {
    283 	    dbg("   in \"%s\"", rpaths->sp_path);
    284 	    result = _rtld_search_directory(rpaths, &info);
    285 	    if (result >= Search_FoundHigher)	/* Exact? */
    286 		break;
    287 	}
    288     }
    289     if (result < Search_FoundHigher) {	/* Exact? */
    290 	dbg("  checking default paths..");
    291 	for (path = paths; path != NULL; path = path->sp_next) {
    292 	    dbg("   in \"%s\"", path->sp_path);
    293 	    result = _rtld_search_directory(path, &info);
    294 	    if (result >= Search_FoundHigher)	/* Exact? */
    295 		break;
    296 	}
    297     }
    298 
    299     if (result >= Search_FoundHigher)
    300 	return info.si_best_fullpath;
    301 
    302     if (info.si_best_fullpath != NULL)
    303 	free(info.si_best_fullpath);
    304     return NULL;
    305 }
    306 
    307 /*
    308  * Find the library with the given name, and return its full pathname.
    309  * The returned string is dynamically allocated.  Generates an error
    310  * message and returns NULL if the library cannot be found.
    311  *
    312  * If the second argument is non-NULL, then it refers to an already-
    313  * loaded shared object, whose library search path will be searched.
    314  */
    315 char *
    316 _rtld_find_library(
    317     const char *name,
    318     const Obj_Entry *refobj)
    319 {
    320     char *pathname;
    321 
    322     if (strchr(name, '/') != NULL) {	/* Hard coded pathname */
    323 	if (name[0] != '/' && !_rtld_trust) {
    324 	    _rtld_error("Absolute pathname required for shared object \"%s\"",
    325 			name);
    326 	    return NULL;
    327 	}
    328 #ifdef SVR4_LIBDIR
    329 	if (strncmp(name, SVR4_LIBDIR, SVR4_LIBDIRLEN) == 0
    330 	        && name[SVR4_LIBDIRLEN] == '/') {	/* In "/usr/lib" */
    331 	    /* Map hard-coded "/usr/lib" onto our ELF library directory. */
    332 	    pathname = xmalloc(strlen(name) + LIBDIRLEN - SVR4_LIBDIRLEN + 1);
    333 	    strcpy(pathname, LIBDIR);
    334 	    strcpy(pathname + LIBDIRLEN, name + SVR4_LIBDIRLEN);
    335 	    return pathname;
    336 	}
    337 #endif /* SVR4_LIBDIR */
    338 	return xstrdup(name);
    339     }
    340 
    341     dbg(" Searching for \"%s\" (%p)", name, refobj);
    342 
    343     pathname = _rtld_search_library_paths(name, _rtld_paths,
    344 					  refobj ? refobj->rpaths : NULL);
    345     if (pathname == NULL)
    346 	_rtld_error("Shared object \"%s\" not found", name);
    347     return pathname;
    348 }
    349