1 /* vi: set sw=4 ts=4: */
3 * A small little ldd implementation for uClibc
5 * Copyright (C) 2000-2006 Erik Andersen <andersen@uclibc.org>
7 * Several functions in this file (specifically, elf_find_section_type(),
8 * elf_find_phdr_type(), and elf_find_dynamic(), were stolen from elflib.c from
9 * elfvector (http://www.BitWagon.com/elfvector.html) by John F. Reiser
10 * <jreiser@BitWagon.com>, which is copyright 2000 BitWagon Software LLC
13 * Licensed under GPLv2 or later
18 #if defined(__alpha__)
19 #define MATCH_MACHINE(x) (x == EM_ALPHA)
20 #define ELFCLASSM ELFCLASS64
23 #if defined(__arm__) || defined(__thumb__)
24 #define MATCH_MACHINE(x) (x == EM_ARM)
25 #define ELFCLASSM ELFCLASS32
28 #if defined(__avr32__)
29 #define MATCH_MACHINE(x) (x == EM_AVR32)
30 #define ELFCLASSM ELFCLASS32
34 #define MATCH_MACHINE(x) (x == EM_S390)
35 #define ELFCLASSM ELFCLASS32
39 #define MATCH_MACHINE(x) (x == EM_PARISC)
41 #define ELFCLASSM ELFCLASS64
43 #define ELFCLASSM ELFCLASS32
49 #define MATCH_MACHINE(x) (x == EM_386)
51 #define MATCH_MACHINE(x) (x == EM_386 || x == EM_486)
53 #define ELFCLASSM ELFCLASS32
57 #define MATCH_MACHINE(x) (x == EM_IA_64)
58 #define ELFCLASSM ELFCLASS64
61 #if defined(__mc68000__)
62 #define MATCH_MACHINE(x) (x == EM_68K)
63 #define ELFCLASSM ELFCLASS32
67 #define MATCH_MACHINE(x) (x == EM_MIPS || x == EM_MIPS_RS3_LE)
68 #define ELFCLASSM ELFCLASS32
71 #if defined(__powerpc64__)
72 #define MATCH_MACHINE(x) (x == EM_PPC64)
73 #define ELFCLASSM ELFCLASS64
74 #elif defined(__powerpc__)
75 #define MATCH_MACHINE(x) (x == EM_PPC)
76 #define ELFCLASSM ELFCLASS32
80 #define MATCH_MACHINE(x) (x == EM_SH)
81 #define ELFCLASSM ELFCLASS32
84 #if defined(__v850e__)
85 #define MATCH_MACHINE(x) ((x) == EM_V850 || (x) == EM_CYGNUS_V850)
86 #define ELFCLASSM ELFCLASS32
89 #if defined(__sparc__)
90 #define MATCH_MACHINE(x) ((x) == EM_SPARC || (x) == EM_SPARC32PLUS)
91 #define ELFCLASSM ELFCLASS32
95 #define MATCH_MACHINE(x) (x == EM_CRIS)
96 #define ELFCLASSM ELFCLASS32
99 #if defined(__x86_64__)
100 #define MATCH_MACHINE(x) (x == EM_X86_64)
101 #define ELFCLASSM ELFCLASS64
104 #ifndef MATCH_MACHINE
106 # include <asm/elf.h>
109 # define MATCH_MACHINE(x) (x == ELF_ARCH)
112 # define ELFCLASSM ELF_CLASS
115 #ifndef MATCH_MACHINE
116 # warning "You really should add a MATCH_MACHINE() macro for your architecture"
119 #if UCLIBC_ENDIAN_HOST == UCLIBC_ENDIAN_LITTLE
120 #define ELFDATAM ELFDATA2LSB
121 #elif UCLIBC_ENDIAN_HOST == UCLIBC_ENDIAN_BIG
122 #define ELFDATAM ELFDATA2MSB
129 struct library *next;
131 static struct library *lib_list = NULL;
132 static char not_found[] = "not found";
133 static char *interp_name = NULL;
134 static char *interp_dir = NULL;
136 static int interpreter_already_found = 0;
138 static __inline__ uint32_t byteswap32_to_host(uint32_t value)
141 return (bswap_32(value));
146 static __inline__ uint64_t byteswap64_to_host(uint64_t value)
149 return (bswap_64(value));
155 #if ELFCLASSM == ELFCLASS32
156 # define byteswap_to_host(x) byteswap32_to_host(x)
158 # define byteswap_to_host(x) byteswap64_to_host(x)
161 static ElfW(Shdr) *elf_find_section_type(uint32_t key, ElfW(Ehdr) *ehdr)
165 shdr = (ElfW(Shdr) *) (ehdr->e_shoff + (char *)ehdr);
166 for (j = ehdr->e_shnum; --j >= 0; ++shdr) {
167 if (key == byteswap32_to_host(shdr->sh_type)) {
174 static ElfW(Phdr) *elf_find_phdr_type(uint32_t type, ElfW(Ehdr) *ehdr)
177 ElfW(Phdr) *phdr = (ElfW(Phdr) *) (ehdr->e_phoff + (char *)ehdr);
178 for (j = ehdr->e_phnum; --j >= 0; ++phdr) {
179 if (type == byteswap32_to_host(phdr->p_type)) {
186 /* Returns value if return_val==1, ptr otherwise */
187 static void *elf_find_dynamic(int64_t const key, ElfW(Dyn) *dynp,
188 ElfW(Ehdr) *ehdr, int return_val)
190 ElfW(Phdr) *pt_text = elf_find_phdr_type(PT_LOAD, ehdr);
191 unsigned tx_reloc = byteswap_to_host(pt_text->p_vaddr) - byteswap_to_host(pt_text->p_offset);
192 for (; DT_NULL != byteswap_to_host(dynp->d_tag); ++dynp) {
193 if (key == byteswap_to_host(dynp->d_tag)) {
195 return (void *)byteswap_to_host(dynp->d_un.d_val);
197 return (void *)(byteswap_to_host(dynp->d_un.d_val) - tx_reloc + (char *)ehdr);
203 static char *elf_find_rpath(ElfW(Ehdr) *ehdr, ElfW(Dyn) *dynamic)
207 for (dyns = dynamic; byteswap_to_host(dyns->d_tag) != DT_NULL; ++dyns) {
208 if (DT_RPATH == byteswap_to_host(dyns->d_tag)) {
210 strtab = (char *)elf_find_dynamic(DT_STRTAB, dynamic, ehdr, 0);
211 return ((char *)strtab + byteswap_to_host(dyns->d_un.d_val));
217 static int check_elf_header(ElfW(Ehdr) *const ehdr)
219 if (!ehdr || *(uint32_t*)ehdr != ELFMAG_U32
220 || ehdr->e_ident[EI_CLASS] != ELFCLASSM
221 || ehdr->e_ident[EI_VERSION] != EV_CURRENT
226 /* Check if the target endianness matches the host's endianness */
228 if (UCLIBC_ENDIAN_HOST == UCLIBC_ENDIAN_LITTLE) {
229 if (ehdr->e_ident[5] == ELFDATA2MSB)
231 } else if (UCLIBC_ENDIAN_HOST == UCLIBC_ENDIAN_BIG) {
232 if (ehdr->e_ident[5] == ELFDATA2LSB)
236 /* Be very lazy, and only byteswap the stuff we use */
238 ehdr->e_type = bswap_16(ehdr->e_type);
239 ehdr->e_phoff = byteswap_to_host(ehdr->e_phoff);
240 ehdr->e_shoff = byteswap_to_host(ehdr->e_shoff);
241 ehdr->e_phnum = bswap_16(ehdr->e_phnum);
242 ehdr->e_shnum = bswap_16(ehdr->e_shnum);
248 #ifdef __LDSO_CACHE_SUPPORT__
249 static caddr_t cache_addr = NULL;
250 static size_t cache_size = 0;
252 static int map_cache(void)
260 if (cache_addr == (caddr_t) - 1)
262 else if (cache_addr != NULL)
265 if (stat(LDSO_CACHE, &st) || (fd = open(LDSO_CACHE, O_RDONLY)) < 0) {
266 fprintf(stderr, "ldd: can't open cache '%s'\n", LDSO_CACHE);
267 cache_addr = (caddr_t) - 1; /* so we won't try again */
271 cache_size = st.st_size;
272 cache_addr = mmap(0, cache_size, PROT_READ, MAP_SHARED, fd, 0);
274 if (cache_addr == MAP_FAILED) {
275 fprintf(stderr, "ldd: can't map cache '%s'\n", LDSO_CACHE);
279 header = (header_t *) cache_addr;
281 if (cache_size < sizeof(header_t)
282 || memcmp(header->magic, LDSO_CACHE_MAGIC, LDSO_CACHE_MAGIC_LEN)
283 || memcmp(header->version, LDSO_CACHE_VER, LDSO_CACHE_VER_LEN)
284 || cache_size < (sizeof(header_t) + header->nlibs * sizeof(libentry_t))
285 || cache_addr[cache_size - 1] != '\0')
287 fprintf(stderr, "ldd: cache '%s' is corrupt\n", LDSO_CACHE);
291 strtabsize = cache_size - sizeof(header_t) - header->nlibs * sizeof(libentry_t);
292 libent = (libentry_t *) & header[1];
294 for (i = 0; i < header->nlibs; i++) {
295 if (libent[i].sooffset >= strtabsize || libent[i].liboffset >= strtabsize) {
296 fprintf(stderr, "ldd: cache '%s' is corrupt\n", LDSO_CACHE);
304 munmap(cache_addr, cache_size);
305 cache_addr = (caddr_t) - 1;
309 static int unmap_cache(void)
311 if (cache_addr == NULL || cache_addr == (caddr_t) - 1)
315 munmap(cache_addr, cache_size);
322 static __inline__ void map_cache(void)
325 static __inline__ void unmap_cache(void)
330 /* This function's behavior must exactly match that
331 * in uClibc/ldso/ldso/dl-elf.c */
332 static void search_for_named_library(char *name, char *result,
333 const char *path_list)
337 struct stat filestat;
339 /* We need a writable copy of this string */
340 path = strdup(path_list);
342 fprintf(stderr, "%s: Out of memory!\n", __func__);
345 /* Eliminate all double //s */
347 while ((path_n = strstr(path_n, "//"))) {
349 memmove(path_n, path_n + 1, i - 1);
350 *(path_n + i - 1) = '\0';
353 /* Replace colons with zeros in path_list and count them */
354 for (i = strlen(path); i > 0; i--) {
355 if (path[i] == ':') {
361 for (i = 0; i < count; i++) {
362 strcpy(result, path_n);
364 strcat(result, name);
365 if (stat(result, &filestat) == 0 && filestat.st_mode & S_IRUSR) {
369 path_n += (strlen(path_n) + 1);
375 static void locate_library_file(ElfW(Ehdr) *ehdr, ElfW(Dyn) *dynamic,
376 int is_suid, struct library *lib)
380 struct stat filestat;
382 /* If this is a fully resolved name, our job is easy */
383 if (stat(lib->name, &filestat) == 0) {
384 lib->path = strdup(lib->name);
388 /* We need some elbow room here. Make some room... */
391 fprintf(stderr, "%s: Out of memory!\n", __func__);
395 /* This function must match the behavior of _dl_load_shared_library
396 * in readelflib1.c or things won't work out as expected... */
398 /* The ABI specifies that RPATH is searched first, so do that now. */
399 path = elf_find_rpath(ehdr, dynamic);
401 search_for_named_library(lib->name, buf, path);
408 /* Next check LD_{ELF_}LIBRARY_PATH if specified and allowed.
409 * Since this app doesn't actually run an executable I will skip
410 * the suid check, and just use LD_{ELF_}LIBRARY_PATH if set */
414 path = getenv("LD_LIBRARY_PATH");
416 search_for_named_library(lib->name, buf, path);
422 #ifdef __LDSO_CACHE_SUPPORT__
423 if (cache_addr != NULL && cache_addr != (caddr_t) - 1) {
425 header_t *header = (header_t *) cache_addr;
426 libentry_t *libent = (libentry_t *) & header[1];
427 char *strs = (char *)&libent[header->nlibs];
429 for (i = 0; i < header->nlibs; i++) {
430 if ((libent[i].flags == LIB_ELF ||
431 libent[i].flags == LIB_ELF_LIBC0 ||
432 libent[i].flags == LIB_ELF_LIBC5) &&
433 strcmp(lib->name, strs + libent[i].sooffset) == 0)
435 lib->path = strdup(strs + libent[i].liboffset);
442 /* Next look for libraries wherever the shared library
443 * loader was installed -- this is usually where we
444 * should find things... */
446 search_for_named_library(lib->name, buf, interp_dir);
453 /* Lastly, search the standard list of paths for the library.
454 This list must exactly match the list in uClibc/ldso/ldso/dl-elf.c */
455 path = UCLIBC_RUNTIME_PREFIX "lib:" UCLIBC_RUNTIME_PREFIX "usr/lib"
456 #ifndef __LDSO_CACHE_SUPPORT__
457 ":" UCLIBC_RUNTIME_PREFIX "usr/X11R6/lib"
460 search_for_named_library(lib->name, buf, path);
465 lib->path = not_found;
469 static int add_library(ElfW(Ehdr) *ehdr, ElfW(Dyn) *dynamic, int is_setuid, char *s)
471 char *tmp, *tmp1, *tmp2;
472 struct library *cur, *newlib = lib_list;
474 if (!s || !strlen(s))
484 /* We add ldso elsewhere */
485 if (interpreter_already_found && (tmp = strrchr(interp_name, '/')) != NULL) {
486 int len = strlen(interp_dir);
487 if (strcmp(s, interp_name + 1 + len) == 0)
491 for (cur = lib_list; cur; cur = cur->next) {
492 /* Check if this library is already in the list */
493 tmp1 = tmp2 = cur->name;
499 if (strcmp(tmp2, s) == 0) {
500 /*printf("find_elf_interpreter is skipping '%s' (already in list)\n", cur->name); */
505 /* Ok, this lib needs to be added to the list */
506 newlib = malloc(sizeof(struct library));
509 newlib->name = malloc(strlen(s) + 1);
510 strcpy(newlib->name, s);
511 newlib->resolved = 0;
515 /* Now try and locate where this library might be living... */
516 locate_library_file(ehdr, dynamic, is_setuid, newlib);
518 /*printf("add_library is adding '%s' to '%s'\n", newlib->name, newlib->path); */
522 for (cur = lib_list; cur->next; cur = cur->next) ; /* nothing */
528 static void find_needed_libraries(ElfW(Ehdr) *ehdr, ElfW(Dyn) *dynamic, int is_setuid)
532 for (dyns = dynamic; byteswap_to_host(dyns->d_tag) != DT_NULL; ++dyns) {
533 if (DT_NEEDED == byteswap_to_host(dyns->d_tag)) {
535 strtab = (char *)elf_find_dynamic(DT_STRTAB, dynamic, ehdr, 0);
536 add_library(ehdr, dynamic, is_setuid, (char *)strtab + byteswap_to_host(dyns->d_un.d_val));
541 static struct library *find_elf_interpreter(ElfW(Ehdr) *ehdr)
545 if (interpreter_already_found == 1)
547 phdr = elf_find_phdr_type(PT_INTERP, ehdr);
549 struct library *cur, *newlib = NULL;
550 char *s = (char *)ehdr + byteswap_to_host(phdr->p_offset);
553 interp_name = strdup(s);
554 interp_dir = strdup(s);
555 tmp = strrchr(interp_dir, '/');
560 interp_dir = interp_name;
568 for (cur = lib_list; cur; cur = cur->next) {
569 /* Check if this library is already in the list */
570 if (strcmp(cur->name, tmp1) == 0) {
571 /*printf("find_elf_interpreter is replacing '%s' (already in list)\n", cur->name); */
574 if (newlib->path != not_found) {
583 newlib = malloc(sizeof(struct library));
586 newlib->name = malloc(strlen(s) + 1);
587 strcpy(newlib->name, s);
588 newlib->path = strdup(newlib->name);
589 newlib->resolved = 1;
593 /*printf("find_elf_interpreter is adding '%s' to '%s'\n", newlib->name, newlib->path); */
597 for (cur = lib_list; cur->next; cur = cur->next) ; /* nothing */
601 interpreter_already_found = 1;
607 /* map the .so, and locate interesting pieces */
609 #warning "There may be two warnings here about vfork() clobbering, ignore them"
611 static int find_dependencies(char *filename)
615 struct library *interp;
617 ElfW(Ehdr) *ehdr = NULL;
618 ElfW(Shdr) *dynsec = NULL;
619 ElfW(Dyn) *dynamic = NULL;
621 if (filename == not_found)
625 fprintf(stderr, "No filename specified.\n");
628 if (!(thefile = fopen(filename, "r"))) {
632 if (fstat(fileno(thefile), &statbuf) < 0) {
638 if ((size_t) statbuf.st_size < sizeof(ElfW(Ehdr)))
641 if (!S_ISREG(statbuf.st_mode))
644 /* mmap the file to make reading stuff from it effortless */
645 ehdr = mmap(0, statbuf.st_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fileno(thefile), 0);
646 if (ehdr == MAP_FAILED) {
648 fprintf(stderr, "mmap(%s) failed: %s\n", filename, strerror(errno));
655 /* Check if this looks like a legit ELF file */
656 if (check_elf_header(ehdr)) {
657 fprintf(stderr, "%s: not an ELF file.\n", filename);
660 /* Check if this is the right kind of ELF file */
661 if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) {
662 fprintf(stderr, "%s: not a dynamic executable\n", filename);
665 if (ehdr->e_type == ET_EXEC || ehdr->e_type == ET_DYN) {
666 if (statbuf.st_mode & S_ISUID)
668 if ((statbuf.st_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
672 fprintf(stderr, "%s: is setuid\n", filename);
675 interpreter_already_found = 0;
676 interp = find_elf_interpreter(ehdr);
678 #ifdef __LDSO_LDD_SUPPORT__
680 && (ehdr->e_type == ET_EXEC || ehdr->e_type == ET_DYN)
681 && ehdr->e_ident[EI_CLASS] == ELFCLASSM
682 && ehdr->e_ident[EI_DATA] == ELFDATAM
683 && ehdr->e_ident[EI_VERSION] == EV_CURRENT
684 && MATCH_MACHINE(ehdr->e_machine))
687 if (stat(interp->path, &st) == 0 && S_ISREG(st.st_mode)) {
690 static const char *const environment[] = {
691 "PATH=/usr/bin:/bin:/usr/sbin:/sbin",
693 "LD_TRACE_LOADED_OBJECTS=1",
697 if ((pid = vfork()) == 0) {
698 /* Cool, it looks like we should be able to actually
699 * run this puppy. Do so now... */
700 execle(filename, filename, NULL, environment);
704 /* Wait till it returns */
705 waitpid(pid, &status, 0);
706 if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
710 /* If the exec failed, we fall through to trying to find
711 * all the needed libraries ourselves by rummaging about
712 * in the ELF headers... */
717 dynsec = elf_find_section_type(SHT_DYNAMIC, ehdr);
719 dynamic = (ElfW(Dyn) *) (byteswap_to_host(dynsec->sh_offset) + (char *)ehdr);
720 find_needed_libraries(ehdr, dynamic, is_suid);
726 int main(int argc, char **argv)
730 char *filename = NULL;
734 fprintf(stderr, "ldd: missing file arguments\n"
735 "Try `ldd --help' for more information.\n");
744 if (strcmp(*argv, "--") == 0) {
749 if (strcmp(*argv, "--help") == 0 || strcmp(*argv, "-h") == 0) {
750 fprintf(stderr, "Usage: ldd [OPTION]... FILE...\n"
751 "\t--help\t\tprint this help and exit\n");
757 fprintf(stderr, "No filename specified.\n");
762 printf("%s:\n", *argv);
767 if (find_dependencies(filename) != 0)
772 /* Keep walking the list till everybody is resolved */
773 for (cur = lib_list; cur; cur = cur->next) {
774 if (cur->resolved == 0 && cur->path) {
776 printf("checking sub-depends for '%s'\n", cur->path);
777 find_dependencies(cur->path);
787 for (cur = lib_list; cur; cur = cur->next) {
789 printf("\t%s => %s (0x00000000)\n", cur->name, cur->path);
791 if (interp_name && interpreter_already_found == 1)
792 printf("\t%s => %s (0x00000000)\n", interp_name, interp_name);
794 printf("\tnot a dynamic executable\n");
796 for (cur = lib_list; cur; cur = cur->next) {
799 if (cur->path && cur->path != not_found) {