/* $OpenBSD: loader.c,v 1.75 2004/05/24 20:24:54 mickey 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 #include #include #include #include #include #include #include #include #include "syscall.h" #include "archdep.h" #include "resolve.h" #include "sod.h" #include "stdlib.h" /* * Local decls. */ static char *_dl_getenv(const char *, char **); static void _dl_unsetenv(const char *, char **); unsigned long _dl_boot(const char **, char **, const long, long *); void _dl_debug_state(void); void _dl_setup_env(char **); void _dl_dtors(void); void _dl_boot_bind(const long, long *, Elf_Dyn *); void _dl_fixup_user_env(void); const char *_dl_progname; int _dl_pagesz; char *_dl_libpath; char *_dl_preload; char *_dl_bindnow; char *_dl_traceld; char *_dl_debug; char *_dl_showmap; char *_dl_norandom; struct r_debug *_dl_debug_map; void _dl_dopreload(char *paths); void _dl_debug_state(void) { /* Debugger stub */ } /* * Routine to walk through all of the objects except the first * (main executable). */ void _dl_run_dtors(elf_object_t *object) { DL_DEB(("doing dtors: [%s]\n", object->load_name)); if (object->dyn.fini) (*object->dyn.fini)(); if (object->next) _dl_run_dtors(object->next); } void _dl_dtors(void) { DL_DEB(("doing dtors\n")); if (_dl_objects->next) _dl_run_dtors(_dl_objects->next); } void _dl_dopreload(char *paths) { char *cp, *dp; elf_object_t *shlib; dp = paths = _dl_strdup(paths); if (dp == NULL) { _dl_printf("preload: out of memory"); _dl_exit(1); } while ((cp = _dl_strsep(&dp, ":")) != NULL) { shlib = _dl_load_shlib(cp, _dl_objects, OBJTYPE_LIB, DL_LAZY|RTLD_GLOBAL); if (shlib == NULL) { _dl_printf("%s: can't load library '%s'\n", _dl_progname, cp); _dl_exit(4); } _dl_add_object(shlib); _dl_link_sub(shlib, _dl_objects); } _dl_free(paths); return; } /* * grab interesting environment variables, zap bad env vars if * issetugid */ char **_dl_so_envp; void _dl_setup_env(char **envp) { /* * Get paths to various things we are going to use. */ _dl_libpath = _dl_getenv("LD_LIBRARY_PATH", envp); _dl_preload = _dl_getenv("LD_PRELOAD", envp); _dl_bindnow = _dl_getenv("LD_BIND_NOW", envp); _dl_traceld = _dl_getenv("LD_TRACE_LOADED_OBJECTS", envp); _dl_debug = _dl_getenv("LD_DEBUG", envp); _dl_norandom = _dl_getenv("LD_NORANDOM", envp); /* * Don't allow someone to change the search paths if he runs * a suid program without credentials high enough. */ if (_dl_issetugid()) { /* Zap paths if s[ug]id... */ if (_dl_libpath) { _dl_libpath = NULL; _dl_unsetenv("LD_LIBRARY_PATH", envp); } if (_dl_preload) { _dl_preload = NULL; _dl_unsetenv("LD_PRELOAD", envp); } if (_dl_bindnow) { _dl_bindnow = NULL; _dl_unsetenv("LD_BIND_NOW", envp); } if (_dl_debug) { _dl_debug = NULL; _dl_unsetenv("LD_DEBUG", envp); } if (_dl_norandom) { _dl_norandom = NULL; _dl_unsetenv("LD_NORANDOM", envp); } } _dl_so_envp = envp; } /* * This is the dynamic loader entrypoint. When entering here, depending * on architecture type, the stack and registers are set up according * to the architectures ABI specification. The first thing required * to do is to dig out all information we need to accomplish our task. */ unsigned long _dl_boot(const char **argv, char **envp, const long loff, long *dl_data) { struct elf_object *exe_obj; /* Pointer to executable object */ struct elf_object *dyn_obj; /* Pointer to executable object */ struct r_debug **map_link; /* Where to put pointer for gdb */ struct r_debug *debug_map; Elf_Dyn *dynp; elf_object_t *dynobj; Elf_Phdr *phdp; char *us = ""; unsigned int i; int libcnt = 0; _dl_setup_env(envp); _dl_progname = argv[0]; if (dl_data[AUX_pagesz] != 0) _dl_pagesz = dl_data[AUX_pagesz]; else _dl_pagesz = 4096; /* * now that GOT and PLT has been relocated, and we know * page size, protect it from modification */ { extern char *__got_start; extern char *__got_end; #ifdef RTLD_PROTECT_PLT extern char *__plt_start; extern char *__plt_end; #endif _dl_mprotect((void *)ELF_TRUNC((long)&__got_start, _dl_pagesz), ELF_ROUND((long)&__got_end,_dl_pagesz) - ELF_TRUNC((long)&__got_start, _dl_pagesz), GOT_PERMS); #ifdef RTLD_PROTECT_PLT /* only for DATA_PLT or BSS_PLT */ _dl_mprotect((void *)ELF_TRUNC((long)&__plt_start, _dl_pagesz), ELF_ROUND((long)&__plt_end,_dl_pagesz) - ELF_TRUNC((long)&__plt_start, _dl_pagesz), PROT_READ|PROT_EXEC); #endif } DL_DEB(("rtld loading: '%s'\n", _dl_progname)); exe_obj = NULL; /* * Examine the user application and set up object information. */ phdp = (Elf_Phdr *)dl_data[AUX_phdr]; for (i = 0; i < dl_data[AUX_phnum]; i++) { if (phdp->p_type == PT_DYNAMIC) { exe_obj = _dl_finalize_object(argv[0], (Elf_Dyn *)phdp->p_vaddr, dl_data, OBJTYPE_EXE, 0, 0); _dl_add_object(exe_obj); } else if (phdp->p_type == PT_INTERP) { us = _dl_strdup((char *)phdp->p_vaddr); } phdp++; } if (_dl_preload != NULL) _dl_dopreload(_dl_preload); /* * Now, pick up and 'load' all libraries required. Start * with the first on the list and then do whatever gets * added along the tour. */ dynobj = _dl_objects; for (dynobj = _dl_objects; dynobj != NULL; dynobj = dynobj->next) { DL_DEB(("examining: '%s'\n", dynobj->load_name)); libcnt = 0; for (dynp = dynobj->load_dyn; dynp->d_tag; dynp++) { if (dynp->d_tag == DT_NEEDED) { libcnt++; } } if ( libcnt != 0) { struct listent { Elf_Dyn *dynp; elf_object_t *dynobj; } *liblist; int *randomlist; liblist = _dl_malloc(libcnt * sizeof(struct listent)); randomlist = _dl_malloc(libcnt * sizeof(int)); if (liblist == NULL) _dl_exit(5); for (dynp = dynobj->load_dyn, i = 0; dynp->d_tag; dynp++) { if (dynp->d_tag == DT_NEEDED) { liblist[i++].dynp = dynp; } } /* Randomize these */ for (i = 0; i < libcnt; i++) randomlist[i] = i; if (!_dl_norandom) for (i = 1; i < libcnt; i++) { unsigned int rnd; int cur; rnd = _dl_random(); rnd = rnd % (i+1); cur = randomlist[rnd]; randomlist[rnd] = randomlist[i]; randomlist[i] = cur; } for (i = 0; i < libcnt; i++) { elf_object_t *depobj; const char *libname; libname = dynobj->dyn.strtab; libname += liblist[randomlist[i]].dynp->d_un.d_val; DL_DEB(("needs: '%s'\n", libname)); depobj = _dl_load_shlib(libname, dynobj, OBJTYPE_LIB, DL_LAZY|RTLD_GLOBAL); if (depobj == 0) { _dl_printf( "%s: can't load library '%s'\n", _dl_progname, libname); _dl_exit(4); } liblist[randomlist[i]].dynobj = depobj; } for (i = 0; i < libcnt; i++) { _dl_add_object(liblist[i].dynobj); _dl_link_sub(liblist[i].dynobj, dynobj); } _dl_free(liblist); } } /* * Now add the dynamic loader itself last in the object list * so we can use the _dl_ code when serving dl.... calls. */ dynp = (Elf_Dyn *)((void *)_DYNAMIC); dyn_obj = _dl_finalize_object(us, dynp, 0, OBJTYPE_LDR, dl_data[AUX_base], loff); _dl_add_object(dyn_obj); dyn_obj->status |= STAT_RELOC_DONE; /* * Everything should be in place now for doing the relocation * and binding. Call _dl_rtld to do the job. Fingers crossed. */ if (_dl_traceld == NULL) _dl_rtld(_dl_objects); if (_dl_debug || _dl_traceld) _dl_show_objects(); DL_DEB(("dynamic loading done.\n")); if (_dl_traceld) _dl_exit(0); _dl_fixup_user_env(); /* * The first object is the executable itself, * it is responsible for running it's own ctors/dtors * thus do NOT run the ctors for the executable, all of * the shared libraries which follow. * Do not run init code if run from ldd. */ if (_dl_objects->next != NULL) { _dl_objects->status |= STAT_INIT_DONE; _dl_call_init(_dl_objects); } /* * Finally make something to help gdb when poking around in the code. */ #ifdef __mips__ map_link = (struct r_debug **)(exe_obj->Dyn.info[DT_MIPS_RLD_MAP - DT_LOPROC + DT_NUM]); #else map_link = NULL; for (dynp = exe_obj->load_dyn; dynp->d_tag; dynp++) { if (dynp->d_tag == DT_DEBUG) { map_link = (struct r_debug **)&dynp->d_un.d_ptr; break; } } if (dynp->d_tag != DT_DEBUG) DL_DEB(("failed to mark DTDEBUG\n")); #endif if (map_link) { debug_map = (struct r_debug *)_dl_malloc(sizeof(*debug_map)); debug_map->r_version = 1; debug_map->r_map = (struct link_map *)_dl_objects; debug_map->r_brk = (Elf_Addr)_dl_debug_state; debug_map->r_state = RT_CONSISTENT; debug_map->r_ldbase = loff; _dl_debug_map = debug_map; *map_link = _dl_debug_map; } _dl_debug_state(); /* * Schedule a routine to be run at shutdown, by using atexit. * Cannot call atexit directly from ld.so? * Do not schedule destructors if run from ldd. */ { const Elf_Sym *sym; Elf_Addr ooff; sym = NULL; ooff = _dl_find_symbol("atexit", _dl_objects, &sym, SYM_SEARCH_ALL|SYM_NOWARNNOTFOUND|SYM_PLT, 0, dyn_obj); if (sym == NULL) _dl_printf("cannot find atexit, destructors will not be run!\n"); else (*(void (*)(Elf_Addr))(sym->st_value + ooff)) ((Elf_Addr)_dl_dtors); } DL_DEB(("entry point: 0x%lx\n", dl_data[AUX_entry])); /* * Return the entry point. */ return(dl_data[AUX_entry]); } void _dl_boot_bind(const long sp, long *dl_data, Elf_Dyn *dynamicp) { struct elf_object dynld; /* Resolver data for the loader */ AuxInfo *auxstack; long *stack; Elf_Dyn *dynp; int n, argc; char **argv, **envp; long loff; /* * Scan argument and environment vectors. Find dynamic * data vector put after them. */ stack = (long *)sp; argc = *stack++; argv = (char **)stack; envp = &argv[argc + 1]; stack = (long *)envp; while (*stack++ != NULL) ; /* * Zero out dl_data. */ for (n = 0; n < AUX_entry; n++) dl_data[n] = 0; /* * Dig out auxiliary data set up by exec call. Move all known * tags to an indexed local table for easy access. */ for (auxstack = (AuxInfo *)stack; auxstack->au_id != AUX_null; auxstack++) { if (auxstack->au_id > AUX_entry) continue; dl_data[auxstack->au_id] = auxstack->au_v; } loff = dl_data[AUX_base]; /* XXX assumes linked at 0x0 */ /* * We need to do 'selfreloc' in case the code weren't * loaded at the address it was linked to. * * Scan the DYNAMIC section for the loader. * Cache the data for easier access. */ #if defined(__alpha__) dynp = (Elf_Dyn *)((long)_DYNAMIC); #elif defined(__sparc__) || defined(__sparc64__) || defined(__powerpc__) dynp = dynamicp; #else dynp = (Elf_Dyn *)((long)_DYNAMIC + loff); #endif while (dynp != NULL && dynp->d_tag != DT_NULL) { if (dynp->d_tag < DT_NUM) dynld.Dyn.info[dynp->d_tag] = dynp->d_un.d_val; else if (dynp->d_tag >= DT_LOPROC && dynp->d_tag < DT_LOPROC + DT_PROCNUM) dynld.Dyn.info[dynp->d_tag - DT_LOPROC + DT_NUM] = dynp->d_un.d_val; if (dynp->d_tag == DT_TEXTREL) dynld.dyn.textrel = 1; dynp++; } /* * Do the 'bootstrap relocation'. This is really only needed if * the code was loaded at another location than it was linked to. * We don't do undefined symbols resolving (to difficult..) */ /* "relocate" dyn.X values if they represent addresses */ { int i, val; /* must be code, not pic data */ int table[20]; i = 0; table[i++] = DT_PLTGOT; table[i++] = DT_HASH; table[i++] = DT_STRTAB; table[i++] = DT_SYMTAB; table[i++] = DT_RELA; table[i++] = DT_INIT; table[i++] = DT_FINI; table[i++] = DT_REL; table[i++] = DT_JMPREL; /* other processors insert their extras here */ table[i++] = DT_NULL; for (i = 0; table[i] != DT_NULL; i++) { val = table[i]; if (val > DT_HIPROC) /* ??? */ continue; if (val > DT_LOPROC) val -= DT_LOPROC + DT_NUM; if (dynld.Dyn.info[val] != 0) dynld.Dyn.info[val] += loff; } } { u_int32_t rs; Elf_Rel *rp; int i; rp = (Elf_Rel *)(dynld.Dyn.info[DT_REL]); rs = dynld.dyn.relsz; for (i = 0; i < rs; i += sizeof (Elf_Rel)) { Elf_Addr *ra; const Elf_Sym *sp; sp = dynld.dyn.symtab; sp += ELF_R_SYM(rp->r_info); if (ELF_R_SYM(rp->r_info) && sp->st_value == 0) { #if 0 /* cannot printf in this function */ _dl_wrstderr("Dynamic loader failure: self bootstrapping impossible.\n"); _dl_wrstderr("Undefined symbol: "); _dl_wrstderr((char *)dynld.dyn.strtab + sp->st_name); #endif _dl_exit(5); } ra = (Elf_Addr *)(rp->r_offset + loff); RELOC_REL(rp, sp, ra, loff); rp++; } } for (n = 0; n < 2; n++) { unsigned long rs; Elf_RelA *rp; int i; switch (n) { case 0: rp = (Elf_RelA *)(dynld.Dyn.info[DT_JMPREL]); rs = dynld.dyn.pltrelsz; break; case 1: rp = (Elf_RelA *)(dynld.Dyn.info[DT_RELA]); rs = dynld.dyn.relasz; break; default: rp = NULL; rs = 0; } for (i = 0; i < rs; i += sizeof (Elf_RelA)) { Elf_Addr *ra; const Elf_Sym *sp; sp = dynld.dyn.symtab; sp += ELF_R_SYM(rp->r_info); if (ELF_R_SYM(rp->r_info) && sp->st_value == 0) { #if 0 _dl_wrstderr("Dynamic loader failure: self bootstrapping impossible.\n"); _dl_wrstderr("Undefined symbol: "); _dl_wrstderr((char *)dynld.dyn.strtab + sp->st_name); #endif _dl_exit(6); } ra = (Elf_Addr *)(rp->r_offset + loff); RELOC_RELA(rp, sp, ra, loff); rp++; } } RELOC_GOT(&dynld, loff); /* * we have been fully relocated here, so most things no longer * need the loff adjustment */ } #define DL_SM_SYMBUF_CNT 512 sym_cache _dl_sm_symcache_buffer[DL_SM_SYMBUF_CNT]; void _dl_rtld(elf_object_t *object) { size_t sz; if (object->next) _dl_rtld(object->next); if (object->status & STAT_RELOC_DONE) return; sz = 0; if (object->nchains < DL_SM_SYMBUF_CNT) { _dl_symcache = _dl_sm_symcache_buffer; DL_DEB(("using static buffer for %d entries\n", object->nchains)); _dl_memset(_dl_symcache, 0, sizeof (sym_cache) * object->nchains); } else { sz = ELF_ROUND(sizeof (sym_cache) * object->nchains, _dl_pagesz); DL_DEB(("allocating symcache sz %x with mmap\n", sz)); _dl_symcache = (void *)_dl_mmap(0, sz, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0); if (_dl_symcache == (void *)MAP_FAILED) { sz = 0; _dl_symcache = NULL; } } /* * Do relocation information first, then GOT. */ _dl_md_reloc(object, DT_REL, DT_RELSZ); _dl_md_reloc(object, DT_RELA, DT_RELASZ); _dl_md_reloc_got(object, !(_dl_bindnow || object->dyn.bind_now)); if (_dl_symcache != NULL) { if (sz != 0) _dl_munmap( _dl_symcache, sz); _dl_symcache = NULL; } object->status |= STAT_RELOC_DONE; } void _dl_call_init(elf_object_t *object) { struct dep_node *n; for (n = object->first_child; n; n = n->next_sibling) { if (n->data->status & STAT_INIT_DONE) continue; _dl_call_init(n->data); } if (object->status & STAT_INIT_DONE) return; DL_DEB(("doing ctors: [%s]\n", object->load_name)); if (object->dyn.init) (*object->dyn.init)(); /* What about loops? */ object->status |= STAT_INIT_DONE; } static char * _dl_getenv(const char *var, char **env) { const char *ep; while ((ep = *env++)) { const char *vp = var; while (*vp && *vp == *ep) { vp++; ep++; } if (*vp == '\0' && *ep++ == '=') return((char *)ep); } return(NULL); } static void _dl_unsetenv(const char *var, char **env) { char *ep; while ((ep = *env)) { const char *vp = var; while (*vp && *vp == *ep) { vp++; ep++; } if (*vp == '\0' && *ep++ == '=') { char **P; for (P = env;; ++P) if (!(*P = *(P + 1))) break; } env++; } } /* * _dl_fixup_user_env() * * Set the user environment so that programs can use the environment * while running constructors. Specifically, MALLOC_OPTIONS= for malloc() */ void _dl_fixup_user_env(void) { const Elf_Sym *sym; Elf_Addr ooff; struct elf_object dummy_obj; dummy_obj.dyn.symbolic = 0; dummy_obj.load_name = "ld.so"; sym = NULL; ooff = _dl_find_symbol("environ", _dl_objects, &sym, SYM_SEARCH_ALL|SYM_NOWARNNOTFOUND|SYM_PLT, 0, &dummy_obj); if (sym != NULL) *((char ***)(sym->st_value + ooff)) = _dl_so_envp; }