diff options
Diffstat (limited to 'linker')
| -rw-r--r-- | linker/dlfcn.c | 12 | ||||
| -rw-r--r-- | linker/linker.c | 132 | ||||
| -rw-r--r-- | linker/linker.h | 2 |
3 files changed, 111 insertions, 35 deletions
diff --git a/linker/dlfcn.c b/linker/dlfcn.c index b54674f..053713c 100644 --- a/linker/dlfcn.c +++ b/linker/dlfcn.c @@ -74,7 +74,7 @@ const char *dlerror(void) void *dlsym(void *handle, const char *symbol) { - unsigned base; + soinfo *found; Elf32_Sym *sym; unsigned bind; @@ -90,19 +90,19 @@ void *dlsym(void *handle, const char *symbol) } if(handle == RTLD_DEFAULT) { - sym = lookup(symbol, &base); + sym = lookup(symbol, &found); } else if(handle == RTLD_NEXT) { - sym = lookup(symbol, &base); + sym = lookup(symbol, &found); } else { - sym = lookup_in_library((soinfo*) handle, symbol); - base = ((soinfo*) handle)->base; + found = (soinfo*)handle; + sym = lookup_in_library(found, symbol); } if(likely(sym != 0)) { bind = ELF32_ST_BIND(sym->st_info); if(likely((bind == STB_GLOBAL) && (sym->st_shndx != 0))) { - unsigned ret = sym->st_value + base; + unsigned ret = sym->st_value + found->base; pthread_mutex_unlock(&dl_lock); return (void*)ret; } diff --git a/linker/linker.c b/linker/linker.c index 27fe9d7..7a1e9a4 100644 --- a/linker/linker.c +++ b/linker/linker.c @@ -51,6 +51,7 @@ #include "ba.h" +#define ALLOW_SYMBOLS_FROM_MAIN 1 #define SO_MAX 96 /* Assume average path length of 64 and max 8 paths */ @@ -86,6 +87,15 @@ static soinfo sopool[SO_MAX]; static soinfo *freelist = NULL; static soinfo *solist = &libdl_info; static soinfo *sonext = &libdl_info; +#if ALLOW_SYMBOLS_FROM_MAIN +static soinfo *somain; /* main process, always the one after libdl_info */ +#endif + +static inline int validate_soinfo(soinfo *si) +{ + return (si >= sopool && si < sopool + SO_MAX) || + si == &libdl_info; +} static char ldpaths_buf[LDPATH_BUFSIZE]; static const char *ldpaths[LDPATH_MAX + 1]; @@ -422,41 +432,92 @@ _do_lookup_in_so(soinfo *si, const char *name, unsigned *elf_hash) return _elf_lookup (si, *elf_hash, name); } -/* This is used by dl_sym() */ +static Elf32_Sym * +_do_lookup(soinfo *si, const char *name, unsigned *base) +{ + unsigned elf_hash = 0; + Elf32_Sym *s; + unsigned *d; + soinfo *lsi = si; + + /* Look for symbols in the local scope first (the object who is + * searching). This happens with C++ templates on i386 for some + * reason. */ + s = _do_lookup_in_so(si, name, &elf_hash); + if(s != NULL) + goto done; + + for(d = si->dynamic; *d; d += 2) { + if(d[0] == DT_NEEDED){ + lsi = (soinfo *)d[1]; + if (!validate_soinfo(lsi)) { + DL_ERR("%5d bad DT_NEEDED pointer in %s", + pid, si->name); + return 0; + } + + DEBUG("%5d %s: looking up %s in %s\n", + pid, si->name, name, lsi->name); + s = _do_lookup_in_so(lsi, name, &elf_hash); + if(s != NULL) + goto done; + } + } + +#if ALLOW_SYMBOLS_FROM_MAIN + /* If we are resolving relocations while dlopen()ing a library, it's OK for + * the library to resolve a symbol that's defined in the executable itself, + * although this is rare and is generally a bad idea. + */ + if (somain) { + lsi = somain; + DEBUG("%5d %s: looking up %s in executable %s\n", + pid, si->name, name, lsi->name); + s = _do_lookup_in_so(lsi, name, &elf_hash); + } +#endif + +done: + if(s != NULL) { + TRACE_TYPE(LOOKUP, "%5d si %s sym %s s->st_value = 0x%08x, " + "found in %s, base = 0x%08x\n", + pid, si->name, name, s->st_value, lsi->name, lsi->base); + *base = lsi->base; + return s; + } + + return 0; +} + +/* This is used by dl_sym(). It performs symbol lookup only within the + specified soinfo object and not in any of its dependencies. + */ Elf32_Sym *lookup_in_library(soinfo *si, const char *name) { unsigned unused = 0; return _do_lookup_in_so(si, name, &unused); } -static Elf32_Sym * -_do_lookup(soinfo *user_si, const char *name, unsigned *base) +/* This is used by dl_sym(). It performs a global symbol lookup. + */ +Elf32_Sym *lookup(const char *name, soinfo **found) { unsigned elf_hash = 0; Elf32_Sym *s = NULL; soinfo *si; - /* Look for symbols in the local scope first (the object who is - * searching). This happens with C++ templates on i386 for some - * reason. */ - if (user_si) { - s = _do_lookup_in_so(user_si, name, &elf_hash); - if (s != NULL) - *base = user_si->base; - } - for(si = solist; (s == NULL) && (si != NULL); si = si->next) { - if((si->flags & FLAG_ERROR) || (si == user_si)) + if(si->flags & FLAG_ERROR) continue; s = _do_lookup_in_so(si, name, &elf_hash); if (s != NULL) { - *base = si->base; + *found = si; break; } } - if (s != NULL) { + if(s != NULL) { TRACE_TYPE(LOOKUP, "%5d %s s->st_value = 0x%08x, " "si->base = 0x%08x\n", pid, name, s->st_value, si->base); return s; @@ -465,12 +526,6 @@ _do_lookup(soinfo *user_si, const char *name, unsigned *base) return 0; } -/* This is used by dl_sym() */ -Elf32_Sym *lookup(const char *name, unsigned *base) -{ - return _do_lookup(NULL, name, base); -} - #if 0 static void dump(soinfo *si) { @@ -1086,7 +1141,10 @@ soinfo *find_library(const char *name) for(si = solist; si != 0; si = si->next){ if(!strcmp(bname, si->name)) { - if(si->flags & FLAG_ERROR) return 0; + if(si->flags & FLAG_ERROR) { + DL_ERR("%5d '%s' failed to load previously", pid, bname); + return NULL; + } if(si->flags & FLAG_LINKED) return si; DL_ERR("OOPS: %5d recursive link to '%s'", pid, si->name); return NULL; @@ -1114,14 +1172,16 @@ unsigned unload_library(soinfo *si) for(d = si->dynamic; *d; d += 2) { if(d[0] == DT_NEEDED){ - TRACE("%5d %s needs to unload %s\n", pid, - si->name, si->strtab + d[1]); - soinfo *lsi = find_library(si->strtab + d[1]); - if(lsi) + soinfo *lsi = (soinfo *)d[1]; + d[1] = 0; + if (validate_soinfo(lsi)) { + TRACE("%5d %s needs to unload %s\n", pid, + si->name, lsi->name); unload_library(lsi); + } else - DL_ERR("%5d could not unload '%s'", - pid, si->strtab + d[1]); + DL_ERR("%5d %s: could not unload dependent library", + pid, si->name); } } @@ -1639,6 +1699,14 @@ static int link_image(soinfo *si, unsigned wr_offset) pid, si->strtab + d[1], si->name, tmp_err_buf); goto fail; } + /* Save the soinfo of the loaded DT_NEEDED library in the payload + of the DT_NEEDED entry itself, so that we can retrieve the + soinfo directly later from the dynamic segment. This is a hack, + but it allows us to map from DT_NEEDED to soinfo efficiently + later on when we resolve relocations, trying to look up a symgol + with dlsym(). + */ + d[1] = (unsigned)lsi; lsi->refcount++; } } @@ -1844,6 +1912,14 @@ unsigned __linker_init(unsigned **elfdata) exit(-1); } +#if ALLOW_SYMBOLS_FROM_MAIN + /* Set somain after we've loaded all the libraries in order to prevent + * linking of symbols back to the main image, which is not set up at that + * point yet. + */ + somain = si; +#endif + #if TIMING gettimeofday(&t1,NULL); PRINT("LINKER TIME: %s: %d microseconds\n", argv[0], (int) ( diff --git a/linker/linker.h b/linker/linker.h index 69042c0..d289c81 100644 --- a/linker/linker.h +++ b/linker/linker.h @@ -203,7 +203,7 @@ extern soinfo libdl_info; soinfo *find_library(const char *name); unsigned unload_library(soinfo *si); Elf32_Sym *lookup_in_library(soinfo *si, const char *name); -Elf32_Sym *lookup(const char *name, unsigned *base); +Elf32_Sym *lookup(const char *name, soinfo **found); const char *linker_get_error(void); #ifdef ANDROID_ARM_LINKER |