| /* |
| * Copyright (C) 2008, 2009 The Android Open Source Project |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * 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 COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "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 |
| * COPYRIGHT OWNER OR CONTRIBUTORS 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. |
| */ |
| |
| #include <dlfcn.h> |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <linux/auxvec.h> |
| #include <pthread.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <sys/atomics.h> |
| #include <sys/mman.h> |
| #include <sys/stat.h> |
| #include <unistd.h> |
| |
| // Private C library headers. |
| #include <private/bionic_tls.h> |
| #include <private/KernelArgumentBlock.h> |
| #include <private/ScopedPthreadMutexLocker.h> |
| |
| #include "linker.h" |
| #include "linker_debug.h" |
| #include "linker_environ.h" |
| #include "linker_phdr.h" |
| |
| /* Assume average path length of 64 and max 8 paths */ |
| #define LDPATH_BUFSIZE 512 |
| #define LDPATH_MAX 8 |
| |
| #define LDPRELOAD_BUFSIZE 512 |
| #define LDPRELOAD_MAX 8 |
| |
| /* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<< |
| * |
| * Do NOT use malloc() and friends or pthread_*() code here. |
| * Don't use printf() either; it's caused mysterious memory |
| * corruption in the past. |
| * The linker runs before we bring up libc and it's easiest |
| * to make sure it does not depend on any complex libc features |
| * |
| * open issues / todo: |
| * |
| * - are we doing everything we should for ARM_COPY relocations? |
| * - cleaner error reporting |
| * - after linking, set as much stuff as possible to READONLY |
| * and NOEXEC |
| */ |
| |
| static bool soinfo_link_image(soinfo* si); |
| |
| // We can't use malloc(3) in the dynamic linker. We use a linked list of anonymous |
| // maps, each a single page in size. The pages are broken up into as many struct soinfo |
| // objects as will fit, and they're all threaded together on a free list. |
| #define SOINFO_PER_POOL ((PAGE_SIZE - sizeof(soinfo_pool_t*)) / sizeof(soinfo)) |
| struct soinfo_pool_t { |
| soinfo_pool_t* next; |
| soinfo info[SOINFO_PER_POOL]; |
| }; |
| static struct soinfo_pool_t* gSoInfoPools = NULL; |
| static soinfo* gSoInfoFreeList = NULL; |
| |
| static soinfo* solist = &libdl_info; |
| static soinfo* sonext = &libdl_info; |
| static soinfo* somain; /* main process, always the one after libdl_info */ |
| |
| static const char* const gSoPaths[] = { |
| "/vendor/lib", |
| "/system/lib", |
| NULL |
| }; |
| |
| static char gLdPathsBuffer[LDPATH_BUFSIZE]; |
| static const char* gLdPaths[LDPATH_MAX + 1]; |
| |
| static char gLdPreloadsBuffer[LDPRELOAD_BUFSIZE]; |
| static const char* gLdPreloadNames[LDPRELOAD_MAX + 1]; |
| |
| static soinfo* gLdPreloads[LDPRELOAD_MAX + 1]; |
| |
| __LIBC_HIDDEN__ int gLdDebugVerbosity; |
| |
| __LIBC_HIDDEN__ abort_msg_t* gAbortMessage = NULL; // For debuggerd. |
| |
| enum RelocationKind { |
| kRelocAbsolute = 0, |
| kRelocRelative, |
| kRelocCopy, |
| kRelocSymbol, |
| kRelocMax |
| }; |
| |
| #if STATS |
| struct linker_stats_t { |
| int count[kRelocMax]; |
| }; |
| |
| static linker_stats_t linker_stats; |
| |
| static void count_relocation(RelocationKind kind) { |
| ++linker_stats.count[kind]; |
| } |
| #else |
| static void count_relocation(RelocationKind) { |
| } |
| #endif |
| |
| #if COUNT_PAGES |
| static unsigned bitmask[4096]; |
| #define MARK(offset) \ |
| do { \ |
| bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \ |
| } while(0) |
| #else |
| #define MARK(x) do {} while (0) |
| #endif |
| |
| // You shouldn't try to call memory-allocating functions in the dynamic linker. |
| // Guard against the most obvious ones. |
| #define DISALLOW_ALLOCATION(return_type, name, ...) \ |
| return_type name __VA_ARGS__ \ |
| { \ |
| const char* msg = "ERROR: " #name " called from the dynamic linker!\n"; \ |
| __libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg); \ |
| write(2, msg, strlen(msg)); \ |
| abort(); \ |
| } |
| #define UNUSED __attribute__((unused)) |
| DISALLOW_ALLOCATION(void*, malloc, (size_t u UNUSED)); |
| DISALLOW_ALLOCATION(void, free, (void* u UNUSED)); |
| DISALLOW_ALLOCATION(void*, realloc, (void* u1 UNUSED, size_t u2 UNUSED)); |
| DISALLOW_ALLOCATION(void*, calloc, (size_t u1 UNUSED, size_t u2 UNUSED)); |
| |
| static char tmp_err_buf[768]; |
| static char __linker_dl_err_buf[768]; |
| |
| char* linker_get_error_buffer() { |
| return &__linker_dl_err_buf[0]; |
| } |
| |
| size_t linker_get_error_buffer_size() { |
| return sizeof(__linker_dl_err_buf); |
| } |
| |
| /* |
| * This function is an empty stub where GDB locates a breakpoint to get notified |
| * about linker activity. |
| */ |
| extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); |
| |
| static r_debug _r_debug = {1, NULL, &rtld_db_dlactivity, RT_CONSISTENT, 0}; |
| static link_map_t* r_debug_tail = 0; |
| |
| static pthread_mutex_t gDebugMutex = PTHREAD_MUTEX_INITIALIZER; |
| |
| static void insert_soinfo_into_debug_map(soinfo * info) { |
| // Copy the necessary fields into the debug structure. |
| link_map_t* map = &(info->link_map); |
| map->l_addr = info->base; |
| map->l_name = (char*) info->name; |
| map->l_ld = (uintptr_t)info->dynamic; |
| |
| /* Stick the new library at the end of the list. |
| * gdb tends to care more about libc than it does |
| * about leaf libraries, and ordering it this way |
| * reduces the back-and-forth over the wire. |
| */ |
| if (r_debug_tail) { |
| r_debug_tail->l_next = map; |
| map->l_prev = r_debug_tail; |
| map->l_next = 0; |
| } else { |
| _r_debug.r_map = map; |
| map->l_prev = 0; |
| map->l_next = 0; |
| } |
| r_debug_tail = map; |
| } |
| |
| static void remove_soinfo_from_debug_map(soinfo* info) { |
| link_map_t* map = &(info->link_map); |
| |
| if (r_debug_tail == map) { |
| r_debug_tail = map->l_prev; |
| } |
| |
| if (map->l_prev) { |
| map->l_prev->l_next = map->l_next; |
| } |
| if (map->l_next) { |
| map->l_next->l_prev = map->l_prev; |
| } |
| } |
| |
| static void notify_gdb_of_load(soinfo* info) { |
| if (info->flags & FLAG_EXE) { |
| // GDB already knows about the main executable |
| return; |
| } |
| |
| ScopedPthreadMutexLocker locker(&gDebugMutex); |
| |
| _r_debug.r_state = RT_ADD; |
| rtld_db_dlactivity(); |
| |
| insert_soinfo_into_debug_map(info); |
| |
| _r_debug.r_state = RT_CONSISTENT; |
| rtld_db_dlactivity(); |
| } |
| |
| static void notify_gdb_of_unload(soinfo* info) { |
| if (info->flags & FLAG_EXE) { |
| // GDB already knows about the main executable |
| return; |
| } |
| |
| ScopedPthreadMutexLocker locker(&gDebugMutex); |
| |
| _r_debug.r_state = RT_DELETE; |
| rtld_db_dlactivity(); |
| |
| remove_soinfo_from_debug_map(info); |
| |
| _r_debug.r_state = RT_CONSISTENT; |
| rtld_db_dlactivity(); |
| } |
| |
| void notify_gdb_of_libraries() { |
| _r_debug.r_state = RT_ADD; |
| rtld_db_dlactivity(); |
| _r_debug.r_state = RT_CONSISTENT; |
| rtld_db_dlactivity(); |
| } |
| |
| static bool ensure_free_list_non_empty() { |
| if (gSoInfoFreeList != NULL) { |
| return true; |
| } |
| |
| // Allocate a new pool. |
| soinfo_pool_t* pool = reinterpret_cast<soinfo_pool_t*>(mmap(NULL, sizeof(*pool), |
| PROT_READ|PROT_WRITE, |
| MAP_PRIVATE|MAP_ANONYMOUS, 0, 0)); |
| if (pool == MAP_FAILED) { |
| return false; |
| } |
| |
| // Add the pool to our list of pools. |
| pool->next = gSoInfoPools; |
| gSoInfoPools = pool; |
| |
| // Chain the entries in the new pool onto the free list. |
| gSoInfoFreeList = &pool->info[0]; |
| soinfo* next = NULL; |
| for (int i = SOINFO_PER_POOL - 1; i >= 0; --i) { |
| pool->info[i].next = next; |
| next = &pool->info[i]; |
| } |
| |
| return true; |
| } |
| |
| static void set_soinfo_pool_protection(int protection) { |
| for (soinfo_pool_t* p = gSoInfoPools; p != NULL; p = p->next) { |
| if (mprotect(p, sizeof(*p), protection) == -1) { |
| abort(); // Can't happen. |
| } |
| } |
| } |
| |
| static soinfo* soinfo_alloc(const char* name) { |
| if (strlen(name) >= SOINFO_NAME_LEN) { |
| DL_ERR("library name \"%s\" too long", name); |
| return NULL; |
| } |
| |
| if (!ensure_free_list_non_empty()) { |
| DL_ERR("out of memory when loading \"%s\"", name); |
| return NULL; |
| } |
| |
| // Take the head element off the free list. |
| soinfo* si = gSoInfoFreeList; |
| gSoInfoFreeList = gSoInfoFreeList->next; |
| |
| // Initialize the new element. |
| memset(si, 0, sizeof(soinfo)); |
| strlcpy(si->name, name, sizeof(si->name)); |
| sonext->next = si; |
| sonext = si; |
| |
| TRACE("name %s: allocated soinfo @ %p", name, si); |
| return si; |
| } |
| |
| static void soinfo_free(soinfo* si) |
| { |
| if (si == NULL) { |
| return; |
| } |
| |
| soinfo *prev = NULL, *trav; |
| |
| TRACE("name %s: freeing soinfo @ %p", si->name, si); |
| |
| for (trav = solist; trav != NULL; trav = trav->next) { |
| if (trav == si) |
| break; |
| prev = trav; |
| } |
| if (trav == NULL) { |
| /* si was not in solist */ |
| DL_ERR("name \"%s\" is not in solist!", si->name); |
| return; |
| } |
| |
| /* prev will never be NULL, because the first entry in solist is |
| always the static libdl_info. |
| */ |
| prev->next = si->next; |
| if (si == sonext) { |
| sonext = prev; |
| } |
| si->next = gSoInfoFreeList; |
| gSoInfoFreeList = si; |
| } |
| |
| |
| static void parse_path(const char* path, const char* delimiters, |
| const char** array, char* buf, size_t buf_size, size_t max_count) { |
| if (path == NULL) { |
| return; |
| } |
| |
| size_t len = strlcpy(buf, path, buf_size); |
| |
| size_t i = 0; |
| char* buf_p = buf; |
| while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { |
| if (*array[i] != '\0') { |
| ++i; |
| } |
| } |
| |
| // Forget the last path if we had to truncate; this occurs if the 2nd to |
| // last char isn't '\0' (i.e. wasn't originally a delimiter). |
| if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { |
| array[i - 1] = NULL; |
| } else { |
| array[i] = NULL; |
| } |
| } |
| |
| static void parse_LD_LIBRARY_PATH(const char* path) { |
| parse_path(path, ":", gLdPaths, |
| gLdPathsBuffer, sizeof(gLdPathsBuffer), LDPATH_MAX); |
| } |
| |
| static void parse_LD_PRELOAD(const char* path) { |
| // We have historically supported ':' as well as ' ' in LD_PRELOAD. |
| parse_path(path, " :", gLdPreloadNames, |
| gLdPreloadsBuffer, sizeof(gLdPreloadsBuffer), LDPRELOAD_MAX); |
| } |
| |
| #ifdef ANDROID_ARM_LINKER |
| |
| /* For a given PC, find the .so that it belongs to. |
| * Returns the base address of the .ARM.exidx section |
| * for that .so, and the number of 8-byte entries |
| * in that section (via *pcount). |
| * |
| * Intended to be called by libc's __gnu_Unwind_Find_exidx(). |
| * |
| * This function is exposed via dlfcn.cpp and libdl.so. |
| */ |
| _Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount) |
| { |
| soinfo *si; |
| unsigned addr = (unsigned)pc; |
| |
| for (si = solist; si != 0; si = si->next){ |
| if ((addr >= si->base) && (addr < (si->base + si->size))) { |
| *pcount = si->ARM_exidx_count; |
| return (_Unwind_Ptr)si->ARM_exidx; |
| } |
| } |
| *pcount = 0; |
| return NULL; |
| } |
| |
| #elif defined(ANDROID_X86_LINKER) || defined(ANDROID_MIPS_LINKER) |
| |
| /* Here, we only have to provide a callback to iterate across all the |
| * loaded libraries. gcc_eh does the rest. */ |
| int |
| dl_iterate_phdr(int (*cb)(dl_phdr_info *info, size_t size, void *data), |
| void *data) |
| { |
| int rv = 0; |
| for (soinfo* si = solist; si != NULL; si = si->next) { |
| dl_phdr_info dl_info; |
| dl_info.dlpi_addr = si->link_map.l_addr; |
| dl_info.dlpi_name = si->link_map.l_name; |
| dl_info.dlpi_phdr = si->phdr; |
| dl_info.dlpi_phnum = si->phnum; |
| rv = cb(&dl_info, sizeof(dl_phdr_info), data); |
| if (rv != 0) { |
| break; |
| } |
| } |
| return rv; |
| } |
| |
| #endif |
| |
| static Elf32_Sym* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) { |
| Elf32_Sym* symtab = si->symtab; |
| const char* strtab = si->strtab; |
| |
| TRACE_TYPE(LOOKUP, "SEARCH %s in %s@0x%08x %08x %d", |
| name, si->name, si->base, hash, hash % si->nbucket); |
| |
| for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { |
| Elf32_Sym* s = symtab + n; |
| if (strcmp(strtab + s->st_name, name)) continue; |
| |
| /* only concern ourselves with global and weak symbol definitions */ |
| switch(ELF32_ST_BIND(s->st_info)){ |
| case STB_GLOBAL: |
| case STB_WEAK: |
| if (s->st_shndx == SHN_UNDEF) { |
| continue; |
| } |
| |
| TRACE_TYPE(LOOKUP, "FOUND %s in %s (%08x) %d", |
| name, si->name, s->st_value, s->st_size); |
| return s; |
| } |
| } |
| |
| return NULL; |
| } |
| |
| static unsigned elfhash(const char* _name) { |
| const unsigned char* name = (const unsigned char*) _name; |
| unsigned h = 0, g; |
| |
| while(*name) { |
| h = (h << 4) + *name++; |
| g = h & 0xf0000000; |
| h ^= g; |
| h ^= g >> 24; |
| } |
| return h; |
| } |
| |
| static Elf32_Sym* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { |
| unsigned elf_hash = elfhash(name); |
| Elf32_Sym* s = NULL; |
| |
| if (si != NULL && somain != NULL) { |
| |
| /* |
| * Local scope is executable scope. Just start looking into it right away |
| * for the shortcut. |
| */ |
| |
| if (si == somain) { |
| s = soinfo_elf_lookup(si, elf_hash, name); |
| if (s != NULL) { |
| *lsi = si; |
| goto done; |
| } |
| } else { |
| /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ |
| |
| /* |
| * If this object was built with symbolic relocations disabled, the |
| * first place to look to resolve external references is the main |
| * executable. |
| */ |
| |
| if (!si->has_DT_SYMBOLIC) { |
| DEBUG("%s: looking up %s in executable %s", |
| si->name, name, somain->name); |
| s = soinfo_elf_lookup(somain, elf_hash, name); |
| if (s != NULL) { |
| *lsi = somain; |
| goto done; |
| } |
| } |
| |
| /* Look for symbols in the local scope (the object who is |
| * searching). This happens with C++ templates on i386 for some |
| * reason. |
| * |
| * Notes on weak symbols: |
| * The ELF specs are ambiguous about treatment of weak definitions in |
| * dynamic linking. Some systems return the first definition found |
| * and some the first non-weak definition. This is system dependent. |
| * Here we return the first definition found for simplicity. */ |
| |
| s = soinfo_elf_lookup(si, elf_hash, name); |
| if (s != NULL) { |
| *lsi = si; |
| goto done; |
| } |
| |
| /* |
| * If this object was built with -Bsymbolic and symbol is not found |
| * in the local scope, try to find the symbol in the main executable. |
| */ |
| |
| if (si->has_DT_SYMBOLIC) { |
| DEBUG("%s: looking up %s in executable %s after local scope", |
| si->name, name, somain->name); |
| s = soinfo_elf_lookup(somain, elf_hash, name); |
| if (s != NULL) { |
| *lsi = somain; |
| goto done; |
| } |
| } |
| } |
| } |
| |
| /* Next, look for it in the preloads list */ |
| for (int i = 0; gLdPreloads[i] != NULL; i++) { |
| s = soinfo_elf_lookup(gLdPreloads[i], elf_hash, name); |
| if (s != NULL) { |
| *lsi = gLdPreloads[i]; |
| goto done; |
| } |
| } |
| |
| for (int i = 0; needed[i] != NULL; i++) { |
| DEBUG("%s: looking up %s in %s", |
| si->name, name, needed[i]->name); |
| s = soinfo_elf_lookup(needed[i], elf_hash, name); |
| if (s != NULL) { |
| *lsi = needed[i]; |
| goto done; |
| } |
| } |
| |
| done: |
| if (s != NULL) { |
| TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = 0x%08x, " |
| "found in %s, base = 0x%08x, load bias = 0x%08x", |
| si->name, name, s->st_value, |
| (*lsi)->name, (*lsi)->base, (*lsi)->load_bias); |
| return s; |
| } |
| |
| return NULL; |
| } |
| |
| /* This is used by dlsym(3). It performs symbol lookup only within the |
| specified soinfo object and not in any of its dependencies. |
| |
| TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says |
| that it should do a breadth first search through the dependency |
| tree. This agrees with the ELF spec (aka System V Application |
| Binary Interface) where in Chapter 5 it discuss resolving "Shared |
| Object Dependencies" in breadth first search order. |
| */ |
| Elf32_Sym* dlsym_handle_lookup(soinfo* si, const char* name) |
| { |
| return soinfo_elf_lookup(si, elfhash(name), name); |
| } |
| |
| /* This is used by dlsym(3) to performs a global symbol lookup. If the |
| start value is null (for RTLD_DEFAULT), the search starts at the |
| beginning of the global solist. Otherwise the search starts at the |
| specified soinfo (for RTLD_NEXT). |
| */ |
| Elf32_Sym* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) { |
| unsigned elf_hash = elfhash(name); |
| |
| if (start == NULL) { |
| start = solist; |
| } |
| |
| Elf32_Sym* s = NULL; |
| for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { |
| s = soinfo_elf_lookup(si, elf_hash, name); |
| if (s != NULL) { |
| *found = si; |
| break; |
| } |
| } |
| |
| if (s != NULL) { |
| TRACE_TYPE(LOOKUP, "%s s->st_value = 0x%08x, found->base = 0x%08x", |
| name, s->st_value, (*found)->base); |
| } |
| |
| return s; |
| } |
| |
| soinfo* find_containing_library(const void* p) { |
| Elf32_Addr address = reinterpret_cast<Elf32_Addr>(p); |
| for (soinfo* si = solist; si != NULL; si = si->next) { |
| if (address >= si->base && address - si->base < si->size) { |
| return si; |
| } |
| } |
| return NULL; |
| } |
| |
| Elf32_Sym* dladdr_find_symbol(soinfo* si, const void* addr) { |
| Elf32_Addr soaddr = reinterpret_cast<Elf32_Addr>(addr) - si->base; |
| |
| // Search the library's symbol table for any defined symbol which |
| // contains this address. |
| for (size_t i = 0; i < si->nchain; ++i) { |
| Elf32_Sym* sym = &si->symtab[i]; |
| if (sym->st_shndx != SHN_UNDEF && |
| soaddr >= sym->st_value && |
| soaddr < sym->st_value + sym->st_size) { |
| return sym; |
| } |
| } |
| |
| return NULL; |
| } |
| |
| #if 0 |
| static void dump(soinfo* si) |
| { |
| Elf32_Sym* s = si->symtab; |
| for (unsigned n = 0; n < si->nchain; n++) { |
| TRACE("%04d> %08x: %02x %04x %08x %08x %s", n, s, |
| s->st_info, s->st_shndx, s->st_value, s->st_size, |
| si->strtab + s->st_name); |
| s++; |
| } |
| } |
| #endif |
| |
| static int open_library_on_path(const char* name, const char* const paths[]) { |
| char buf[512]; |
| for (size_t i = 0; paths[i] != NULL; ++i) { |
| int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); |
| if (n < 0 || n >= static_cast<int>(sizeof(buf))) { |
| PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); |
| continue; |
| } |
| int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); |
| if (fd != -1) { |
| return fd; |
| } |
| } |
| return -1; |
| } |
| |
| static int open_library(const char* name) { |
| TRACE("[ opening %s ]", name); |
| |
| // If the name contains a slash, we should attempt to open it directly and not search the paths. |
| if (strchr(name, '/') != NULL) { |
| int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); |
| if (fd != -1) { |
| return fd; |
| } |
| // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. |
| } |
| |
| // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. |
| int fd = open_library_on_path(name, gLdPaths); |
| if (fd == -1) { |
| fd = open_library_on_path(name, gSoPaths); |
| } |
| return fd; |
| } |
| |
| static soinfo* load_library(const char* name) { |
| // Open the file. |
| int fd = open_library(name); |
| if (fd == -1) { |
| DL_ERR("library \"%s\" not found", name); |
| return NULL; |
| } |
| |
| // Read the ELF header and load the segments. |
| ElfReader elf_reader(name, fd); |
| if (!elf_reader.Load()) { |
| return NULL; |
| } |
| |
| const char* bname = strrchr(name, '/'); |
| soinfo* si = soinfo_alloc(bname ? bname + 1 : name); |
| if (si == NULL) { |
| return NULL; |
| } |
| si->base = elf_reader.load_start(); |
| si->size = elf_reader.load_size(); |
| si->load_bias = elf_reader.load_bias(); |
| si->flags = 0; |
| si->entry = 0; |
| si->dynamic = NULL; |
| si->phnum = elf_reader.phdr_count(); |
| si->phdr = elf_reader.loaded_phdr(); |
| return si; |
| } |
| |
| static soinfo *find_loaded_library(const char *name) |
| { |
| soinfo *si; |
| const char *bname; |
| |
| // TODO: don't use basename only for determining libraries |
| // http://code.google.com/p/android/issues/detail?id=6670 |
| |
| bname = strrchr(name, '/'); |
| bname = bname ? bname + 1 : name; |
| |
| for (si = solist; si != NULL; si = si->next) { |
| if (!strcmp(bname, si->name)) { |
| return si; |
| } |
| } |
| return NULL; |
| } |
| |
| static soinfo* find_library_internal(const char* name) { |
| if (name == NULL) { |
| return somain; |
| } |
| |
| soinfo* si = find_loaded_library(name); |
| if (si != NULL) { |
| if (si->flags & FLAG_LINKED) { |
| return si; |
| } |
| DL_ERR("OOPS: recursive link to \"%s\"", si->name); |
| return NULL; |
| } |
| |
| TRACE("[ '%s' has not been loaded yet. Locating...]", name); |
| si = load_library(name); |
| if (si == NULL) { |
| return NULL; |
| } |
| |
| // At this point we know that whatever is loaded @ base is a valid ELF |
| // shared library whose segments are properly mapped in. |
| TRACE("[ init_library base=0x%08x sz=0x%08x name='%s' ]", |
| si->base, si->size, si->name); |
| |
| if (!soinfo_link_image(si)) { |
| munmap(reinterpret_cast<void*>(si->base), si->size); |
| soinfo_free(si); |
| return NULL; |
| } |
| |
| return si; |
| } |
| |
| static soinfo* find_library(const char* name) { |
| soinfo* si = find_library_internal(name); |
| if (si != NULL) { |
| si->ref_count++; |
| } |
| return si; |
| } |
| |
| static int soinfo_unload(soinfo* si) { |
| if (si->ref_count == 1) { |
| TRACE("unloading '%s'", si->name); |
| si->CallDestructors(); |
| |
| for (Elf32_Dyn* d = si->dynamic; d->d_tag != DT_NULL; ++d) { |
| if (d->d_tag == DT_NEEDED) { |
| const char* library_name = si->strtab + d->d_un.d_val; |
| TRACE("%s needs to unload %s", si->name, library_name); |
| soinfo_unload(find_loaded_library(library_name)); |
| } |
| } |
| |
| munmap(reinterpret_cast<void*>(si->base), si->size); |
| notify_gdb_of_unload(si); |
| soinfo_free(si); |
| si->ref_count = 0; |
| } else { |
| si->ref_count--; |
| TRACE("not unloading '%s', decrementing ref_count to %d", si->name, si->ref_count); |
| } |
| return 0; |
| } |
| |
| void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { |
| if (!get_AT_SECURE()) { |
| parse_LD_LIBRARY_PATH(ld_library_path); |
| } |
| } |
| |
| soinfo* do_dlopen(const char* name, int flags) { |
| if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL)) != 0) { |
| DL_ERR("invalid flags to dlopen: %x", flags); |
| return NULL; |
| } |
| set_soinfo_pool_protection(PROT_READ | PROT_WRITE); |
| soinfo* si = find_library(name); |
| if (si != NULL) { |
| si->CallConstructors(); |
| } |
| set_soinfo_pool_protection(PROT_READ); |
| return si; |
| } |
| |
| int do_dlclose(soinfo* si) { |
| set_soinfo_pool_protection(PROT_READ | PROT_WRITE); |
| int result = soinfo_unload(si); |
| set_soinfo_pool_protection(PROT_READ); |
| return result; |
| } |
| |
| /* TODO: don't use unsigned for addrs below. It works, but is not |
| * ideal. They should probably be either uint32_t, Elf32_Addr, or unsigned |
| * long. |
| */ |
| static int soinfo_relocate(soinfo* si, Elf32_Rel* rel, unsigned count, |
| soinfo* needed[]) |
| { |
| Elf32_Sym* symtab = si->symtab; |
| const char* strtab = si->strtab; |
| Elf32_Sym* s; |
| Elf32_Rel* start = rel; |
| soinfo* lsi; |
| |
| for (size_t idx = 0; idx < count; ++idx, ++rel) { |
| unsigned type = ELF32_R_TYPE(rel->r_info); |
| unsigned sym = ELF32_R_SYM(rel->r_info); |
| Elf32_Addr reloc = static_cast<Elf32_Addr>(rel->r_offset + si->load_bias); |
| Elf32_Addr sym_addr = 0; |
| char* sym_name = NULL; |
| |
| DEBUG("Processing '%s' relocation at index %d", si->name, idx); |
| if (type == 0) { // R_*_NONE |
| continue; |
| } |
| if (sym != 0) { |
| sym_name = (char *)(strtab + symtab[sym].st_name); |
| s = soinfo_do_lookup(si, sym_name, &lsi, needed); |
| if (s == NULL) { |
| /* We only allow an undefined symbol if this is a weak |
| reference.. */ |
| s = &symtab[sym]; |
| if (ELF32_ST_BIND(s->st_info) != STB_WEAK) { |
| DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); |
| return -1; |
| } |
| |
| /* IHI0044C AAELF 4.5.1.1: |
| |
| Libraries are not searched to resolve weak references. |
| It is not an error for a weak reference to remain |
| unsatisfied. |
| |
| During linking, the value of an undefined weak reference is: |
| - Zero if the relocation type is absolute |
| - The address of the place if the relocation is pc-relative |
| - The address of nominal base address if the relocation |
| type is base-relative. |
| */ |
| |
| switch (type) { |
| #if defined(ANDROID_ARM_LINKER) |
| case R_ARM_JUMP_SLOT: |
| case R_ARM_GLOB_DAT: |
| case R_ARM_ABS32: |
| case R_ARM_RELATIVE: /* Don't care. */ |
| #elif defined(ANDROID_X86_LINKER) |
| case R_386_JMP_SLOT: |
| case R_386_GLOB_DAT: |
| case R_386_32: |
| case R_386_RELATIVE: /* Dont' care. */ |
| #endif /* ANDROID_*_LINKER */ |
| /* sym_addr was initialized to be zero above or relocation |
| code below does not care about value of sym_addr. |
| No need to do anything. */ |
| break; |
| |
| #if defined(ANDROID_X86_LINKER) |
| case R_386_PC32: |
| sym_addr = reloc; |
| break; |
| #endif /* ANDROID_X86_LINKER */ |
| |
| #if defined(ANDROID_ARM_LINKER) |
| case R_ARM_COPY: |
| /* Fall through. Can't really copy if weak symbol is |
| not found in run-time. */ |
| #endif /* ANDROID_ARM_LINKER */ |
| default: |
| DL_ERR("unknown weak reloc type %d @ %p (%d)", |
| type, rel, (int) (rel - start)); |
| return -1; |
| } |
| } else { |
| /* We got a definition. */ |
| #if 0 |
| if ((base == 0) && (si->base != 0)) { |
| /* linking from libraries to main image is bad */ |
| DL_ERR("cannot locate \"%s\"...", |
| strtab + symtab[sym].st_name); |
| return -1; |
| } |
| #endif |
| sym_addr = static_cast<Elf32_Addr>(s->st_value + lsi->load_bias); |
| } |
| count_relocation(kRelocSymbol); |
| } else { |
| s = NULL; |
| } |
| |
| /* TODO: This is ugly. Split up the relocations by arch into |
| * different files. |
| */ |
| switch(type){ |
| #if defined(ANDROID_ARM_LINKER) |
| case R_ARM_JUMP_SLOT: |
| count_relocation(kRelocAbsolute); |
| MARK(rel->r_offset); |
| TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); |
| *reinterpret_cast<Elf32_Addr*>(reloc) = sym_addr; |
| break; |
| case R_ARM_GLOB_DAT: |
| count_relocation(kRelocAbsolute); |
| MARK(rel->r_offset); |
| TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); |
| *reinterpret_cast<Elf32_Addr*>(reloc) = sym_addr; |
| break; |
| case R_ARM_ABS32: |
| count_relocation(kRelocAbsolute); |
| MARK(rel->r_offset); |
| TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); |
| *reinterpret_cast<Elf32_Addr*>(reloc) += sym_addr; |
| break; |
| case R_ARM_REL32: |
| count_relocation(kRelocRelative); |
| MARK(rel->r_offset); |
| TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", |
| reloc, sym_addr, rel->r_offset, sym_name); |
| *reinterpret_cast<Elf32_Addr*>(reloc) += sym_addr - rel->r_offset; |
| break; |
| #elif defined(ANDROID_X86_LINKER) |
| case R_386_JMP_SLOT: |
| count_relocation(kRelocAbsolute); |
| MARK(rel->r_offset); |
| TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); |
| *reinterpret_cast<Elf32_Addr*>(reloc) = sym_addr; |
| break; |
| case R_386_GLOB_DAT: |
| count_relocation(kRelocAbsolute); |
| MARK(rel->r_offset); |
| TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); |
| *reinterpret_cast<Elf32_Addr*>(reloc) = sym_addr; |
| break; |
| #elif defined(ANDROID_MIPS_LINKER) |
| case R_MIPS_REL32: |
| count_relocation(kRelocAbsolute); |
| MARK(rel->r_offset); |
| TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x %s", |
| reloc, sym_addr, (sym_name) ? sym_name : "*SECTIONHDR*"); |
| if (s) { |
| *reinterpret_cast<Elf32_Addr*>(reloc) += sym_addr; |
| } else { |
| *reinterpret_cast<Elf32_Addr*>(reloc) += si->base; |
| } |
| break; |
| #endif /* ANDROID_*_LINKER */ |
| |
| #if defined(ANDROID_ARM_LINKER) |
| case R_ARM_RELATIVE: |
| #elif defined(ANDROID_X86_LINKER) |
| case R_386_RELATIVE: |
| #endif /* ANDROID_*_LINKER */ |
| count_relocation(kRelocRelative); |
| MARK(rel->r_offset); |
| if (sym) { |
| DL_ERR("odd RELATIVE form..."); |
| return -1; |
| } |
| TRACE_TYPE(RELO, "RELO RELATIVE %08x <- +%08x", reloc, si->base); |
| *reinterpret_cast<Elf32_Addr*>(reloc) += si->base; |
| break; |
| |
| #if defined(ANDROID_X86_LINKER) |
| case R_386_32: |
| count_relocation(kRelocRelative); |
| MARK(rel->r_offset); |
| |
| TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); |
| *reinterpret_cast<Elf32_Addr*>(reloc) += sym_addr; |
| break; |
| |
| case R_386_PC32: |
| count_relocation(kRelocRelative); |
| MARK(rel->r_offset); |
| TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", |
| reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); |
| *reinterpret_cast<Elf32_Addr*>(reloc) += (sym_addr - reloc); |
| break; |
| #endif /* ANDROID_X86_LINKER */ |
| |
| #ifdef ANDROID_ARM_LINKER |
| case R_ARM_COPY: |
| if ((si->flags & FLAG_EXE) == 0) { |
| /* |
| * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf |
| * |
| * Section 4.7.1.10 "Dynamic relocations" |
| * R_ARM_COPY may only appear in executable objects where e_type is |
| * set to ET_EXEC. |
| * |
| * TODO: FLAG_EXE is set for both ET_DYN and ET_EXEC executables. |
| * We should explicitly disallow ET_DYN executables from having |
| * R_ARM_COPY relocations. |
| */ |
| DL_ERR("%s R_ARM_COPY relocations only supported for ET_EXEC", si->name); |
| return -1; |
| } |
| count_relocation(kRelocCopy); |
| MARK(rel->r_offset); |
| TRACE_TYPE(RELO, "RELO %08x <- %d @ %08x %s", reloc, s->st_size, sym_addr, sym_name); |
| if (reloc == sym_addr) { |
| Elf32_Sym *src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); |
| |
| if (src == NULL) { |
| DL_ERR("%s R_ARM_COPY relocation source cannot be resolved", si->name); |
| return -1; |
| } |
| if (lsi->has_DT_SYMBOLIC) { |
| DL_ERR("%s invalid R_ARM_COPY relocation against DT_SYMBOLIC shared " |
| "library %s (built with -Bsymbolic?)", si->name, lsi->name); |
| return -1; |
| } |
| if (s->st_size < src->st_size) { |
| DL_ERR("%s R_ARM_COPY relocation size mismatch (%d < %d)", |
| si->name, s->st_size, src->st_size); |
| return -1; |
| } |
| memcpy((void*)reloc, (void*)(src->st_value + lsi->load_bias), src->st_size); |
| } else { |
| DL_ERR("%s R_ARM_COPY relocation target cannot be resolved", si->name); |
| return -1; |
| } |
| break; |
| #endif /* ANDROID_ARM_LINKER */ |
| |
| default: |
| DL_ERR("unknown reloc type %d @ %p (%d)", |
| type, rel, (int) (rel - start)); |
| return -1; |
| } |
| } |
| return 0; |
| } |
| |
| #ifdef ANDROID_MIPS_LINKER |
| static int mips_relocate_got(soinfo* si, soinfo* needed[]) { |
| unsigned *got; |
| unsigned local_gotno, gotsym, symtabno; |
| Elf32_Sym *symtab, *sym; |
| unsigned g; |
| |
| got = si->plt_got; |
| local_gotno = si->mips_local_gotno; |
| gotsym = si->mips_gotsym; |
| symtabno = si->mips_symtabno; |
| symtab = si->symtab; |
| |
| /* |
| * got[0] is address of lazy resolver function |
| * got[1] may be used for a GNU extension |
| * set it to a recognizable address in case someone calls it |
| * (should be _rtld_bind_start) |
| * FIXME: maybe this should be in a separate routine |
| */ |
| |
| if ((si->flags & FLAG_LINKER) == 0) { |
| g = 0; |
| got[g++] = 0xdeadbeef; |
| if (got[g] & 0x80000000) { |
| got[g++] = 0xdeadfeed; |
| } |
| /* |
| * Relocate the local GOT entries need to be relocated |
| */ |
| for (; g < local_gotno; g++) { |
| got[g] += si->load_bias; |
| } |
| } |
| |
| /* Now for the global GOT entries */ |
| sym = symtab + gotsym; |
| got = si->plt_got + local_gotno; |
| for (g = gotsym; g < symtabno; g++, sym++, got++) { |
| const char* sym_name; |
| Elf32_Sym* s; |
| soinfo* lsi; |
| |
| /* This is an undefined reference... try to locate it */ |
| sym_name = si->strtab + sym->st_name; |
| s = soinfo_do_lookup(si, sym_name, &lsi, needed); |
| if (s == NULL) { |
| /* We only allow an undefined symbol if this is a weak |
| reference.. */ |
| s = &symtab[g]; |
| if (ELF32_ST_BIND(s->st_info) != STB_WEAK) { |
| DL_ERR("cannot locate \"%s\"...", sym_name); |
| return -1; |
| } |
| *got = 0; |
| } |
| else { |
| /* FIXME: is this sufficient? |
| * For reference see NetBSD link loader |
| * http://cvsweb.netbsd.org/bsdweb.cgi/src/libexec/ld.elf_so/arch/mips/mips_reloc.c?rev=1.53&content-type=text/x-cvsweb-markup |
| */ |
| *got = lsi->load_bias + s->st_value; |
| } |
| } |
| return 0; |
| } |
| #endif |
| |
| void soinfo::CallArray(const char* array_name UNUSED, linker_function_t* functions, size_t count, bool reverse) { |
| if (functions == NULL) { |
| return; |
| } |
| |
| TRACE("[ Calling %s (size %d) @ %p for '%s' ]", array_name, count, functions, name); |
| |
| int begin = reverse ? (count - 1) : 0; |
| int end = reverse ? -1 : count; |
| int step = reverse ? -1 : 1; |
| |
| for (int i = begin; i != end; i += step) { |
| TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); |
| CallFunction("function", functions[i]); |
| } |
| |
| TRACE("[ Done calling %s for '%s' ]", array_name, name); |
| } |
| |
| void soinfo::CallFunction(const char* function_name UNUSED, linker_function_t function) { |
| if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { |
| return; |
| } |
| |
| TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); |
| function(); |
| TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); |
| |
| // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures |
| // are still writable. This happens with our debug malloc (see http://b/7941716). |
| set_soinfo_pool_protection(PROT_READ | PROT_WRITE); |
| } |
| |
| void soinfo::CallPreInitConstructors() { |
| // DT_PREINIT_ARRAY functions are called before any other constructors for executables, |
| // but ignored in a shared library. |
| CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); |
| } |
| |
| void soinfo::CallConstructors() { |
| if (constructors_called) { |
| return; |
| } |
| |
| // We set constructors_called before actually calling the constructors, otherwise it doesn't |
| // protect against recursive constructor calls. One simple example of constructor recursion |
| // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: |
| // 1. The program depends on libc, so libc's constructor is called here. |
| // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. |
| // 3. dlopen() calls the constructors on the newly created |
| // soinfo for libc_malloc_debug_leak.so. |
| // 4. The debug .so depends on libc, so CallConstructors is |
| // called again with the libc soinfo. If it doesn't trigger the early- |
| // out above, the libc constructor will be called again (recursively!). |
| constructors_called = true; |
| |
| if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { |
| // The GNU dynamic linker silently ignores these, but we warn the developer. |
| PRINT("\"%s\": ignoring %d-entry DT_PREINIT_ARRAY in shared library!", |
| name, preinit_array_count); |
| } |
| |
| if (dynamic != NULL) { |
| for (Elf32_Dyn* d = dynamic; d->d_tag != DT_NULL; ++d) { |
| if (d->d_tag == DT_NEEDED) { |
| const char* library_name = strtab + d->d_un.d_val; |
| TRACE("\"%s\": calling constructors in DT_NEEDED \"%s\"", name, library_name); |
| find_loaded_library(library_name)->CallConstructors(); |
| } |
| } |
| } |
| |
| TRACE("\"%s\": calling constructors", name); |
| |
| // DT_INIT should be called before DT_INIT_ARRAY if both are present. |
| CallFunction("DT_INIT", init_func); |
| CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); |
| } |
| |
| void soinfo::CallDestructors() { |
| TRACE("\"%s\": calling destructors", name); |
| |
| // DT_FINI_ARRAY must be parsed in reverse order. |
| CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); |
| |
| // DT_FINI should be called after DT_FINI_ARRAY if both are present. |
| CallFunction("DT_FINI", fini_func); |
| } |
| |
| /* Force any of the closed stdin, stdout and stderr to be associated with |
| /dev/null. */ |
| static int nullify_closed_stdio() { |
| int dev_null, i, status; |
| int return_value = 0; |
| |
| dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); |
| if (dev_null < 0) { |
| DL_ERR("cannot open /dev/null: %s", strerror(errno)); |
| return -1; |
| } |
| TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); |
| |
| /* If any of the stdio file descriptors is valid and not associated |
| with /dev/null, dup /dev/null to it. */ |
| for (i = 0; i < 3; i++) { |
| /* If it is /dev/null already, we are done. */ |
| if (i == dev_null) { |
| continue; |
| } |
| |
| TRACE("[ Nullifying stdio file descriptor %d]", i); |
| status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); |
| |
| /* If file is opened, we are good. */ |
| if (status != -1) { |
| continue; |
| } |
| |
| /* The only error we allow is that the file descriptor does not |
| exist, in which case we dup /dev/null to it. */ |
| if (errno != EBADF) { |
| DL_ERR("fcntl failed: %s", strerror(errno)); |
| return_value = -1; |
| continue; |
| } |
| |
| /* Try dupping /dev/null to this stdio file descriptor and |
| repeat if there is a signal. Note that any errors in closing |
| the stdio descriptor are lost. */ |
| status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); |
| if (status < 0) { |
| DL_ERR("dup2 failed: %s", strerror(errno)); |
| return_value = -1; |
| continue; |
| } |
| } |
| |
| /* If /dev/null is not one of the stdio file descriptors, close it. */ |
| if (dev_null > 2) { |
| TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); |
| status = TEMP_FAILURE_RETRY(close(dev_null)); |
| if (status == -1) { |
| DL_ERR("close failed: %s", strerror(errno)); |
| return_value = -1; |
| } |
| } |
| |
| return return_value; |
| } |
| |
| static bool soinfo_link_image(soinfo* si) { |
| /* "base" might wrap around UINT32_MAX. */ |
| Elf32_Addr base = si->load_bias; |
| const Elf32_Phdr *phdr = si->phdr; |
| int phnum = si->phnum; |
| bool relocating_linker = (si->flags & FLAG_LINKER) != 0; |
| |
| /* We can't debug anything until the linker is relocated */ |
| if (!relocating_linker) { |
| INFO("[ linking %s ]", si->name); |
| DEBUG("si->base = 0x%08x si->flags = 0x%08x", si->base, si->flags); |
| } |
| |
| /* Extract dynamic section */ |
| size_t dynamic_count; |
| Elf32_Word dynamic_flags; |
| phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, |
| &dynamic_count, &dynamic_flags); |
| if (si->dynamic == NULL) { |
| if (!relocating_linker) { |
| DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); |
| } |
| return false; |
| } else { |
| if (!relocating_linker) { |
| DEBUG("dynamic = %p", si->dynamic); |
| } |
| } |
| |
| #ifdef ANDROID_ARM_LINKER |
| (void) phdr_table_get_arm_exidx(phdr, phnum, base, |
| &si->ARM_exidx, &si->ARM_exidx_count); |
| #endif |
| |
| // Extract useful information from dynamic section. |
| uint32_t needed_count = 0; |
| for (Elf32_Dyn* d = si->dynamic; d->d_tag != DT_NULL; ++d) { |
| DEBUG("d = %p, d[0](tag) = 0x%08x d[1](val) = 0x%08x", d, d->d_tag, d->d_un.d_val); |
| switch(d->d_tag){ |
| case DT_HASH: |
| si->nbucket = ((unsigned *) (base + d->d_un.d_ptr))[0]; |
| si->nchain = ((unsigned *) (base + d->d_un.d_ptr))[1]; |
| si->bucket = (unsigned *) (base + d->d_un.d_ptr + 8); |
| si->chain = (unsigned *) (base + d->d_un.d_ptr + 8 + si->nbucket * 4); |
| break; |
| case DT_STRTAB: |
| si->strtab = (const char *) (base + d->d_un.d_ptr); |
| break; |
| case DT_SYMTAB: |
| si->symtab = (Elf32_Sym *) (base + d->d_un.d_ptr); |
| break; |
| case DT_PLTREL: |
| if (d->d_un.d_val != DT_REL) { |
| DL_ERR("unsupported DT_RELA in \"%s\"", si->name); |
| return false; |
| } |
| break; |
| case DT_JMPREL: |
| si->plt_rel = (Elf32_Rel*) (base + d->d_un.d_ptr); |
| break; |
| case DT_PLTRELSZ: |
| si->plt_rel_count = d->d_un.d_val / sizeof(Elf32_Rel); |
| break; |
| case DT_REL: |
| si->rel = (Elf32_Rel*) (base + d->d_un.d_ptr); |
| break; |
| case DT_RELSZ: |
| si->rel_count = d->d_un.d_val / sizeof(Elf32_Rel); |
| break; |
| case DT_PLTGOT: |
| /* Save this in case we decide to do lazy binding. We don't yet. */ |
| si->plt_got = (unsigned *)(base + d->d_un.d_ptr); |
| break; |
| case DT_DEBUG: |
| // Set the DT_DEBUG entry to the address of _r_debug for GDB |
| // if the dynamic table is writable |
| if ((dynamic_flags & PF_W) != 0) { |
| d->d_un.d_val = (int) &_r_debug; |
| } |
| break; |
| case DT_RELA: |
| DL_ERR("unsupported DT_RELA in \"%s\"", si->name); |
| return false; |
| case DT_INIT: |
| si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); |
| DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); |
| break; |
| case DT_FINI: |
| si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); |
| DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); |
| break; |
| case DT_INIT_ARRAY: |
| si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); |
| DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); |
| break; |
| case DT_INIT_ARRAYSZ: |
| si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(Elf32_Addr); |
| break; |
| case DT_FINI_ARRAY: |
| si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); |
| DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); |
| break; |
| case DT_FINI_ARRAYSZ: |
| si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(Elf32_Addr); |
| break; |
| case DT_PREINIT_ARRAY: |
| si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); |
| DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); |
| break; |
| case DT_PREINIT_ARRAYSZ: |
| si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(Elf32_Addr); |
| break; |
| case DT_TEXTREL: |
| si->has_text_relocations = true; |
| break; |
| case DT_SYMBOLIC: |
| si->has_DT_SYMBOLIC = true; |
| break; |
| case DT_NEEDED: |
| ++needed_count; |
| break; |
| #if defined DT_FLAGS |
| // TODO: why is DT_FLAGS not defined? |
| case DT_FLAGS: |
| if (d->d_un.d_val & DF_TEXTREL) { |
| si->has_text_relocations = true; |
| } |
| if (d->d_un.d_val & DF_SYMBOLIC) { |
| si->has_DT_SYMBOLIC = true; |
| } |
| break; |
| #endif |
| #if defined(ANDROID_MIPS_LINKER) |
| case DT_STRSZ: |
| case DT_SYMENT: |
| case DT_RELENT: |
| break; |
| case DT_MIPS_RLD_MAP: |
| // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. |
| { |
| r_debug** dp = (r_debug**) d->d_un.d_ptr; |
| *dp = &_r_debug; |
| } |
| break; |
| case DT_MIPS_RLD_VERSION: |
| case DT_MIPS_FLAGS: |
| case DT_MIPS_BASE_ADDRESS: |
| case DT_MIPS_UNREFEXTNO: |
| break; |
| |
| case DT_MIPS_SYMTABNO: |
| si->mips_symtabno = d->d_un.d_val; |
| break; |
| |
| case DT_MIPS_LOCAL_GOTNO: |
| si->mips_local_gotno = d->d_un.d_val; |
| break; |
| |
| case DT_MIPS_GOTSYM: |
| si->mips_gotsym = d->d_un.d_val; |
| break; |
| |
| default: |
| DEBUG("Unused DT entry: type 0x%08x arg 0x%08x", d->d_tag, d->d_un.d_val); |
| break; |
| #endif |
| } |
| } |
| |
| DEBUG("si->base = 0x%08x, si->strtab = %p, si->symtab = %p", |
| si->base, si->strtab, si->symtab); |
| |
| // Sanity checks. |
| if (relocating_linker && needed_count != 0) { |
| DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); |
| return false; |
| } |
| if (si->nbucket == 0) { |
| DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); |
| return false; |
| } |
| if (si->strtab == 0) { |
| DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); |
| return false; |
| } |
| if (si->symtab == 0) { |
| DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); |
| return false; |
| } |
| |
| // If this is the main executable, then load all of the libraries from LD_PRELOAD now. |
| if (si->flags & FLAG_EXE) { |
| memset(gLdPreloads, 0, sizeof(gLdPreloads)); |
| size_t preload_count = 0; |
| for (size_t i = 0; gLdPreloadNames[i] != NULL; i++) { |
| soinfo* lsi = find_library(gLdPreloadNames[i]); |
| if (lsi != NULL) { |
| gLdPreloads[preload_count++] = lsi; |
| } else { |
| // As with glibc, failure to load an LD_PRELOAD library is just a warning. |
| DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", |
| gLdPreloadNames[i], si->name, linker_get_error_buffer()); |
| } |
| } |
| } |
| |
| soinfo** needed = (soinfo**) alloca((1 + needed_count) * sizeof(soinfo*)); |
| soinfo** pneeded = needed; |
| |
| for (Elf32_Dyn* d = si->dynamic; d->d_tag != DT_NULL; ++d) { |
| if (d->d_tag == DT_NEEDED) { |
| const char* library_name = si->strtab + d->d_un.d_val; |
| DEBUG("%s needs %s", si->name, library_name); |
| soinfo* lsi = find_library(library_name); |
| if (lsi == NULL) { |
| strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); |
| DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", |
| library_name, si->name, tmp_err_buf); |
| return false; |
| } |
| *pneeded++ = lsi; |
| } |
| } |
| *pneeded = NULL; |
| |
| if (si->has_text_relocations) { |
| /* Unprotect the segments, i.e. make them writable, to allow |
| * text relocations to work properly. We will later call |
| * phdr_table_protect_segments() after all of them are applied |
| * and all constructors are run. |
| */ |
| DL_WARN("%s has text relocations. This is wasting memory and is " |
| "a security risk. Please fix.", si->name); |
| if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { |
| DL_ERR("can't unprotect loadable segments for \"%s\": %s", |
| si->name, strerror(errno)); |
| return false; |
| } |
| } |
| |
| if (si->plt_rel != NULL) { |
| DEBUG("[ relocating %s plt ]", si->name ); |
| if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { |
| return false; |
| } |
| } |
| if (si->rel != NULL) { |
| DEBUG("[ relocating %s ]", si->name ); |
| if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { |
| return false; |
| } |
| } |
| |
| #ifdef ANDROID_MIPS_LINKER |
| if (mips_relocate_got(si, needed)) { |
| return false; |
| } |
| #endif |
| |
| si->flags |= FLAG_LINKED; |
| DEBUG("[ finished linking %s ]", si->name); |
| |
| if (si->has_text_relocations) { |
| /* All relocations are done, we can protect our segments back to |
| * read-only. */ |
| if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { |
| DL_ERR("can't protect segments for \"%s\": %s", |
| si->name, strerror(errno)); |
| return false; |
| } |
| } |
| |
| /* We can also turn on GNU RELRO protection */ |
| if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { |
| DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", |
| si->name, strerror(errno)); |
| return false; |
| } |
| |
| notify_gdb_of_load(si); |
| return true; |
| } |
| |
| /* |
| * This function add vdso to internal dso list. |
| * It helps to stack unwinding through signal handlers. |
| * Also, it makes bionic more like glibc. |
| */ |
| static void add_vdso(KernelArgumentBlock& args UNUSED) { |
| #ifdef AT_SYSINFO_EHDR |
| Elf32_Ehdr* ehdr_vdso = reinterpret_cast<Elf32_Ehdr*>(args.getauxval(AT_SYSINFO_EHDR)); |
| |
| soinfo* si = soinfo_alloc("[vdso]"); |
| si->phdr = reinterpret_cast<Elf32_Phdr*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); |
| si->phnum = ehdr_vdso->e_phnum; |
| si->link_map.l_name = si->name; |
| for (size_t i = 0; i < si->phnum; ++i) { |
| if (si->phdr[i].p_type == PT_LOAD) { |
| si->link_map.l_addr = reinterpret_cast<Elf32_Addr>(ehdr_vdso) - si->phdr[i].p_vaddr; |
| break; |
| } |
| } |
| #endif |
| } |
| |
| /* |
| * This code is called after the linker has linked itself and |
| * fixed it's own GOT. It is safe to make references to externs |
| * and other non-local data at this point. |
| */ |
| static Elf32_Addr __linker_init_post_relocation(KernelArgumentBlock& args, Elf32_Addr linker_base) { |
| /* NOTE: we store the args pointer on a special location |
| * of the temporary TLS area in order to pass it to |
| * the C Library's runtime initializer. |
| * |
| * The initializer must clear the slot and reset the TLS |
| * to point to a different location to ensure that no other |
| * shared library constructor can access it. |
| */ |
| __libc_init_tls(args); |
| |
| #if TIMING |
| struct timeval t0, t1; |
| gettimeofday(&t0, 0); |
| #endif |
| |
| // Initialize environment functions, and get to the ELF aux vectors table. |
| linker_env_init(args); |
| |
| // If this is a setuid/setgid program, close the security hole described in |
| // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc |
| if (get_AT_SECURE()) { |
| nullify_closed_stdio(); |
| } |
| |
| debuggerd_init(); |
| |
| // Get a few environment variables. |
| const char* LD_DEBUG = linker_env_get("LD_DEBUG"); |
| if (LD_DEBUG != NULL) { |
| gLdDebugVerbosity = atoi(LD_DEBUG); |
| } |
| |
| // Normally, these are cleaned by linker_env_init, but the test |
| // doesn't cost us anything. |
| const char* ldpath_env = NULL; |
| const char* ldpreload_env = NULL; |
| if (!get_AT_SECURE()) { |
| ldpath_env = linker_env_get("LD_LIBRARY_PATH"); |
| ldpreload_env = linker_env_get("LD_PRELOAD"); |
| } |
| |
| INFO("[ android linker & debugger ]"); |
| |
| soinfo* si = soinfo_alloc(args.argv[0]); |
| if (si == NULL) { |
| exit(EXIT_FAILURE); |
| } |
| |
| /* bootstrap the link map, the main exe always needs to be first */ |
| si->flags |= FLAG_EXE; |
| link_map_t* map = &(si->link_map); |
| |
| map->l_addr = 0; |
| map->l_name = args.argv[0]; |
| map->l_prev = NULL; |
| map->l_next = NULL; |
| |
| _r_debug.r_map = map; |
| r_debug_tail = map; |
| |
| /* gdb expects the linker to be in the debug shared object list. |
| * Without this, gdb has trouble locating the linker's ".text" |
| * and ".plt" sections. Gdb could also potentially use this to |
| * relocate the offset of our exported 'rtld_db_dlactivity' symbol. |
| * Don't use soinfo_alloc(), because the linker shouldn't |
| * be on the soinfo list. |
| */ |
| { |
| static soinfo linker_soinfo; |
| strlcpy(linker_soinfo.name, "/system/bin/linker", sizeof(linker_soinfo.name)); |
| linker_soinfo.flags = 0; |
| linker_soinfo.base = linker_base; |
| |
| /* |
| * Set the dynamic field in the link map otherwise gdb will complain with |
| * the following: |
| * warning: .dynamic section for "/system/bin/linker" is not at the |
| * expected address (wrong library or version mismatch?) |
| */ |
| Elf32_Ehdr *elf_hdr = (Elf32_Ehdr *) linker_base; |
| Elf32_Phdr *phdr = (Elf32_Phdr*)((unsigned char*) linker_base + elf_hdr->e_phoff); |
| phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, |
| &linker_soinfo.dynamic, NULL, NULL); |
| insert_soinfo_into_debug_map(&linker_soinfo); |
| } |
| |
| // Extract information passed from the kernel. |
| si->phdr = reinterpret_cast<Elf32_Phdr*>(args.getauxval(AT_PHDR)); |
| si->phnum = args.getauxval(AT_PHNUM); |
| si->entry = args.getauxval(AT_ENTRY); |
| |
| /* Compute the value of si->base. We can't rely on the fact that |
| * the first entry is the PHDR because this will not be true |
| * for certain executables (e.g. some in the NDK unit test suite) |
| */ |
| si->base = 0; |
| si->size = phdr_table_get_load_size(si->phdr, si->phnum); |
| si->load_bias = 0; |
| for (size_t i = 0; i < si->phnum; ++i) { |
| if (si->phdr[i].p_type == PT_PHDR) { |
| si->load_bias = reinterpret_cast<Elf32_Addr>(si->phdr) - si->phdr[i].p_vaddr; |
| si->base = reinterpret_cast<Elf32_Addr>(si->phdr) - si->phdr[i].p_offset; |
| break; |
| } |
| } |
| si->dynamic = NULL; |
| si->ref_count = 1; |
| |
| // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). |
| parse_LD_LIBRARY_PATH(ldpath_env); |
| parse_LD_PRELOAD(ldpreload_env); |
| |
| somain = si; |
| |
| if (!soinfo_link_image(si)) { |
| __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); |
| exit(EXIT_FAILURE); |
| } |
| |
| add_vdso(args); |
| |
| si->CallPreInitConstructors(); |
| |
| for (size_t i = 0; gLdPreloads[i] != NULL; ++i) { |
| gLdPreloads[i]->CallConstructors(); |
| } |
| |
| /* After the link_image, the si->load_bias is initialized. |
| * For so lib, the map->l_addr will be updated in notify_gdb_of_load. |
| * We need to update this value for so exe here. So Unwind_Backtrace |
| * for some arch like x86 could work correctly within so exe. |
| */ |
| map->l_addr = si->load_bias; |
| si->CallConstructors(); |
| |
| #if TIMING |
| gettimeofday(&t1,NULL); |
| PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( |
| (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - |
| (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec) |
| )); |
| #endif |
| #if STATS |
| PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], |
| linker_stats.count[kRelocAbsolute], |
| linker_stats.count[kRelocRelative], |
| linker_stats.count[kRelocCopy], |
| linker_stats.count[kRelocSymbol]); |
| #endif |
| #if COUNT_PAGES |
| { |
| unsigned n; |
| unsigned i; |
| unsigned count = 0; |
| for (n = 0; n < 4096; n++) { |
| if (bitmask[n]) { |
| unsigned x = bitmask[n]; |
| for (i = 0; i < 8; i++) { |
| if (x & 1) { |
| count++; |
| } |
| x >>= 1; |
| } |
| } |
| } |
| PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); |
| } |
| #endif |
| |
| #if TIMING || STATS || COUNT_PAGES |
| fflush(stdout); |
| #endif |
| |
| TRACE("[ Ready to execute '%s' @ 0x%08x ]", si->name, si->entry); |
| return si->entry; |
| } |
| |
| /* Compute the load-bias of an existing executable. This shall only |
| * be used to compute the load bias of an executable or shared library |
| * that was loaded by the kernel itself. |
| * |
| * Input: |
| * elf -> address of ELF header, assumed to be at the start of the file. |
| * Return: |
| * load bias, i.e. add the value of any p_vaddr in the file to get |
| * the corresponding address in memory. |
| */ |
| static Elf32_Addr get_elf_exec_load_bias(const Elf32_Ehdr* elf) { |
| Elf32_Addr offset = elf->e_phoff; |
| const Elf32_Phdr* phdr_table = (const Elf32_Phdr*)((char*)elf + offset); |
| const Elf32_Phdr* phdr_end = phdr_table + elf->e_phnum; |
| |
| for (const Elf32_Phdr* phdr = phdr_table; phdr < phdr_end; phdr++) { |
| if (phdr->p_type == PT_LOAD) { |
| return reinterpret_cast<Elf32_Addr>(elf) + phdr->p_offset - phdr->p_vaddr; |
| } |
| } |
| return 0; |
| } |
| |
| /* |
| * This is the entry point for the linker, called from begin.S. This |
| * method is responsible for fixing the linker's own relocations, and |
| * then calling __linker_init_post_relocation(). |
| * |
| * Because this method is called before the linker has fixed it's own |
| * relocations, any attempt to reference an extern variable, extern |
| * function, or other GOT reference will generate a segfault. |
| */ |
| extern "C" Elf32_Addr __linker_init(void* raw_args) { |
| KernelArgumentBlock args(raw_args); |
| |
| Elf32_Addr linker_addr = args.getauxval(AT_BASE); |
| |
| Elf32_Ehdr* elf_hdr = (Elf32_Ehdr*) linker_addr; |
| Elf32_Phdr* phdr = (Elf32_Phdr*)((unsigned char*) linker_addr + elf_hdr->e_phoff); |
| |
| soinfo linker_so; |
| memset(&linker_so, 0, sizeof(soinfo)); |
| |
| linker_so.base = linker_addr; |
| linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); |
| linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); |
| linker_so.dynamic = NULL; |
| linker_so.phdr = phdr; |
| linker_so.phnum = elf_hdr->e_phnum; |
| linker_so.flags |= FLAG_LINKER; |
| |
| if (!soinfo_link_image(&linker_so)) { |
| // It would be nice to print an error message, but if the linker |
| // can't link itself, there's no guarantee that we'll be able to |
| // call write() (because it involves a GOT reference). |
| // |
| // This situation should never occur unless the linker itself |
| // is corrupt. |
| exit(EXIT_FAILURE); |
| } |
| |
| // We have successfully fixed our own relocations. It's safe to run |
| // the main part of the linker now. |
| args.abort_message_ptr = &gAbortMessage; |
| Elf32_Addr start_address = __linker_init_post_relocation(args, linker_addr); |
| |
| set_soinfo_pool_protection(PROT_READ); |
| |
| // Return the address that the calling assembly stub should jump to. |
| return start_address; |
| } |