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Diffstat (limited to 'src/linker/linker.c')
| -rw-r--r-- | src/linker/linker.c | 2541 |
1 files changed, 2541 insertions, 0 deletions
diff --git a/src/linker/linker.c b/src/linker/linker.c new file mode 100644 index 0000000..8f95472 --- /dev/null +++ b/src/linker/linker.c @@ -0,0 +1,2541 @@ +/* + * 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. + */ + +#ifdef APKENV_DEBUG +# define LINKER_DEBUG_PRINTF(...) PRINT(__VA_ARGS__) +#else +# define LINKER_DEBUG_PRINTF(...) +#endif + + +#include <linux/auxvec.h> + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <fcntl.h> +#include <errno.h> +#include <dlfcn.h> +#include <sys/stat.h> +#include <assert.h> + +#include <pthread.h> + +#include <sys/mman.h> + +/* special private C library header - see Android.mk */ +#include "bionic_tls.h" + +#include "strlcpy.h" + +/* for apkenv_get_hooked_symbol */ +// #include "../compat/hooks.h" +/* for create_wrapper */ +// #include "../debug/wrappers.h" + +#include "linker.h" +#include "linker_debug.h" +#include "linker_environ.h" +#include "linker_format.h" + +#define ALLOW_SYMBOLS_FROM_MAIN 1 +#define SO_MAX 128 + +/* 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 + * - linker hardcodes PAGE_SIZE and PAGE_MASK because the kernel + * headers provide versions that are negative... + * - allocate space for soinfo structs dynamically instead of + * having a hard limit (64) +*/ + + +static int apkenv_link_image(soinfo *si, unsigned wr_offset); + +static int apkenv_socount = 0; +static soinfo apkenv_sopool[SO_MAX]; +static soinfo *apkenv_freelist = NULL; +static soinfo *apkenv_solist = &apkenv_libdl_info; +static soinfo *apkenv_sonext = &apkenv_libdl_info; +#if ALLOW_SYMBOLS_FROM_MAIN +static soinfo *apkenv_somain; /* main process, always the one after apkenv_libdl_info */ +#endif + + +static inline int apkenv_validate_soinfo(soinfo *si) +{ + return (si >= apkenv_sopool && si < apkenv_sopool + SO_MAX) || + si == &apkenv_libdl_info; +} + +static char apkenv_ldpaths_buf[LDPATH_BUFSIZE]; +static const char *apkenv_ldpaths[LDPATH_MAX + 1]; + +static char apkenv_ldpreloads_buf[LDPRELOAD_BUFSIZE]; +static const char *apkenv_ldpreload_names[LDPRELOAD_MAX + 1]; + +static soinfo *apkenv_preloads[LDPRELOAD_MAX + 1]; + +#if LINKER_DEBUG +int apkenv_debug_verbosity = 5; +#endif + +static int apkenv_pid; + +/* This boolean is set if the program being loaded is setuid */ +static int apkenv_program_is_setuid; + +#if STATS +struct _link_stats apkenv_linker_stats; +#endif + +#if COUNT_PAGES +unsigned apkenv_bitmask[4096]; +#endif + +#ifndef PT_ARM_EXIDX +#define PT_ARM_EXIDX 0x70000001 /* .ARM.exidx segment */ +#endif + +static char apkenv_tmp_err_buf[768]; +static char apkenv___linker_dl_err_buf[768]; +#define DL_ERR(fmt, x...) \ + do { \ + format_buffer(apkenv___linker_dl_err_buf, sizeof(apkenv___linker_dl_err_buf), \ + "%s[%d]: " fmt, __func__, __LINE__, ##x); \ + ERROR(fmt "\n", ##x); \ + } while(0) + +const char *apkenv_linker_get_error(void) +{ + return (const char *)&apkenv___linker_dl_err_buf[0]; +} + +enum { + WRAPPER_DYNHOOK, + WRAPPER_THUMB_INJECTION, + WRAPPER_UNHOOKED, + WRAPPER_ARM_INJECTION, +}; + +static void +trace(const char *const symbol) +{ + printf("trace: %s\n", symbol); +} + +__asm__( + "wrapper_start: nop\n" + "wrapper_symbol: pushl $0xFAFBFCFD\n" + "wrapper_trace: movl $0xFAFBFCFD, %eax\ncall *%eax\npop %eax\n" + "wrapper_call: movl $0xFAFBFCFD, %eax\njmp *%eax\n" + "wrapper_end: nop\n" +); + +extern char wrapper_start, wrapper_symbol, wrapper_trace, wrapper_call, wrapper_end; + +void* +create_wrapper(const char *const symbol, void *function, int wrapper_type) +{ + const size_t sz = &wrapper_end - &wrapper_start; + unsigned char *fun = mmap(NULL, sz, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + assert(fun != MAP_FAILED); + memcpy(fun, &wrapper_start, sz); + memcpy(fun + (&wrapper_symbol - &wrapper_start) + 1, &symbol, sizeof(symbol)); + memcpy(fun + (&wrapper_trace - &wrapper_start) + 1, (uintptr_t[]){ (uintptr_t)trace }, sizeof(uintptr_t)); + memcpy(fun + (&wrapper_call - &wrapper_start) + 1, &function, sizeof(function)); + mprotect(fun, sz, PROT_READ | PROT_EXEC); + return fun; +} + +/* + * This function is an empty stub where GDB locates a breakpoint to get notified + * about linker activity. + */ +//extern void __attribute__((noinline)) rtld_db_dlactivity(void); + +//static struct r_debug _r_debug = {1, NULL, &rtld_db_dlactivity, +// RT_CONSISTENT, 0}; +/* apkenv */ +#define rtld_db_dlactivity() ((void (*)(void))_r_debug.r_brk)() + +static struct link_map *apkenv_r_debug_head, *apkenv_r_debug_tail; + +static pthread_mutex_t apkenv__r_debug_lock = PTHREAD_MUTEX_INITIALIZER; + +static void apkenv_insert_soinfo_into_debug_map(soinfo * info) +{ + struct link_map * map; + + /* Copy the necessary fields into the debug structure. + */ + map = &(info->linkmap); + map->l_addr = info->base; + map->l_name = info->fullpath; + map->l_ld = (void *)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 (apkenv_r_debug_tail) { + apkenv_r_debug_tail->l_next = map; + map->l_prev = apkenv_r_debug_tail; + map->l_next = 0; + } else { + /* apkenv: for sending to gdb */ + apkenv_r_debug_head = map; + map->l_prev = 0; + map->l_next = 0; + } + apkenv_r_debug_tail = map; +} + +static void apkenv_remove_soinfo_from_debug_map(soinfo * info) +{ + struct link_map * map = &(info->linkmap); + + if (apkenv_r_debug_tail == map) + apkenv_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; +} + +void apkenv_notify_gdb_of_libraries(void); + +static void apkenv_notify_gdb_of_load(soinfo * info) +{ + if (info->flags & FLAG_EXE) { + // GDB already knows about the main executable + return; + } + + pthread_mutex_lock(&apkenv__r_debug_lock); + + _r_debug.r_state = RT_ADD; + rtld_db_dlactivity(); + + apkenv_insert_soinfo_into_debug_map(info); + + _r_debug.r_state = RT_CONSISTENT; + rtld_db_dlactivity(); + + apkenv_notify_gdb_of_libraries(); + pthread_mutex_unlock(&apkenv__r_debug_lock); +} + +static void apkenv_notify_gdb_of_unload(soinfo * info) +{ + if (info->flags & FLAG_EXE) { + // GDB already knows about the main executable + return; + } + + pthread_mutex_lock(&apkenv__r_debug_lock); + + _r_debug.r_state = RT_DELETE; + rtld_db_dlactivity(); + + apkenv_remove_soinfo_from_debug_map(info); + + _r_debug.r_state = RT_CONSISTENT; + rtld_db_dlactivity(); + + apkenv_notify_gdb_of_libraries(); + pthread_mutex_unlock(&apkenv__r_debug_lock); +} + +void apkenv_notify_gdb_of_libraries(void) +{ + struct link_map *tmap = _r_debug.r_map; + while (tmap->l_next != NULL) + tmap = tmap->l_next; + + _r_debug.r_state = RT_ADD; + rtld_db_dlactivity(); + + /* append android libs before notifying gdb */ + tmap->l_next = apkenv_r_debug_head; + apkenv_r_debug_head->l_prev = tmap; + + _r_debug.r_state = RT_CONSISTENT; + rtld_db_dlactivity(); + + /* restore so that ld-linux doesn't freak out */ + tmap->l_next = NULL; +} + +static soinfo *apkenv_alloc_info(const char *name) +{ + soinfo *si; + + if(strlen(name) >= SOINFO_NAME_LEN) { + DL_ERR("%5d library name %s too long", apkenv_pid, name); + return NULL; + } + + /* The apkenv_freelist is populated when we call apkenv_free_info(), which in turn is + done only by dlclose(), which is not likely to be used. + */ + if (!apkenv_freelist) { + if(apkenv_socount == SO_MAX) { + DL_ERR("%5d too many libraries when loading %s", apkenv_pid, name); + return NULL; + } + apkenv_freelist = apkenv_sopool + apkenv_socount++; + apkenv_freelist->next = NULL; + } + + si = apkenv_freelist; + apkenv_freelist = apkenv_freelist->next; + + /* Make sure we get a clean block of soinfo */ + memset(si, 0, sizeof(soinfo)); + apkenv_strlcpy((char*) si->name, name, sizeof(si->name)); + apkenv_sonext->next = si; + si->next = NULL; + si->refcount = 0; + apkenv_sonext = si; + + TRACE("%5d name %s: allocated soinfo @ %p\n", apkenv_pid, name, si); + return si; +} + +static void apkenv_free_info(soinfo *si) +{ + soinfo *prev = NULL, *trav; + + TRACE("%5d name %s: freeing soinfo @ %p\n", apkenv_pid, si->name, si); + + for(trav = apkenv_solist; trav != NULL; trav = trav->next){ + if (trav == si) + break; + prev = trav; + } + if (trav == NULL) { + /* si was not ni apkenv_solist */ + DL_ERR("%5d name %s is not in apkenv_solist!", apkenv_pid, si->name); + return; + } + + /* prev will never be NULL, because the first entry in apkenv_solist is + always the static apkenv_libdl_info. + */ + prev->next = si->next; + if (si == apkenv_sonext) apkenv_sonext = prev; + si->next = apkenv_freelist; + apkenv_freelist = si; +} + +static const char *apkenv_addr_to_name(unsigned addr) +{ + soinfo *si; + + for(si = apkenv_solist; si != 0; si = si->next){ + if((addr >= si->base) && (addr < (si->base + si->size))) { + return si->name; + } + } + + return ""; +} + +/* 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.c and libdl.so. + */ +#ifdef ANDROID_ARM_LINKER +_Unwind_Ptr apkenv_android_dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount) +{ + soinfo *si; + unsigned addr = (unsigned)pc; + + for (si = apkenv_solist; si != 0; si = si->next){ + if ((addr >= si->base) && (addr < (si->base + si->size))) { + *pcount = si->ARM_exidx_count; + return (_Unwind_Ptr)(si->base + (unsigned long)si->ARM_exidx); + } + } + *pcount = 0; + return NULL; +} +#elif defined(ANDROID_X86_LINKER) +/* Here, we only have to provide a callback to iterate across all the + * loaded libraries. gcc_eh does the rest. */ +int +apkenv_android_dl_iterate_phdr(int (*cb)(struct dl_phdr_info *info, size_t size, void *data), + void *data) +{ + soinfo *si; + struct dl_phdr_info dl_info; + int rv = 0; + + for (si = apkenv_solist; si != NULL; si = si->next) { + dl_info.dlpi_addr = si->linkmap.l_addr; + dl_info.dlpi_name = si->linkmap.l_name; + dl_info.dlpi_phdr = (void*)si->phdr; + dl_info.dlpi_phnum = si->phnum; + rv = cb(&dl_info, sizeof (struct dl_phdr_info), data); + if (rv != 0) + break; + } + return rv; +} +#endif + +static Elf32_Sym *apkenv__elf_lookup(soinfo *si, unsigned hash, const char *name) +{ + Elf32_Sym *s; + Elf32_Sym *symtab = si->symtab; + const char *strtab = si->strtab; + unsigned n; + + TRACE_TYPE(LOOKUP, "%5d SEARCH %s in %s@0x%08x %08x %d\n", apkenv_pid, + name, si->name, si->base, hash, hash % si->nbucket); + if (si->nbucket == 0) { + return NULL; + } + n = hash % si->nbucket; + + for(n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]){ + 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: + /* no section == undefined */ + if(s->st_shndx == 0) continue; + + TRACE_TYPE(LOOKUP, "%5d FOUND %s in %s (%08x) %d\n", apkenv_pid, + name, si->name, s->st_value, s->st_size); + return s; + } + } + + return NULL; +} + +static unsigned apkenv_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; +} + +const char *apkenv_last_library_used = NULL; + +static Elf32_Sym * +apkenv__do_lookup(soinfo *si, const char *name, unsigned *base) +{ + unsigned elf_hash = apkenv_elfhash(name); + Elf32_Sym *s; + unsigned *d; + soinfo *lsi = si; + int i; + + /* 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 ambigious 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 = apkenv__elf_lookup(si, elf_hash, name); + if(s != NULL) + goto done; + + /* Next, look for it in the apkenv_preloads list */ + for(i = 0; apkenv_preloads[i] != NULL; i++) { + lsi = apkenv_preloads[i]; + s = apkenv__elf_lookup(lsi, elf_hash, name); + if(s != NULL) + goto done; + } + + for(d = si->dynamic; *d; d += 2) { + if(d[0] == DT_NEEDED){ + lsi = (soinfo *)d[1]; + if (!apkenv_validate_soinfo(lsi)) { + DL_ERR("%5d bad DT_NEEDED pointer in %s", + apkenv_pid, si->name); + return NULL; + } + + DEBUG("%5d %s: looking up %s in %s\n", + apkenv_pid, si->name, name, lsi->name); + s = apkenv__elf_lookup(lsi, elf_hash, name); + if ((s != NULL) && (s->st_shndx != SHN_UNDEF)) + 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 (apkenv_somain) { + lsi = apkenv_somain; + DEBUG("%5d %s: looking up %s in executable %s\n", + apkenv_pid, si->name, name, lsi->name); + s = apkenv__elf_lookup(lsi, elf_hash, name); + } +#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", + apkenv_pid, si->name, name, s->st_value, lsi->name, lsi->base); + apkenv_last_library_used = lsi->name; + *base = lsi->base; + return s; + } + + return NULL; +} + +/* 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 *apkenv_lookup_in_library(soinfo *si, const char *name) +{ + return apkenv__elf_lookup(si, apkenv_elfhash(name), name); +} + +/* This is used by dl_sym(). It performs a global symbol lookup. + */ +Elf32_Sym *apkenv_lookup(const char *name, soinfo **found, soinfo *start) +{ + unsigned elf_hash = apkenv_elfhash(name); + Elf32_Sym *s = NULL; + soinfo *si; + + if(start == NULL) { + start = apkenv_solist; + } + + for(si = start; (s == NULL) && (si != NULL); si = si->next) + { + if(si->flags & FLAG_ERROR) + continue; + s = apkenv__elf_lookup(si, elf_hash, name); + if (s != NULL) { + *found = si; + break; + } + } + + if(s != NULL) { + TRACE_TYPE(LOOKUP, "%5d %s s->st_value = 0x%08x, " + "si->base = 0x%08x\n", apkenv_pid, name, s->st_value, si->base); + return s; + } + + return NULL; +} + +soinfo *apkenv_find_containing_library(const void *addr) +{ + soinfo *si; + + for(si = apkenv_solist; si != NULL; si = si->next) + { + if((unsigned)addr >= si->base && (unsigned)addr - si->base < si->size) { + return si; + } + } + + return NULL; +} + +Elf32_Sym *apkenv_find_containing_symbol(const void *addr, soinfo *si) +{ + unsigned int i; + unsigned soaddr = (unsigned)addr - si->base; + + /* Search the library's symbol table for any defined symbol which + * contains this address */ + for(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; + unsigned n; + + for(n = 0; n < si->nchain; n++) { + TRACE("%5d %04d> %08x: %02x %04x %08x %08x %s\n", apkenv_pid, n, s, + s->st_info, s->st_shndx, s->st_value, s->st_size, + si->strtab + s->st_name); + s++; + } +} +#endif + +#define SOPATH_MAX 8 + +static const char *apkenv_sopaths[SOPATH_MAX + 1] = { + "/vendor/lib", + "/system/lib", + // APKENV_PREFIX "/lib/" APKENV_TARGET "/bionic/", +#ifdef APKENV_LOCAL_BIONIC_PATH + APKENV_LOCAL_BIONIC_PATH, +#endif +}; + +int apkenv_add_sopath(const char *path) +{ + int i; + for (i = 0; i < SOPATH_MAX; i++) { + if (apkenv_sopaths[i] == NULL) { + apkenv_sopaths[i] = path; + return 0; + } + + if (strcmp(path, apkenv_sopaths[i]) == 0) + return 0; + } + + ERROR("too many apkenv_sopaths\n"); + return -1; +} + +static int apkenv__open_lib(const char *name) +{ + int fd; + struct stat filestat; + + if ((stat(name, &filestat) >= 0) && S_ISREG(filestat.st_mode)) { + if ((fd = open(name, O_RDONLY)) >= 0) + return fd; + } + + return -1; +} + +static int apkenv_open_library(const char *name, char *fullpath) +{ + int fd; + char buf[512]; + const char **path; + int n; + + TRACE("[ %5d opening %s ]\n", apkenv_pid, name); + + if(name == 0) return -1; + if(strlen(name) > 256) return -1; + + strcpy(fullpath, name); + + if ((name[0] == '/') && ((fd = apkenv__open_lib(name)) >= 0)) + return fd; + + if (((fd = apkenv__open_lib(name)) >= 0)) + return fd; + + for (path = apkenv_ldpaths; *path; path++) { + n = format_buffer(buf, sizeof(buf), "%s/%s", *path, name); + if (n < 0 || n >= (int)sizeof(buf)) { + WARN("Ignoring very long library path: %s/%s\n", *path, name); + continue; + } + if ((fd = apkenv__open_lib(buf)) >= 0) { + strcpy(fullpath, buf); + return fd; + } + } + for (path = apkenv_sopaths; *path; path++) { + n = format_buffer(buf, sizeof(buf), "%s/%s", *path, name); + if (n < 0 || n >= (int)sizeof(buf)) { + WARN("Ignoring very long library path: %s/%s\n", *path, name); + continue; + } + if ((fd = apkenv__open_lib(buf)) >= 0) { + strcpy(fullpath, buf); + return fd; + } + } + + return -1; +} + +typedef struct { + long mmap_addr; + char tag[4]; /* 'P', 'R', 'E', ' ' */ +} prelink_info_t; + +/* Returns the requested base address if the library is prelinked, + * and 0 otherwise. */ +static unsigned long +apkenv_is_prelinked(int fd, const char *name) +{ + off_t sz; + prelink_info_t info; + + sz = lseek(fd, -sizeof(prelink_info_t), SEEK_END); + if (sz < 0) { + DL_ERR("lseek() failed!"); + return 0; + } + + if (read(fd, &info, sizeof(info)) != sizeof(info)) { + WARN("Could not read prelink_info_t structure for `%s`\n", name); + return 0; + } + + if (strncmp(info.tag, "PRE ", 4)) { + WARN("`%s` is not a prelinked library\n", name); + return 0; + } + + return (unsigned long)info.mmap_addr; +} + +/* apkenv_verify_elf_object + * Verifies if the object @ base is a valid ELF object + * + * Args: + * + * Returns: + * 0 on success + * -1 if no valid ELF object is found @ base. + */ +static int +apkenv_verify_elf_object(void *base, const char *name) +{ + Elf32_Ehdr *hdr = (Elf32_Ehdr *) base; + + if (hdr->e_ident[EI_MAG0] != ELFMAG0) return -1; + if (hdr->e_ident[EI_MAG1] != ELFMAG1) return -1; + if (hdr->e_ident[EI_MAG2] != ELFMAG2) return -1; + if (hdr->e_ident[EI_MAG3] != ELFMAG3) return -1; + + /* TODO: Should we verify anything else in the header? */ +#ifdef ANDROID_ARM_LINKER + if (hdr->e_machine != EM_ARM) return -1; +#elif defined(ANDROID_X86_LINKER) + if (hdr->e_machine != EM_386) return -1; +#endif + return 0; +} + + +/* apkenv_get_lib_extents + * Retrieves the base (*base) address where the ELF object should be + * mapped and its overall memory size (*total_sz). + * + * Args: + * fd: Opened file descriptor for the library + * name: The name of the library + * _hdr: Pointer to the header page of the library + * total_sz: Total size of the memory that should be allocated for + * this library + * + * Returns: + * -1 if there was an error while trying to get the lib extents. + * The possible reasons are: + * - Could not determine if the library was prelinked. + * - The library provided is not a valid ELF object + * 0 if the library did not request a specific base offset (normal + * for non-prelinked libs) + * > 0 if the library requests a specific address to be mapped to. + * This indicates a pre-linked library. + */ +static unsigned +apkenv_get_lib_extents(int fd, const char *name, void *__hdr, unsigned *total_sz) +{ + unsigned req_base; + unsigned min_vaddr = 0xffffffff; + unsigned max_vaddr = 0; + unsigned char *_hdr = (unsigned char *)__hdr; + Elf32_Ehdr *ehdr = (Elf32_Ehdr *)_hdr; + Elf32_Phdr *phdr; + int cnt; + + TRACE("[ %5d Computing extents for '%s'. ]\n", apkenv_pid, name); + if (apkenv_verify_elf_object(_hdr, name) < 0) { + DL_ERR("%5d - %s is not a valid ELF object", apkenv_pid, name); + return (unsigned)-1; + } + + req_base = (unsigned) apkenv_is_prelinked(fd, name); + if (req_base == (unsigned)-1) + return -1; + else if (req_base != 0) { + TRACE("[ %5d - Prelinked library '%s' requesting base @ 0x%08x ]\n", + apkenv_pid, name, req_base); + } else { + TRACE("[ %5d - Non-prelinked library '%s' found. ]\n", apkenv_pid, name); + } + + phdr = (Elf32_Phdr *)(_hdr + ehdr->e_phoff); + + /* find the min/max p_vaddrs from all the PT_LOAD segments so we can + * get the range. */ + for (cnt = 0; cnt < ehdr->e_phnum; ++cnt, ++phdr) { + if (phdr->p_type == PT_LOAD) { + if ((phdr->p_vaddr + phdr->p_memsz) > max_vaddr) + max_vaddr = phdr->p_vaddr + phdr->p_memsz; + if (phdr->p_vaddr < min_vaddr) + min_vaddr = phdr->p_vaddr; + } + } + + if ((min_vaddr == 0xffffffff) && (max_vaddr == 0)) { + DL_ERR("%5d - No loadable segments found in %s.", apkenv_pid, name); + return (unsigned)-1; + } + + /* truncate min_vaddr down to page boundary */ + min_vaddr &= ~PAGE_MASK; + + /* round max_vaddr up to the next page */ + max_vaddr = (max_vaddr + PAGE_SIZE - 1) & ~PAGE_MASK; + + *total_sz = (max_vaddr - min_vaddr); + return (unsigned)req_base; +} + +/* apkenv_reserve_mem_region + * + * This function reserves a chunk of memory to be used for mapping in + * a prelinked shared library. We reserve the entire memory region here, and + * then the rest of the linker will relocate the individual loadable + * segments into the correct locations within this memory range. + * + * Args: + * si->base: The requested base of the allocation. + * si->size: The size of the allocation. + * + * Returns: + * -1 on failure, and 0 on success. On success, si->base will contain + * the virtual address at which the library will be mapped. + */ + +static int apkenv_reserve_mem_region(soinfo *si) +{ + void *base = mmap((void *)si->base, si->size, PROT_NONE, + MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (base == MAP_FAILED) { + DL_ERR("%5d can NOT map (%sprelinked) library '%s' at 0x%08x " + "as requested, will try general pool: %d (%s)", + apkenv_pid, (si->base ? "" : "non-"), si->name, si->base, + errno, strerror(errno)); + return -1; + } else if (base != (void *)si->base) { + DL_ERR("OOPS: %5d %sprelinked library '%s' mapped at 0x%08x, " + "not at 0x%08x", apkenv_pid, (si->base ? "" : "non-"), + si->name, (unsigned)base, si->base); + munmap(base, si->size); + return -1; + } + return 0; +} + +static int apkenv_alloc_mem_region(soinfo *si) +{ + if (si->base) { + /* Attempt to mmap a prelinked library. */ + return apkenv_reserve_mem_region(si); + } + + /* This is not a prelinked library, so we use the kernel's default + allocator. + */ + + void *base = mmap(NULL, si->size, PROT_NONE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (base == MAP_FAILED) { + DL_ERR("%5d mmap of library '%s' failed: %d (%s)\n", + apkenv_pid, si->name, + errno, strerror(errno)); + goto err; + } + si->base = (unsigned) base; + PRINT("%5d mapped library '%s' to %08x via kernel allocator.\n", + apkenv_pid, si->name, si->base); + return 0; + +err: + DL_ERR("OOPS: %5d cannot map library '%s'. no vspace available.", + apkenv_pid, si->name); + return -1; +} + +#define MAYBE_MAP_FLAG(x,from,to) (((x) & (from)) ? (to) : 0) +#define PFLAGS_TO_PROT(x) (MAYBE_MAP_FLAG((x), PF_X, PROT_EXEC) | \ + MAYBE_MAP_FLAG((x), PF_R, PROT_READ) | \ + MAYBE_MAP_FLAG((x), PF_W, PROT_WRITE)) +/* apkenv_load_segments + * + * This function loads all the loadable (PT_LOAD) segments into memory + * at their appropriate memory offsets off the base address. + * + * Args: + * fd: Open file descriptor to the library to load. + * header: Pointer to a header page that contains the ELF header. + * This is needed since we haven't mapped in the real file yet. + * si: ptr to soinfo struct describing the shared object. + * + * Returns: + * 0 on success, -1 on failure. + */ +static int +apkenv_load_segments(int fd, void *header, soinfo *si) +{ + Elf32_Ehdr *ehdr = (Elf32_Ehdr *)header; + Elf32_Phdr *phdr = (Elf32_Phdr *)((unsigned char *)header + ehdr->e_phoff); + Elf32_Addr base = (Elf32_Addr) si->base; + int cnt; + unsigned len; + Elf32_Addr tmp; + unsigned char *pbase; + unsigned char *extra_base; + unsigned extra_len; + unsigned total_sz = 0; + + si->wrprotect_start = 0xffffffff; + si->wrprotect_end = 0; + + TRACE("[ %5d - Begin loading segments for '%s' @ 0x%08x ]\n", + apkenv_pid, si->name, (unsigned)si->base); + /* Now go through all the PT_LOAD segments and map them into memory + * at the appropriate locations. */ + for (cnt = 0; cnt < ehdr->e_phnum; ++cnt, ++phdr) { + if (phdr->p_type == PT_LOAD) { + DEBUG_DUMP_PHDR(phdr, "PT_LOAD", apkenv_pid); + /* we want to map in the segment on a page boundary */ + tmp = base + (phdr->p_vaddr & (~PAGE_MASK)); + /* add the # of bytes we masked off above to the total length. */ + len = phdr->p_filesz + (phdr->p_vaddr & PAGE_MASK); + + TRACE("[ %d - Trying to load segment from '%s' @ 0x%08x " + "(0x%08x). p_vaddr=0x%08x p_offset=0x%08x ]\n", apkenv_pid, si->name, + (unsigned)tmp, len, phdr->p_vaddr, phdr->p_offset); + pbase = mmap((void *)tmp, len, PFLAGS_TO_PROT(phdr->p_flags), + MAP_PRIVATE | MAP_FIXED, fd, + phdr->p_offset & (~PAGE_MASK)); + if (pbase == MAP_FAILED) { + DL_ERR("%d failed to map segment from '%s' @ 0x%08x (0x%08x). " + "p_vaddr=0x%08x p_offset=0x%08x", apkenv_pid, si->name, + (unsigned)tmp, len, phdr->p_vaddr, phdr->p_offset); + goto fail; + } + + /* If 'len' didn't end on page boundary, and it's a writable + * segment, zero-fill the rest. */ + if ((len & PAGE_MASK) && (phdr->p_flags & PF_W)) + memset((void *)(pbase + len), 0, PAGE_SIZE - (len & PAGE_MASK)); + + /* Check to see if we need to extend the map for this segment to + * cover the diff between filesz and memsz (i.e. for bss). + * + * base _+---------------------+ page boundary + * . . + * | | + * . . + * pbase _+---------------------+ page boundary + * | | + * . . + * base + p_vaddr _| | + * . \ \ . + * . | filesz | . + * pbase + len _| / | | + * <0 pad> . . . + * extra_base _+------------|--------+ page boundary + * / . . . + * | . . . + * | +------------|--------+ page boundary + * extra_len-> | | | | + * | . | memsz . + * | . | . + * \ _| / | + * . . + * | | + * _+---------------------+ page boundary + */ + tmp = (Elf32_Addr)(((unsigned)pbase + len + PAGE_SIZE - 1) & + (~PAGE_MASK)); + if (tmp < (base + phdr->p_vaddr + phdr->p_memsz)) { + extra_len = base + phdr->p_vaddr + phdr->p_memsz - tmp; + TRACE("[ %5d - Need to extend segment from '%s' @ 0x%08x " + "(0x%08x) ]\n", apkenv_pid, si->name, (unsigned)tmp, extra_len); + /* map in the extra page(s) as anonymous into the range. + * This is probably not necessary as we already mapped in + * the entire region previously, but we just want to be + * sure. This will also set the right flags on the region + * (though we can probably accomplish the same thing with + * mprotect). + */ + extra_base = mmap((void *)tmp, extra_len, + PFLAGS_TO_PROT(phdr->p_flags), + MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, + -1, 0); + if (extra_base == MAP_FAILED) { + DL_ERR("[ %5d - failed to extend segment from '%s' @ 0x%08x" + " (0x%08x) ]", apkenv_pid, si->name, (unsigned)tmp, + extra_len); + goto fail; + } + /* TODO: Check if we need to memset-0 this region. + * Anonymous mappings are zero-filled copy-on-writes, so we + * shouldn't need to. */ + TRACE("[ %5d - Segment from '%s' extended @ 0x%08x " + "(0x%08x)\n", apkenv_pid, si->name, (unsigned)extra_base, + extra_len); + } + /* set the len here to show the full extent of the segment we + * just loaded, mostly for debugging */ + len = (((unsigned)base + phdr->p_vaddr + phdr->p_memsz + + PAGE_SIZE - 1) & (~PAGE_MASK)) - (unsigned)pbase; + TRACE("[ %5d - Successfully loaded segment from '%s' @ 0x%08x " + "(0x%08x). p_vaddr=0x%08x p_offset=0x%08x\n", apkenv_pid, si->name, + (unsigned)pbase, len, phdr->p_vaddr, phdr->p_offset); + total_sz += len; + /* Make the section writable just in case we'll have to write to + * it during relocation (i.e. text segment). However, we will + * remember what range of addresses should be write protected. + * + */ + if (!(phdr->p_flags & PF_W)) { + if ((unsigned)pbase < si->wrprotect_start) + si->wrprotect_start = (unsigned)pbase; + if (((unsigned)pbase + len) > si->wrprotect_end) + si->wrprotect_end = (unsigned)pbase + len; + mprotect(pbase, len, + PFLAGS_TO_PROT(phdr->p_flags) | PROT_WRITE); + } + } else if (phdr->p_type == PT_DYNAMIC) { + DEBUG_DUMP_PHDR(phdr, "PT_DYNAMIC", apkenv_pid); + /* this segment contains the dynamic linking information */ + si->dynamic = (unsigned *)(base + phdr->p_vaddr); + } else if (phdr->p_type == PT_GNU_RELRO) { + if ((phdr->p_vaddr >= si->size) + || ((phdr->p_vaddr + phdr->p_memsz) > si->size) + || ((base + phdr->p_vaddr + phdr->p_memsz) < base)) { + DL_ERR("%d invalid GNU_RELRO in '%s' " + "p_vaddr=0x%08x p_memsz=0x%08x", apkenv_pid, si->name, + phdr->p_vaddr, phdr->p_memsz); + goto fail; + } + si->gnu_relro_start = (Elf32_Addr) (base + phdr->p_vaddr); + si->gnu_relro_len = (unsigned) phdr->p_memsz; + } else { +#ifdef ANDROID_ARM_LINKER + if (phdr->p_type == PT_ARM_EXIDX) { + DEBUG_DUMP_PHDR(phdr, "PT_ARM_EXIDX", apkenv_pid); + /* exidx entries (used for stack unwinding) are 8 bytes each. + */ + si->ARM_exidx = (unsigned *)phdr->p_vaddr; + si->ARM_exidx_count = phdr->p_memsz / 8; + } +#endif + } + + } + + /* Sanity check */ + if (total_sz > si->size) { + DL_ERR("%5d - Total length (0x%08x) of mapped segments from '%s' is " + "greater than what was allocated (0x%08x). THIS IS BAD!", + apkenv_pid, total_sz, si->name, si->size); + goto fail; + } + + TRACE("[ %5d - Finish loading segments for '%s' @ 0x%08x. " + "Total memory footprint: 0x%08x bytes ]\n", apkenv_pid, si->name, + (unsigned)si->base, si->size); + return 0; + +fail: + /* We can just blindly unmap the entire region even though some things + * were mapped in originally with anonymous and others could have been + * been mapped in from the file before we failed. The kernel will unmap + * all the pages in the range, irrespective of how they got there. + */ + munmap((void *)si->base, si->size); + si->flags |= FLAG_ERROR; + return -1; +} + +/* TODO: Implement this to take care of the fact that Android ARM + * ELF objects shove everything into a single loadable segment that has the + * write bit set. wr_offset is then used to set non-(data|bss) pages to be + * non-writable. + */ +#if 0 +static unsigned +get_wr_offset(int fd, const char *name, Elf32_Ehdr *ehdr) +{ + Elf32_Shdr *shdr_start; + Elf32_Shdr *shdr; + int shdr_sz = ehdr->e_shnum * sizeof(Elf32_Shdr); + int cnt; + unsigned wr_offset = 0xffffffff; + + shdr_start = mmap(0, shdr_sz, PROT_READ, MAP_PRIVATE, fd, + ehdr->e_shoff & (~PAGE_MASK)); + if (shdr_start == MAP_FAILED) { + WARN("%5d - Could not read section header info from '%s'. Will not " + "not be able to determine write-protect offset.\n", apkenv_pid, name); + return (unsigned)-1; + } + + for(cnt = 0, shdr = shdr_start; cnt < ehdr->e_shnum; ++cnt, ++shdr) { + if ((shdr->sh_type != SHT_NULL) && (shdr->sh_flags & SHF_WRITE) && + (shdr->sh_addr < wr_offset)) { + wr_offset = shdr->sh_addr; + } + } + + munmap(shdr_start, shdr_sz); + return wr_offset; +} +#endif + +static soinfo * +apkenv_load_library(const char *name) +{ + char fullpath[512]; + int fd = apkenv_open_library(name, fullpath); + int cnt; + unsigned ext_sz; + unsigned req_base; + const char *bname; + soinfo *si = NULL; + Elf32_Ehdr *hdr; + + if(fd == -1) { +#if !LINKER_DEBUG + if (!is_lib_optional(name)) +#endif + DL_ERR("Library '%s' not found", name); + return NULL; + } + + off_t end; + if ((end = lseek(fd, 0, SEEK_END)) < 0) { + DL_ERR("lseek() failed!"); + goto fail; + } + + uint8_t *bytes; + if (!(bytes = calloc(1, end))) { + DL_ERR("calloc() failed!"); + goto fail; + } + + /* We have to read the ELF header to figure out what to do with this image + */ + if (lseek(fd, 0, SEEK_SET) < 0) { + DL_ERR("lseek() failed!"); + goto fail; + } + + + if ((cnt = read(fd, bytes, end)) < 0) { + DL_ERR("read() failed!"); + goto fail; + } + + /* Parse the ELF header and get the size of the memory footprint for + * the library */ + req_base = apkenv_get_lib_extents(fd, name, bytes, &ext_sz); + if (req_base == (unsigned)-1) + goto fail; + TRACE("[ %5d - '%s' (%s) wants base=0x%08x sz=0x%08x ]\n", apkenv_pid, name, + (req_base ? "prelinked" : "not pre-linked"), req_base, ext_sz); + + /* Now configure the soinfo struct where we'll store all of our data + * for the ELF object. If the loading fails, we waste the entry, but + * same thing would happen if we failed during linking. Configuring the + * soinfo struct here is a lot more convenient. + */ + bname = strrchr(name, '/'); + si = apkenv_alloc_info(bname ? bname + 1 : name); + if (si == NULL) + goto fail; + + /* apkenv */ + strncpy(si->fullpath, fullpath, sizeof(si->fullpath)); + si->fullpath[sizeof(si->fullpath) - 1] = 0; + + /* Carve out a chunk of memory where we will map in the individual + * segments */ + si->base = req_base; + si->size = ext_sz; + si->flags = 0; + si->entry = 0; + si->dynamic = (unsigned *)-1; + if (apkenv_alloc_mem_region(si) < 0) + goto fail; + + TRACE("[ %5d allocated memory for %s @ %p (0x%08x) ]\n", + apkenv_pid, name, (void *)si->base, (unsigned) ext_sz); + + /* Now actually load the library's segments into right places in memory */ + if (apkenv_load_segments(fd, bytes, si) < 0) { + goto fail; + } + + /* this might not be right. Technically, we don't even need this info + * once we go through 'apkenv_load_segments'. */ + hdr = (Elf32_Ehdr *)si->base; + si->phdr = (Elf32_Phdr *)((unsigned char *)si->base + hdr->e_phoff); + si->phnum = hdr->e_phnum; + /**/ + + close(fd); + return si; + +fail: + if (si) apkenv_free_info(si); + close(fd); + return NULL; +} + +static soinfo * +apkenv_init_library(soinfo *si) +{ + unsigned wr_offset = 0xffffffff; + + /* At this point we know that whatever is loaded @ base is a valid ELF + * shared library whose segments are properly mapped in. */ + TRACE("[ %5d apkenv_init_library base=0x%08x sz=0x%08x name='%s') ]\n", + apkenv_pid, si->base, si->size, si->name); + if(apkenv_link_image(si, wr_offset)) { + /* We failed to link. However, we can only restore libbase + ** if no additional libraries have moved it since we updated it. + */ + munmap((void *)si->base, si->size); + return NULL; + } + + return si; +} + +soinfo *apkenv_find_library(const char *name) +{ + soinfo *si; + const char *bname; + +#if ALLOW_SYMBOLS_FROM_MAIN + if (name == NULL) + return apkenv_somain; +#else + if (name == NULL) + return NULL; +#endif + + bname = strrchr(name, '/'); + bname = bname ? bname + 1 : name; + + for(si = apkenv_solist; si != 0; si = si->next){ + if(!strcmp(bname, si->name)) { + if(si->flags & FLAG_ERROR) { + DL_ERR("%5d '%s' failed to load previously", apkenv_pid, bname); + return NULL; + } + if(si->flags & FLAG_LINKED) return si; + DL_ERR("OOPS: %5d recursive link to '%s'", apkenv_pid, si->name); + return NULL; + } + } + + TRACE("[ %5d '%s' has not been loaded yet. Locating...]\n", apkenv_pid, name); + si = apkenv_load_library(name); + if(si == NULL) + return NULL; + return apkenv_init_library(si); +} + +/* TODO: + * notify gdb of unload + * for non-prelinked libraries, find a way to decrement libbase + */ +static void apkenv_call_destructors(soinfo *si); +unsigned apkenv_unload_library(soinfo *si) +{ + unsigned *d; + if (si->refcount == 1) { + TRACE("%5d unloading '%s'\n", apkenv_pid, si->name); + apkenv_call_destructors(si); + + /* + * Make sure that we undo the PT_GNU_RELRO protections we added + * in apkenv_link_image. This is needed to undo the DT_NEEDED hack below. + */ + if ((si->gnu_relro_start != 0) && (si->gnu_relro_len != 0)) { + Elf32_Addr start = (si->gnu_relro_start & ~PAGE_MASK); + unsigned len = (si->gnu_relro_start - start) + si->gnu_relro_len; + if (mprotect((void *) start, len, PROT_READ | PROT_WRITE) < 0) + DL_ERR("%5d %s: could not undo GNU_RELRO protections. " + "Expect a crash soon. errno=%d (%s)", + apkenv_pid, si->name, errno, strerror(errno)); + + } + + for(d = si->dynamic; *d; d += 2) { + if(d[0] == DT_NEEDED){ + soinfo *lsi = (soinfo *)d[1]; + + // The next line will segfault if the we don't undo the + // PT_GNU_RELRO protections (see comments above and in + // apkenv_link_image(). + d[1] = 0; + + if (apkenv_validate_soinfo(lsi)) { + TRACE("%5d %s needs to unload %s\n", apkenv_pid, + si->name, lsi->name); + apkenv_unload_library(lsi); + } + else + DL_ERR("%5d %s: could not unload dependent library", + apkenv_pid, si->name); + } + } + + munmap((char *)si->base, si->size); + apkenv_notify_gdb_of_unload(si); + apkenv_free_info(si); + si->refcount = 0; + } + else { + si->refcount--; + PRINT("%5d not unloading '%s', decrementing refcount to %d\n", + apkenv_pid, si->name, si->refcount); + } + return si->refcount; +} + +#define MIN(a,b) (((a)<(b))?(a):(b)) + +/* 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 apkenv_reloc_library(soinfo *si, Elf32_Rel *rel, unsigned count) +{ + Elf32_Sym *symtab = si->symtab; + const char *strtab = si->strtab; + Elf32_Sym *s; + unsigned base; + Elf32_Rel *start = rel; + unsigned idx; + + for (idx = 0; idx < count; ++idx) { + unsigned type = ELF32_R_TYPE(rel->r_info); + unsigned sym = ELF32_R_SYM(rel->r_info); + unsigned reloc = (unsigned)(rel->r_offset + si->base); + unsigned sym_addr = 0; + char *sym_name = NULL; + char wrap_sym_name[1024] = { 'b', 'i', 'o', 'n', 'i', 'c', '_' }; + + DEBUG("%5d Processing '%s' relocation at index %d\n", apkenv_pid, + si->name, idx); + if(sym != 0) { + sym_name = (char *)(strtab + symtab[sym].st_name); + memcpy(wrap_sym_name + 7, sym_name, MIN(sizeof(wrap_sym_name) - 7, strlen(sym_name))); + sym_addr = 0; + if ((sym_addr = dlsym(RTLD_DEFAULT, wrap_sym_name))) { + LINKER_DEBUG_PRINTF("%s hooked symbol %s to %x\n", si->name, wrap_sym_name, sym_addr); + } else if ((sym_addr = dlsym(RTLD_DEFAULT, sym_name))) { + LINKER_DEBUG_PRINTF("%s hooked symbol %s to %x\n", si->name, sym_name, sym_addr); + } +#if 0 + if ((sym_addr = (unsigned)apkenv_get_hooked_symbol(sym_name, 1)) != 0) { + LINKER_DEBUG_PRINTF("%s hooked symbol %s to %x\n", si->name, sym_name, sym_addr); + } +#endif + else + { + s = apkenv__do_lookup(si, sym_name, &base); + } + if(sym_addr != 0) + { + sym_addr = (unsigned)create_wrapper(sym_name, (void*)sym_addr, WRAPPER_UNHOOKED); + } else + 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("%5d cannot locate '%s'...\n", apkenv_pid, sym_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 nominial 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. */ + case R_ARM_NONE: /* Don't care. */ +#elif defined(ANDROID_X86_LINKER) + case R_386_JUMP_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("%5d unknown weak reloc type %d @ %p (%d)\n", + apkenv_pid, 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("%5d cannot locate '%s'...", + apkenv_pid, strtab + symtab[sym].st_name); + return -1; + } +#endif + sym_addr = (unsigned)(s->st_value + base); + LINKER_DEBUG_PRINTF("%s symbol (from %s) %s to %x\n", si->name, apkenv_last_library_used, sym_name, sym_addr); + if(ELF32_ST_TYPE(s->st_info) == STT_FUNC) { + sym_addr = (unsigned)create_wrapper(sym_name, (void*)sym_addr, WRAPPER_UNHOOKED); + } + + } + COUNT_RELOC(RELOC_SYMBOL); + } 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_RELOC(RELOC_ABSOLUTE); + MARK(rel->r_offset); + TRACE_TYPE(RELO, "%5d RELO JMP_SLOT %08x <- %08x %s\n", apkenv_pid, + reloc, sym_addr, sym_name); + *((unsigned*)reloc) = sym_addr; + break; + case R_ARM_GLOB_DAT: + COUNT_RELOC(RELOC_ABSOLUTE); + MARK(rel->r_offset); + TRACE_TYPE(RELO, "%5d RELO GLOB_DAT %08x <- %08x %s\n", apkenv_pid, + reloc, sym_addr, sym_name); + *((unsigned*)reloc) = sym_addr; + break; + case R_ARM_ABS32: + COUNT_RELOC(RELOC_ABSOLUTE); + MARK(rel->r_offset); + TRACE_TYPE(RELO, "%5d RELO ABS %08x <- %08x %s\n", apkenv_pid, + reloc, sym_addr, sym_name); + *((unsigned*)reloc) += sym_addr; + break; + case R_ARM_REL32: + COUNT_RELOC(RELOC_RELATIVE); + MARK(rel->r_offset); + TRACE_TYPE(RELO, "%5d RELO REL32 %08x <- %08x - %08x %s\n", apkenv_pid, + reloc, sym_addr, rel->r_offset, sym_name); + *((unsigned*)reloc) += sym_addr - rel->r_offset; + break; +#elif defined(ANDROID_X86_LINKER) + case R_386_JUMP_SLOT: + COUNT_RELOC(RELOC_ABSOLUTE); + MARK(rel->r_offset); + TRACE_TYPE(RELO, "%5d RELO JMP_SLOT %08x <- %08x %s\n", apkenv_pid, + reloc, sym_addr, sym_name); + *((unsigned*)reloc) = sym_addr; + break; + case R_386_GLOB_DAT: + COUNT_RELOC(RELOC_ABSOLUTE); + MARK(rel->r_offset); + TRACE_TYPE(RELO, "%5d RELO GLOB_DAT %08x <- %08x %s\n", apkenv_pid, + reloc, sym_addr, sym_name); + *((unsigned*)reloc) = sym_addr; + 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_RELOC(RELOC_RELATIVE); + MARK(rel->r_offset); + if(sym){ + DL_ERR("%5d odd RELATIVE form...", apkenv_pid); + return -1; + } + TRACE_TYPE(RELO, "%5d RELO RELATIVE %08x <- +%08x\n", apkenv_pid, + reloc, si->base); + *((unsigned*)reloc) += si->base; + break; + +#if defined(ANDROID_X86_LINKER) + case R_386_32: + COUNT_RELOC(RELOC_RELATIVE); + MARK(rel->r_offset); + + TRACE_TYPE(RELO, "%5d RELO R_386_32 %08x <- +%08x %s\n", apkenv_pid, + reloc, sym_addr, sym_name); + *((unsigned *)reloc) += (unsigned)sym_addr; + break; + + case R_386_PC32: + COUNT_RELOC(RELOC_RELATIVE); + MARK(rel->r_offset); + TRACE_TYPE(RELO, "%5d RELO R_386_PC32 %08x <- " + "+%08x (%08x - %08x) %s\n", apkenv_pid, reloc, + (sym_addr - reloc), sym_addr, reloc, sym_name); + *((unsigned *)reloc) += (unsigned)(sym_addr - reloc); + break; +#endif /* ANDROID_X86_LINKER */ + +#ifdef ANDROID_ARM_LINKER + case R_ARM_COPY: + COUNT_RELOC(RELOC_COPY); + MARK(rel->r_offset); + TRACE_TYPE(RELO, "%5d RELO %08x <- %d @ %08x %s\n", apkenv_pid, + reloc, s->st_size, sym_addr, sym_name); + memcpy((void*)reloc, (void*)sym_addr, s->st_size); + break; + case R_ARM_NONE: + break; +#endif /* ANDROID_ARM_LINKER */ + + default: + DL_ERR("%5d unknown reloc type %d @ %p (%d)", + apkenv_pid, type, rel, (int) (rel - start)); + return -1; + } + rel++; + } + return 0; +} + +/* Please read the "Initialization and Termination functions" functions. + * of the linker design note in bionic/linker/README.TXT to understand + * what the following code is doing. + * + * The important things to remember are: + * + * DT_PREINIT_ARRAY must be called first for executables, and should + * not appear in shared libraries. + * + * DT_INIT should be called before DT_INIT_ARRAY if both are present + * + * DT_FINI should be called after DT_FINI_ARRAY if both are present + * + * DT_FINI_ARRAY must be parsed in reverse order. + */ + +static void apkenv_call_array(unsigned *ctor, int count, int reverse) +{ + int n, inc = 1; + + if (reverse) { + ctor += (count-1); + inc = -1; + } + + for(n = count; n > 0; n--) { + TRACE("[ %5d Looking at %s *0x%08x == 0x%08x ]\n", apkenv_pid, + reverse ? "dtor" : "ctor", + (unsigned)ctor, (unsigned)*ctor); + void (*func)() = (void (*)()) *ctor; + ctor += inc; + if(((int) func == 0) || ((int) func == -1)) continue; + TRACE("[ %5d Calling func @ 0x%08x ]\n", apkenv_pid, (unsigned)func); + func(); + } +} + +void apkenv_call_constructors_recursive(soinfo *si) +{ + if (si->constructors_called) + return; + if (strcmp(si->name, "libc.so") == 0) +return; + // Set this 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 apkenv_call_constructors_recursive() with the newly created + // soinfo for libc_malloc_debug_leak.so. + // 4. The debug so depends on libc, so apkenv_call_constructors_recursive() is + // called again with the libc soinfo. If it doesn't trigger the early- + // out above, the libc constructor will be called again (recursively!). + si->constructors_called = 1; + + if (si->flags & FLAG_EXE) { + TRACE("[ %5d Calling preinit_array @ 0x%08x [%d] for '%s' ]\n", + apkenv_pid, (unsigned)si->preinit_array, si->preinit_array_count, + si->name); + apkenv_call_array(si->preinit_array, si->preinit_array_count, 0); + TRACE("[ %5d Done calling preinit_array for '%s' ]\n", apkenv_pid, si->name); + } else { + if (si->preinit_array) { + DL_ERR("%5d Shared library '%s' has a preinit_array table @ 0x%08x." + " This is INVALID.", apkenv_pid, si->name, + (unsigned)si->preinit_array); + } + } + + if (si->dynamic) { + unsigned *d; + for(d = si->dynamic; *d; d += 2) { + if(d[0] == DT_NEEDED){ + soinfo* lsi = (soinfo *)d[1]; + if (!apkenv_validate_soinfo(lsi)) { + DL_ERR("%5d bad DT_NEEDED pointer in %s", + apkenv_pid, si->name); + } else { + apkenv_call_constructors_recursive(lsi); + } + } + } + } + + if (si->init_func) { + TRACE("[ %5d Calling init_func @ 0x%08x for '%s' ]\n", apkenv_pid, + (unsigned)si->init_func, si->name); + si->init_func(); + TRACE("[ %5d Done calling init_func for '%s' ]\n", apkenv_pid, si->name); + } + + if (si->init_array) { + TRACE("[ %5d Calling init_array @ 0x%08x [%d] for '%s' ]\n", apkenv_pid, + (unsigned)si->init_array, si->init_array_count, si->name); + apkenv_call_array(si->init_array, si->init_array_count, 0); + TRACE("[ %5d Done calling init_array for '%s' ]\n", apkenv_pid, si->name); + } + +} + +static void apkenv_call_destructors(soinfo *si) +{ + if (si->fini_array) { + TRACE("[ %5d Calling fini_array @ 0x%08x [%d] for '%s' ]\n", apkenv_pid, + (unsigned)si->fini_array, si->fini_array_count, si->name); + apkenv_call_array(si->fini_array, si->fini_array_count, 1); + TRACE("[ %5d Done calling fini_array for '%s' ]\n", apkenv_pid, si->name); + } + + if (si->fini_func) { + TRACE("[ %5d Calling fini_func @ 0x%08x for '%s' ]\n", apkenv_pid, + (unsigned)si->fini_func, si->name); + si->fini_func(); + TRACE("[ %5d Done calling fini_func for '%s' ]\n", apkenv_pid, si->name); + } +} + +/* Force any of the closed stdin, stdout and stderr to be associated with + /dev/null. */ +static int apkenv_nullify_closed_stdio (void) +{ + int dev_null, i, status; + int return_value = 0; + + dev_null = open("/dev/null", O_RDWR); + if (dev_null < 0) { + DL_ERR("Cannot open /dev/null."); + return -1; + } + TRACE("[ %5d Opened /dev/null file-descriptor=%d]\n", apkenv_pid, 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("[ %5d Nullifying stdio file descriptor %d]\n", apkenv_pid, i); + /* The man page of fcntl does not say that fcntl(..,F_GETFL) + can be interrupted but we do this just to be safe. */ + do { + status = fcntl(i, F_GETFL); + } while (status < 0 && errno == EINTR); + + /* If file is openned, we are good. */ + if (status >= 0) + 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("nullify_stdio: unhandled error %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. */ + do { + status = dup2(dev_null, i); + } while (status < 0 && errno == EINTR); + + if (status < 0) { + DL_ERR("nullify_stdio: dup2 error %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("[ %5d Closing /dev/null file-descriptor=%d]\n", apkenv_pid, dev_null); + do { + status = close(dev_null); + } while (status < 0 && errno == EINTR); + + if (status < 0) { + DL_ERR("nullify_stdio: close error %s", strerror(errno)); + return_value = -1; + } + } + + return return_value; +} + +static void apkenv_wrap_function(void *sym_addr, char *sym_name, int is_thumb, soinfo *si) +{ + void *hook = NULL; +#ifdef APKENV_LATEHOOKS + if((hook = apkenv_get_hooked_symbol(sym_name, 0)) != NULL) + { + // if we have a hook redirect the call to that by overwriting + // the first 2 instruction of the function + // this should work in any case unless the hook is wrong + // or the function shorter than 64-bit (2 32-Bit instructions) + if(!is_thumb) + { + DEBUG("HOOKING INTERNAL (ARM) FUNCTION %s@%x (in %s) TO: %x\n",sym_name,sym_addr,si->name,hook); + ((int32_t*)sym_addr)[0] = 0xe51ff004; // ldr pc, [pc, -#4] (load the hooks address into pc) + ((int32_t*)sym_addr)[1] = (uint32_t)create_wrapper(sym_name, hook, WRAPPER_LATEHOOK); + + __clear_cache((int32_t*)sym_addr, (int32_t*)sym_addr + 2); + } + else + { + DEBUG("HOOKING INTERNAL (THUMB) FUNCTION %s@%x (in %s) TO: %x\n",sym_name,sym_addr,si->name,hook); + sym_addr = (void*)((char*)sym_addr - 1); // get actual sym_addr + + ((int16_t*)sym_addr)[0] = 0xB401; /* push {r0} */ + ((int16_t*)sym_addr)[1] = 0xF8DF; /* ldr r0, [pc, #8] */ + ((int16_t*)sym_addr)[2] = 0x0008; /* continuation of last instruction */ + ((int16_t*)sym_addr)[3] = 0x4684; /* mov ip, r0 */ + ((int16_t*)sym_addr)[4] = 0xBC01; /* pop {r0} */ + ((int16_t*)sym_addr)[5] = 0x4760; /* bx ip */ + + void *wrp = create_wrapper(sym_name, hook, WRAPPER_LATEHOOK); + + // store the hooks address + ((int16_t*)sym_addr)[6] = (uint32_t)wrp & 0x0000FFFF; + ((int16_t*)sym_addr)[7] = (uint32_t)wrp >> 16; + + __clear_cache((int16_t*)sym_addr, (int16_t*)sym_addr + 8); + } + } + else +#endif /* APKENV_LATEHOOKS */ + // TODO: this will fail if the first 2 instructions do something pc related + // (this DOES NOT happen very often) + if(sym_addr && !is_thumb) + { + DEBUG("CREATING ARM WRAPPER FOR: %s@%x (in %s)\n", sym_name, (unsigned)sym_addr, si->name); + + create_wrapper(sym_name, sym_addr, WRAPPER_ARM_INJECTION); + } + // TODO: this will fail if the first 2-5 instructions do something pc related + // (this DOES happen very often) + else if(sym_addr && is_thumb) + { + DEBUG("CREATING THUMB WRAPPER FOR: %s@%x (in %s)\n",sym_name, (unsigned)sym_addr,si->name); + + create_wrapper(sym_name, sym_addr, WRAPPER_THUMB_INJECTION); + } +} + + +/* Franz-Josef Haider apkenv_create_latehook_wrappers */ +static void apkenv_create_latehook_wrappers(soinfo *si) +{ + Elf32_Sym *s; + + unsigned int n = 0; + for(n=0;n<si->nchain;n++) + { + s = si->symtab + n; + switch(ELF32_ST_BIND(s->st_info)) + { + case STB_GLOBAL: + case STB_WEAK: + if(s->st_shndx == 0) continue; + + if(ELF32_ST_TYPE(s->st_info) == STT_FUNC) // only wrap functions + { + char *sym_name = (char*)(si->strtab + s->st_name); + void *sym_addr = (void*)(intptr_t)(si->base + s->st_value); + + int is_thumb = ((int32_t)(intptr_t)sym_addr) & 0x00000001; + + apkenv_wrap_function(sym_addr,sym_name,is_thumb,si); + } + } + } +} + + +static int apkenv_link_image(soinfo *si, unsigned wr_offset) +{ + unsigned *d; + Elf32_Phdr *phdr = si->phdr; + int phnum = si->phnum; + + INFO("[ %5d linking %s ]\n", apkenv_pid, si->name); + DEBUG("%5d si->base = 0x%08x si->flags = 0x%08x\n", apkenv_pid, + si->base, si->flags); + + if (si->flags & (FLAG_EXE | FLAG_LINKER)) { + /* Locate the needed program segments (DYNAMIC/ARM_EXIDX) for + * linkage info if this is the executable or the linker itself. + * If this was a dynamic lib, that would have been done at load time. + * + * TODO: It's unfortunate that small pieces of this are + * repeated from the apkenv_load_library routine. Refactor this just + * slightly to reuse these bits. + */ + si->size = 0; + for(; phnum > 0; --phnum, ++phdr) { +#ifdef ANDROID_ARM_LINKER + if(phdr->p_type == PT_ARM_EXIDX) { + /* exidx entries (used for stack unwinding) are 8 bytes each. + */ + si->ARM_exidx = (unsigned *)phdr->p_vaddr; + si->ARM_exidx_count = phdr->p_memsz / 8; + } +#endif + if (phdr->p_type == PT_LOAD) { + /* For the executable, we use the si->size field only in + dl_unwind_find_exidx(), so the meaning of si->size + is not the size of the executable; it is the distance + between the load location of the executable and the last + address of the loadable part of the executable. + We use the range [si->base, si->base + si->size) to + determine whether a PC value falls within the executable + section. Of course, if a value is between si->base and + (si->base + phdr->p_vaddr), it's not in the executable + section, but a) we shouldn't be asking for such a value + anyway, and b) if we have to provide an EXIDX for such a + value, then the executable's EXIDX is probably the better + choice. + */ + DEBUG_DUMP_PHDR(phdr, "PT_LOAD", apkenv_pid); + if (phdr->p_vaddr + phdr->p_memsz > si->size) + si->size = phdr->p_vaddr + phdr->p_memsz; + /* try to remember what range of addresses should be write + * protected */ + if (!(phdr->p_flags & PF_W)) { + unsigned _end; + + if (si->base + phdr->p_vaddr < si->wrprotect_start) + si->wrprotect_start = si->base + phdr->p_vaddr; + _end = (((si->base + phdr->p_vaddr + phdr->p_memsz + PAGE_SIZE - 1) & + (~PAGE_MASK))); + if (_end > si->wrprotect_end) + si->wrprotect_end = _end; + /* Make the section writable just in case we'll have to + * write to it during relocation (i.e. text segment). + * However, we will remember what range of addresses + * should be write protected. + */ + mprotect((void *) (si->base + phdr->p_vaddr), + phdr->p_memsz, + PFLAGS_TO_PROT(phdr->p_flags) | PROT_WRITE); + } + } else if (phdr->p_type == PT_DYNAMIC) { + if (si->dynamic != (unsigned *)-1) { + DL_ERR("%5d multiple PT_DYNAMIC segments found in '%s'. " + "Segment at 0x%08x, previously one found at 0x%08x", + apkenv_pid, si->name, si->base + phdr->p_vaddr, + (unsigned)si->dynamic); + goto fail; + } + DEBUG_DUMP_PHDR(phdr, "PT_DYNAMIC", apkenv_pid); + si->dynamic = (unsigned *) (si->base + phdr->p_vaddr); + } else if (phdr->p_type == PT_GNU_RELRO) { + if ((phdr->p_vaddr >= si->size) + || ((phdr->p_vaddr + phdr->p_memsz) > si->size) + || ((si->base + phdr->p_vaddr + phdr->p_memsz) < si->base)) { + DL_ERR("%d invalid GNU_RELRO in '%s' " + "p_vaddr=0x%08x p_memsz=0x%08x", apkenv_pid, si->name, + phdr->p_vaddr, phdr->p_memsz); + goto fail; + } + si->gnu_relro_start = (Elf32_Addr) (si->base + phdr->p_vaddr); + si->gnu_relro_len = (unsigned) phdr->p_memsz; + } + } + } + + if (si->dynamic == (unsigned *)-1) { + DL_ERR("%5d missing PT_DYNAMIC?!", apkenv_pid); + goto fail; + } + + DEBUG("%5d dynamic = %p\n", apkenv_pid, si->dynamic); + + /* extract useful information from dynamic section */ + for(d = si->dynamic; *d; d++){ + DEBUG("%5d d = %p, d[0] = 0x%08x d[1] = 0x%08x\n", apkenv_pid, d, d[0], d[1]); + switch(*d++){ + case DT_HASH: + si->nbucket = ((unsigned *) (si->base + *d))[0]; + si->nchain = ((unsigned *) (si->base + *d))[1]; + si->bucket = (unsigned *) (si->base + *d + 8); + si->chain = (unsigned *) (si->base + *d + 8 + si->nbucket * 4); + break; + case DT_STRTAB: + si->strtab = (const char *) (si->base + *d); + break; + case DT_SYMTAB: + si->symtab = (Elf32_Sym *) (si->base + *d); + break; + case DT_PLTREL: + if(*d != DT_REL) { + DL_ERR("DT_RELA not supported"); + goto fail; + } + break; + case DT_JMPREL: + si->plt_rel = (Elf32_Rel*) (si->base + *d); + break; + case DT_PLTRELSZ: + si->plt_rel_count = *d / 8; + break; + case DT_REL: + si->rel = (Elf32_Rel*) (si->base + *d); + break; + case DT_RELSZ: + si->rel_count = *d / 8; + break; + case DT_PLTGOT: + /* Save this in case we decide to do lazy binding. We don't yet. */ + si->plt_got = (unsigned *)(si->base + *d); + break; + case DT_DEBUG: + // Set the DT_DEBUG entry to the addres of _r_debug for GDB + *d = (int) &_r_debug; + break; + case DT_RELA: + DL_ERR("%5d DT_RELA not supported", apkenv_pid); + goto fail; + case DT_INIT: + si->init_func = (void (*)(void))(si->base + *d); + DEBUG("%5d %s constructors (init func) found at %p\n", + apkenv_pid, si->name, si->init_func); + break; + case DT_FINI: + si->fini_func = (void (*)(void))(si->base + *d); + DEBUG("%5d %s destructors (fini func) found at %p\n", + apkenv_pid, si->name, si->fini_func); + break; + case DT_INIT_ARRAY: + si->init_array = (unsigned *)(si->base + *d); + DEBUG("%5d %s constructors (init_array) found at %p\n", + apkenv_pid, si->name, si->init_array); + break; + case DT_INIT_ARRAYSZ: + si->init_array_count = ((unsigned)*d) / sizeof(Elf32_Addr); + break; + case DT_FINI_ARRAY: + si->fini_array = (unsigned *)(si->base + *d); + DEBUG("%5d %s destructors (fini_array) found at %p\n", + apkenv_pid, si->name, si->fini_array); + break; + case DT_FINI_ARRAYSZ: + si->fini_array_count = ((unsigned)*d) / sizeof(Elf32_Addr); + break; + case DT_PREINIT_ARRAY: + si->preinit_array = (unsigned *)(si->base + *d); + DEBUG("%5d %s constructors (preinit_array) found at %p\n", + apkenv_pid, si->name, si->preinit_array); + break; + case DT_PREINIT_ARRAYSZ: + si->preinit_array_count = ((unsigned)*d) / sizeof(Elf32_Addr); + break; + case DT_TEXTREL: + /* TODO: make use of this. */ + /* this means that we might have to write into where the text + * segment was loaded during relocation... Do something with + * it. + */ + DEBUG("%5d Text segment should be writable during relocation.\n", + apkenv_pid); + break; + } + } + + DEBUG("%5d si->base = 0x%08x, si->strtab = %p, si->symtab = %p\n", + apkenv_pid, si->base, si->strtab, si->symtab); + + if((si->strtab == 0) || (si->symtab == 0)) { + DL_ERR("%5d missing essential tables", apkenv_pid); + goto fail; + } + + /* if this is the main executable, then load all of the apkenv_preloads now */ + if(si->flags & FLAG_EXE) { + int i; + memset(apkenv_preloads, 0, sizeof(apkenv_preloads)); + for(i = 0; apkenv_ldpreload_names[i] != NULL; i++) { + soinfo *lsi = apkenv_find_library(apkenv_ldpreload_names[i]); + if(lsi == 0) { + apkenv_strlcpy(apkenv_tmp_err_buf, apkenv_linker_get_error(), sizeof(apkenv_tmp_err_buf)); + DL_ERR("%5d could not load needed library '%s' for '%s' (%s)", + apkenv_pid, apkenv_ldpreload_names[i], si->name, apkenv_tmp_err_buf); + goto fail; + } + lsi->refcount++; + apkenv_preloads[i] = lsi; + } + } + + for(d = si->dynamic; *d; d += 2) { + if(d[0] == DT_NEEDED){ + DEBUG("%5d %s needs %s\n", apkenv_pid, si->name, si->strtab + d[1]); + soinfo *lsi = NULL; +#if 1 + // if (get_builtin_lib_handle(si->strtab + d[1]) == NULL) + lsi = apkenv_find_library(si->strtab + d[1]); + if (!lsi && dlopen(si->strtab + d[1], RTLD_NOW | RTLD_GLOBAL)) { + DEBUG("Loaded %s with glibc dlopen\n", si->strtab + d[1]); + } +#endif + if(lsi == 0) { + /** + * XXX Dirty Hack Alarm --thp XXX + * + * For libraries that are not found, simply use libdl's soinfo, + * in order to not break downstream users of the library while + * still allowing the application to start up. + **/ + lsi = &apkenv_libdl_info; + //apkenv_strlcpy(apkenv_tmp_err_buf, apkenv_linker_get_error(), sizeof(apkenv_tmp_err_buf)); + //DL_ERR("%5d could not load needed library '%s' for '%s' (%s)", + // apkenv_pid, si->strtab + d[1], si->name, apkenv_tmp_err_buf); + //continue; + //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 symbol + with dlsym(). + */ + d[1] = (intptr_t)lsi; + lsi->refcount++; + } + } + + if(si->plt_rel) { + DEBUG("[ %5d relocating %s plt ]\n", apkenv_pid, si->name ); + if(apkenv_reloc_library(si, si->plt_rel, si->plt_rel_count)) + goto fail; + } + if(si->rel) { + DEBUG("[ %5d relocating %s ]\n", apkenv_pid, si->name ); + if(apkenv_reloc_library(si, si->rel, si->rel_count)) + goto fail; + } + + apkenv_create_latehook_wrappers(si); + + si->flags |= FLAG_LINKED; + DEBUG("[ %5d finished linking %s ]\n", apkenv_pid, si->name); + +#if 0 + /* This is the way that the old dynamic linker did protection of + * non-writable areas. It would scan section headers and find where + * .text ended (rather where .data/.bss began) and assume that this is + * the upper range of the non-writable area. This is too coarse, + * and is kept here for reference until we fully move away from single + * segment elf objects. See the code in get_wr_offset (also #if'd 0) + * that made this possible. + */ + if(wr_offset < 0xffffffff){ + mprotect((void*) si->base, wr_offset, PROT_READ | PROT_EXEC); + } +#else + /* TODO: Verify that this does the right thing in all cases, as it + * presently probably does not. It is possible that an ELF image will + * come with multiple read-only segments. What we ought to do is scan + * the program headers again and mprotect all the read-only segments. + * To prevent re-scanning the program header, we would have to build a + * list of loadable segments in si, and then scan that instead. */ + if (si->wrprotect_start != 0xffffffff && si->wrprotect_end != 0) { + mprotect((void *)(intptr_t)si->wrprotect_start, + si->wrprotect_end - si->wrprotect_start, + PROT_READ | PROT_EXEC); + } +#endif + + if (si->gnu_relro_start != 0 && si->gnu_relro_len != 0) { + Elf32_Addr start = (si->gnu_relro_start & ~PAGE_MASK); + unsigned len = (si->gnu_relro_start - start) + si->gnu_relro_len; + if (mprotect((void *)(intptr_t)start, len, PROT_READ) < 0) { + DL_ERR("%5d GNU_RELRO mprotect of library '%s' failed: %d (%s)\n", + apkenv_pid, si->name, errno, strerror(errno)); + goto fail; + } + } + + /* If this is a SET?ID program, dup /dev/null to opened stdin, + stdout and stderr to close a security hole described in: + + ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc + + */ + if (apkenv_program_is_setuid) + apkenv_nullify_closed_stdio (); + apkenv_notify_gdb_of_load(si); + return 0; + +fail: + ERROR("failed to link %s\n", si->name); + si->flags |= FLAG_ERROR; + return -1; +} + +void apkenv_parse_library_path(const char *path, char *delim) +{ + size_t len; + char *apkenv_ldpaths_bufp = apkenv_ldpaths_buf; + int i = 0; + + len = apkenv_strlcpy(apkenv_ldpaths_buf, path, sizeof(apkenv_ldpaths_buf)); + + while (i < LDPATH_MAX && (apkenv_ldpaths[i] = strsep(&apkenv_ldpaths_bufp, delim))) { + if (*apkenv_ldpaths[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. not originally a delim). */ + if (i > 0 && len >= sizeof(apkenv_ldpaths_buf) && + apkenv_ldpaths_buf[sizeof(apkenv_ldpaths_buf) - 2] != '\0') { + apkenv_ldpaths[i - 1] = NULL; + } else { + apkenv_ldpaths[i] = NULL; + } +} + +static void apkenv_parse_apkenv_preloads(const char *path, char *delim) +{ + size_t len; + char *apkenv_ldpreloads_bufp = apkenv_ldpreloads_buf; + int i = 0; + + len = apkenv_strlcpy(apkenv_ldpreloads_buf, path, sizeof(apkenv_ldpreloads_buf)); + + while (i < LDPRELOAD_MAX && (apkenv_ldpreload_names[i] = strsep(&apkenv_ldpreloads_bufp, delim))) { + if (*apkenv_ldpreload_names[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. not originally a delim). */ + if (i > 0 && len >= sizeof(apkenv_ldpreloads_buf) && + apkenv_ldpreloads_buf[sizeof(apkenv_ldpreloads_buf) - 2] != '\0') { + apkenv_ldpreload_names[i - 1] = NULL; + } else { + apkenv_ldpreload_names[i] = NULL; + } +} + +/* + * 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 unsigned apkenv___linker_init_post_relocation(unsigned **elfdata) +{ + static soinfo linker_soinfo; + + int argc = (int)(intptr_t)*elfdata; + char **argv = (char**) (elfdata + 1); + unsigned *vecs = (unsigned*) (argv + argc + 1); + unsigned *v; + soinfo *si; + struct link_map * map; + const char *ldpath_env = NULL; + const char *ldpreload_env = NULL; + + /* NOTE: we store the elfdata 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. + */ +#if 0 + __libc_init_tls(elfdata); +#endif + + apkenv_pid = getpid(); + +#if TIMING + struct timeval t0, t1; + gettimeofday(&t0, 0); +#endif + + /* Initialize environment functions, and get to the ELF aux vectors table */ + vecs = apkenv_linker_env_init(vecs); + + /* Check auxv for AT_SECURE first to see if program is setuid, setgid, + has file caps, or caused a SELinux/AppArmor domain transition. */ + for (v = vecs; v[0]; v += 2) { + if (v[0] == AT_SECURE) { + /* kernel told us whether to enable secure mode */ + apkenv_program_is_setuid = v[1]; + goto sanitize; + } + } + + /* Kernel did not provide AT_SECURE - fall back on legacy test. */ + apkenv_program_is_setuid = (getuid() != geteuid()) || (getgid() != getegid()); + +sanitize: + /* Sanitize environment if we're loading a setuid program */ + if (apkenv_program_is_setuid) + apkenv_linker_env_secure(); + +#if 0 + apkenv_debugger_init(); +#endif + + /* Get a few environment variables */ + { +#if LINKER_DEBUG + const char* env; + env = apkenv_linker_env_get("DEBUG"); /* XXX: TODO: Change to LD_DEBUG */ + if (env) + apkenv_debug_verbosity = atoi(env); +#endif + + /* Normally, these are cleaned by linker_env_secure, but the test + * against apkenv_program_is_setuid doesn't cost us anything */ + if (!apkenv_program_is_setuid) { + ldpath_env = getenv("LD_LIBRARY_PATH"); + ldpreload_env = getenv("LD_PRELOAD"); + } + } + + INFO("[ android linker & debugger ]\n"); + DEBUG("%5d elfdata @ 0x%08x\n", apkenv_pid, (unsigned)elfdata); + + si = apkenv_alloc_info(argv[0]); + if(si == 0) { + exit(-1); + } + + /* bootstrap the link map, the main exe always needs to be first */ + si->flags |= FLAG_EXE; + map = &(si->linkmap); + + map->l_addr = 0; + map->l_name = argv[0]; + map->l_prev = NULL; + map->l_next = NULL; + + _r_debug.r_map = map; + apkenv_r_debug_tail = map; + + /* gdb expects the linker to be in the debug shared object list, + * and we need to make sure that the reported load address is zero. + * Without this, gdb gets the wrong idea of where rtld_db_dlactivity() + * is. Don't use apkenv_alloc_info(), because the linker shouldn't + * be on the soinfo list. + */ + apkenv_strlcpy((char*) linker_soinfo.name, "/system/bin/linker", sizeof linker_soinfo.name); + linker_soinfo.flags = 0; + linker_soinfo.base = 0; // This is the important part; must be zero. + apkenv_insert_soinfo_into_debug_map(&linker_soinfo); + + /* extract information passed from the kernel */ + while(vecs[0] != 0){ + switch(vecs[0]){ + case AT_PHDR: + si->phdr = (Elf32_Phdr*)(intptr_t)vecs[1]; + break; + case AT_PHNUM: + si->phnum = (int) vecs[1]; + break; + case AT_ENTRY: + si->entry = vecs[1]; + break; + } + vecs += 2; + } + + /* 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) + */ + int nn; + si->base = 0; + for ( nn = 0; nn < si->phnum; nn++ ) { + if (si->phdr[nn].p_type == PT_PHDR) { + si->base = (Elf32_Addr)(intptr_t)si->phdr - si->phdr[nn].p_vaddr; + break; + } + } + si->dynamic = (unsigned *)-1; + si->wrprotect_start = 0xffffffff; + si->wrprotect_end = 0; + si->refcount = 1; + si->gnu_relro_start = 0; + si->gnu_relro_len = 0; + + /* Use LD_LIBRARY_PATH if we aren't setuid/setgid */ + if (ldpath_env) + apkenv_parse_library_path(ldpath_env, ":"); + + if (ldpreload_env) { + apkenv_parse_apkenv_preloads(ldpreload_env, " :"); + } + if(apkenv_link_image(si, 0)) { + char errmsg[] = "CANNOT LINK EXECUTABLE\n"; + write(2, apkenv___linker_dl_err_buf, strlen(apkenv___linker_dl_err_buf)); + write(2, errmsg, sizeof(errmsg)); + exit(-1); + } + + apkenv_call_constructors_recursive(si); + +#if ALLOW_SYMBOLS_FROM_MAIN + /* Set apkenv_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. + */ + apkenv_somain = si; +#endif + +#if TIMING + gettimeofday(&t1,NULL); + PRINT("LINKER TIME: %s: %d microseconds\n", 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\n", argv[0], + apkenv_linker_stats.reloc[RELOC_ABSOLUTE], + apkenv_linker_stats.reloc[RELOC_RELATIVE], + apkenv_linker_stats.reloc[RELOC_COPY], + apkenv_linker_stats.reloc[RELOC_SYMBOL]); +#endif +#if COUNT_PAGES + { + unsigned n; + unsigned i; + unsigned count = 0; + for(n = 0; n < 4096; n++){ + if(apkenv_bitmask[n]){ + unsigned x = apkenv_bitmask[n]; + for(i = 0; i < 8; i++){ + if(x & 1) count++; + x >>= 1; + } + } + } + PRINT("PAGES MODIFIED: %s: %d (%dKB)\n", argv[0], count, count * 4); + } +#endif + +#if TIMING || STATS || COUNT_PAGES + fflush(stdout); +#endif + + TRACE("[ %5d Ready to execute '%s' @ 0x%08x ]\n", apkenv_pid, si->name, + si->entry); + return si->entry; +} + +/* + * Find the value of AT_BASE passed to us by the kernel. This is the load + * location of the linker. + */ +static unsigned apkenv_find_linker_base(unsigned **elfdata) { + int argc = (int)(intptr_t)*elfdata; + char **argv = (char**) (elfdata + 1); + unsigned *vecs = (unsigned*) (argv + argc + 1); + while (vecs[0] != 0) { + vecs++; + } + + /* The end of the environment block is marked by two NULL pointers */ + vecs++; + + while(vecs[0]) { + if (vecs[0] == AT_BASE) { + return vecs[1]; + } + vecs += 2; + } + + return 0; // should never happen +} + +/* + * 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 apkenv___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. + */ +unsigned apkenv___linker_init(unsigned **elfdata) { + unsigned linker_addr = apkenv_find_linker_base(elfdata); + Elf32_Ehdr *elf_hdr = (Elf32_Ehdr *)(intptr_t)linker_addr; + Elf32_Phdr *phdr = + (Elf32_Phdr *)((unsigned char *)(intptr_t)linker_addr + elf_hdr->e_phoff); + + soinfo linker_so; + memset(&linker_so, 0, sizeof(soinfo)); + + linker_so.base = linker_addr; + linker_so.dynamic = (unsigned *) -1; + linker_so.phdr = phdr; + linker_so.phnum = elf_hdr->e_phnum; + linker_so.flags |= FLAG_LINKER; + linker_so.wrprotect_start = 0xffffffff; + linker_so.wrprotect_end = 0; + linker_so.gnu_relro_start = 0; + linker_so.gnu_relro_len = 0; + if (apkenv_link_image(&linker_so, 0)) { + // 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(-1); + } + + // We have successfully fixed our own relocations. It's safe to run + // the main part of the linker now. + return apkenv___linker_init_post_relocation(elfdata); +} |