安卓Linker源码(可修改编译).zip

// // linker.cpp // ArmVM // // Created by denghui on 19/6/21. // Copyright © 2019年 denghui. All rights reserved. // #include "linker.h" #include "dlfcn.h" #include "linker_phdr.h" #include <errno.h> #include <fcntl.h> #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/mman.h> #include <sys/stat.h> #include <unistd.h> #define LDPATH_BUFSIZE 512 #define LDPATH_MAX 8 #define LDPRELOAD_BUFSIZE 512 #define LDPRELOAD_MAX 8 static bool soinfo_link_image(soinfo* si); #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]; soinfo libdl_info; 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 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) { DL_ERR("mprotect fail: %s",strerror(errno)); abort(); // Can't happen. } } } static soinfo* soinfo_alloc(const char* name) { if (strlen(name) >= SOINFO_NAME_LEN) { DL_ERR("library name \"%s\" too long\n", name); return NULL; } if (!ensure_free_list_non_empty()) { DL_ERR("out of memory when loading \"%s\"\n", 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\n", 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); } 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 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 = snprintf(buf, sizeof(buf), "%s/%s", paths[i], name); if (n < 0 || n >= static_cast<int>(sizeof(buf))) { TRACE("Warning: ignoring very long library path: %s/%s\n", paths[i], name); continue; } int fd = (open(buf, O_RDONLY | O_CLOEXEC)); if (fd != -1) { return fd; } } return -1; } static int open_library(const char* name) { TRACE("[ opening %s ]\n", 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 = 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. DL_DEBUG("load_library: %s", name); int fd = open_library(name); if (fd == -1) { DL_ERR("library \"%s\" not found\n", 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(