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Merge "Make it possible for code to query the dynamic linker's default search path."

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This commit is contained in:
Elliott Hughes
2014-01-14 20:03:20 +00:00
committed by Gerrit Code Review
parent b5e211031b a4aafd1560
commit d971f72905
4 changed files with 53 additions and 47 deletions
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3
libdl/libdl.c
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@@ -15,6 +15,8 @@
*/
#include <dlfcn.h>
#include <stdlib.h>
/* These are stubs for functions that are actually defined
* in the dynamic linker (dlfcn.c), and hijacked at runtime.
*/
@@ -24,6 +26,7 @@ void *dlsym(void *handle, const char *symbol) { return 0; }
int dladdr(const void *addr, Dl_info *info) { return 0; }
int dlclose(void *handle) { return 0; }
void android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { }
void android_update_LD_LIBRARY_PATH(const char* ld_library_path) { }
#if defined(__arm__)

71
linker/dlfcn.cpp
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@@ -54,6 +54,11 @@ const char* dlerror() {
return old_value;
}
void android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
ScopedPthreadMutexLocker locker(&gDlMutex);
do_android_get_LD_LIBRARY_PATH(buffer, buffer_size);
}
void android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
ScopedPthreadMutexLocker locker(&gDlMutex);
do_android_update_LD_LIBRARY_PATH(ld_library_path);
@@ -143,20 +148,6 @@ int dlclose(void* handle) {
return do_dlclose(reinterpret_cast<soinfo*>(handle));
}
#if defined(__arm__)
// 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888 8888888
// 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012 3456789
#define ANDROID_LIBDL_STRTAB \
"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0dl_iterate_phdr\0dl_unwind_find_exidx\0"
#elif defined(__aarch64__) || defined(__i386__) || defined(__mips__) || defined(__x86_64__)
// 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667
// 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890
#define ANDROID_LIBDL_STRTAB \
"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0dl_iterate_phdr\0"
#else
#error Unsupported architecture. Only aarch64, arm, mips, x86, and x86_64 are presently supported.
#endif
// name_offset: starting index of the name in libdl_info.strtab
#define ELF32_SYM_INITIALIZER(name_offset, value, shndx) \
{ name_offset, \
@@ -182,6 +173,20 @@ int dlclose(void* handle) {
# define ELF_SYM_INITIALIZER ELF32_SYM_INITIALIZER
#endif
#if defined(__arm__)
// 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 9999900000000001 1
// 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1
# define ANDROID_LIBDL_STRTAB \
"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_iterate_phdr\0dl_unwind_find_exidx\0"
#elif defined(__aarch64__) || defined(__i386__) || defined(__mips__) || defined(__x86_64__)
// 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 9999900000000001 1
// 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1
# define ANDROID_LIBDL_STRTAB \
"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_iterate_phdr\0"
#else
# error Unsupported architecture. Only aarch64, arm, mips, x86, and x86_64 are presently supported.
#endif
static Elf_Sym gLibDlSymtab[] = {
// Total length of libdl_info.strtab, including trailing 0.
// This is actually the STH_UNDEF entry. Technically, it's
@@ -190,39 +195,33 @@ static Elf_Sym gLibDlSymtab[] = {
ELF_SYM_INITIALIZER(sizeof(ANDROID_LIBDL_STRTAB) - 1, NULL, 0),
ELF_SYM_INITIALIZER( 0, &dlopen, 1),
ELF_SYM_INITIALIZER( 7, &dlclose, 1),
ELF_SYM_INITIALIZER(15, &dlsym, 1),
ELF_SYM_INITIALIZER(21, &dlerror, 1),
ELF_SYM_INITIALIZER(29, &dladdr, 1),
ELF_SYM_INITIALIZER(36, &android_update_LD_LIBRARY_PATH, 1),
ELF_SYM_INITIALIZER(67, &dl_iterate_phdr, 1),
ELF_SYM_INITIALIZER( 15, &dlsym, 1),
ELF_SYM_INITIALIZER( 21, &dlerror, 1),
ELF_SYM_INITIALIZER( 29, &dladdr, 1),
ELF_SYM_INITIALIZER( 36, &android_update_LD_LIBRARY_PATH, 1),
ELF_SYM_INITIALIZER( 67, &android_get_LD_LIBRARY_PATH, 1),
ELF_SYM_INITIALIZER( 95, &dl_iterate_phdr, 1),
#if defined(__arm__)
ELF_SYM_INITIALIZER(83, &dl_unwind_find_exidx, 1),
ELF_SYM_INITIALIZER(111, &dl_unwind_find_exidx, 1),
#endif
};
// Fake out a hash table with a single bucket.
// A search of the hash table will look through
// gLibDlSymtab starting with index [1], then
// use gLibDlChains to find the next index to
// look at. gLibDlChains should be set up to
// walk through every element in gLibDlSymtab,
// and then end with 0 (sentinel value).
//
// That is, gLibDlChains should look like
// { 0, 2, 3, ... N, 0 } where N is the number
// of actual symbols, or nelems(gLibDlSymtab)-1
// (since the first element of gLibDlSymtab is not
// a real symbol).
// A search of the hash table will look through gLibDlSymtab starting with index 1, then
// use gLibDlChains to find the next index to look at. gLibDlChains should be set up to
// walk through every element in gLibDlSymtab, and then end with 0 (sentinel value).
//
// (see soinfo_elf_lookup())
// That is, gLibDlChains should look like { 0, 2, 3, ... N, 0 } where N is the number
// of actual symbols, or nelems(gLibDlSymtab)-1 (since the first element of gLibDlSymtab is not
// a real symbol). (See soinfo_elf_lookup().)
//
// Note that adding any new symbols here requires
// stubbing them out in libdl.
// Note that adding any new symbols here requires stubbing them out in libdl.
static unsigned gLibDlBuckets[1] = { 1 };
#if defined(__arm__)
static unsigned gLibDlChains[9] = { 0, 2, 3, 4, 5, 6, 7, 8, 0 };
static unsigned gLibDlChains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
#else
static unsigned gLibDlChains[8] = { 0, 2, 3, 4, 5, 6, 7, 0 };
static unsigned gLibDlChains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 0 };
#endif
// This is used by the dynamic linker. Every process gets these symbols for free.

21
linker/linker.cpp
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@@ -50,13 +50,6 @@
#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.
@@ -91,7 +84,7 @@ 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[] = {
static const char* const gDefaultLdPaths[] = {
#if defined(__LP64__)
"/vendor/lib64",
"/system/lib64",
@@ -102,6 +95,12 @@ static const char* const gSoPaths[] = {
NULL
};
#define LDPATH_BUFSIZE (LDPATH_MAX*64)
#define LDPATH_MAX 8
#define LDPRELOAD_BUFSIZE (LDPRELOAD_MAX*64)
#define LDPRELOAD_MAX 8
static char gLdPathsBuffer[LDPATH_BUFSIZE];
static const char* gLdPaths[LDPATH_MAX + 1];
@@ -708,7 +707,7 @@ static int open_library(const char* name) {
// 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);
fd = open_library_on_path(name, gDefaultLdPaths);
}
return fd;
}
@@ -828,6 +827,10 @@ static int soinfo_unload(soinfo* si) {
return 0;
}
void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
snprintf(buffer, buffer_size, "%s:%s", gDefaultLdPaths[0], gDefaultLdPaths[1]);
}
void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
if (!get_AT_SECURE()) {
parse_LD_LIBRARY_PATH(ld_library_path);

1
linker/linker.h
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@@ -196,6 +196,7 @@ struct soinfo {
extern soinfo libdl_info;
void do_android_get_LD_LIBRARY_PATH(char*, size_t);
void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path);
soinfo* do_dlopen(const char* name, int flags);
int do_dlclose(soinfo* si);