| //===---------- emutls.c - Implements __emutls_get_address ---------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include <stdint.h> |
| #include <stdlib.h> |
| #include <string.h> |
| |
| #include "int_lib.h" |
| |
| #ifdef __BIONIC__ |
| // There are 4 pthread key cleanup rounds on Bionic. Delay emutls deallocation |
| // to round 2. We need to delay deallocation because: |
| // - Android versions older than M lack __cxa_thread_atexit_impl, so apps |
| // use a pthread key destructor to call C++ destructors. |
| // - Apps might use __thread/thread_local variables in pthread destructors. |
| // We can't wait until the final two rounds, because jemalloc needs two rounds |
| // after the final malloc/free call to free its thread-specific data (see |
| // https://reviews.llvm.org/D46978#1107507). |
| #define EMUTLS_SKIP_DESTRUCTOR_ROUNDS 1 |
| #else |
| #define EMUTLS_SKIP_DESTRUCTOR_ROUNDS 0 |
| #endif |
| |
| #if defined(_MSC_VER) && !defined(__clang__) |
| // MSVC raises a warning about a nonstandard extension being used for the 0 |
| // sized element in this array. Disable this for warn-as-error builds. |
| #pragma warning(push) |
| #pragma warning(disable : 4200) |
| #endif |
| |
| typedef struct emutls_address_array { |
| uintptr_t skip_destructor_rounds; |
| uintptr_t size; // number of elements in the 'data' array |
| void *data[]; |
| } emutls_address_array; |
| |
| #if defined(_MSC_VER) && !defined(__clang__) |
| #pragma warning(pop) |
| #endif |
| |
| static void emutls_shutdown(emutls_address_array *array); |
| |
| #ifndef _WIN32 |
| |
| #include <pthread.h> |
| |
| static pthread_mutex_t emutls_mutex = PTHREAD_MUTEX_INITIALIZER; |
| static pthread_key_t emutls_pthread_key; |
| static bool emutls_key_created = false; |
| |
| typedef unsigned int gcc_word __attribute__((mode(word))); |
| typedef unsigned int gcc_pointer __attribute__((mode(pointer))); |
| |
| // Default is not to use posix_memalign, so systems like Android |
| // can use thread local data without heavier POSIX memory allocators. |
| #ifndef EMUTLS_USE_POSIX_MEMALIGN |
| #define EMUTLS_USE_POSIX_MEMALIGN 0 |
| #endif |
| |
| static __inline void *emutls_memalign_alloc(size_t align, size_t size) { |
| void *base; |
| #if EMUTLS_USE_POSIX_MEMALIGN |
| if (posix_memalign(&base, align, size) != 0) |
| abort(); |
| #else |
| #define EXTRA_ALIGN_PTR_BYTES (align - 1 + sizeof(void *)) |
| char *object; |
| if ((object = (char *)malloc(EXTRA_ALIGN_PTR_BYTES + size)) == NULL) |
| abort(); |
| base = (void *)(((uintptr_t)(object + EXTRA_ALIGN_PTR_BYTES)) & |
| ~(uintptr_t)(align - 1)); |
| |
| ((void **)base)[-1] = object; |
| #endif |
| return base; |
| } |
| |
| static __inline void emutls_memalign_free(void *base) { |
| #if EMUTLS_USE_POSIX_MEMALIGN |
| free(base); |
| #else |
| // The mallocated address is in ((void**)base)[-1] |
| free(((void **)base)[-1]); |
| #endif |
| } |
| |
| static __inline void emutls_setspecific(emutls_address_array *value) { |
| pthread_setspecific(emutls_pthread_key, (void *)value); |
| } |
| |
| static __inline emutls_address_array *emutls_getspecific(void) { |
| return (emutls_address_array *)pthread_getspecific(emutls_pthread_key); |
| } |
| |
| static void emutls_key_destructor(void *ptr) { |
| emutls_address_array *array = (emutls_address_array *)ptr; |
| if (array->skip_destructor_rounds > 0) { |
| // emutls is deallocated using a pthread key destructor. These |
| // destructors are called in several rounds to accommodate destructor |
| // functions that (re)initialize key values with pthread_setspecific. |
| // Delay the emutls deallocation to accommodate other end-of-thread |
| // cleanup tasks like calling thread_local destructors (e.g. the |
| // __cxa_thread_atexit fallback in libc++abi). |
| array->skip_destructor_rounds--; |
| emutls_setspecific(array); |
| } else { |
| emutls_shutdown(array); |
| free(ptr); |
| } |
| } |
| |
| static __inline void emutls_init(void) { |
| if (pthread_key_create(&emutls_pthread_key, emutls_key_destructor) != 0) |
| abort(); |
| emutls_key_created = true; |
| } |
| |
| static __inline void emutls_init_once(void) { |
| static pthread_once_t once = PTHREAD_ONCE_INIT; |
| pthread_once(&once, emutls_init); |
| } |
| |
| static __inline void emutls_lock(void) { pthread_mutex_lock(&emutls_mutex); } |
| |
| static __inline void emutls_unlock(void) { pthread_mutex_unlock(&emutls_mutex); } |
| |
| #else // _WIN32 |
| |
| #include <assert.h> |
| #include <malloc.h> |
| #include <stdio.h> |
| #include <windows.h> |
| |
| static LPCRITICAL_SECTION emutls_mutex; |
| static DWORD emutls_tls_index = TLS_OUT_OF_INDEXES; |
| |
| typedef uintptr_t gcc_word; |
| typedef void *gcc_pointer; |
| |
| static void win_error(DWORD last_err, const char *hint) { |
| char *buffer = NULL; |
| if (FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | |
| FORMAT_MESSAGE_FROM_SYSTEM | |
| FORMAT_MESSAGE_MAX_WIDTH_MASK, |
| NULL, last_err, 0, (LPSTR)&buffer, 1, NULL)) { |
| fprintf(stderr, "Windows error: %s\n", buffer); |
| } else { |
| fprintf(stderr, "Unknown Windows error: %s\n", hint); |
| } |
| LocalFree(buffer); |
| } |
| |
| static __inline void win_abort(DWORD last_err, const char *hint) { |
| win_error(last_err, hint); |
| abort(); |
| } |
| |
| static __inline void *emutls_memalign_alloc(size_t align, size_t size) { |
| void *base = _aligned_malloc(size, align); |
| if (!base) |
| win_abort(GetLastError(), "_aligned_malloc"); |
| return base; |
| } |
| |
| static __inline void emutls_memalign_free(void *base) { _aligned_free(base); } |
| |
| static void emutls_exit(void) { |
| if (emutls_mutex) { |
| DeleteCriticalSection(emutls_mutex); |
| _aligned_free(emutls_mutex); |
| emutls_mutex = NULL; |
| } |
| if (emutls_tls_index != TLS_OUT_OF_INDEXES) { |
| emutls_shutdown((emutls_address_array *)TlsGetValue(emutls_tls_index)); |
| TlsFree(emutls_tls_index); |
| emutls_tls_index = TLS_OUT_OF_INDEXES; |
| } |
| } |
| |
| static BOOL CALLBACK emutls_init(PINIT_ONCE p0, PVOID p1, PVOID *p2) { |
| (void)p0; |
| (void)p1; |
| (void)p2; |
| emutls_mutex = |
| (LPCRITICAL_SECTION)_aligned_malloc(sizeof(CRITICAL_SECTION), 16); |
| if (!emutls_mutex) { |
| win_error(GetLastError(), "_aligned_malloc"); |
| return FALSE; |
| } |
| InitializeCriticalSection(emutls_mutex); |
| |
| emutls_tls_index = TlsAlloc(); |
| if (emutls_tls_index == TLS_OUT_OF_INDEXES) { |
| emutls_exit(); |
| win_error(GetLastError(), "TlsAlloc"); |
| return FALSE; |
| } |
| atexit(&emutls_exit); |
| return TRUE; |
| } |
| |
| static __inline void emutls_init_once(void) { |
| static INIT_ONCE once; |
| InitOnceExecuteOnce(&once, emutls_init, NULL, NULL); |
| } |
| |
| static __inline void emutls_lock(void) { EnterCriticalSection(emutls_mutex); } |
| |
| static __inline void emutls_unlock(void) { LeaveCriticalSection(emutls_mutex); } |
| |
| static __inline void emutls_setspecific(emutls_address_array *value) { |
| if (TlsSetValue(emutls_tls_index, (LPVOID)value) == 0) |
| win_abort(GetLastError(), "TlsSetValue"); |
| } |
| |
| static __inline emutls_address_array *emutls_getspecific(void) { |
| LPVOID value = TlsGetValue(emutls_tls_index); |
| if (value == NULL) { |
| const DWORD err = GetLastError(); |
| if (err != ERROR_SUCCESS) |
| win_abort(err, "TlsGetValue"); |
| } |
| return (emutls_address_array *)value; |
| } |
| |
| // Provide atomic load/store functions for emutls_get_index if built with MSVC. |
| #if !defined(__ATOMIC_RELEASE) |
| #include <intrin.h> |
| |
| enum { __ATOMIC_ACQUIRE = 2, __ATOMIC_RELEASE = 3 }; |
| |
| static __inline uintptr_t __atomic_load_n(void *ptr, unsigned type) { |
| assert(type == __ATOMIC_ACQUIRE); |
| // These return the previous value - but since we do an OR with 0, |
| // it's equivalent to a plain load. |
| #ifdef _WIN64 |
| return InterlockedOr64(ptr, 0); |
| #else |
| return InterlockedOr(ptr, 0); |
| #endif |
| } |
| |
| static __inline void __atomic_store_n(void *ptr, uintptr_t val, unsigned type) { |
| assert(type == __ATOMIC_RELEASE); |
| InterlockedExchangePointer((void *volatile *)ptr, (void *)val); |
| } |
| |
| #endif // __ATOMIC_RELEASE |
| |
| #endif // _WIN32 |
| |
| static size_t emutls_num_object = 0; // number of allocated TLS objects |
| |
| // Free the allocated TLS data |
| static void emutls_shutdown(emutls_address_array *array) { |
| if (array) { |
| uintptr_t i; |
| for (i = 0; i < array->size; ++i) { |
| if (array->data[i]) |
| emutls_memalign_free(array->data[i]); |
| } |
| } |
| } |
| |
| // For every TLS variable xyz, |
| // there is one __emutls_control variable named __emutls_v.xyz. |
| // If xyz has non-zero initial value, __emutls_v.xyz's "value" |
| // will point to __emutls_t.xyz, which has the initial value. |
| typedef struct __emutls_control { |
| // Must use gcc_word here, instead of size_t, to match GCC. When |
| // gcc_word is larger than size_t, the upper extra bits are all |
| // zeros. We can use variables of size_t to operate on size and |
| // align. |
| gcc_word size; // size of the object in bytes |
| gcc_word align; // alignment of the object in bytes |
| union { |
| uintptr_t index; // data[index-1] is the object address |
| void *address; // object address, when in single thread env |
| } object; |
| void *value; // null or non-zero initial value for the object |
| } __emutls_control; |
| |
| // Emulated TLS objects are always allocated at run-time. |
| static __inline void *emutls_allocate_object(__emutls_control *control) { |
| // Use standard C types, check with gcc's emutls.o. |
| COMPILE_TIME_ASSERT(sizeof(uintptr_t) == sizeof(gcc_pointer)); |
| COMPILE_TIME_ASSERT(sizeof(uintptr_t) == sizeof(void *)); |
| |
| size_t size = control->size; |
| size_t align = control->align; |
| void *base; |
| if (align < sizeof(void *)) |
| align = sizeof(void *); |
| // Make sure that align is power of 2. |
| if ((align & (align - 1)) != 0) |
| abort(); |
| |
| base = emutls_memalign_alloc(align, size); |
| if (control->value) |
| memcpy(base, control->value, size); |
| else |
| memset(base, 0, size); |
| return base; |
| } |
| |
| // Returns control->object.index; set index if not allocated yet. |
| static __inline uintptr_t emutls_get_index(__emutls_control *control) { |
| uintptr_t index = __atomic_load_n(&control->object.index, __ATOMIC_ACQUIRE); |
| if (!index) { |
| emutls_init_once(); |
| emutls_lock(); |
| index = control->object.index; |
| if (!index) { |
| index = ++emutls_num_object; |
| __atomic_store_n(&control->object.index, index, __ATOMIC_RELEASE); |
| } |
| emutls_unlock(); |
| } |
| return index; |
| } |
| |
| // Updates newly allocated thread local emutls_address_array. |
| static __inline void emutls_check_array_set_size(emutls_address_array *array, |
| uintptr_t size) { |
| if (array == NULL) |
| abort(); |
| array->size = size; |
| emutls_setspecific(array); |
| } |
| |
| // Returns the new 'data' array size, number of elements, |
| // which must be no smaller than the given index. |
| static __inline uintptr_t emutls_new_data_array_size(uintptr_t index) { |
| // Need to allocate emutls_address_array with extra slots |
| // to store the header. |
| // Round up the emutls_address_array size to multiple of 16. |
| uintptr_t header_words = sizeof(emutls_address_array) / sizeof(void *); |
| return ((index + header_words + 15) & ~((uintptr_t)15)) - header_words; |
| } |
| |
| // Returns the size in bytes required for an emutls_address_array with |
| // N number of elements for data field. |
| static __inline uintptr_t emutls_asize(uintptr_t N) { |
| return N * sizeof(void *) + sizeof(emutls_address_array); |
| } |
| |
| // Returns the thread local emutls_address_array. |
| // Extends its size if necessary to hold address at index. |
| static __inline emutls_address_array * |
| emutls_get_address_array(uintptr_t index) { |
| emutls_address_array *array = emutls_getspecific(); |
| if (array == NULL) { |
| uintptr_t new_size = emutls_new_data_array_size(index); |
| array = (emutls_address_array *)malloc(emutls_asize(new_size)); |
| if (array) { |
| memset(array->data, 0, new_size * sizeof(void *)); |
| array->skip_destructor_rounds = EMUTLS_SKIP_DESTRUCTOR_ROUNDS; |
| } |
| emutls_check_array_set_size(array, new_size); |
| } else if (index > array->size) { |
| uintptr_t orig_size = array->size; |
| uintptr_t new_size = emutls_new_data_array_size(index); |
| array = (emutls_address_array *)realloc(array, emutls_asize(new_size)); |
| if (array) |
| memset(array->data + orig_size, 0, |
| (new_size - orig_size) * sizeof(void *)); |
| emutls_check_array_set_size(array, new_size); |
| } |
| return array; |
| } |
| |
| #ifndef _WIN32 |
| // Our emulated TLS implementation relies on local state (e.g. for the pthread |
| // key), and if we duplicate this state across different shared libraries, |
| // accesses to the same TLS variable from different shared libraries will yield |
| // different results (see https://github.com/android/ndk/issues/1551 for an |
| // example). __emutls_get_address is the only external entry point for emulated |
| // TLS, and by making it default visibility and weak, we can rely on the dynamic |
| // linker to coalesce multiple copies at runtime and ensure a single unique copy |
| // of TLS state. This is a best effort; it won't work if the user is linking |
| // with -Bsymbolic or -Bsymbolic-functions, and it also won't work on Windows, |
| // where the dynamic linker has no notion of coalescing weak symbols at runtime. |
| // A more robust solution would be to create a separate shared library for |
| // emulated TLS, to ensure a single copy of its state. |
| __attribute__((visibility("default"), weak)) |
| #endif |
| void *__emutls_get_address(__emutls_control *control) { |
| uintptr_t index = emutls_get_index(control); |
| emutls_address_array *array = emutls_get_address_array(index--); |
| if (array->data[index] == NULL) |
| array->data[index] = emutls_allocate_object(control); |
| return array->data[index]; |
| } |
| |
| #ifdef __BIONIC__ |
| // Called by Bionic on dlclose to delete the emutls pthread key. |
| __attribute__((visibility("hidden"))) void __emutls_unregister_key(void) { |
| if (emutls_key_created) { |
| pthread_key_delete(emutls_pthread_key); |
| emutls_key_created = false; |
| } |
| } |
| #endif |