/* ===---------- emutls.c - Implements __emutls_get_address ---------------===
*
* The LLVM Compiler Infrastructure
*
* This file is dual licensed under the MIT and the University of Illinois Open
* Source Licenses. See LICENSE.TXT for details.
*
* ===----------------------------------------------------------------------===
*/
#include <pthread.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include "int_lib.h"
#include "int_util.h"
/* 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
/* 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 unsigned int gcc_word __attribute__((mode(word)));
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;
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 = 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
}
/* 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. */
typedef unsigned int gcc_pointer __attribute__((mode(pointer)));
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;
}
static pthread_mutex_t emutls_mutex = PTHREAD_MUTEX_INITIALIZER;
static size_t emutls_num_object = 0; /* number of allocated TLS objects */
typedef struct emutls_address_array {
uintptr_t size; /* number of elements in the 'data' array */
void* data[];
} emutls_address_array;
static pthread_key_t emutls_pthread_key;
static void emutls_key_destructor(void* ptr) {
emutls_address_array* array = (emutls_address_array*)ptr;
uintptr_t i;
for (i = 0; i < array->size; ++i) {
if (array->data[i])
emutls_memalign_free(array->data[i]);
}
free(ptr);
}
static void emutls_init(void) {
if (pthread_key_create(&emutls_pthread_key, emutls_key_destructor) != 0)
abort();
}
/* 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) {
static pthread_once_t once = PTHREAD_ONCE_INIT;
pthread_once(&once, emutls_init);
pthread_mutex_lock(&emutls_mutex);
index = control->object.index;
if (!index) {
index = ++emutls_num_object;
__atomic_store_n(&control->object.index, index, __ATOMIC_RELEASE);
}
pthread_mutex_unlock(&emutls_mutex);
}
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;
pthread_setspecific(emutls_pthread_key, (void*)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 one extra slot
* to store the data array size.
* Round up the emutls_address_array size to multiple of 16.
*/
return ((index + 1 + 15) & ~((uintptr_t)15)) - 1;
}
/* 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 = pthread_getspecific(emutls_pthread_key);
if (array == NULL) {
uintptr_t new_size = emutls_new_data_array_size(index);
array = malloc(new_size * sizeof(void *) + sizeof(emutls_address_array));
if (array)
memset(array->data, 0, new_size * sizeof(void*));
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 = realloc(array, new_size * sizeof(void *) + sizeof(emutls_address_array));
if (array)
memset(array->data + orig_size, 0,
(new_size - orig_size) * sizeof(void*));
emutls_check_array_set_size(array, new_size);
}
return array;
}
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 - 1] == NULL)
array->data[index - 1] = emutls_allocate_object(control);
return array->data[index - 1];
}
