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Signed-off-by: sisungo <[email protected]>
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sisungo
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.gitignore
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*.so.*
build.sh
Executable
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#!/bin/sh
cd $(dirname $0)
# Build `libgcc_s.so.1`
${CC} ${LDFLAGS} -shared \
-o libgcc_s.so.1 \
-Wl,--no-as-needed -lunwind -Wl,--no-undefined \
-Wl,-soname,libgcc_s.so.1
# Build `libatomic.so.1`
${CC} ${CFLAGS} -shared \
-o libatomic.so.1 \
-O3 -std=c11 \
libatomic/atomic.c
libatomic/LICENSE.txt
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libatomic/README.md
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# libatomic-chimera
This is a replacement for GCC libatomic. It's ABI-compatible with libatomic
and provides the same compiler helpers and other APIs.
It does not come with a header file. Its purposes are two:
* to provide a compatibility library for existing binaries
* to provide emulation symbols for compiler intrinsics
To build and install it, just use the supplied Makefile, or compile it by hand.
The Clang compiler is needed to build this; it may not compile with GCC.
The code is based on `atomic.c` from LLVM's `compiler-rt`, and therefore is
available under the same license (Apache-2.0). Extra implementations have been
added for completeness/compatibility with GCC libatomic.
libatomic/atomic.c
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// this is an implementation of libatomic created for Chimera Linux
//
// based on atomic.c from llvm's compiler-rt builtins
//
// missing implementations were filled in, some parts were rewritten
//
// changes by q66 <[email protected]>
//
// provided under the same license as llvm (apache-2.0)
//
// original header follows:
//
//===-- atomic.c - Implement support functions for atomic operations.------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// atomic.c defines a set of functions for performing atomic accesses on
// arbitrary-sized memory locations. This design uses locks that should
// be fast in the uncontended case, for two reasons:
//
// 1) This code must work with C programs that do not link to anything
// (including pthreads) and so it should not depend on any pthread
// functions.
// 2) Atomic operations, rather than explicit mutexes, are most commonly used
// on code where contended operations are rate.
//
// To avoid needing a per-object lock, this code allocates an array of
// locks and hashes the object pointers to find the one that it should use.
// For operations that must be atomic on two locations, the lower lock is
// always acquired first, to avoid deadlock.
//
//===----------------------------------------------------------------------===//
#include <stdbool.h>
#include <string.h>
#include <stddef.h>
#include <stdint.h>
#include <fenv.h>
#define SPINLOCK_COUNT (1 << 10)
static const long SPINLOCK_MASK = SPINLOCK_COUNT - 1;
/// lock implementation; clear and tas are guaranteed to be lock free
typedef bool lock_t;
static inline __attribute__((always_inline)) void unlock(lock_t *l) {
__atomic_clear(l, __ATOMIC_RELEASE);
}
static inline __attribute__((always_inline)) void lock(lock_t *l) {
while (__atomic_test_and_set(l, __ATOMIC_ACQUIRE));
}
static lock_t locks[SPINLOCK_COUNT];
static inline __attribute__((always_inline)) lock_t *lock_for_pointer(void *ptr) {
intptr_t hash = (intptr_t)ptr;
// Disregard the lowest 4 bits. We want all values that may be part of the
// same memory operation to hash to the same value and therefore use the same
// lock.
hash >>= 4;
// Use the next bits as the basis for the hash
intptr_t low = hash & SPINLOCK_MASK;
// Now use the high(er) set of bits to perturb the hash, so that we don't
// get collisions from atomic fields in a single object
hash >>= 16;
hash ^= low;
// Return a pointer to the word to use
return locks + (hash & SPINLOCK_MASK);
}
/// Macros for determining whether a size is lock free.
#define ATOMIC_ALWAYS_LOCK_FREE_OR_ALIGNED_LOCK_FREE(size, p) \
(__atomic_always_lock_free(size, p) || \
(__atomic_always_lock_free(size, 0) && ((uintptr_t)p % size) == 0))
#define IS_LOCK_FREE_1(p) ATOMIC_ALWAYS_LOCK_FREE_OR_ALIGNED_LOCK_FREE(1, p)
#define IS_LOCK_FREE_2(p) ATOMIC_ALWAYS_LOCK_FREE_OR_ALIGNED_LOCK_FREE(2, p)
#define IS_LOCK_FREE_4(p) ATOMIC_ALWAYS_LOCK_FREE_OR_ALIGNED_LOCK_FREE(4, p)
#define IS_LOCK_FREE_8(p) ATOMIC_ALWAYS_LOCK_FREE_OR_ALIGNED_LOCK_FREE(8, p)
#define IS_LOCK_FREE_16(p) ATOMIC_ALWAYS_LOCK_FREE_OR_ALIGNED_LOCK_FREE(16, p)
/// Macro that calls the compiler-generated lock-free versions of functions
/// when they exist.
#define TRY_LOCK_FREE_CASE(n, type, ptr) \
case n: \
if (IS_LOCK_FREE_##n(ptr)) { \
LOCK_FREE_ACTION(type); \
} \
break;
#ifdef __SIZEOF_INT128__
#define TRY_LOCK_FREE_CASE_16(p) TRY_LOCK_FREE_CASE(16, __uint128_t, p)
#else
#define TRY_LOCK_FREE_CASE_16(p) /* __uint128_t not available */
#endif
#define LOCK_FREE_CASES(ptr) \
do { \
switch (size) { \
TRY_LOCK_FREE_CASE(1, uint8_t, ptr) \
TRY_LOCK_FREE_CASE(2, uint16_t, ptr) \
TRY_LOCK_FREE_CASE(4, uint32_t, ptr) \
TRY_LOCK_FREE_CASE(8, uint64_t, ptr) \
TRY_LOCK_FREE_CASE_16(ptr) /* __uint128_t may not be supported */ \
default: \
break; \
} \
} while (0)
/// Whether atomic operations for the given size (and alignment) are lock-free.
#pragma redefine_extname __atomic_is_lock_free_c __atomic_is_lock_free
bool __atomic_is_lock_free_c(size_t size, void *ptr) {
#define LOCK_FREE_ACTION(type) return true;
LOCK_FREE_CASES(ptr);
#undef LOCK_FREE_ACTION
return false;
}
/// An atomic load operation. This is atomic with respect to the source
/// pointer only.
#pragma redefine_extname __atomic_load_c __atomic_load
void __atomic_load_c(int size, void *src, void *dest, int model) {
#define LOCK_FREE_ACTION(type) \
*((type *)dest) = __atomic_load_n((type *)src, model); \
return;
LOCK_FREE_CASES(src);
#undef LOCK_FREE_ACTION
lock_t *l = lock_for_pointer(src);
lock(l);
memcpy(dest, src, size);
unlock(l);
}
/// An atomic store operation. This is atomic with respect to the destination
/// pointer only.
#pragma redefine_extname __atomic_store_c __atomic_store
void __atomic_store_c(int size, void *dest, void *src, int model) {
#define LOCK_FREE_ACTION(type) \
__atomic_store_n((type *)dest, *(type *)src, model); \
return;
LOCK_FREE_CASES(dest);
#undef LOCK_FREE_ACTION
lock_t *l = lock_for_pointer(dest);
lock(l);
memcpy(dest, src, size);
unlock(l);
}
/// Atomic compare and exchange operation. If the value at *ptr is identical
/// to the value at *expected, then this copies value at *desired to *ptr. If
/// they are not, then this stores the current value from *ptr in *expected.
///
/// This function returns 1 if the exchange takes place or 0 if it fails.
#pragma redefine_extname __atomic_compare_exchange_c __atomic_compare_exchange
int __atomic_compare_exchange_c(int size, void *ptr, void *expected,
void *desired, int success, int failure) {
#define LOCK_FREE_ACTION(type) \
return __atomic_compare_exchange_n( \
(type *)ptr, (type *)expected, *(type *)desired, 0, success, \
failure)
LOCK_FREE_CASES(ptr);
#undef LOCK_FREE_ACTION
lock_t *l = lock_for_pointer(ptr);
lock(l);
if (memcmp(ptr, expected, size) == 0) {
memcpy(ptr, desired, size);
unlock(l);
return 1;
}
memcpy(expected, ptr, size);
unlock(l);
return 0;
}
/// Performs an atomic exchange operation between two pointers. This is atomic
/// with respect to the target address.
#pragma redefine_extname __atomic_exchange_c __atomic_exchange
void __atomic_exchange_c(int size, void *ptr, void *val, void *old, int model) {
#define LOCK_FREE_ACTION(type) \
*(type *)old = \
__atomic_exchange_n((type *)ptr, *(type *)val, model); \
return;
LOCK_FREE_CASES(ptr);
#undef LOCK_FREE_ACTION
lock_t *l = lock_for_pointer(ptr);
lock(l);
memcpy(old, ptr, size);
memcpy(ptr, val, size);
unlock(l);
}
////////////////////////////////////////////////////////////////////////////////
// Where the size is known at compile time, the compiler may emit calls to
// specialised versions of the above functions.
////////////////////////////////////////////////////////////////////////////////
#ifdef __SIZEOF_INT128__
#define OPTIMISED_CASES \
OPTIMISED_CASE(1, IS_LOCK_FREE_1, uint8_t) \
OPTIMISED_CASE(2, IS_LOCK_FREE_2, uint16_t) \
OPTIMISED_CASE(4, IS_LOCK_FREE_4, uint32_t) \
OPTIMISED_CASE(8, IS_LOCK_FREE_8, uint64_t) \
OPTIMISED_CASE(16, IS_LOCK_FREE_16, __uint128_t)
#else
#define OPTIMISED_CASES \
OPTIMISED_CASE(1, IS_LOCK_FREE_1, uint8_t) \
OPTIMISED_CASE(2, IS_LOCK_FREE_2, uint16_t) \
OPTIMISED_CASE(4, IS_LOCK_FREE_4, uint32_t) \
OPTIMISED_CASE(8, IS_LOCK_FREE_8, uint64_t)
#endif
#define OPTIMISED_CASE(n, lockfree, type) \
type __atomic_load_##n(type *src, int model) { \
if (lockfree(src)) \
return __atomic_load_n(src, model); \
lock_t *l = lock_for_pointer(src); \
lock(l); \
type val = *src; \
unlock(l); \
return val; \
}
OPTIMISED_CASES
#undef OPTIMISED_CASE
#define OPTIMISED_CASE(n, lockfree, type) \
void __atomic_store_##n(type *dest, type val, int model) { \
if (lockfree(dest)) { \
__atomic_store_n(dest, val, model); \
return; \
} \
lock_t *l = lock_for_pointer(dest); \
lock(l); \
*dest = val; \
unlock(l); \
return; \
}
OPTIMISED_CASES
#undef OPTIMISED_CASE
#define OPTIMISED_CASE(n, lockfree, type) \
type __atomic_exchange_##n(type *dest, type val, int model) { \
if (lockfree(dest)) \
return __atomic_exchange_n(dest, val, model); \
lock_t *l = lock_for_pointer(dest); \
lock(l); \
type tmp = *dest; \
*dest = val; \
unlock(l); \
return tmp; \
}
OPTIMISED_CASES
#undef OPTIMISED_CASE
#define OPTIMISED_CASE(n, lockfree, type) \
bool __atomic_compare_exchange_##n(type *ptr, type *expected, type desired, \
int success, int failure) { \
if (lockfree(ptr)) \
return __atomic_compare_exchange_n( \
ptr, expected, desired, 0, success, failure); \
lock_t *l = lock_for_pointer(ptr); \
lock(l); \
if (*ptr == *expected) { \
*ptr = desired; \
unlock(l); \
return true; \
} \
*expected = *ptr; \
unlock(l); \
return false; \
}
OPTIMISED_CASES
#undef OPTIMISED_CASE
////////////////////////////////////////////////////////////////////////////////
// Atomic read-modify-write operations for integers of various sizes.
////////////////////////////////////////////////////////////////////////////////
#define ATOMIC_RMW(n, lockfree, type, opname, op) \
type __atomic_fetch_##opname##_##n(type *ptr, type val, int model) { \
if (lockfree(ptr)) \
return __atomic_fetch_##opname(ptr, val, model); \
lock_t *l = lock_for_pointer(ptr); \
lock(l); \
type tmp = *ptr; \
*ptr = tmp op val; \
unlock(l); \
return tmp; \
} \
\
type __atomic_##opname##_fetch_##n(type *ptr, type val, int model) { \
if (lockfree(ptr)) \
return __atomic_##opname##_fetch(ptr, val, model); \
lock_t *l = lock_for_pointer(ptr); \
lock(l); \
type tmp = *ptr; \
tmp = tmp op val; \
*ptr = tmp; \
unlock(l); \
return tmp; \
}
#define ATOMIC_RMW_NAND(n, lockfree, type) \
type __atomic_fetch_nand_##n(type *ptr, type val, int model) { \
if (lockfree(ptr)) \
return __atomic_fetch_nand(ptr, val, model); \
lock_t *l = lock_for_pointer(ptr); \
lock(l); \
type tmp = *ptr; \
*ptr = ~(tmp & val); \
unlock(l); \
return tmp; \
} \
\
type __atomic_nand_fetch_##n(type *ptr, type val, int model) { \
if (lockfree(ptr)) \
return __atomic_nand_fetch(ptr, val, model); \
lock_t *l = lock_for_pointer(ptr); \
lock(l); \
type tmp = *ptr; \
tmp = ~(tmp & val); \
*ptr = tmp; \
unlock(l); \
return tmp; \
}
#define ATOMIC_TAS(n, lockfree, type) \
bool __atomic_test_and_set_##n(type *ptr, int model) { \
if (lockfree(ptr)) \
return __atomic_test_and_set(ptr, model); \
lock_t *l = lock_for_pointer(ptr); \
lock(l); \
type tmp = *ptr; \
*ptr = 1; \
unlock(l); \
return !!tmp; \
}
#define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW(n, lockfree, type, add, +)
OPTIMISED_CASES
#undef OPTIMISED_CASE
#define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW(n, lockfree, type, sub, -)
OPTIMISED_CASES
#undef OPTIMISED_CASE
#define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW(n, lockfree, type, and, &)
OPTIMISED_CASES
#undef OPTIMISED_CASE
#define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW(n, lockfree, type, or, |)
OPTIMISED_CASES
#undef OPTIMISED_CASE
#define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW(n, lockfree, type, xor, ^)
OPTIMISED_CASES
#undef OPTIMISED_CASE
#define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW_NAND(n, lockfree, type)
OPTIMISED_CASES
#undef OPTIMISED_CASE
#define OPTIMISED_CASE(n, lockfree, type) ATOMIC_TAS(n, lockfree, type)
OPTIMISED_CASES
#undef OPTIMISED_CASE
/* atomic_flag */
typedef struct atomic_flag { bool v; } atomic_flag;
void atomic_flag_clear(volatile atomic_flag *o) {
__atomic_clear(&o->v, __ATOMIC_SEQ_CST);
}
void atomic_flag_clear_explicit(volatile atomic_flag *o, int model) {
__atomic_clear(&o->v, model);
}
bool atomic_flag_test_and_set(volatile atomic_flag *o) {
return __atomic_test_and_set(&o->v, __ATOMIC_SEQ_CST);
}
bool atomic_flag_test_and_set_explicit(volatile atomic_flag *o, int model) {
return __atomic_test_and_set(&o->v, model);
}
/* fence */
void atomic_thread_fence(int model) {
__atomic_thread_fence(model);
}
void atomic_signal_fence(int model) {
__atomic_signal_fence(model);
}
/* provided by gcc libatomic */
void __atomic_feraiseexcept(int e) {
volatile float r __attribute__((unused));
#ifdef FE_INVALID
if (e & FE_INVALID) {
volatile float z = 0.0f;
r = z / z;
}
#endif
#ifdef FE_DIVBYZERO
if (e & FE_DIVBYZERO) {
volatile float z = 0.0f;
r = 1.0f / z;
}
#endif
#ifdef FE_OVERFLOW
if (e & FE_OVERFLOW) {
volatile float m = __FLT_MAX__;
r = m * m;
}
#endif
#ifdef FE_UNDERFLOW
if (e & FE_UNDERFLOW) {
volatile float m = __FLT_MIN__;
r = m * m;
}
#endif
#ifdef FE_INEXACT
if (e & FE_INEXACT) {
volatile float t = 3.0f;
r = 1.0f / t;
}
#endif
}