kaguya
71 lines
1.9 KiB
C++
71 lines
1.9 KiB
C++
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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#include <mlibc/debug.hpp>
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#include <mlibc/internal-sysdeps.hpp>
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namespace {
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// Itanium ABI static initialization guard.
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struct Guard {
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// bit of the mutex member variable.
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// indicates that the mutex is locked.
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static constexpr int32_t locked = 1;
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void lock() {
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uint32_t v = 0;
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if(__atomic_compare_exchange_n(&mutex, &v, Guard::locked, false,
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__ATOMIC_ACQUIRE, __ATOMIC_RELAXED))
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return;
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mlibc::sys_libc_log("__cxa_guard_acquire contention");
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__builtin_trap();
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}
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void unlock() {
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__atomic_store_n(&mutex, 0, __ATOMIC_RELEASE);
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}
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// the first byte's meaning is fixed by the ABI.
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// it indicates whether initialization has already been completed.
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uint8_t complete;
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// padding to ensure correct alignment on certain platforms.
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uint8_t padding[3];
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// we use some of the remaining bytes to implement a mutex.
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uint32_t mutex;
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};
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static_assert(sizeof(Guard) == sizeof(int64_t));
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} // namespace
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extern "C" [[ gnu::visibility("hidden") ]] void __cxa_pure_virtual() {
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mlibc::panicLogger() << "mlibc: Pure virtual function called from IP "
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<< (void *)__builtin_return_address(0) << frg::endlog;
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}
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extern "C" [[ gnu::visibility("hidden") ]] int __cxa_guard_acquire(int64_t *ptr) {
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auto guard = reinterpret_cast<Guard *>(ptr);
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guard->lock();
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// relaxed ordering is sufficient because
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// Guard::complete is only modified while the mutex is held.
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if(__atomic_load_n(&guard->complete, __ATOMIC_RELAXED)) {
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guard->unlock();
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return 0;
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}else{
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return 1;
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}
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}
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extern "C" [[ gnu::visibility("hidden") ]] void __cxa_guard_release(int64_t *ptr) {
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auto guard = reinterpret_cast<Guard *>(ptr);
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// do a store-release so that compiler generated code can skip calling
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// __cxa_guard_acquire by doing a load-acquire on Guard::complete.
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__atomic_store_n(&guard->complete, 1, __ATOMIC_RELEASE);
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guard->unlock();
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}
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