70 lines
2.2 KiB
C++
70 lines
2.2 KiB
C++
//===-- sanitizer_persistent_allocator.h ------------------------*- C++ -*-===//
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// A fast memory allocator that does not support free() nor realloc().
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// All allocations are forever.
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//===----------------------------------------------------------------------===//
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#ifndef SANITIZER_PERSISTENT_ALLOCATOR_H
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#define SANITIZER_PERSISTENT_ALLOCATOR_H
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#include "sanitizer_internal_defs.h"
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#include "sanitizer_mutex.h"
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#include "sanitizer_atomic.h"
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#include "sanitizer_common.h"
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namespace __sanitizer {
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class PersistentAllocator {
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public:
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void *alloc(uptr size);
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private:
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void *tryAlloc(uptr size);
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StaticSpinMutex mtx; // Protects alloc of new blocks for region allocator.
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atomic_uintptr_t region_pos; // Region allocator for Node's.
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atomic_uintptr_t region_end;
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};
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inline void *PersistentAllocator::tryAlloc(uptr size) {
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// Optimisic lock-free allocation, essentially try to bump the region ptr.
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for (;;) {
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uptr cmp = atomic_load(®ion_pos, memory_order_acquire);
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uptr end = atomic_load(®ion_end, memory_order_acquire);
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if (cmp == 0 || cmp + size > end) return 0;
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if (atomic_compare_exchange_weak(®ion_pos, &cmp, cmp + size,
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memory_order_acquire))
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return (void *)cmp;
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}
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}
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inline void *PersistentAllocator::alloc(uptr size) {
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// First, try to allocate optimisitically.
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void *s = tryAlloc(size);
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if (s) return s;
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// If failed, lock, retry and alloc new superblock.
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SpinMutexLock l(&mtx);
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for (;;) {
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s = tryAlloc(size);
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if (s) return s;
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atomic_store(®ion_pos, 0, memory_order_relaxed);
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uptr allocsz = 64 * 1024;
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if (allocsz < size) allocsz = size;
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uptr mem = (uptr)MmapOrDie(allocsz, "stack depot");
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atomic_store(®ion_end, mem + allocsz, memory_order_release);
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atomic_store(®ion_pos, mem, memory_order_release);
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}
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}
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extern PersistentAllocator thePersistentAllocator;
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inline void *PersistentAlloc(uptr sz) {
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return thePersistentAllocator.alloc(sz);
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}
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} // namespace __sanitizer
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#endif // SANITIZER_PERSISTENT_ALLOCATOR_H
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