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- // Copyright (c) 2020 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_INL_H_
- #define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_INL_H_
- #include <algorithm>
- #include <cstring>
- #include "base/allocator/partition_allocator/partition_alloc_base/compiler_specific.h"
- #include "base/allocator/partition_allocator/partition_alloc_base/debug/debugging_buildflags.h"
- #include "base/allocator/partition_allocator/partition_ref_count.h"
- #include "base/allocator/partition_allocator/random.h"
- #include "base/allocator/partition_allocator/tagging.h"
- #include "build/build_config.h"
- // Prefetch *x into memory.
- #if defined(__clang__) || defined(COMPILER_GCC)
- #define PA_PREFETCH(x) __builtin_prefetch(x)
- #else
- #define PA_PREFETCH(x)
- #endif
- namespace partition_alloc::internal {
- // This is a `memset` that resists being optimized away. Adapted from
- // boringssl/src/crypto/mem.c. (Copying and pasting is bad, but //base can't
- // depend on //third_party, and this is small enough.)
- PA_ALWAYS_INLINE void SecureMemset(void* ptr, uint8_t value, size_t size) {
- memset(ptr, value, size);
- // As best as we can tell, this is sufficient to break any optimisations that
- // might try to eliminate "superfluous" memsets. If there's an easy way to
- // detect memset_s, it would be better to use that.
- __asm__ __volatile__("" : : "r"(ptr) : "memory");
- }
- // Used to memset() memory for debugging purposes only.
- PA_ALWAYS_INLINE void DebugMemset(void* ptr, int value, size_t size) {
- // Only set the first 512kiB of the allocation. This is enough to detect uses
- // of uininitialized / freed memory, and makes tests run significantly
- // faster. Note that for direct-mapped allocations, memory is decomitted at
- // free() time, so freed memory usage cannot happen.
- size_t size_to_memset = std::min(size, size_t{1} << 19);
- memset(ptr, value, size_to_memset);
- }
- // Returns true if we've hit the end of a random-length period. We don't want to
- // invoke `RandomValue` too often, because we call this function in a hot spot
- // (`Free`), and `RandomValue` incurs the cost of atomics.
- #if !BUILDFLAG(PA_DCHECK_IS_ON)
- PA_ALWAYS_INLINE bool RandomPeriod() {
- static thread_local uint8_t counter = 0;
- if (PA_UNLIKELY(counter == 0)) {
- // It's OK to truncate this value.
- counter = static_cast<uint8_t>(RandomValue());
- }
- // If `counter` is 0, this will wrap. That is intentional and OK.
- counter--;
- return counter == 0;
- }
- #endif // !BUILDFLAG(PA_DCHECK_IS_ON)
- PA_ALWAYS_INLINE uintptr_t ObjectInnerPtr2Addr(const void* ptr) {
- return UntagPtr(ptr);
- }
- PA_ALWAYS_INLINE uintptr_t ObjectPtr2Addr(const void* object) {
- // TODO(bartekn): Check that |object| is indeed an object start.
- return ObjectInnerPtr2Addr(object);
- }
- PA_ALWAYS_INLINE void* SlotStartAddr2Ptr(uintptr_t slot_start) {
- // TODO(bartekn): Check that |slot_start| is indeed a slot start.
- return TagAddr(slot_start);
- }
- PA_ALWAYS_INLINE uintptr_t SlotStartPtr2Addr(const void* slot_start) {
- // TODO(bartekn): Check that |slot_start| is indeed a slot start.
- return UntagPtr(slot_start);
- }
- } // namespace partition_alloc::internal
- #endif // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_INL_H_
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