| // Copyright (c) 2013 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. |
| |
| #include "third_party/base/allocator/partition_allocator/page_allocator.h" |
| |
| #include <limits.h> |
| |
| #include <atomic> |
| |
| #include "build/build_config.h" |
| #include "third_party/base/allocator/partition_allocator/address_space_randomization.h" |
| #include "third_party/base/allocator/partition_allocator/page_allocator_internal.h" |
| #include "third_party/base/allocator/partition_allocator/spin_lock.h" |
| #include "third_party/base/bits.h" |
| #include "third_party/base/check_op.h" |
| #include "third_party/base/numerics/safe_math.h" |
| |
| #if BUILDFLAG(IS_WIN) |
| #include <windows.h> |
| #endif |
| |
| #if BUILDFLAG(IS_WIN) |
| #include "third_party/base/allocator/partition_allocator/page_allocator_internals_win.h" |
| #elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) |
| #include "third_party/base/allocator/partition_allocator/page_allocator_internals_posix.h" |
| #else |
| #error Platform not supported. |
| #endif |
| |
| namespace pdfium { |
| namespace base { |
| |
| namespace { |
| |
| // We may reserve/release address space on different threads. |
| subtle::SpinLock* GetReserveLock() { |
| static subtle::SpinLock* s_reserveLock = nullptr; |
| if (!s_reserveLock) |
| s_reserveLock = new subtle::SpinLock(); |
| return s_reserveLock; |
| } |
| |
| // We only support a single block of reserved address space. |
| void* s_reservation_address = nullptr; |
| size_t s_reservation_size = 0; |
| |
| void* AllocPagesIncludingReserved(void* address, |
| size_t length, |
| PageAccessibilityConfiguration accessibility, |
| PageTag page_tag, |
| bool commit) { |
| void* ret = |
| SystemAllocPages(address, length, accessibility, page_tag, commit); |
| if (ret == nullptr) { |
| const bool cant_alloc_length = kHintIsAdvisory || address == nullptr; |
| if (cant_alloc_length) { |
| // The system cannot allocate |length| bytes. Release any reserved address |
| // space and try once more. |
| ReleaseReservation(); |
| ret = SystemAllocPages(address, length, accessibility, page_tag, commit); |
| } |
| } |
| return ret; |
| } |
| |
| // Trims |base| to given |trim_length| and |alignment|. |
| // |
| // On failure, on Windows, this function returns nullptr and frees |base|. |
| void* TrimMapping(void* base, |
| size_t base_length, |
| size_t trim_length, |
| uintptr_t alignment, |
| PageAccessibilityConfiguration accessibility, |
| bool commit) { |
| size_t pre_slack = reinterpret_cast<uintptr_t>(base) & (alignment - 1); |
| if (pre_slack) { |
| pre_slack = alignment - pre_slack; |
| } |
| size_t post_slack = base_length - pre_slack - trim_length; |
| DCHECK(base_length >= trim_length || pre_slack || post_slack); |
| DCHECK(pre_slack < base_length); |
| DCHECK(post_slack < base_length); |
| return TrimMappingInternal(base, base_length, trim_length, accessibility, |
| commit, pre_slack, post_slack); |
| } |
| |
| } // namespace |
| |
| void* SystemAllocPages(void* hint, |
| size_t length, |
| PageAccessibilityConfiguration accessibility, |
| PageTag page_tag, |
| bool commit) { |
| DCHECK(!(length & PageAllocationGranularityOffsetMask())); |
| DCHECK(!(reinterpret_cast<uintptr_t>(hint) & |
| PageAllocationGranularityOffsetMask())); |
| DCHECK(commit || accessibility == PageInaccessible); |
| return SystemAllocPagesInternal(hint, length, accessibility, page_tag, |
| commit); |
| } |
| |
| void* AllocPages(void* address, |
| size_t length, |
| size_t align, |
| PageAccessibilityConfiguration accessibility, |
| PageTag page_tag, |
| bool commit) { |
| DCHECK(length >= PageAllocationGranularity()); |
| DCHECK(!(length & PageAllocationGranularityOffsetMask())); |
| DCHECK(align >= PageAllocationGranularity()); |
| // Alignment must be power of 2 for masking math to work. |
| DCHECK(pdfium::base::bits::IsPowerOfTwo(align)); |
| DCHECK(!(reinterpret_cast<uintptr_t>(address) & |
| PageAllocationGranularityOffsetMask())); |
| uintptr_t align_offset_mask = align - 1; |
| uintptr_t align_base_mask = ~align_offset_mask; |
| DCHECK(!(reinterpret_cast<uintptr_t>(address) & align_offset_mask)); |
| |
| // If the client passed null as the address, choose a good one. |
| if (address == nullptr) { |
| address = GetRandomPageBase(); |
| address = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(address) & |
| align_base_mask); |
| } |
| |
| // First try to force an exact-size, aligned allocation from our random base. |
| #if defined(ARCH_CPU_32_BITS) |
| // On 32 bit systems, first try one random aligned address, and then try an |
| // aligned address derived from the value of |ret|. |
| constexpr int kExactSizeTries = 2; |
| #else |
| // On 64 bit systems, try 3 random aligned addresses. |
| constexpr int kExactSizeTries = 3; |
| #endif |
| |
| for (int i = 0; i < kExactSizeTries; ++i) { |
| void* ret = AllocPagesIncludingReserved(address, length, accessibility, |
| page_tag, commit); |
| if (ret != nullptr) { |
| // If the alignment is to our liking, we're done. |
| if (!(reinterpret_cast<uintptr_t>(ret) & align_offset_mask)) |
| return ret; |
| // Free the memory and try again. |
| FreePages(ret, length); |
| } else { |
| // |ret| is null; if this try was unhinted, we're OOM. |
| if (kHintIsAdvisory || address == nullptr) |
| return nullptr; |
| } |
| |
| #if defined(ARCH_CPU_32_BITS) |
| // For small address spaces, try the first aligned address >= |ret|. Note |
| // |ret| may be null, in which case |address| becomes null. |
| address = reinterpret_cast<void*>( |
| (reinterpret_cast<uintptr_t>(ret) + align_offset_mask) & |
| align_base_mask); |
| #else // defined(ARCH_CPU_64_BITS) |
| // Keep trying random addresses on systems that have a large address space. |
| address = GetRandomPageBase(); |
| address = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(address) & |
| align_base_mask); |
| #endif |
| } |
| |
| // Make a larger allocation so we can force alignment. |
| size_t try_length = length + (align - PageAllocationGranularity()); |
| CHECK(try_length >= length); |
| void* ret; |
| |
| do { |
| // Continue randomizing only on POSIX. |
| address = kHintIsAdvisory ? GetRandomPageBase() : nullptr; |
| ret = AllocPagesIncludingReserved(address, try_length, accessibility, |
| page_tag, commit); |
| // The retries are for Windows, where a race can steal our mapping on |
| // resize. |
| } while (ret != nullptr && |
| (ret = TrimMapping(ret, try_length, length, align, accessibility, |
| commit)) == nullptr); |
| |
| return ret; |
| } |
| |
| void FreePages(void* address, size_t length) { |
| DCHECK(!(reinterpret_cast<uintptr_t>(address) & |
| PageAllocationGranularityOffsetMask())); |
| DCHECK(!(length & PageAllocationGranularityOffsetMask())); |
| FreePagesInternal(address, length); |
| } |
| |
| bool TrySetSystemPagesAccess(void* address, |
| size_t length, |
| PageAccessibilityConfiguration accessibility) { |
| DCHECK(!(length & SystemPageOffsetMask())); |
| return TrySetSystemPagesAccessInternal(address, length, accessibility); |
| } |
| |
| void SetSystemPagesAccess(void* address, |
| size_t length, |
| PageAccessibilityConfiguration accessibility) { |
| DCHECK(!(length & SystemPageOffsetMask())); |
| SetSystemPagesAccessInternal(address, length, accessibility); |
| } |
| |
| void DecommitSystemPages(void* address, size_t length) { |
| DCHECK_EQ(0UL, length & SystemPageOffsetMask()); |
| DecommitSystemPagesInternal(address, length); |
| } |
| |
| bool RecommitSystemPages(void* address, |
| size_t length, |
| PageAccessibilityConfiguration accessibility) { |
| DCHECK_EQ(0UL, length & SystemPageOffsetMask()); |
| DCHECK(PageInaccessible != accessibility); |
| return RecommitSystemPagesInternal(address, length, accessibility); |
| } |
| |
| void DiscardSystemPages(void* address, size_t length) { |
| DCHECK_EQ(0UL, length & SystemPageOffsetMask()); |
| DiscardSystemPagesInternal(address, length); |
| } |
| |
| bool ReserveAddressSpace(size_t size) { |
| // To avoid deadlock, call only SystemAllocPages. |
| subtle::SpinLock::Guard guard(*GetReserveLock()); |
| if (s_reservation_address == nullptr) { |
| void* mem = SystemAllocPages(nullptr, size, PageInaccessible, |
| PageTag::kChromium, false); |
| if (mem != nullptr) { |
| // We guarantee this alignment when reserving address space. |
| DCHECK(!(reinterpret_cast<uintptr_t>(mem) & |
| PageAllocationGranularityOffsetMask())); |
| s_reservation_address = mem; |
| s_reservation_size = size; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| bool ReleaseReservation() { |
| // To avoid deadlock, call only FreePages. |
| subtle::SpinLock::Guard guard(*GetReserveLock()); |
| if (!s_reservation_address) |
| return false; |
| |
| FreePages(s_reservation_address, s_reservation_size); |
| s_reservation_address = nullptr; |
| s_reservation_size = 0; |
| return true; |
| } |
| |
| uint32_t GetAllocPageErrorCode() { |
| return s_allocPageErrorCode; |
| } |
| |
| } // namespace base |
| } // namespace pdfium |