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| 1 // Copyright 2014 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #ifndef BASE_MAC_SCOPED_MACH_VM_H_ | |
| 6 #define BASE_MAC_SCOPED_MACH_VM_H_ | |
| 7 | |
| 8 #include <mach/mach.h> | |
| 9 | |
| 10 #include <algorithm> | |
| 11 | |
| 12 #include "base/base_export.h" | |
| 13 #include "base/basictypes.h" | |
| 14 #include "base/logging.h" | |
| 15 | |
| 16 // Use ScopedMachVM to supervise ownership of pages in the current process | |
| 17 // through the Mach VM subsystem. Pages allocated with vm_allocate can be | |
| 18 // released when exiting a scope with ScopedMachVM. | |
| 19 // | |
| 20 // The Mach VM subsystem operates on a page-by-page basis, and a single VM | |
| 21 // allocation managed by a ScopedMachVM object may span multiple pages. As far | |
| 22 // as Mach is concerned, allocated pages may be deallocated individually. This | |
| 23 // is in contrast to higher-level allocators such as malloc, where the base | |
| 24 // address of an allocation implies the size of an allocated block. | |
| 25 // Consequently, it is not sufficient to just pass the base address of an | |
| 26 // allocation to ScopedMachVM, it also needs to know the size of the | |
| 27 // allocation. To avoid any confusion, both the base address and size must | |
| 28 // be page-aligned. | |
| 29 // | |
| 30 // When dealing with Mach VM, base addresses will naturally be page-aligned, | |
| 31 // but user-specified sizes may not be. If there's a concern that a size is | |
| 32 // not page-aligned, use the mach_vm_round_page macro to correct it. | |
| 33 // | |
| 34 // Example: | |
| 35 // | |
| 36 // vm_address_t address = 0; | |
| 37 // vm_size_t size = 12345; // This requested size is not page-aligned. | |
| 38 // kern_return_t kr = | |
| 39 // vm_allocate(mach_task_self(), &address, size, VM_FLAGS_ANYWHERE); | |
| 40 // if (kr != KERN_SUCCESS) { | |
| 41 // return false; | |
| 42 // } | |
| 43 // ScopedMachVM vm_owner(address, mach_vm_round_page(size)); | |
| 44 | |
| 45 namespace base { | |
| 46 namespace mac { | |
| 47 | |
| 48 class BASE_EXPORT ScopedMachVM { | |
| 49 public: | |
| 50 explicit ScopedMachVM(vm_address_t address = 0, vm_size_t size = 0) | |
| 51 : address_(address), size_(size) { | |
| 52 DCHECK_EQ(address % PAGE_SIZE, 0u); | |
| 53 DCHECK_EQ(size % PAGE_SIZE, 0u); | |
| 54 } | |
| 55 | |
| 56 ~ScopedMachVM() { | |
| 57 if (size_) { | |
| 58 vm_deallocate(mach_task_self(), address_, size_); | |
| 59 } | |
| 60 } | |
| 61 | |
| 62 void reset(vm_address_t address = 0, vm_size_t size = 0); | |
| 63 | |
| 64 vm_address_t address() const { | |
| 65 return address_; | |
| 66 } | |
| 67 | |
| 68 vm_size_t size() const { | |
| 69 return size_; | |
| 70 } | |
| 71 | |
| 72 void swap(ScopedMachVM& that) { | |
| 73 std::swap(address_, that.address_); | |
| 74 std::swap(size_, that.size_); | |
| 75 } | |
| 76 | |
| 77 void release() { | |
| 78 address_ = 0; | |
| 79 size_ = 0; | |
| 80 } | |
| 81 | |
| 82 private: | |
| 83 vm_address_t address_; | |
| 84 vm_size_t size_; | |
| 85 | |
| 86 DISALLOW_COPY_AND_ASSIGN(ScopedMachVM); | |
| 87 }; | |
| 88 | |
| 89 } // namespace mac | |
| 90 } // namespace base | |
| 91 | |
| 92 #endif // BASE_MAC_SCOPED_MACH_VM_H_ | |
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