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 #include <stddef.h> 10 11 #include <algorithm> 12 13 #include "base/base_export.h" 14 #include "base/logging.h" 15 #include "base/macros.h" 16 17 // Use ScopedMachVM to supervise ownership of pages in the current process 18 // through the Mach VM subsystem. Pages allocated with vm_allocate can be 19 // released when exiting a scope with ScopedMachVM. 20 // 21 // The Mach VM subsystem operates on a page-by-page basis, and a single VM 22 // allocation managed by a ScopedMachVM object may span multiple pages. As far 23 // as Mach is concerned, allocated pages may be deallocated individually. This 24 // is in contrast to higher-level allocators such as malloc, where the base 25 // address of an allocation implies the size of an allocated block. 26 // Consequently, it is not sufficient to just pass the base address of an 27 // allocation to ScopedMachVM, it also needs to know the size of the 28 // allocation. To avoid any confusion, both the base address and size must 29 // be page-aligned. 30 // 31 // When dealing with Mach VM, base addresses will naturally be page-aligned, 32 // but user-specified sizes may not be. If there's a concern that a size is 33 // not page-aligned, use the mach_vm_round_page macro to correct it. 34 // 35 // Example: 36 // 37 // vm_address_t address = 0; 38 // vm_size_t size = 12345; // This requested size is not page-aligned. 39 // kern_return_t kr = 40 // vm_allocate(mach_task_self(), &address, size, VM_FLAGS_ANYWHERE); 41 // if (kr != KERN_SUCCESS) { 42 // return false; 43 // } 44 // ScopedMachVM vm_owner(address, mach_vm_round_page(size)); 45 46 namespace base { 47 namespace mac { 48 49 class BASE_EXPORT ScopedMachVM { 50 public: 51 explicit ScopedMachVM(vm_address_t address = 0, vm_size_t size = 0) address_(address)52 : address_(address), size_(size) { 53 DCHECK_EQ(address % PAGE_SIZE, 0u); 54 DCHECK_EQ(size % PAGE_SIZE, 0u); 55 } 56 ~ScopedMachVM()57 ~ScopedMachVM() { 58 if (size_) { 59 vm_deallocate(mach_task_self(), address_, size_); 60 } 61 } 62 63 void reset(vm_address_t address = 0, vm_size_t size = 0); 64 address()65 vm_address_t address() const { 66 return address_; 67 } 68 size()69 vm_size_t size() const { 70 return size_; 71 } 72 swap(ScopedMachVM & that)73 void swap(ScopedMachVM& that) { 74 std::swap(address_, that.address_); 75 std::swap(size_, that.size_); 76 } 77 release()78 void release() { 79 address_ = 0; 80 size_ = 0; 81 } 82 83 private: 84 vm_address_t address_; 85 vm_size_t size_; 86 87 DISALLOW_COPY_AND_ASSIGN(ScopedMachVM); 88 }; 89 90 } // namespace mac 91 } // namespace base 92 93 #endif // BASE_MAC_SCOPED_MACH_VM_H_ 94