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      1 // Copyright 2017 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 #include "base/memory/protected_memory.h"
      6 
      7 #include <stdint.h>
      8 #include <sys/mman.h>
      9 #include <unistd.h>
     10 
     11 #if defined(OS_LINUX)
     12 #include <sys/resource.h>
     13 #endif  // defined(OS_LINUX)
     14 
     15 #if defined(OS_MACOSX) && !defined(OS_IOS)
     16 #include <mach/mach.h>
     17 #include <mach/mach_vm.h>
     18 #endif  // defined(OS_MACOSX) && !defined(OS_IOS)
     19 
     20 #include "base/posix/eintr_wrapper.h"
     21 #include "base/process/process_metrics.h"
     22 #include "base/synchronization/lock.h"
     23 #include "build/build_config.h"
     24 
     25 namespace base {
     26 
     27 namespace {
     28 
     29 bool SetMemory(void* start, void* end, int prot) {
     30   DCHECK(end > start);
     31   const uintptr_t page_mask = ~(base::GetPageSize() - 1);
     32   const uintptr_t page_start = reinterpret_cast<uintptr_t>(start) & page_mask;
     33   return mprotect(reinterpret_cast<void*>(page_start),
     34                   reinterpret_cast<uintptr_t>(end) - page_start, prot) == 0;
     35 }
     36 
     37 }  // namespace
     38 
     39 bool AutoWritableMemory::SetMemoryReadWrite(void* start, void* end) {
     40   return SetMemory(start, end, PROT_READ | PROT_WRITE);
     41 }
     42 
     43 bool AutoWritableMemory::SetMemoryReadOnly(void* start, void* end) {
     44   return SetMemory(start, end, PROT_READ);
     45 }
     46 
     47 #if defined(OS_LINUX)
     48 void AssertMemoryIsReadOnly(const void* ptr) {
     49 #if DCHECK_IS_ON()
     50   const uintptr_t page_mask = ~(base::GetPageSize() - 1);
     51   const uintptr_t page_start = reinterpret_cast<uintptr_t>(ptr) & page_mask;
     52 
     53   // Note: We've casted away const here, which should not be meaningful since
     54   // if the memory is written to we will abort immediately.
     55   int result =
     56       getrlimit(RLIMIT_NPROC, reinterpret_cast<struct rlimit*>(page_start));
     57   DCHECK_EQ(result, -1);
     58   DCHECK_EQ(errno, EFAULT);
     59 #endif  // DCHECK_IS_ON()
     60 }
     61 #elif defined(OS_MACOSX) && !defined(OS_IOS)
     62 void AssertMemoryIsReadOnly(const void* ptr) {
     63 #if DCHECK_IS_ON()
     64   mach_port_t object_name;
     65   vm_region_basic_info_64 region_info;
     66   mach_vm_size_t size = 1;
     67   mach_msg_type_number_t count = VM_REGION_BASIC_INFO_COUNT_64;
     68 
     69   kern_return_t kr = mach_vm_region(
     70       mach_task_self(), reinterpret_cast<mach_vm_address_t*>(&ptr), &size,
     71       VM_REGION_BASIC_INFO_64, reinterpret_cast<vm_region_info_t>(&region_info),
     72       &count, &object_name);
     73   DCHECK_EQ(kr, KERN_SUCCESS);
     74   DCHECK_EQ(region_info.protection, VM_PROT_READ);
     75 #endif  // DCHECK_IS_ON()
     76 }
     77 #endif  // defined(OS_LINUX) || (defined(OS_MACOSX) && !defined(OS_IOS))
     78 
     79 }  // namespace base
     80