| // Copyright 2018 The Crashpad Authors. All rights reserved. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| #include "test/scoped_guarded_page.h" |
| |
| #include <sys/mman.h> |
| |
| #include "base/check.h" |
| #include "base/memory/page_size.h" |
| |
| namespace crashpad { |
| namespace test { |
| |
| ScopedGuardedPage::ScopedGuardedPage() { |
| ptr_ = mmap(nullptr, |
| base::GetPageSize() * 2, |
| PROT_READ | PROT_WRITE, |
| MAP_PRIVATE | MAP_ANONYMOUS, |
| -1, |
| 0); |
| PCHECK(ptr_ != MAP_FAILED) << "mmap"; |
| |
| // Simply mprotect()ing the guard page PROT_NONE does not make it inaccessible |
| // using ptrace() or /proc/$pid/mem so we munmap() the following page instead. |
| // Unfortunately, this means that the guarded page is not thread safe from |
| // other threads mapping a single page into the empty region. |
| char* second_page = static_cast<char*>(ptr_) + base::GetPageSize(); |
| PCHECK(munmap(second_page, base::GetPageSize()) >= 0) << "munmap"; |
| } |
| |
| ScopedGuardedPage::~ScopedGuardedPage() { |
| PCHECK(munmap(ptr_, base::GetPageSize()) >= 0) << "munmap"; |
| } |
| |
| } // namespace test |
| } // namespace crashpad |