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// 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/logging.h"
#include "base/process/process_metrics.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