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1 /*
2  * Copyright (C) 2014 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #define NS_PER_S 1'000'000'000LL
20 
21 // Size of the shadow call stack. This can be small because these stacks only
22 // contain return addresses. This must be a power of 2 so the mask trick works.
23 // See the SCS commentary in pthread_internal.h for more detail.
24 // SCS_SIZE must be a multiple of page size.
25 // We used 8KiB until V but switched to 16KiB in V to experiment with 16KiB pages.
26 #define SCS_SIZE (16 * 1024)
27 #define SCS_MASK (SCS_SIZE - 1)
28 
29 // The shadow call stack is allocated at an aligned address within a guard region of this size. The
30 // guard region must be large enough that we can allocate an SCS_SIZE-aligned SCS while ensuring
31 // that there is at least one guard page after the SCS so that a stack overflow results in a SIGSEGV
32 // instead of corrupting the allocation that comes after it.
33 #define SCS_GUARD_REGION_SIZE (16 * 1024 * 1024)
34