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platform_bionic/libc/bionic/heap_zero_init.cpp

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Add an API for per-process disabling memory initialization. Introduce an android_mallopt(M_DISABLE_MEMORY_MITIGATIONS) API call that may be used to disable zero- or pattern-init on non-MTE hardware, or memory tagging on MTE hardware. The intent is that this function may be called at any time, including when there are multiple threads running. Disabling zero- or pattern-init is quite trivial, we just need to set a global variable to 0 via a Scudo API call (although there will be some separate work required on the Scudo side to make this operation thread-safe). It is a bit more tricky to disable MTE across a process, because the kernel does not provide an API for disabling tag checking in all threads in a process, only per-thread. We need to send a signal to each of the process's threads with a handler that issues the required prctl call, and lock thread creation for the duration of the API call to avoid races between thread enumeration and calls to pthread_create(). Bug: 135772972 Change-Id: I81ece86ace916eb6b435ab516cd431ec4b48a3bf
2020-09-12 00:05:17 +02:00
/*
* Copyright (C) 2020 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
[MemInit] Remove old API, introduce new MemInit API. Introduces new heap-zero-init API. We've realised that it's better to be able to individually control MTE and heap zero-init. Having heap-zero-init not be controllable without affecting MTE affects our ability to turn off heap-zero-init in zygote-forked applications. Bug: 135772972 Test: On FVP: atest -s localhost:5555 malloc#zero_init \ Test: malloc#disable_mte heap_tagging_level Change-Id: I8c6722502733259934c699f4f1269eaf1641a09f
2021-01-21 01:03:27 +01:00
#include "heap_zero_init.h"
Add an API for per-process disabling memory initialization. Introduce an android_mallopt(M_DISABLE_MEMORY_MITIGATIONS) API call that may be used to disable zero- or pattern-init on non-MTE hardware, or memory tagging on MTE hardware. The intent is that this function may be called at any time, including when there are multiple threads running. Disabling zero- or pattern-init is quite trivial, we just need to set a global variable to 0 via a Scudo API call (although there will be some separate work required on the Scudo side to make this operation thread-safe). It is a bit more tricky to disable MTE across a process, because the kernel does not provide an API for disabling tag checking in all threads in a process, only per-thread. We need to send a signal to each of the process's threads with a handler that issues the required prctl call, and lock thread creation for the duration of the API call to avoid races between thread enumeration and calls to pthread_create(). Bug: 135772972 Change-Id: I81ece86ace916eb6b435ab516cd431ec4b48a3bf
2020-09-12 00:05:17 +02:00
[MemInit] Remove old API, introduce new MemInit API. Introduces new heap-zero-init API. We've realised that it's better to be able to individually control MTE and heap zero-init. Having heap-zero-init not be controllable without affecting MTE affects our ability to turn off heap-zero-init in zygote-forked applications. Bug: 135772972 Test: On FVP: atest -s localhost:5555 malloc#zero_init \ Test: malloc#disable_mte heap_tagging_level Change-Id: I8c6722502733259934c699f4f1269eaf1641a09f
2021-01-21 01:03:27 +01:00
extern "C" void scudo_malloc_set_zero_contents(int zero_contents);
Add an API for per-process disabling memory initialization. Introduce an android_mallopt(M_DISABLE_MEMORY_MITIGATIONS) API call that may be used to disable zero- or pattern-init on non-MTE hardware, or memory tagging on MTE hardware. The intent is that this function may be called at any time, including when there are multiple threads running. Disabling zero- or pattern-init is quite trivial, we just need to set a global variable to 0 via a Scudo API call (although there will be some separate work required on the Scudo side to make this operation thread-safe). It is a bit more tricky to disable MTE across a process, because the kernel does not provide an API for disabling tag checking in all threads in a process, only per-thread. We need to send a signal to each of the process's threads with a handler that issues the required prctl call, and lock thread creation for the duration of the API call to avoid races between thread enumeration and calls to pthread_create(). Bug: 135772972 Change-Id: I81ece86ace916eb6b435ab516cd431ec4b48a3bf
2020-09-12 00:05:17 +02:00
[MemInit] Remove old API, introduce new MemInit API. Introduces new heap-zero-init API. We've realised that it's better to be able to individually control MTE and heap zero-init. Having heap-zero-init not be controllable without affecting MTE affects our ability to turn off heap-zero-init in zygote-forked applications. Bug: 135772972 Test: On FVP: atest -s localhost:5555 malloc#zero_init \ Test: malloc#disable_mte heap_tagging_level Change-Id: I8c6722502733259934c699f4f1269eaf1641a09f
2021-01-21 01:03:27 +01:00
bool SetHeapZeroInitialize(bool zero_init __attribute__((__unused__))) {
#ifdef USE_SCUDO
scudo_malloc_set_zero_contents(zero_init);
return true;
#endif
return false;
}
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