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platform_bionic/libc/private/linker_native_bridge.h

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Reorganize static TLS memory for ELF TLS For ELF TLS "local-exec" accesses, the static linker assumes that an executable's TLS segment is located at a statically-known offset from the thread pointer (i.e. "variant 1" for ARM and "variant 2" for x86). Because these layouts are incompatible, Bionic generally needs to allocate its TLS slots differently between different architectures. To allow per-architecture TLS slots: - Replace the TLS_SLOT_xxx enumerators with macros. New ARM slots are generally negative, while new x86 slots are generally positive. - Define a bionic_tcb struct that provides two things: - a void* raw_slots_storage[BIONIC_TLS_SLOTS] field - an inline accessor function: void*& tls_slot(size_t tpindex); For ELF TLS, it's necessary to allocate a temporary TCB (i.e. TLS slots), because the runtime linker doesn't know how large the static TLS area is until after it has loaded all of the initial solibs. To accommodate Golang, it's necessary to allocate the pthread keys at a fixed, small, positive offset from the thread pointer. This CL moves the pthread keys into bionic_tls, then allocates a single mapping per thread that looks like so: - stack guard - stack [omitted for main thread and with pthread_attr_setstack] - static TLS: - bionic_tcb [exec TLS will either precede or succeed the TCB] - bionic_tls [prefixed by the pthread keys] - [solib TLS segments will be placed here] - guard page As before, if the new mapping includes a stack, the pthread_internal_t is allocated on it. At startup, Bionic allocates a temporary bionic_tcb object on the stack, then allocates a temporary bionic_tls object using mmap. This mmap is delayed because the linker can't currently call async_safe_fatal() before relocating itself. Later, Bionic allocates a stack-less thread mapping for the main thread, and copies slots from the temporary TCB to the new TCB. (See *::copy_from_bootstrap methods.) Bug: http://b/78026329 Test: bionic unit tests Test: verify that a Golang app still works Test: verify that a Golang app crashes if bionic_{tls,tcb} are swapped Change-Id: I6543063752f4ec8ef6dc9c7f2a06ce2a18fc5af3
2019-01-03 11:51:30 +01:00
/*
* Copyright (C) 2019 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.
*/
#pragma once
extern "C" void __linker_reserve_bionic_tls_in_static_tls();
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