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Diffstat (limited to 'libc/private/bionic_asm_tls.h')
| -rw-r--r-- | libc/private/bionic_asm_tls.h | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/libc/private/bionic_asm_tls.h b/libc/private/bionic_asm_tls.h new file mode 100644 index 000000000..06e3dce00 --- /dev/null +++ b/libc/private/bionic_asm_tls.h @@ -0,0 +1,119 @@ +/* + * Copyright (C) 2018 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 + +/** WARNING WARNING WARNING + ** + ** This header file is *NOT* part of the public Bionic ABI/API and should not + ** be used/included by user-serviceable parts of the system (e.g. + ** applications). + ** + ** It is only provided here for the benefit of Android components that need a + ** pre-allocated slot for performance reasons (including ART, the OpenGL + ** subsystem, and sanitizers). + **/ + +// Bionic TCB / TLS slots: +// +// - TLS_SLOT_SELF: On x86-{32,64}, the kernel makes TLS memory available via +// the gs/fs segments. To get the address of a TLS variable, the first slot +// of TLS memory (accessed using %gs:0 / %fs:0) holds the address of the +// gs/fs segment. This slot is used by: +// - OpenGL and compiler-rt +// - Accesses of x86 ELF TLS variables +// +// - TLS_SLOT_OPENGL and TLS_SLOT_OPENGL_API: These two aren't used by bionic +// itself, but allow the graphics code to access TLS directly rather than +// using the pthread API. +// +// - TLS_SLOT_STACK_GUARD: Used for -fstack-protector by: +// - Clang targeting Android/arm64 +// - gcc targeting Linux/x86-{32,64} +// +// - TLS_SLOT_SANITIZER: Lets sanitizers avoid using pthread_getspecific for +// finding the current thread state. +// +// - TLS_SLOT_DTV: Pointer to ELF TLS dynamic thread vector. +// +// - TLS_SLOT_ART_THREAD_SELF: Fast storage for Thread::Current() in ART. +// +// - TLS_SLOT_BIONIC_TLS: Optimizes accesses to bionic_tls by one load versus +// finding it using __get_thread(). + +#if defined(__arm__) || defined(__aarch64__) + +// The ARM ELF TLS ABI specifies[1] that the thread pointer points at a 2-word +// TCB followed by the executable's TLS segment. Both the TCB and the +// executable's segment are aligned according to the segment, so Bionic requires +// a minimum segment alignment, which effectively reserves an 8-word TCB. The +// ARM spec allocates the first TCB word to the DTV. +// +// [1] "Addenda to, and Errata in, the ABI for the ARM Architecture". Section 3. +// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0045e/IHI0045E_ABI_addenda.pdf + +#define MIN_TLS_SLOT -1 // update this value when reserving a slot +#define TLS_SLOT_BIONIC_TLS -1 +#define TLS_SLOT_DTV 0 +#define TLS_SLOT_THREAD_ID 1 +// Slot 2 is free (was historically used for TLS_SLOT_ERRNO) +#define TLS_SLOT_OPENGL 3 +#define TLS_SLOT_OPENGL_API 4 +#define TLS_SLOT_STACK_GUARD 5 +#define TLS_SLOT_SANITIZER 6 // was historically used for dlerror +#define TLS_SLOT_ART_THREAD_SELF 7 +#define TLS_SLOT_TSAN 8 // should be replaced with TLS_SLOT_SANITIZER + +// The maximum slot is fixed by the minimum TLS alignment in Bionic executables. +// It should be changed to 7 once TLS_SLOT_TSAN is removed. +#define MAX_TLS_SLOT 8 + +#elif defined(__i386__) || defined(__x86_64__) + +// x86 uses variant 2 ELF TLS layout, which places the executable's TLS segment +// immediately before the thread pointer. New slots are allocated at positive +// offsets from the thread pointer. + +#define MIN_TLS_SLOT 0 + +#define TLS_SLOT_SELF 0 +#define TLS_SLOT_THREAD_ID 1 +// Slot 2 is free (was historically used for TLS_SLOT_ERRNO) +#define TLS_SLOT_OPENGL 3 +#define TLS_SLOT_OPENGL_API 4 +#define TLS_SLOT_STACK_GUARD 5 +#define TLS_SLOT_SANITIZER 6 // was historically used for dlerror +#define TLS_SLOT_ART_THREAD_SELF 7 +#define TLS_SLOT_TSAN 8 // should be replaced with TLS_SLOT_SANITIZER +#define TLS_SLOT_DTV 9 +#define TLS_SLOT_BIONIC_TLS 10 +#define MAX_TLS_SLOT 10 // update this value when reserving a slot + +#endif + +#define BIONIC_TLS_SLOTS (MAX_TLS_SLOT - MIN_TLS_SLOT + 1) |