1a78fbb5c8
Since e19d702b8e, dlsym and friends use recursive mutexes that
require the current thread id, which is not available before the libc
constructor. This prevents us from using dlsym() in .preinit_array.
This change moves TLS initialization from libc constructor to the earliest
possible point - immediately after linker itself is relocated. As a result,
pthread_internal_t for the initial thread is available from the start.
As a bonus, values stored in TLS in .preinit_array are not lost when libc is
initialized.
Change-Id: Iee5a710ee000173bff63e924adeb4a4c600c1e2d
143 lines
5.2 KiB
C
143 lines
5.2 KiB
C
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef _SYS_TLS_H
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#define _SYS_TLS_H
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#include <sys/cdefs.h>
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__BEGIN_DECLS
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/** WARNING WARNING WARNING
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**
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** This header file is *NOT* part of the public Bionic ABI/API
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** and should not be used/included by user-serviceable parts of
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** the system (e.g. applications).
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**
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** It is only provided here for the benefit of the system dynamic
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** linker and the OpenGL sub-system (which needs to access the
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** pre-allocated slot directly for performance reason).
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**/
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/* maximum number of elements in the TLS array */
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#define BIONIC_TLS_SLOTS 64
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/* note that slot 0, called TLS_SLOT_SELF must point to itself.
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* this is required to implement thread-local storage with the x86
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* Linux kernel, that reads the TLS from fs:[0], where 'fs' is a
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* thread-specific segment descriptor...
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*/
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/* Well known TLS slots */
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#define TLS_SLOT_SELF 0
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#define TLS_SLOT_THREAD_ID 1
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#define TLS_SLOT_ERRNO 2
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#define TLS_SLOT_OPENGL_API 3
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#define TLS_SLOT_OPENGL 4
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/* this slot is only used to pass information from the dynamic linker to
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* libc.so when the C library is loaded in to memory. The C runtime init
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* function will then clear it. Since its use is extremely temporary,
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* we reuse an existing location.
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*/
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#define TLS_SLOT_BIONIC_PREINIT (TLS_SLOT_ERRNO+1)
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/* small technical note: it is not possible to call pthread_setspecific
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* on keys that are <= TLS_SLOT_MAX_WELL_KNOWN, which is why it is set to
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* TLS_SLOT_ERRNO.
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*
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* later slots like TLS_SLOT_OPENGL are pre-allocated through the use of
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* TLS_DEFAULT_ALLOC_MAP. this means that there is no need to use
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* pthread_key_create() to initialize them. on the other hand, there is
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* no destructor associated to them (we might need to implement this later)
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*/
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#define TLS_SLOT_MAX_WELL_KNOWN TLS_SLOT_ERRNO
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#define TLS_DEFAULT_ALLOC_MAP 0x0000001F
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/* set the Thread Local Storage, must contain at least BIONIC_TLS_SLOTS pointers */
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extern void __init_tls(void** tls, void* thread_info);
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/* syscall only, do not call directly */
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extern int __set_tls(void *ptr);
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/* get the TLS */
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#ifdef __arm__
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/* The standard way to get the TLS is to call a kernel helper
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* function (i.e. a function provided at a fixed address in a
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* "magic page" mapped in all user-space address spaces ), which
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* contains the most appropriate code path for the target device.
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*
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* However, for performance reasons, we're going to use our own
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* machine code for the system's C shared library.
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*
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* We cannot use this optimization in the static version of the
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* C library, because we don't know where the corresponding code
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* is going to run.
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*/
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# ifdef LIBC_STATIC
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/* Use the kernel helper in static C library. */
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typedef volatile void* (__kernel_get_tls_t)(void);
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# define __get_tls() (*(__kernel_get_tls_t *)0xffff0fe0)()
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# else /* !LIBC_STATIC */
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/* Use optimized code path.
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* Note that HAVE_ARM_TLS_REGISTER is build-specific
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* (it must match your kernel configuration)
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*/
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# ifdef HAVE_ARM_TLS_REGISTER
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/* We can read the address directly from a coprocessor
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* register, which avoids touching the data cache
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* completely.
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*/
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# define __get_tls() \
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({ register unsigned int __val asm("r0"); \
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asm ("mrc p15, 0, r0, c13, c0, 3" : "=r"(__val) ); \
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(volatile void*)__val; })
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# else /* !HAVE_ARM_TLS_REGISTER */
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/* The kernel provides the address of the TLS at a fixed
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* address of the magic page too.
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*/
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# define __get_tls() ( *((volatile void **) 0xffff0ff0) )
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# endif
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# endif /* !LIBC_STATIC */
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#else /* !ARM */
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extern void* __get_tls( void );
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#endif /* !ARM */
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/* return the stack base and size, used by our malloc debugger */
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extern void* __get_stack_base(int *p_stack_size);
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/* Initialize the TLS. */
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extern void __libc_init_tls(unsigned** elfdata);
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__END_DECLS
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#endif /* _SYS_TLS_H */
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