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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *  * Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *  * Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in
     12  *    the documentation and/or other materials provided with the
     13  *    distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
     22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 #ifndef _SYS_TLS_H
     29 #define _SYS_TLS_H
     30 
     31 #include <sys/cdefs.h>
     32 
     33 __BEGIN_DECLS
     34 
     35 /** WARNING WARNING WARNING
     36  **
     37  ** This header file is *NOT* part of the public Bionic ABI/API
     38  ** and should not be used/included by user-serviceable parts of
     39  ** the system (e.g. applications).
     40  **
     41  ** It is only provided here for the benefit of the system dynamic
     42  ** linker and the OpenGL sub-system (which needs to access the
     43  ** pre-allocated slot directly for performance reason).
     44  **/
     45 
     46 /* Well-known TLS slots. What data goes in which slot is arbitrary unless otherwise noted. */
     47 enum {
     48   TLS_SLOT_SELF = 0, /* The kernel requires this specific slot for x86. */
     49   TLS_SLOT_THREAD_ID,
     50   TLS_SLOT_ERRNO,
     51 
     52   /* These two aren't used by bionic itself, but allow the graphics code to
     53    * access TLS directly rather than using the pthread API. */
     54   TLS_SLOT_OPENGL_API = 3,
     55   TLS_SLOT_OPENGL = 4,
     56 
     57   /* This slot is only used to pass information from the dynamic linker to
     58    * libc.so when the C library is loaded in to memory. The C runtime init
     59    * function will then clear it. Since its use is extremely temporary,
     60    * we reuse an existing location that isn't needed during libc startup. */
     61   TLS_SLOT_BIONIC_PREINIT = TLS_SLOT_OPENGL_API,
     62 
     63   TLS_SLOT_STACK_GUARD = 5, /* GCC requires this specific slot for x86. */
     64   TLS_SLOT_DLERROR,
     65 
     66   TLS_SLOT_FIRST_USER_SLOT /* Must come last! */
     67 };
     68 
     69 /*
     70  * Maximum number of elements in the TLS array.
     71  * POSIX says this must be at least 128, but Android has traditionally had only 64, minus those
     72  * ones used internally by bionic itself.
     73  * There are two kinds of slot used internally by bionic --- there are the well-known slots
     74  * enumerated above, and then there are those that are allocated during startup by calls to
     75  * pthread_key_create; grep for GLOBAL_INIT_THREAD_LOCAL_BUFFER to find those. We need to manually
     76  * maintain that second number, but pthread_test will fail if we forget.
     77  */
     78 #define GLOBAL_INIT_THREAD_LOCAL_BUFFER_COUNT 4
     79 /*
     80  * This is PTHREAD_KEYS_MAX + TLS_SLOT_FIRST_USER_SLOT + GLOBAL_INIT_THREAD_LOCAL_BUFFER_COUNT
     81  * rounded up to maintain stack alignment.
     82  */
     83 #define BIONIC_ALIGN(x, a) (((x) + (a - 1)) & ~(a - 1))
     84 #define BIONIC_TLS_SLOTS BIONIC_ALIGN(128 + TLS_SLOT_FIRST_USER_SLOT + GLOBAL_INIT_THREAD_LOCAL_BUFFER_COUNT, 4)
     85 
     86 /* syscall only, do not call directly */
     87 extern int __set_tls(void* ptr);
     88 
     89 /* get the TLS */
     90 #if defined(__arm__)
     91 # define __get_tls() \
     92     ({ register unsigned int __val; \
     93        asm ("mrc p15, 0, %0, c13, c0, 3" : "=r"(__val)); \
     94        (volatile void*) __val; })
     95 #elif defined(__mips__)
     96 # define __get_tls() \
     97     /* On mips32r1, this goes via a kernel illegal instruction trap that's optimized for v1. */ \
     98     ({ register unsigned int __val asm("v1"); \
     99        asm ("   .set    push\n" \
    100             "   .set    mips32r2\n" \
    101             "   rdhwr   %0,$29\n" \
    102             "   .set    pop\n" : "=r"(__val)); \
    103        (volatile void*) __val; })
    104 #elif defined(__i386__)
    105 # define __get_tls() \
    106     ({ register void* __val; \
    107        asm ("movl %%gs:0, %0" : "=r"(__val)); \
    108        (volatile void*) __val; })
    109 #else
    110 #error unsupported architecture
    111 #endif
    112 
    113 __END_DECLS
    114 
    115 #if defined(__cplusplus)
    116 struct KernelArgumentBlock;
    117 extern __LIBC_HIDDEN__ void __libc_init_tls(KernelArgumentBlock& args);
    118 #endif
    119 
    120 #endif /* _SYS_TLS_H */
    121