bionic_tls.h revision edad1e1558bf5a561ffb33c5bf5ca0553711e1ee 
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. */
47enum {
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 */
87extern 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)
116class KernelArgumentBlock;
117extern __LIBC_HIDDEN__ void __libc_init_tls(KernelArgumentBlock& args);
118#endif
119
120#endif /* _SYS_TLS_H */
121