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1/* Thread-local storage handling in the ELF dynamic linker. s390 version.
2 Copyright (C) 2003-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19
20/* Type used for the representation of TLS information in the GOT. */
21typedef struct
22{
23 unsigned long int ti_module;
24 unsigned long int ti_offset;
25} tls_index;
26
27
28#ifdef SHARED
29
30extern unsigned long __tls_get_offset (unsigned long got_offset);
31
32# if IS_IN (rtld)
33
34# include <shlib-compat.h>
35
36/* dl-tls.c declares __tls_get_addr as an exported symbol if it is not defined
37 as a macro. It seems suitable to do that in the generic code because all
38 architectures other than s390 export __tls_get_addr. The declaration causes
39 problems in s390 though, so we define __tls_get_addr here to avoid declaring
40 __tls_get_addr again. */
41# define __tls_get_addr __tls_get_addr
42
43extern void *__tls_get_addr (tls_index *ti) attribute_hidden;
44/* Make a temporary alias of __tls_get_addr to remove the hidden
45 attribute. Then export __tls_get_addr as __tls_get_addr_internal
46 for use from libc. We do not want to export __tls_get_addr, but we
47 do need to use it from libc when looking up the address of a TLS
48 variable. We don't use __tls_get_offset because it requires r12 to
49 be setup and that might not always be true. Either way it's more
50 optimal to use __tls_get_addr directly (that's what
51 __tls_get_offset does anyways). */
52strong_alias (__tls_get_addr, __tls_get_addr_internal_tmp);
53versioned_symbol (ld, __tls_get_addr_internal_tmp,
54 __tls_get_addr_internal, GLIBC_PRIVATE);
55
56/* The special thing about the s390 TLS ABI is that we do not have the
57 standard __tls_get_addr function but the __tls_get_offset function
58 which differs in two important aspects:
59 1) __tls_get_offset gets a got offset instead of a pointer to the
60 tls_index structure
61 2) __tls_get_offset returns the offset of the requested variable to
62 the thread descriptor instead of a pointer to the variable.
63 */
64# ifdef __s390x__
65__asm__("\n\
66 .text\n\
67 .globl __tls_get_offset\n\
68 .type __tls_get_offset, @function\n\
69 .align 4\n\
70__tls_get_offset:\n\
71 la %r2,0(%r2,%r12)\n\
72 jg __tls_get_addr\n\
73");
74# elif defined __s390__
75__asm__("\n\
76 .text\n\
77 .globl __tls_get_offset\n\
78 .type __tls_get_offset, @function\n\
79 .align 4\n\
80__tls_get_offset:\n\
81 basr %r3,0\n\
820: la %r2,0(%r2,%r12)\n\
83 l %r4,1f-0b(%r3)\n\
84 b 0(%r4,%r3)\n\
851: .long __tls_get_addr - 0b\n\
86");
87# endif
88# else /* IS_IN (rtld) */
89extern void *__tls_get_addr_internal (tls_index *ti);
90# endif /* !IS_IN (rtld) */
91
92# define GET_ADDR_OFFSET \
93 (ti->ti_offset - (unsigned long) __builtin_thread_pointer ())
94
95/* Use the privately exported __tls_get_addr_internal instead of
96 __tls_get_offset in order to avoid the __tls_get_offset special
97 linkage requiring the GOT pointer to be set up in r12. The
98 compiler will take care of setting up r12 only if itself issued the
99 __tls_get_offset call. */
100# define __TLS_GET_ADDR(__ti) \
101 ({ __tls_get_addr_internal (__ti) \
102 + (unsigned long) __builtin_thread_pointer (); })
103
104#endif
105

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source code of glibc/sysdeps/s390/dl-tls.h