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c9ff0187 | 1 | /* Thread-local storage handling in the ELF dynamic linker. x86_64 version. |
2b778ceb | 2 | Copyright (C) 2004-2021 Free Software Foundation, Inc. |
c9ff0187 UD |
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 | |
59ba27a6 | 16 | License along with the GNU C Library; if not, see |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
c9ff0187 UD |
18 | |
19 | #include <sysdep.h> | |
20 | #include <tls.h> | |
21 | #include "tlsdesc.h" | |
22 | ||
23 | .text | |
24 | ||
25 | /* This function is used to compute the TP offset for symbols in | |
26 | Static TLS, i.e., whose TP offset is the same for all | |
27 | threads. | |
28 | ||
29 | The incoming %rax points to the TLS descriptor, such that | |
30 | 0(%rax) points to _dl_tlsdesc_return itself, and 8(%rax) holds | |
31 | the TP offset of the symbol corresponding to the object | |
32 | denoted by the argument. */ | |
33 | ||
34 | .hidden _dl_tlsdesc_return | |
35 | .global _dl_tlsdesc_return | |
36 | .type _dl_tlsdesc_return,@function | |
37 | cfi_startproc | |
38 | .align 16 | |
39 | _dl_tlsdesc_return: | |
562837c0 | 40 | _CET_ENDBR |
c9ff0187 UD |
41 | movq 8(%rax), %rax |
42 | ret | |
43 | cfi_endproc | |
44 | .size _dl_tlsdesc_return, .-_dl_tlsdesc_return | |
45 | ||
46 | /* This function is used for undefined weak TLS symbols, for | |
47 | which the base address (i.e., disregarding any addend) should | |
48 | resolve to NULL. | |
49 | ||
50 | %rax points to the TLS descriptor, such that 0(%rax) points to | |
51 | _dl_tlsdesc_undefweak itself, and 8(%rax) holds the addend. | |
52 | We return the addend minus the TP, such that, when the caller | |
53 | adds TP, it gets the addend back. If that's zero, as usual, | |
54 | that's most likely a NULL pointer. */ | |
55 | ||
56 | .hidden _dl_tlsdesc_undefweak | |
57 | .global _dl_tlsdesc_undefweak | |
58 | .type _dl_tlsdesc_undefweak,@function | |
59 | cfi_startproc | |
60 | .align 16 | |
61 | _dl_tlsdesc_undefweak: | |
562837c0 | 62 | _CET_ENDBR |
c9ff0187 UD |
63 | movq 8(%rax), %rax |
64 | subq %fs:0, %rax | |
65 | ret | |
66 | cfi_endproc | |
67 | .size _dl_tlsdesc_undefweak, .-_dl_tlsdesc_undefweak | |
68 | ||
69 | #ifdef SHARED | |
70 | .hidden _dl_tlsdesc_dynamic | |
71 | .global _dl_tlsdesc_dynamic | |
72 | .type _dl_tlsdesc_dynamic,@function | |
73 | ||
74 | /* %rax points to the TLS descriptor, such that 0(%rax) points to | |
75 | _dl_tlsdesc_dynamic itself, and 8(%rax) points to a struct | |
76 | tlsdesc_dynamic_arg object. It must return in %rax the offset | |
77 | between the thread pointer and the object denoted by the | |
78 | argument, without clobbering any registers. | |
79 | ||
80 | The assembly code that follows is a rendition of the following | |
81 | C code, hand-optimized a little bit. | |
82 | ||
83 | ptrdiff_t | |
84 | _dl_tlsdesc_dynamic (register struct tlsdesc *tdp asm ("%rax")) | |
85 | { | |
86 | struct tlsdesc_dynamic_arg *td = tdp->arg; | |
87 | dtv_t *dtv = *(dtv_t **)((char *)__thread_pointer + DTV_OFFSET); | |
88 | if (__builtin_expect (td->gen_count <= dtv[0].counter | |
89 | && (dtv[td->tlsinfo.ti_module].pointer.val | |
90 | != TLS_DTV_UNALLOCATED), | |
91 | 1)) | |
92 | return dtv[td->tlsinfo.ti_module].pointer.val + td->tlsinfo.ti_offset | |
93 | - __thread_pointer; | |
94 | ||
95 | return __tls_get_addr_internal (&td->tlsinfo) - __thread_pointer; | |
96 | } | |
97 | */ | |
98 | cfi_startproc | |
99 | .align 16 | |
100 | _dl_tlsdesc_dynamic: | |
562837c0 | 101 | _CET_ENDBR |
c9ff0187 UD |
102 | /* Preserve call-clobbered registers that we modify. |
103 | We need two scratch regs anyway. */ | |
104 | movq %rsi, -16(%rsp) | |
105 | movq %fs:DTV_OFFSET, %rsi | |
106 | movq %rdi, -8(%rsp) | |
107 | movq TLSDESC_ARG(%rax), %rdi | |
108 | movq (%rsi), %rax | |
109 | cmpq %rax, TLSDESC_GEN_COUNT(%rdi) | |
110 | ja .Lslow | |
111 | movq TLSDESC_MODID(%rdi), %rax | |
112 | salq $4, %rax | |
113 | movq (%rax,%rsi), %rax | |
114 | cmpq $-1, %rax | |
115 | je .Lslow | |
116 | addq TLSDESC_MODOFF(%rdi), %rax | |
117 | .Lret: | |
118 | movq -16(%rsp), %rsi | |
119 | subq %fs:0, %rax | |
120 | movq -8(%rsp), %rdi | |
121 | ret | |
122 | .Lslow: | |
123 | /* Besides rdi and rsi, saved above, save rdx, rcx, r8, r9, | |
124 | r10 and r11. Also, align the stack, that's off by 8 bytes. */ | |
125 | subq $72, %rsp | |
126 | cfi_adjust_cfa_offset (72) | |
127 | movq %rdx, 8(%rsp) | |
128 | movq %rcx, 16(%rsp) | |
129 | movq %r8, 24(%rsp) | |
130 | movq %r9, 32(%rsp) | |
131 | movq %r10, 40(%rsp) | |
132 | movq %r11, 48(%rsp) | |
133 | /* %rdi already points to the tlsinfo data structure. */ | |
050f7298 | 134 | call HIDDEN_JUMPTARGET (__tls_get_addr) |
c9ff0187 UD |
135 | movq 8(%rsp), %rdx |
136 | movq 16(%rsp), %rcx | |
137 | movq 24(%rsp), %r8 | |
138 | movq 32(%rsp), %r9 | |
139 | movq 40(%rsp), %r10 | |
140 | movq 48(%rsp), %r11 | |
141 | addq $72, %rsp | |
142 | cfi_adjust_cfa_offset (-72) | |
143 | jmp .Lret | |
144 | cfi_endproc | |
145 | .size _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic | |
146 | #endif /* SHARED */ |