1 /* Definitions for thread-local data handling. Hurd/x86_64 version.
2 Copyright (C) 2003-2023 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 #ifndef _X86_64_TLS_H
20 #define _X86_64_TLS_H
21
22
23 /* Some things really need not be machine-dependent. */
24 #include <sysdeps/mach/hurd/tls.h>
25
26
27 #ifndef __ASSEMBLER__
28 # include <dl-dtv.h>
29 # include <mach/machine/thread_status.h>
30 # include <errno.h>
31 # include <assert.h>
32
33 /* Type of the TCB. */
34 typedef struct
35 {
36 void *tcb; /* Points to this structure. */
37 dtv_t *dtv; /* Vector of pointers to TLS data. */
38 thread_t self_do_no_use; /* This thread's control port. */
39 int __glibc_padding1;
40 int multiple_threads;
41 int gscope_flag;
42 uintptr_t sysinfo;
43 uintptr_t stack_guard;
44 uintptr_t pointer_guard;
45 long __glibc_padding2[2];
46 int private_futex;
47 int __glibc_padding3;
48 /* Reservation of some values for the TM ABI. */
49 void *__private_tm[4];
50 /* GCC split stack support. */
51 void *__private_ss;
52 /* The lowest address of shadow stack. */
53 unsigned long long int ssp_base;
54
55 /* Keep these fields last, so offsets of fields above can continue being
56 compatible with the x86_64 NPTL version. */
57 mach_port_t reply_port; /* This thread's reply port. */
58 struct hurd_sigstate *_hurd_sigstate;
59
60 /* Used by the exception handling implementation in the dynamic loader. */
61 struct rtld_catch *rtld_catch;
62 } tcbhead_t;
63
64 /* GCC generates %fs:0x28 to access the stack guard. */
65 _Static_assert (offsetof (tcbhead_t, stack_guard) == 0x28,
66 "stack guard offset");
67 /* libgcc uses %fs:0x70 to access the split stack pointer. */
68 _Static_assert (offsetof (tcbhead_t, __private_ss) == 0x70,
69 "split stack pointer offset");
70
71 /* The TCB can have any size and the memory following the address the
72 thread pointer points to is unspecified. Allocate the TCB there. */
73 # define TLS_TCB_AT_TP 1
74 # define TLS_DTV_AT_TP 0
75
76 /* Alignment requirement for TCB.
77
78 Some processors such as Intel Atom pay a big penalty on every
79 access using a segment override if that segment's base is not
80 aligned to the size of a cache line. (See Intel 64 and IA-32
81 Architectures Optimization Reference Manual, section 13.3.3.3,
82 "Segment Base".) On such machines, a cache line is 64 bytes. */
83 # define TCB_ALIGNMENT 64
84
85
86 # define THREAD_SELF \
87 (*(tcbhead_t * __seg_fs *) offsetof (tcbhead_t, tcb))
88 /* Read member of the thread descriptor directly. */
89 # define THREAD_GETMEM(descr, member) \
90 (*(__typeof (descr->member) __seg_fs *) offsetof (tcbhead_t, member))
91 /* Write member of the thread descriptor directly. */
92 # define THREAD_SETMEM(descr, member, value) \
93 (*(__typeof (descr->member) __seg_fs *) offsetof (tcbhead_t, member) = value)
94
95
96 /* Return the TCB address of a thread given its state.
97 Note: this is expensive. */
98 static inline tcbhead_t * __attribute__ ((unused))
99 THREAD_TCB (thread_t thread,
100 const void *all_state __attribute__ ((unused)))
101 {
102 error_t err;
103 /* Fetch the target thread's state. */
104 struct i386_fsgs_base_state state;
105 mach_msg_type_number_t state_count = i386_FSGS_BASE_STATE_COUNT;
106 err = __thread_get_state (thread, i386_FSGS_BASE_STATE,
107 (thread_state_t) &state,
108 &state_count);
109 assert_perror (err);
110 assert (state_count == i386_FSGS_BASE_STATE_COUNT);
111 return (tcbhead_t *) state.fs_base;
112 }
113
114 /* Install new dtv for current thread. */
115 # define INSTALL_NEW_DTV(dtvp) THREAD_SETMEM (THREAD_SELF, dtv, dtvp)
116
117 /* Return the address of the dtv for the current thread. */
118 # define THREAD_DTV() THREAD_GETMEM (THREAD_SELF, dtv)
119
120
121 /* Set the stack guard field in TCB head. */
122 # define THREAD_SET_STACK_GUARD(value) \
123 THREAD_SETMEM (THREAD_SELF, stack_guard, value)
124 # define THREAD_COPY_STACK_GUARD(descr) \
125 ((descr)->stack_guard \
126 = THREAD_GETMEM (THREAD_SELF, stack_guard))
127
128 /* Set the pointer guard field in the TCB head. */
129 # define THREAD_SET_POINTER_GUARD(value) \
130 THREAD_SETMEM (THREAD_SELF, pointer_guard, value)
131 # define THREAD_COPY_POINTER_GUARD(descr) \
132 ((descr)->pointer_guard \
133 = THREAD_GETMEM (THREAD_SELF, pointer_guard))
134
135 /* From hurd.h, reproduced here to avoid a circular include. */
136 extern thread_t __hurd_thread_self (void);
137 libc_hidden_proto (__hurd_thread_self)
138
139 /* Set up TLS in the new thread of a fork child, copying from the original. */
140 static inline kern_return_t __attribute__ ((unused))
141 _hurd_tls_fork (thread_t child, thread_t orig,
142 void *machine_state __attribute__ ((unused)))
143 {
144 error_t err;
145 struct i386_fsgs_base_state state;
146 mach_msg_type_number_t state_count = i386_FSGS_BASE_STATE_COUNT;
147
148 if (orig != __hurd_thread_self ())
149 {
150 err = __thread_get_state (orig, i386_FSGS_BASE_STATE,
151 (thread_state_t) &state,
152 &state_count);
153 if (err)
154 return err;
155 assert (state_count == i386_FSGS_BASE_STATE_COUNT);
156 }
157 else
158 {
159 /* It is illegal to call thread_get_state () on mach_thread_self ().
160 But we're only interested in the value of fs_base, and since we're
161 this thread, we know it points to our TCB. */
162 state.fs_base = (unsigned long) THREAD_SELF;
163 state.gs_base = 0;
164 }
165
166 return __thread_set_state (child, i386_FSGS_BASE_STATE,
167 (thread_state_t) &state,
168 state_count);
169 }
170
171 static inline kern_return_t __attribute__ ((unused))
172 _hurd_tls_new (thread_t child, tcbhead_t *tcb)
173 {
174 struct i386_fsgs_base_state state;
175
176 tcb->tcb = tcb;
177
178 /* Install the TCB address into FS base. */
179 state.fs_base = (uintptr_t) tcb;
180 state.gs_base = 0;
181 return __thread_set_state (child, i386_FSGS_BASE_STATE,
182 (thread_state_t) &state,
183 i386_FSGS_BASE_STATE_COUNT);
184 }
185
186 # if !defined (SHARED) || IS_IN (rtld)
187 extern unsigned char __libc_tls_initialized;
188 # define __LIBC_NO_TLS() __builtin_expect (!__libc_tls_initialized, 0)
189
190 static inline bool __attribute__ ((unused))
191 _hurd_tls_init (tcbhead_t *tcb, bool full)
192 {
193 error_t err;
194 thread_t self = __mach_thread_self ();
195 extern mach_port_t __hurd_reply_port0;
196
197 /* We always at least start the sigthread anyway. */
198 tcb->multiple_threads = 1;
199 if (full)
200 /* Take over the reply port we've been using. */
201 tcb->reply_port = __hurd_reply_port0;
202
203 err = _hurd_tls_new (self, tcb);
204 if (err == 0 && full)
205 {
206 __libc_tls_initialized = 1;
207 /* This port is now owned by the TCB. */
208 __hurd_reply_port0 = MACH_PORT_NULL;
209 }
210 __mach_port_deallocate (__mach_task_self (), self);
211 return err == 0;
212 }
213
214 # define TLS_INIT_TP(descr) _hurd_tls_init ((tcbhead_t *) (descr), 1)
215 # else /* defined (SHARED) && !IS_IN (rtld) */
216 # define __LIBC_NO_TLS() 0
217 # endif
218
219
220
221 /* Global scope switch support. */
222 # define THREAD_GSCOPE_FLAG_UNUSED 0
223 # define THREAD_GSCOPE_FLAG_USED 1
224 # define THREAD_GSCOPE_FLAG_WAIT 2
225
226 # define THREAD_GSCOPE_SET_FLAG() \
227 THREAD_SETMEM (THREAD_SELF, gscope_flag, THREAD_GSCOPE_FLAG_USED)
228
229 # define THREAD_GSCOPE_RESET_FLAG() \
230 ({ \
231 int __flag; \
232 asm volatile ("xchgl %0, %%fs:%P1" \
233 : "=r" (__flag) \
234 : "i" (offsetof (tcbhead_t, gscope_flag)), \
235 "0" (THREAD_GSCOPE_FLAG_UNUSED)); \
236 if (__flag == THREAD_GSCOPE_FLAG_WAIT) \
237 lll_wake (THREAD_SELF->gscope_flag, LLL_PRIVATE); \
238 })
239
240
241
242 #endif /* __ASSEMBLER__ */
243 #endif /* x86_64/tls.h */