1/* Copyright (C) 2002-2021 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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#include <assert.h>
20#include <errno.h>
21#include <limits.h>
22#include <signal.h>
23#include <stdlib.h>
24#include <unistd.h>
25#include <sys/param.h>
26#include <sys/resource.h>
27#include <pthreadP.h>
28#include <atomic.h>
29#include <ldsodefs.h>
30#include <tls.h>
31#include <list.h>
32#include <fork.h>
33#include <version.h>
34#include <shlib-compat.h>
35#include <lowlevellock.h>
36#include <futex-internal.h>
37#include <kernel-features.h>
38#include <libc-pointer-arith.h>
39#include <pthread-pids.h>
40#include <pthread_mutex_conf.h>
41
42#ifndef TLS_MULTIPLE_THREADS_IN_TCB
43/* Pointer to the corresponding variable in libc. */
44int *__libc_multiple_threads_ptr attribute_hidden;
45#endif
46
47/* Size and alignment of static TLS block. */
48size_t __static_tls_size;
49size_t __static_tls_align_m1;
50
51#ifndef __ASSUME_SET_ROBUST_LIST
52/* Negative if we do not have the system call and we can use it. */
53int __set_robust_list_avail;
54# define set_robust_list_not_avail() \
55 __set_robust_list_avail = -1
56#else
57# define set_robust_list_not_avail() do { } while (0)
58#endif
59
60/* Version of the library, used in libthread_db to detect mismatches. */
61static const char nptl_version[] __attribute_used__ = VERSION;
62
63
64#ifdef SHARED
65static
66#else
67extern
68#endif
69void __nptl_set_robust (struct pthread *);
70
71#ifdef SHARED
72static const struct pthread_functions pthread_functions =
73 {
74 .ptr___pthread_cond_broadcast = __pthread_cond_broadcast,
75 .ptr___pthread_cond_signal = __pthread_cond_signal,
76 .ptr___pthread_cond_wait = __pthread_cond_wait,
77 .ptr___pthread_cond_timedwait = __pthread_cond_timedwait,
78# if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_3_2)
79 .ptr___pthread_cond_broadcast_2_0 = __pthread_cond_broadcast_2_0,
80 .ptr___pthread_cond_signal_2_0 = __pthread_cond_signal_2_0,
81 .ptr___pthread_cond_wait_2_0 = __pthread_cond_wait_2_0,
82 .ptr___pthread_cond_timedwait_2_0 = __pthread_cond_timedwait_2_0,
83# endif
84 .ptr___pthread_exit = __pthread_exit,
85 .ptr_pthread_mutex_destroy = __pthread_mutex_destroy,
86 .ptr_pthread_mutex_init = __pthread_mutex_init,
87 .ptr_pthread_mutex_lock = __pthread_mutex_lock,
88 .ptr_pthread_mutex_unlock = __pthread_mutex_unlock,
89 .ptr___pthread_setcancelstate = __pthread_setcancelstate,
90 .ptr_pthread_setcanceltype = __pthread_setcanceltype,
91 .ptr___pthread_cleanup_upto = __pthread_cleanup_upto,
92 .ptr___pthread_once = __pthread_once,
93 .ptr___pthread_rwlock_rdlock = __pthread_rwlock_rdlock,
94 .ptr___pthread_rwlock_wrlock = __pthread_rwlock_wrlock,
95 .ptr___pthread_rwlock_unlock = __pthread_rwlock_unlock,
96 .ptr___pthread_key_create = __pthread_key_create,
97 .ptr___pthread_getspecific = __pthread_getspecific,
98 .ptr___pthread_setspecific = __pthread_setspecific,
99 .ptr__pthread_cleanup_push_defer = __pthread_cleanup_push_defer,
100 .ptr__pthread_cleanup_pop_restore = __pthread_cleanup_pop_restore,
101 .ptr_nthreads = &__nptl_nthreads,
102 .ptr___pthread_unwind = &__pthread_unwind,
103 .ptr__nptl_deallocate_tsd = __nptl_deallocate_tsd,
104 .ptr__nptl_setxid = __nptl_setxid,
105 .ptr_set_robust = __nptl_set_robust
106 };
107# define ptr_pthread_functions &pthread_functions
108#else
109# define ptr_pthread_functions NULL
110#endif
111
112
113#ifdef SHARED
114static
115#endif
116void
117__nptl_set_robust (struct pthread *self)
118{
119 INTERNAL_SYSCALL_CALL (set_robust_list, &self->robust_head,
120 sizeof (struct robust_list_head));
121}
122
123
124/* For asynchronous cancellation we use a signal. This is the handler. */
125static void
126sigcancel_handler (int sig, siginfo_t *si, void *ctx)
127{
128 /* Safety check. It would be possible to call this function for
129 other signals and send a signal from another process. This is not
130 correct and might even be a security problem. Try to catch as
131 many incorrect invocations as possible. */
132 if (sig != SIGCANCEL
133 || si->si_pid != __getpid()
134 || si->si_code != SI_TKILL)
135 return;
136
137 struct pthread *self = THREAD_SELF;
138
139 int oldval = THREAD_GETMEM (self, cancelhandling);
140 while (1)
141 {
142 /* We are canceled now. When canceled by another thread this flag
143 is already set but if the signal is directly send (internally or
144 from another process) is has to be done here. */
145 int newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
146
147 if (oldval == newval || (oldval & EXITING_BITMASK) != 0)
148 /* Already canceled or exiting. */
149 break;
150
151 int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
152 oldval);
153 if (curval == oldval)
154 {
155 /* Set the return value. */
156 THREAD_SETMEM (self, result, PTHREAD_CANCELED);
157
158 /* Make sure asynchronous cancellation is still enabled. */
159 if ((newval & CANCELTYPE_BITMASK) != 0)
160 /* Run the registered destructors and terminate the thread. */
161 __do_cancel ();
162
163 break;
164 }
165
166 oldval = curval;
167 }
168}
169
170
171struct xid_command *__xidcmd attribute_hidden;
172
173/* We use the SIGSETXID signal in the setuid, setgid, etc. implementations to
174 tell each thread to call the respective setxid syscall on itself. This is
175 the handler. */
176static void
177sighandler_setxid (int sig, siginfo_t *si, void *ctx)
178{
179 int result;
180
181 /* Safety check. It would be possible to call this function for
182 other signals and send a signal from another process. This is not
183 correct and might even be a security problem. Try to catch as
184 many incorrect invocations as possible. */
185 if (sig != SIGSETXID
186 || si->si_pid != __getpid ()
187 || si->si_code != SI_TKILL)
188 return;
189
190 result = INTERNAL_SYSCALL_NCS (__xidcmd->syscall_no, 3, __xidcmd->id[0],
191 __xidcmd->id[1], __xidcmd->id[2]);
192 int error = 0;
193 if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result)))
194 error = INTERNAL_SYSCALL_ERRNO (result);
195 __nptl_setxid_error (__xidcmd, error);
196
197 /* Reset the SETXID flag. */
198 struct pthread *self = THREAD_SELF;
199 int flags, newval;
200 do
201 {
202 flags = THREAD_GETMEM (self, cancelhandling);
203 newval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
204 flags & ~SETXID_BITMASK, flags);
205 }
206 while (flags != newval);
207
208 /* And release the futex. */
209 self->setxid_futex = 1;
210 futex_wake (&self->setxid_futex, 1, FUTEX_PRIVATE);
211
212 if (atomic_decrement_val (&__xidcmd->cntr) == 0)
213 futex_wake ((unsigned int *) &__xidcmd->cntr, 1, FUTEX_PRIVATE);
214}
215
216
217/* When using __thread for this, we do it in libc so as not
218 to give libpthread its own TLS segment just for this. */
219extern void **__libc_dl_error_tsd (void) __attribute__ ((const));
220
221
222/* This can be set by the debugger before initialization is complete. */
223static bool __nptl_initial_report_events __attribute_used__;
224
225void
226__pthread_initialize_minimal_internal (void)
227{
228 /* Minimal initialization of the thread descriptor. */
229 struct pthread *pd = THREAD_SELF;
230 __pthread_initialize_pids (pd);
231 THREAD_SETMEM (pd, specific[0], &pd->specific_1stblock[0]);
232 THREAD_SETMEM (pd, user_stack, true);
233
234 /* Initialize the robust mutex data. */
235 {
236#if __PTHREAD_MUTEX_HAVE_PREV
237 pd->robust_prev = &pd->robust_head;
238#endif
239 pd->robust_head.list = &pd->robust_head;
240 pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
241 - offsetof (pthread_mutex_t,
242 __data.__list.__next));
243 int res = INTERNAL_SYSCALL_CALL (set_robust_list, &pd->robust_head,
244 sizeof (struct robust_list_head));
245 if (INTERNAL_SYSCALL_ERROR_P (res))
246 set_robust_list_not_avail ();
247 }
248
249 /* Set initial thread's stack block from 0 up to __libc_stack_end.
250 It will be bigger than it actually is, but for unwind.c/pt-longjmp.c
251 purposes this is good enough. */
252 THREAD_SETMEM (pd, stackblock_size, (size_t) __libc_stack_end);
253
254 /* Before initializing GL (dl_stack_user), the debugger could not
255 find us and had to set __nptl_initial_report_events. Propagate
256 its setting. */
257 THREAD_SETMEM (pd, report_events, __nptl_initial_report_events);
258
259 struct sigaction sa;
260 __sigemptyset (&sa.sa_mask);
261
262 /* Install the cancellation signal handler. If for some reason we
263 cannot install the handler we do not abort. Maybe we should, but
264 it is only asynchronous cancellation which is affected. */
265 sa.sa_sigaction = sigcancel_handler;
266 sa.sa_flags = SA_SIGINFO;
267 (void) __libc_sigaction (SIGCANCEL, &sa, NULL);
268
269 /* Install the handle to change the threads' uid/gid. */
270 sa.sa_sigaction = sighandler_setxid;
271 sa.sa_flags = SA_SIGINFO | SA_RESTART;
272 (void) __libc_sigaction (SIGSETXID, &sa, NULL);
273
274 /* The parent process might have left the signals blocked. Just in
275 case, unblock it. We reuse the signal mask in the sigaction
276 structure. It is already cleared. */
277 __sigaddset (&sa.sa_mask, SIGCANCEL);
278 __sigaddset (&sa.sa_mask, SIGSETXID);
279 INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_UNBLOCK, &sa.sa_mask,
280 NULL, __NSIG_BYTES);
281
282 /* Get the size of the static and alignment requirements for the TLS
283 block. */
284 size_t static_tls_align;
285 _dl_get_tls_static_info (&__static_tls_size, &static_tls_align);
286
287 /* Make sure the size takes all the alignments into account. */
288 if (STACK_ALIGN > static_tls_align)
289 static_tls_align = STACK_ALIGN;
290 __static_tls_align_m1 = static_tls_align - 1;
291
292 __static_tls_size = roundup (__static_tls_size, static_tls_align);
293
294 /* Determine the default allowed stack size. This is the size used
295 in case the user does not specify one. */
296 struct rlimit limit;
297 if (__getrlimit (RLIMIT_STACK, &limit) != 0
298 || limit.rlim_cur == RLIM_INFINITY)
299 /* The system limit is not usable. Use an architecture-specific
300 default. */
301 limit.rlim_cur = ARCH_STACK_DEFAULT_SIZE;
302 else if (limit.rlim_cur < PTHREAD_STACK_MIN)
303 /* The system limit is unusably small.
304 Use the minimal size acceptable. */
305 limit.rlim_cur = PTHREAD_STACK_MIN;
306
307 /* Make sure it meets the minimum size that allocate_stack
308 (allocatestack.c) will demand, which depends on the page size. */
309 const uintptr_t pagesz = GLRO(dl_pagesize);
310 const size_t minstack = pagesz + __static_tls_size + MINIMAL_REST_STACK;
311 if (limit.rlim_cur < minstack)
312 limit.rlim_cur = minstack;
313
314 /* Round the resource limit up to page size. */
315 limit.rlim_cur = ALIGN_UP (limit.rlim_cur, pagesz);
316 lll_lock (__default_pthread_attr_lock, LLL_PRIVATE);
317 __default_pthread_attr.internal.stacksize = limit.rlim_cur;
318 __default_pthread_attr.internal.guardsize = GLRO (dl_pagesize);
319 lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE);
320
321#ifdef SHARED
322 /* Make __rtld_lock_{,un}lock_recursive use pthread_mutex_{,un}lock,
323 keep the lock count from the ld.so implementation. */
324 GL(dl_rtld_lock_recursive) = (void *) __pthread_mutex_lock;
325 GL(dl_rtld_unlock_recursive) = (void *) __pthread_mutex_unlock;
326 unsigned int rtld_lock_count = GL(dl_load_lock).mutex.__data.__count;
327 GL(dl_load_lock).mutex.__data.__count = 0;
328 while (rtld_lock_count-- > 0)
329 __pthread_mutex_lock (&GL(dl_load_lock).mutex);
330
331 GL(dl_make_stack_executable_hook) = &__make_stacks_executable;
332#endif
333
334 GL(dl_init_static_tls) = &__pthread_init_static_tls;
335
336 /* Register the fork generation counter with the libc. */
337#ifndef TLS_MULTIPLE_THREADS_IN_TCB
338 __libc_multiple_threads_ptr =
339#endif
340 __libc_pthread_init (&__fork_generation, __reclaim_stacks,
341 ptr_pthread_functions);
342
343#if HAVE_TUNABLES
344 __pthread_tunables_init ();
345#endif
346}
347strong_alias (__pthread_initialize_minimal_internal,
348 __pthread_initialize_minimal)
349
350
351/* This function is internal (it has a GLIBC_PRIVATE) version, but it
352 is widely used (either via weak symbol, or dlsym) to obtain the
353 __static_tls_size value. This value is then used to adjust the
354 value of the stack size attribute, so that applications receive the
355 full requested stack size, not diminished by the TCB and static TLS
356 allocation on the stack. Once the TCB is separately allocated,
357 this function should be removed or renamed (if it is still
358 necessary at that point). */
359size_t
360__pthread_get_minstack (const pthread_attr_t *attr)
361{
362 return GLRO(dl_pagesize) + __static_tls_size + PTHREAD_STACK_MIN;
363}
364