Merge tag 'pull-testing-gdbstub-plugins-gitdm-061022-3' of https://github.com/stsquad...
[qemu.git] / util / coroutine-ucontext.c
1 /*
2 * ucontext coroutine initialization code
3 *
4 * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
5 * Copyright (C) 2011 Kevin Wolf <kwolf@redhat.com>
6 *
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.0 of the License, or (at your option) any later version.
11 *
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
19 */
20
21 /* XXX Is there a nicer way to disable glibc's stack check for longjmp? */
22 #ifdef _FORTIFY_SOURCE
23 #undef _FORTIFY_SOURCE
24 #endif
25 #include "qemu/osdep.h"
26 #include <ucontext.h>
27 #include "qemu/coroutine_int.h"
28 #include "qemu/coroutine-tls.h"
29
30 #ifdef CONFIG_VALGRIND_H
31 #include <valgrind/valgrind.h>
32 #endif
33
34 #ifdef QEMU_SANITIZE_ADDRESS
35 #ifdef CONFIG_ASAN_IFACE_FIBER
36 #define CONFIG_ASAN 1
37 #include <sanitizer/asan_interface.h>
38 #endif
39 #endif
40
41 #ifdef CONFIG_TSAN
42 #include <sanitizer/tsan_interface.h>
43 #endif
44
45 typedef struct {
46 Coroutine base;
47 void *stack;
48 size_t stack_size;
49 #ifdef CONFIG_SAFESTACK
50 /* Need an unsafe stack for each coroutine */
51 void *unsafe_stack;
52 size_t unsafe_stack_size;
53 #endif
54 sigjmp_buf env;
55
56 #ifdef CONFIG_TSAN
57 void *tsan_co_fiber;
58 void *tsan_caller_fiber;
59 #endif
60
61 #ifdef CONFIG_VALGRIND_H
62 unsigned int valgrind_stack_id;
63 #endif
64
65 } CoroutineUContext;
66
67 /**
68 * Per-thread coroutine bookkeeping
69 */
70 QEMU_DEFINE_STATIC_CO_TLS(Coroutine *, current);
71 QEMU_DEFINE_STATIC_CO_TLS(CoroutineUContext, leader);
72
73 /*
74 * va_args to makecontext() must be type 'int', so passing
75 * the pointer we need may require several int args. This
76 * union is a quick hack to let us do that
77 */
78 union cc_arg {
79 void *p;
80 int i[2];
81 };
82
83 /*
84 * QEMU_ALWAYS_INLINE only does so if __OPTIMIZE__, so we cannot use it.
85 * always_inline is required to avoid TSan runtime fatal errors.
86 */
87 static inline __attribute__((always_inline))
88 void on_new_fiber(CoroutineUContext *co)
89 {
90 #ifdef CONFIG_TSAN
91 co->tsan_co_fiber = __tsan_create_fiber(0); /* flags: sync on switch */
92 co->tsan_caller_fiber = __tsan_get_current_fiber();
93 #endif
94 }
95
96 /* always_inline is required to avoid TSan runtime fatal errors. */
97 static inline __attribute__((always_inline))
98 void finish_switch_fiber(void *fake_stack_save)
99 {
100 #ifdef CONFIG_ASAN
101 CoroutineUContext *leaderp = get_ptr_leader();
102 const void *bottom_old;
103 size_t size_old;
104
105 __sanitizer_finish_switch_fiber(fake_stack_save, &bottom_old, &size_old);
106
107 if (!leaderp->stack) {
108 leaderp->stack = (void *)bottom_old;
109 leaderp->stack_size = size_old;
110 }
111 #endif
112 #ifdef CONFIG_TSAN
113 if (fake_stack_save) {
114 __tsan_release(fake_stack_save);
115 __tsan_switch_to_fiber(fake_stack_save, 0); /* 0=synchronize */
116 }
117 #endif
118 }
119
120 /* always_inline is required to avoid TSan runtime fatal errors. */
121 static inline __attribute__((always_inline))
122 void start_switch_fiber_asan(CoroutineAction action, void **fake_stack_save,
123 const void *bottom, size_t size)
124 {
125 #ifdef CONFIG_ASAN
126 __sanitizer_start_switch_fiber(
127 action == COROUTINE_TERMINATE ? NULL : fake_stack_save,
128 bottom, size);
129 #endif
130 }
131
132 /* always_inline is required to avoid TSan runtime fatal errors. */
133 static inline __attribute__((always_inline))
134 void start_switch_fiber_tsan(void **fake_stack_save,
135 CoroutineUContext *co,
136 bool caller)
137 {
138 #ifdef CONFIG_TSAN
139 void *new_fiber = caller ?
140 co->tsan_caller_fiber :
141 co->tsan_co_fiber;
142 void *curr_fiber = __tsan_get_current_fiber();
143 __tsan_acquire(curr_fiber);
144
145 *fake_stack_save = curr_fiber;
146 __tsan_switch_to_fiber(new_fiber, 0); /* 0=synchronize */
147 #endif
148 }
149
150 static void coroutine_trampoline(int i0, int i1)
151 {
152 union cc_arg arg;
153 CoroutineUContext *self;
154 Coroutine *co;
155 void *fake_stack_save = NULL;
156
157 finish_switch_fiber(NULL);
158
159 arg.i[0] = i0;
160 arg.i[1] = i1;
161 self = arg.p;
162 co = &self->base;
163
164 /* Initialize longjmp environment and switch back the caller */
165 if (!sigsetjmp(self->env, 0)) {
166 CoroutineUContext *leaderp = get_ptr_leader();
167
168 start_switch_fiber_asan(COROUTINE_YIELD, &fake_stack_save,
169 leaderp->stack, leaderp->stack_size);
170 start_switch_fiber_tsan(&fake_stack_save, self, true); /* true=caller */
171 siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
172 }
173
174 finish_switch_fiber(fake_stack_save);
175
176 while (true) {
177 co->entry(co->entry_arg);
178 qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
179 }
180 }
181
182 Coroutine *qemu_coroutine_new(void)
183 {
184 CoroutineUContext *co;
185 ucontext_t old_uc, uc;
186 sigjmp_buf old_env;
187 union cc_arg arg = {0};
188 void *fake_stack_save = NULL;
189
190 /* The ucontext functions preserve signal masks which incurs a
191 * system call overhead. sigsetjmp(buf, 0)/siglongjmp() does not
192 * preserve signal masks but only works on the current stack.
193 * Since we need a way to create and switch to a new stack, use
194 * the ucontext functions for that but sigsetjmp()/siglongjmp() for
195 * everything else.
196 */
197
198 if (getcontext(&uc) == -1) {
199 abort();
200 }
201
202 co = g_malloc0(sizeof(*co));
203 co->stack_size = COROUTINE_STACK_SIZE;
204 co->stack = qemu_alloc_stack(&co->stack_size);
205 #ifdef CONFIG_SAFESTACK
206 co->unsafe_stack_size = COROUTINE_STACK_SIZE;
207 co->unsafe_stack = qemu_alloc_stack(&co->unsafe_stack_size);
208 #endif
209 co->base.entry_arg = &old_env; /* stash away our jmp_buf */
210
211 uc.uc_link = &old_uc;
212 uc.uc_stack.ss_sp = co->stack;
213 uc.uc_stack.ss_size = co->stack_size;
214 uc.uc_stack.ss_flags = 0;
215
216 #ifdef CONFIG_VALGRIND_H
217 co->valgrind_stack_id =
218 VALGRIND_STACK_REGISTER(co->stack, co->stack + co->stack_size);
219 #endif
220
221 arg.p = co;
222
223 on_new_fiber(co);
224 makecontext(&uc, (void (*)(void))coroutine_trampoline,
225 2, arg.i[0], arg.i[1]);
226
227 /* swapcontext() in, siglongjmp() back out */
228 if (!sigsetjmp(old_env, 0)) {
229 start_switch_fiber_asan(COROUTINE_YIELD, &fake_stack_save, co->stack,
230 co->stack_size);
231 start_switch_fiber_tsan(&fake_stack_save,
232 co, false); /* false=not caller */
233
234 #ifdef CONFIG_SAFESTACK
235 /*
236 * Before we swap the context, set the new unsafe stack
237 * The unsafe stack grows just like the normal stack, so start from
238 * the last usable location of the memory area.
239 * NOTE: we don't have to re-set the usp afterwards because we are
240 * coming back to this context through a siglongjmp.
241 * The compiler already wrapped the corresponding sigsetjmp call with
242 * code that saves the usp on the (safe) stack before the call, and
243 * restores it right after (which is where we return with siglongjmp).
244 */
245 void *usp = co->unsafe_stack + co->unsafe_stack_size;
246 __safestack_unsafe_stack_ptr = usp;
247 #endif
248
249 swapcontext(&old_uc, &uc);
250 }
251
252 finish_switch_fiber(fake_stack_save);
253
254 return &co->base;
255 }
256
257 #ifdef CONFIG_VALGRIND_H
258 /* Work around an unused variable in the valgrind.h macro... */
259 #if !defined(__clang__)
260 #pragma GCC diagnostic push
261 #pragma GCC diagnostic ignored "-Wunused-but-set-variable"
262 #endif
263 static inline void valgrind_stack_deregister(CoroutineUContext *co)
264 {
265 VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
266 }
267 #if !defined(__clang__)
268 #pragma GCC diagnostic pop
269 #endif
270 #endif
271
272 void qemu_coroutine_delete(Coroutine *co_)
273 {
274 CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
275
276 #ifdef CONFIG_VALGRIND_H
277 valgrind_stack_deregister(co);
278 #endif
279
280 qemu_free_stack(co->stack, co->stack_size);
281 #ifdef CONFIG_SAFESTACK
282 qemu_free_stack(co->unsafe_stack, co->unsafe_stack_size);
283 #endif
284 g_free(co);
285 }
286
287 /* This function is marked noinline to prevent GCC from inlining it
288 * into coroutine_trampoline(). If we allow it to do that then it
289 * hoists the code to get the address of the TLS variable "current"
290 * out of the while() loop. This is an invalid transformation because
291 * the sigsetjmp() call may be called when running thread A but
292 * return in thread B, and so we might be in a different thread
293 * context each time round the loop.
294 */
295 CoroutineAction __attribute__((noinline))
296 qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
297 CoroutineAction action)
298 {
299 CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
300 CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
301 int ret;
302 void *fake_stack_save = NULL;
303
304 set_current(to_);
305
306 ret = sigsetjmp(from->env, 0);
307 if (ret == 0) {
308 start_switch_fiber_asan(action, &fake_stack_save, to->stack,
309 to->stack_size);
310 start_switch_fiber_tsan(&fake_stack_save,
311 to, false); /* false=not caller */
312 siglongjmp(to->env, action);
313 }
314
315 finish_switch_fiber(fake_stack_save);
316
317 return ret;
318 }
319
320 Coroutine *qemu_coroutine_self(void)
321 {
322 Coroutine *self = get_current();
323 CoroutineUContext *leaderp = get_ptr_leader();
324
325 if (!self) {
326 self = &leaderp->base;
327 set_current(self);
328 }
329 #ifdef CONFIG_TSAN
330 if (!leaderp->tsan_co_fiber) {
331 leaderp->tsan_co_fiber = __tsan_get_current_fiber();
332 }
333 #endif
334 return self;
335 }
336
337 bool qemu_in_coroutine(void)
338 {
339 Coroutine *self = get_current();
340
341 return self && self->caller;
342 }