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Kevin Wolf00dccaf2011-01-17 16:08:14 +00001/*
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 <stdlib.h>
26#include <setjmp.h>
27#include <stdint.h>
28#include <pthread.h>
29#include <ucontext.h>
30#include "qemu-common.h"
Paolo Bonzini737e1502012-12-17 18:19:44 +010031#include "block/coroutine_int.h"
Kevin Wolf00dccaf2011-01-17 16:08:14 +000032
Kevin Wolf3f4349d2012-06-29 13:40:27 +020033#ifdef CONFIG_VALGRIND_H
34#include <valgrind/valgrind.h>
35#endif
36
Kevin Wolf00dccaf2011-01-17 16:08:14 +000037typedef struct {
38 Coroutine base;
39 void *stack;
Peter Maydell6ab7e542013-02-20 15:21:09 +000040 sigjmp_buf env;
Kevin Wolf3f4349d2012-06-29 13:40:27 +020041
42#ifdef CONFIG_VALGRIND_H
43 unsigned int valgrind_stack_id;
44#endif
45
Kevin Wolf00dccaf2011-01-17 16:08:14 +000046} CoroutineUContext;
47
48/**
49 * Per-thread coroutine bookkeeping
50 */
51typedef struct {
52 /** Currently executing coroutine */
53 Coroutine *current;
54
Kevin Wolf00dccaf2011-01-17 16:08:14 +000055 /** The default coroutine */
56 CoroutineUContext leader;
57} CoroutineThreadState;
58
59static pthread_key_t thread_state_key;
60
61/*
62 * va_args to makecontext() must be type 'int', so passing
63 * the pointer we need may require several int args. This
64 * union is a quick hack to let us do that
65 */
66union cc_arg {
67 void *p;
68 int i[2];
69};
70
71static CoroutineThreadState *coroutine_get_thread_state(void)
72{
73 CoroutineThreadState *s = pthread_getspecific(thread_state_key);
74
75 if (!s) {
Anthony Liguori7267c092011-08-20 22:09:37 -050076 s = g_malloc0(sizeof(*s));
Kevin Wolf00dccaf2011-01-17 16:08:14 +000077 s->current = &s->leader.base;
Kevin Wolf00dccaf2011-01-17 16:08:14 +000078 pthread_setspecific(thread_state_key, s);
79 }
80 return s;
81}
82
83static void qemu_coroutine_thread_cleanup(void *opaque)
84{
85 CoroutineThreadState *s = opaque;
Avi Kivity39a7a362011-12-05 19:20:12 +020086
87 g_free(s);
88}
89
Kevin Wolf00dccaf2011-01-17 16:08:14 +000090static void __attribute__((constructor)) coroutine_init(void)
91{
92 int ret;
93
94 ret = pthread_key_create(&thread_state_key, qemu_coroutine_thread_cleanup);
95 if (ret != 0) {
96 fprintf(stderr, "unable to create leader key: %s\n", strerror(errno));
97 abort();
98 }
99}
100
101static void coroutine_trampoline(int i0, int i1)
102{
103 union cc_arg arg;
104 CoroutineUContext *self;
105 Coroutine *co;
106
107 arg.i[0] = i0;
108 arg.i[1] = i1;
109 self = arg.p;
110 co = &self->base;
111
112 /* Initialize longjmp environment and switch back the caller */
Peter Maydell6ab7e542013-02-20 15:21:09 +0000113 if (!sigsetjmp(self->env, 0)) {
114 siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000115 }
116
117 while (true) {
118 co->entry(co->entry_arg);
119 qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
120 }
121}
122
Paolo Bonzini40239782013-02-19 11:59:09 +0100123Coroutine *qemu_coroutine_new(void)
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000124{
125 const size_t stack_size = 1 << 20;
126 CoroutineUContext *co;
127 ucontext_t old_uc, uc;
Peter Maydell6ab7e542013-02-20 15:21:09 +0000128 sigjmp_buf old_env;
malc32b74672011-08-08 13:46:51 +0400129 union cc_arg arg = {0};
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000130
Peter Maydell6ab7e542013-02-20 15:21:09 +0000131 /* The ucontext functions preserve signal masks which incurs a
132 * system call overhead. sigsetjmp(buf, 0)/siglongjmp() does not
133 * preserve signal masks but only works on the current stack.
134 * Since we need a way to create and switch to a new stack, use
135 * the ucontext functions for that but sigsetjmp()/siglongjmp() for
136 * everything else.
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000137 */
138
139 if (getcontext(&uc) == -1) {
140 abort();
141 }
142
Anthony Liguori7267c092011-08-20 22:09:37 -0500143 co = g_malloc0(sizeof(*co));
144 co->stack = g_malloc(stack_size);
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000145 co->base.entry_arg = &old_env; /* stash away our jmp_buf */
146
147 uc.uc_link = &old_uc;
148 uc.uc_stack.ss_sp = co->stack;
149 uc.uc_stack.ss_size = stack_size;
150 uc.uc_stack.ss_flags = 0;
151
Kevin Wolf3f4349d2012-06-29 13:40:27 +0200152#ifdef CONFIG_VALGRIND_H
153 co->valgrind_stack_id =
154 VALGRIND_STACK_REGISTER(co->stack, co->stack + stack_size);
155#endif
156
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000157 arg.p = co;
158
159 makecontext(&uc, (void (*)(void))coroutine_trampoline,
160 2, arg.i[0], arg.i[1]);
161
Peter Maydell6ab7e542013-02-20 15:21:09 +0000162 /* swapcontext() in, siglongjmp() back out */
163 if (!sigsetjmp(old_env, 0)) {
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000164 swapcontext(&old_uc, &uc);
165 }
166 return &co->base;
167}
168
Kevin Wolf3f4349d2012-06-29 13:40:27 +0200169#ifdef CONFIG_VALGRIND_H
Gerd Hoffmanncc6e3ca2013-01-09 10:17:07 +0100170#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
Kevin Wolf3f4349d2012-06-29 13:40:27 +0200171/* Work around an unused variable in the valgrind.h macro... */
Markus Armbrustere6f53fd2013-04-16 13:51:06 +0200172#pragma GCC diagnostic push
Kevin Wolf3f4349d2012-06-29 13:40:27 +0200173#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
Peter Maydell06d71fa2012-07-30 16:13:07 +0100174#endif
Kevin Wolf3f4349d2012-06-29 13:40:27 +0200175static inline void valgrind_stack_deregister(CoroutineUContext *co)
176{
177 VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
178}
Gerd Hoffmanncc6e3ca2013-01-09 10:17:07 +0100179#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
Markus Armbrustere6f53fd2013-04-16 13:51:06 +0200180#pragma GCC diagnostic pop
Kevin Wolf3f4349d2012-06-29 13:40:27 +0200181#endif
Peter Maydell06d71fa2012-07-30 16:13:07 +0100182#endif
Kevin Wolf3f4349d2012-06-29 13:40:27 +0200183
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000184void qemu_coroutine_delete(Coroutine *co_)
185{
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000186 CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
187
Kevin Wolf3f4349d2012-06-29 13:40:27 +0200188#ifdef CONFIG_VALGRIND_H
189 valgrind_stack_deregister(co);
190#endif
191
Anthony Liguori7267c092011-08-20 22:09:37 -0500192 g_free(co->stack);
193 g_free(co);
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000194}
195
196CoroutineAction qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
197 CoroutineAction action)
198{
199 CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
200 CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
201 CoroutineThreadState *s = coroutine_get_thread_state();
202 int ret;
203
204 s->current = to_;
205
Peter Maydell6ab7e542013-02-20 15:21:09 +0000206 ret = sigsetjmp(from->env, 0);
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000207 if (ret == 0) {
Peter Maydell6ab7e542013-02-20 15:21:09 +0000208 siglongjmp(to->env, action);
Kevin Wolf00dccaf2011-01-17 16:08:14 +0000209 }
210 return ret;
211}
212
213Coroutine *qemu_coroutine_self(void)
214{
215 CoroutineThreadState *s = coroutine_get_thread_state();
216
217 return s->current;
218}
219
220bool qemu_in_coroutine(void)
221{
222 CoroutineThreadState *s = pthread_getspecific(thread_state_key);
223
224 return s && s->current->caller;
225}