s390x/sclpconsole-lm: truncate input if line is too long
[qemu.git] / 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 <stdlib.h>
26 #include <setjmp.h>
27 #include <stdint.h>
28 #include <pthread.h>
29 #include <ucontext.h>
30 #include "qemu-common.h"
31 #include "block/coroutine_int.h"
32
33 #ifdef CONFIG_VALGRIND_H
34 #include <valgrind/valgrind.h>
35 #endif
36
37 typedef struct {
38 Coroutine base;
39 void *stack;
40 sigjmp_buf env;
41
42 #ifdef CONFIG_VALGRIND_H
43 unsigned int valgrind_stack_id;
44 #endif
45
46 } CoroutineUContext;
47
48 /**
49 * Per-thread coroutine bookkeeping
50 */
51 typedef struct {
52 /** Currently executing coroutine */
53 Coroutine *current;
54
55 /** The default coroutine */
56 CoroutineUContext leader;
57 } CoroutineThreadState;
58
59 static 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 */
66 union cc_arg {
67 void *p;
68 int i[2];
69 };
70
71 static CoroutineThreadState *coroutine_get_thread_state(void)
72 {
73 CoroutineThreadState *s = pthread_getspecific(thread_state_key);
74
75 if (!s) {
76 s = g_malloc0(sizeof(*s));
77 s->current = &s->leader.base;
78 pthread_setspecific(thread_state_key, s);
79 }
80 return s;
81 }
82
83 static void qemu_coroutine_thread_cleanup(void *opaque)
84 {
85 CoroutineThreadState *s = opaque;
86
87 g_free(s);
88 }
89
90 static 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
101 static 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 */
113 if (!sigsetjmp(self->env, 0)) {
114 siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
115 }
116
117 while (true) {
118 co->entry(co->entry_arg);
119 qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
120 }
121 }
122
123 Coroutine *qemu_coroutine_new(void)
124 {
125 const size_t stack_size = 1 << 20;
126 CoroutineUContext *co;
127 ucontext_t old_uc, uc;
128 sigjmp_buf old_env;
129 union cc_arg arg = {0};
130
131 /* 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.
137 */
138
139 if (getcontext(&uc) == -1) {
140 abort();
141 }
142
143 co = g_malloc0(sizeof(*co));
144 co->stack = g_malloc(stack_size);
145 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
152 #ifdef CONFIG_VALGRIND_H
153 co->valgrind_stack_id =
154 VALGRIND_STACK_REGISTER(co->stack, co->stack + stack_size);
155 #endif
156
157 arg.p = co;
158
159 makecontext(&uc, (void (*)(void))coroutine_trampoline,
160 2, arg.i[0], arg.i[1]);
161
162 /* swapcontext() in, siglongjmp() back out */
163 if (!sigsetjmp(old_env, 0)) {
164 swapcontext(&old_uc, &uc);
165 }
166 return &co->base;
167 }
168
169 #ifdef CONFIG_VALGRIND_H
170 #ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
171 /* Work around an unused variable in the valgrind.h macro... */
172 #pragma GCC diagnostic push
173 #pragma GCC diagnostic ignored "-Wunused-but-set-variable"
174 #endif
175 static inline void valgrind_stack_deregister(CoroutineUContext *co)
176 {
177 VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
178 }
179 #ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
180 #pragma GCC diagnostic pop
181 #endif
182 #endif
183
184 void qemu_coroutine_delete(Coroutine *co_)
185 {
186 CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
187
188 #ifdef CONFIG_VALGRIND_H
189 valgrind_stack_deregister(co);
190 #endif
191
192 g_free(co->stack);
193 g_free(co);
194 }
195
196 CoroutineAction 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
206 ret = sigsetjmp(from->env, 0);
207 if (ret == 0) {
208 siglongjmp(to->env, action);
209 }
210 return ret;
211 }
212
213 Coroutine *qemu_coroutine_self(void)
214 {
215 CoroutineThreadState *s = coroutine_get_thread_state();
216
217 return s->current;
218 }
219
220 bool qemu_in_coroutine(void)
221 {
222 CoroutineThreadState *s = pthread_getspecific(thread_state_key);
223
224 return s && s->current->caller;
225 }