hw/net: fix mcf_fec driver receiver
[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 <ucontext.h>
29 #include "qemu-common.h"
30 #include "block/coroutine_int.h"
31
32 #ifdef CONFIG_VALGRIND_H
33 #include <valgrind/valgrind.h>
34 #endif
35
36 typedef struct {
37 Coroutine base;
38 void *stack;
39 sigjmp_buf env;
40
41 #ifdef CONFIG_VALGRIND_H
42 unsigned int valgrind_stack_id;
43 #endif
44
45 } CoroutineUContext;
46
47 /**
48 * Per-thread coroutine bookkeeping
49 */
50 static __thread CoroutineUContext leader;
51 static __thread Coroutine *current;
52
53 /*
54 * va_args to makecontext() must be type 'int', so passing
55 * the pointer we need may require several int args. This
56 * union is a quick hack to let us do that
57 */
58 union cc_arg {
59 void *p;
60 int i[2];
61 };
62
63 static void coroutine_trampoline(int i0, int i1)
64 {
65 union cc_arg arg;
66 CoroutineUContext *self;
67 Coroutine *co;
68
69 arg.i[0] = i0;
70 arg.i[1] = i1;
71 self = arg.p;
72 co = &self->base;
73
74 /* Initialize longjmp environment and switch back the caller */
75 if (!sigsetjmp(self->env, 0)) {
76 siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
77 }
78
79 while (true) {
80 co->entry(co->entry_arg);
81 qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
82 }
83 }
84
85 Coroutine *qemu_coroutine_new(void)
86 {
87 const size_t stack_size = 1 << 20;
88 CoroutineUContext *co;
89 ucontext_t old_uc, uc;
90 sigjmp_buf old_env;
91 union cc_arg arg = {0};
92
93 /* The ucontext functions preserve signal masks which incurs a
94 * system call overhead. sigsetjmp(buf, 0)/siglongjmp() does not
95 * preserve signal masks but only works on the current stack.
96 * Since we need a way to create and switch to a new stack, use
97 * the ucontext functions for that but sigsetjmp()/siglongjmp() for
98 * everything else.
99 */
100
101 if (getcontext(&uc) == -1) {
102 abort();
103 }
104
105 co = g_malloc0(sizeof(*co));
106 co->stack = g_malloc(stack_size);
107 co->base.entry_arg = &old_env; /* stash away our jmp_buf */
108
109 uc.uc_link = &old_uc;
110 uc.uc_stack.ss_sp = co->stack;
111 uc.uc_stack.ss_size = stack_size;
112 uc.uc_stack.ss_flags = 0;
113
114 #ifdef CONFIG_VALGRIND_H
115 co->valgrind_stack_id =
116 VALGRIND_STACK_REGISTER(co->stack, co->stack + stack_size);
117 #endif
118
119 arg.p = co;
120
121 makecontext(&uc, (void (*)(void))coroutine_trampoline,
122 2, arg.i[0], arg.i[1]);
123
124 /* swapcontext() in, siglongjmp() back out */
125 if (!sigsetjmp(old_env, 0)) {
126 swapcontext(&old_uc, &uc);
127 }
128 return &co->base;
129 }
130
131 #ifdef CONFIG_VALGRIND_H
132 #ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
133 /* Work around an unused variable in the valgrind.h macro... */
134 #pragma GCC diagnostic push
135 #pragma GCC diagnostic ignored "-Wunused-but-set-variable"
136 #endif
137 static inline void valgrind_stack_deregister(CoroutineUContext *co)
138 {
139 VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
140 }
141 #ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
142 #pragma GCC diagnostic pop
143 #endif
144 #endif
145
146 void qemu_coroutine_delete(Coroutine *co_)
147 {
148 CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
149
150 #ifdef CONFIG_VALGRIND_H
151 valgrind_stack_deregister(co);
152 #endif
153
154 g_free(co->stack);
155 g_free(co);
156 }
157
158 /* This function is marked noinline to prevent GCC from inlining it
159 * into coroutine_trampoline(). If we allow it to do that then it
160 * hoists the code to get the address of the TLS variable "current"
161 * out of the while() loop. This is an invalid transformation because
162 * the sigsetjmp() call may be called when running thread A but
163 * return in thread B, and so we might be in a different thread
164 * context each time round the loop.
165 */
166 CoroutineAction __attribute__((noinline))
167 qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
168 CoroutineAction action)
169 {
170 CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
171 CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
172 int ret;
173
174 current = to_;
175
176 ret = sigsetjmp(from->env, 0);
177 if (ret == 0) {
178 siglongjmp(to->env, action);
179 }
180 return ret;
181 }
182
183 Coroutine *qemu_coroutine_self(void)
184 {
185 if (!current) {
186 current = &leader.base;
187 }
188 return current;
189 }
190
191 bool qemu_in_coroutine(void)
192 {
193 return current && current->caller;
194 }