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 | |
29 | #ifdef CONFIG_VALGRIND_H |
30 | #include <valgrind/valgrind.h> |
31 | #endif |
32 | |
33 | #if defined(__SANITIZE_ADDRESS__) || __has_feature(address_sanitizer) |
34 | #ifdef CONFIG_ASAN_IFACE_FIBER |
35 | #define CONFIG_ASAN 1 |
36 | #include <sanitizer/asan_interface.h> |
37 | #endif |
38 | #endif |
39 | |
40 | typedef struct { |
41 | Coroutine base; |
42 | void *stack; |
43 | size_t stack_size; |
44 | sigjmp_buf env; |
45 | |
46 | #ifdef CONFIG_VALGRIND_H |
47 | unsigned int valgrind_stack_id; |
48 | #endif |
49 | |
50 | } CoroutineUContext; |
51 | |
52 | /** |
53 | * Per-thread coroutine bookkeeping |
54 | */ |
55 | static __thread CoroutineUContext leader; |
56 | static __thread Coroutine *current; |
57 | |
58 | /* |
59 | * va_args to makecontext() must be type 'int', so passing |
60 | * the pointer we need may require several int args. This |
61 | * union is a quick hack to let us do that |
62 | */ |
63 | union cc_arg { |
64 | void *p; |
65 | int i[2]; |
66 | }; |
67 | |
68 | static void finish_switch_fiber(void *fake_stack_save) |
69 | { |
70 | #ifdef CONFIG_ASAN |
71 | const void *bottom_old; |
72 | size_t size_old; |
73 | |
74 | __sanitizer_finish_switch_fiber(fake_stack_save, &bottom_old, &size_old); |
75 | |
76 | if (!leader.stack) { |
77 | leader.stack = (void *)bottom_old; |
78 | leader.stack_size = size_old; |
79 | } |
80 | #endif |
81 | } |
82 | |
83 | static void start_switch_fiber(void **fake_stack_save, |
84 | const void *bottom, size_t size) |
85 | { |
86 | #ifdef CONFIG_ASAN |
87 | __sanitizer_start_switch_fiber(fake_stack_save, bottom, size); |
88 | #endif |
89 | } |
90 | |
91 | static void coroutine_trampoline(int i0, int i1) |
92 | { |
93 | union cc_arg arg; |
94 | CoroutineUContext *self; |
95 | Coroutine *co; |
96 | void *fake_stack_save = NULL; |
97 | |
98 | finish_switch_fiber(NULL); |
99 | |
100 | arg.i[0] = i0; |
101 | arg.i[1] = i1; |
102 | self = arg.p; |
103 | co = &self->base; |
104 | |
105 | /* Initialize longjmp environment and switch back the caller */ |
106 | if (!sigsetjmp(self->env, 0)) { |
107 | start_switch_fiber(&fake_stack_save, |
108 | leader.stack, leader.stack_size); |
109 | siglongjmp(*(sigjmp_buf *)co->entry_arg, 1); |
110 | } |
111 | |
112 | finish_switch_fiber(fake_stack_save); |
113 | |
114 | while (true) { |
115 | co->entry(co->entry_arg); |
116 | qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE); |
117 | } |
118 | } |
119 | |
120 | Coroutine *qemu_coroutine_new(void) |
121 | { |
122 | CoroutineUContext *co; |
123 | ucontext_t old_uc, uc; |
124 | sigjmp_buf old_env; |
125 | union cc_arg arg = {0}; |
126 | void *fake_stack_save = NULL; |
127 | |
128 | /* The ucontext functions preserve signal masks which incurs a |
129 | * system call overhead. sigsetjmp(buf, 0)/siglongjmp() does not |
130 | * preserve signal masks but only works on the current stack. |
131 | * Since we need a way to create and switch to a new stack, use |
132 | * the ucontext functions for that but sigsetjmp()/siglongjmp() for |
133 | * everything else. |
134 | */ |
135 | |
136 | if (getcontext(&uc) == -1) { |
137 | abort(); |
138 | } |
139 | |
140 | co = g_malloc0(sizeof(*co)); |
141 | co->stack_size = COROUTINE_STACK_SIZE; |
142 | co->stack = qemu_alloc_stack(&co->stack_size); |
143 | co->base.entry_arg = &old_env; /* stash away our jmp_buf */ |
144 | |
145 | uc.uc_link = &old_uc; |
146 | uc.uc_stack.ss_sp = co->stack; |
147 | uc.uc_stack.ss_size = co->stack_size; |
148 | uc.uc_stack.ss_flags = 0; |
149 | |
150 | #ifdef CONFIG_VALGRIND_H |
151 | co->valgrind_stack_id = |
152 | VALGRIND_STACK_REGISTER(co->stack, co->stack + co->stack_size); |
153 | #endif |
154 | |
155 | arg.p = co; |
156 | |
157 | makecontext(&uc, (void (*)(void))coroutine_trampoline, |
158 | 2, arg.i[0], arg.i[1]); |
159 | |
160 | /* swapcontext() in, siglongjmp() back out */ |
161 | if (!sigsetjmp(old_env, 0)) { |
162 | start_switch_fiber(&fake_stack_save, co->stack, co->stack_size); |
163 | swapcontext(&old_uc, &uc); |
164 | } |
165 | |
166 | finish_switch_fiber(fake_stack_save); |
167 | |
168 | return &co->base; |
169 | } |
170 | |
171 | #ifdef CONFIG_VALGRIND_H |
172 | #if defined(CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE) && !defined(__clang__) |
173 | /* Work around an unused variable in the valgrind.h macro... */ |
174 | #pragma GCC diagnostic push |
175 | #pragma GCC diagnostic ignored "-Wunused-but-set-variable" |
176 | #endif |
177 | static inline void valgrind_stack_deregister(CoroutineUContext *co) |
178 | { |
179 | VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id); |
180 | } |
181 | #if defined(CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE) && !defined(__clang__) |
182 | #pragma GCC diagnostic pop |
183 | #endif |
184 | #endif |
185 | |
186 | void qemu_coroutine_delete(Coroutine *co_) |
187 | { |
188 | CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_); |
189 | |
190 | #ifdef CONFIG_VALGRIND_H |
191 | valgrind_stack_deregister(co); |
192 | #endif |
193 | |
194 | qemu_free_stack(co->stack, co->stack_size); |
195 | g_free(co); |
196 | } |
197 | |
198 | /* This function is marked noinline to prevent GCC from inlining it |
199 | * into coroutine_trampoline(). If we allow it to do that then it |
200 | * hoists the code to get the address of the TLS variable "current" |
201 | * out of the while() loop. This is an invalid transformation because |
202 | * the sigsetjmp() call may be called when running thread A but |
203 | * return in thread B, and so we might be in a different thread |
204 | * context each time round the loop. |
205 | */ |
206 | CoroutineAction __attribute__((noinline)) |
207 | qemu_coroutine_switch(Coroutine *from_, Coroutine *to_, |
208 | CoroutineAction action) |
209 | { |
210 | CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_); |
211 | CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_); |
212 | int ret; |
213 | void *fake_stack_save = NULL; |
214 | |
215 | current = to_; |
216 | |
217 | ret = sigsetjmp(from->env, 0); |
218 | if (ret == 0) { |
219 | start_switch_fiber(action == COROUTINE_TERMINATE ? |
220 | NULL : &fake_stack_save, to->stack, to->stack_size); |
221 | siglongjmp(to->env, action); |
222 | } |
223 | |
224 | finish_switch_fiber(fake_stack_save); |
225 | |
226 | return ret; |
227 | } |
228 | |
229 | Coroutine *qemu_coroutine_self(void) |
230 | { |
231 | if (!current) { |
232 | current = &leader.base; |
233 | } |
234 | return current; |
235 | } |
236 | |
237 | bool qemu_in_coroutine(void) |
238 | { |
239 | return current && current->caller; |
240 | } |
241 | |