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-rw-r--r--contrib/qemu/coroutine-ucontext.c225
1 files changed, 225 insertions, 0 deletions
diff --git a/contrib/qemu/coroutine-ucontext.c b/contrib/qemu/coroutine-ucontext.c
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+++ b/contrib/qemu/coroutine-ucontext.c
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+/*
+ * ucontext coroutine initialization code
+ *
+ * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
+ * Copyright (C) 2011 Kevin Wolf <kwolf@redhat.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.0 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* XXX Is there a nicer way to disable glibc's stack check for longjmp? */
+#ifdef _FORTIFY_SOURCE
+#undef _FORTIFY_SOURCE
+#endif
+#include <stdlib.h>
+#include <setjmp.h>
+#include <stdint.h>
+#include <pthread.h>
+#include <ucontext.h>
+#include "qemu-common.h"
+#include "block/coroutine_int.h"
+
+#ifdef CONFIG_VALGRIND_H
+#include <valgrind/valgrind.h>
+#endif
+
+typedef struct {
+ Coroutine base;
+ void *stack;
+ sigjmp_buf env;
+
+#ifdef CONFIG_VALGRIND_H
+ unsigned int valgrind_stack_id;
+#endif
+
+} CoroutineUContext;
+
+/**
+ * Per-thread coroutine bookkeeping
+ */
+typedef struct {
+ /** Currently executing coroutine */
+ Coroutine *current;
+
+ /** The default coroutine */
+ CoroutineUContext leader;
+} CoroutineThreadState;
+
+static pthread_key_t thread_state_key;
+
+/*
+ * va_args to makecontext() must be type 'int', so passing
+ * the pointer we need may require several int args. This
+ * union is a quick hack to let us do that
+ */
+union cc_arg {
+ void *p;
+ int i[2];
+};
+
+static CoroutineThreadState *coroutine_get_thread_state(void)
+{
+ CoroutineThreadState *s = pthread_getspecific(thread_state_key);
+
+ if (!s) {
+ s = g_malloc0(sizeof(*s));
+ s->current = &s->leader.base;
+ pthread_setspecific(thread_state_key, s);
+ }
+ return s;
+}
+
+static void qemu_coroutine_thread_cleanup(void *opaque)
+{
+ CoroutineThreadState *s = opaque;
+
+ g_free(s);
+}
+
+static void __attribute__((constructor)) coroutine_init(void)
+{
+ int ret;
+
+ ret = pthread_key_create(&thread_state_key, qemu_coroutine_thread_cleanup);
+ if (ret != 0) {
+ fprintf(stderr, "unable to create leader key: %s\n", strerror(errno));
+ abort();
+ }
+}
+
+static void coroutine_trampoline(int i0, int i1)
+{
+ union cc_arg arg;
+ CoroutineUContext *self;
+ Coroutine *co;
+
+ arg.i[0] = i0;
+ arg.i[1] = i1;
+ self = arg.p;
+ co = &self->base;
+
+ /* Initialize longjmp environment and switch back the caller */
+ if (!sigsetjmp(self->env, 0)) {
+ siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
+ }
+
+ while (true) {
+ co->entry(co->entry_arg);
+ qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
+ }
+}
+
+Coroutine *qemu_coroutine_new(void)
+{
+ const size_t stack_size = 1 << 20;
+ CoroutineUContext *co;
+ ucontext_t old_uc, uc;
+ sigjmp_buf old_env;
+ union cc_arg arg = {0};
+
+ /* The ucontext functions preserve signal masks which incurs a
+ * system call overhead. sigsetjmp(buf, 0)/siglongjmp() does not
+ * preserve signal masks but only works on the current stack.
+ * Since we need a way to create and switch to a new stack, use
+ * the ucontext functions for that but sigsetjmp()/siglongjmp() for
+ * everything else.
+ */
+
+ if (getcontext(&uc) == -1) {
+ abort();
+ }
+
+ co = g_malloc0(sizeof(*co));
+ co->stack = g_malloc(stack_size);
+ co->base.entry_arg = &old_env; /* stash away our jmp_buf */
+
+ uc.uc_link = &old_uc;
+ uc.uc_stack.ss_sp = co->stack;
+ uc.uc_stack.ss_size = stack_size;
+ uc.uc_stack.ss_flags = 0;
+
+#ifdef CONFIG_VALGRIND_H
+ co->valgrind_stack_id =
+ VALGRIND_STACK_REGISTER(co->stack, co->stack + stack_size);
+#endif
+
+ arg.p = co;
+
+ makecontext(&uc, (void (*)(void))coroutine_trampoline,
+ 2, arg.i[0], arg.i[1]);
+
+ /* swapcontext() in, siglongjmp() back out */
+ if (!sigsetjmp(old_env, 0)) {
+ swapcontext(&old_uc, &uc);
+ }
+ return &co->base;
+}
+
+#ifdef CONFIG_VALGRIND_H
+#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
+/* Work around an unused variable in the valgrind.h macro... */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
+#endif
+static inline void valgrind_stack_deregister(CoroutineUContext *co)
+{
+ VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
+}
+#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
+#pragma GCC diagnostic pop
+#endif
+#endif
+
+void qemu_coroutine_delete(Coroutine *co_)
+{
+ CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
+
+#ifdef CONFIG_VALGRIND_H
+ valgrind_stack_deregister(co);
+#endif
+
+ g_free(co->stack);
+ g_free(co);
+}
+
+CoroutineAction qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
+ CoroutineAction action)
+{
+ CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
+ CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
+ CoroutineThreadState *s = coroutine_get_thread_state();
+ int ret;
+
+ s->current = to_;
+
+ ret = sigsetjmp(from->env, 0);
+ if (ret == 0) {
+ siglongjmp(to->env, action);
+ }
+ return ret;
+}
+
+Coroutine *qemu_coroutine_self(void)
+{
+ CoroutineThreadState *s = coroutine_get_thread_state();
+
+ return s->current;
+}
+
+bool qemu_in_coroutine(void)
+{
+ CoroutineThreadState *s = pthread_getspecific(thread_state_key);
+
+ return s && s->current->caller;
+}