+++ /dev/null
-/*
- * sigaltstack coroutine initialization code
- *
- * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
- * Copyright (C) 2011 Kevin Wolf <kwolf@redhat.com>
- * Copyright (C) 2012 Alex Barcelo <abarcelo@ac.upc.edu>
-** This file is partly based on pth_mctx.c, from the GNU Portable Threads
-** Copyright (c) 1999-2006 Ralf S. Engelschall <rse@engelschall.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 2.1 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 <signal.h>
-#include "qemu-common.h"
-#include "block/coroutine_int.h"
-
-typedef struct {
- Coroutine base;
- void *stack;
- sigjmp_buf env;
-} CoroutineUContext;
-
-/**
- * Per-thread coroutine bookkeeping
- */
-typedef struct {
- /** Currently executing coroutine */
- Coroutine *current;
-
- /** The default coroutine */
- CoroutineUContext leader;
-
- /** Information for the signal handler (trampoline) */
- sigjmp_buf tr_reenter;
- volatile sig_atomic_t tr_called;
- void *tr_handler;
-} CoroutineThreadState;
-
-static pthread_key_t thread_state_key;
-
-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();
- }
-}
-
-/* "boot" function
- * This is what starts the coroutine, is called from the trampoline
- * (from the signal handler when it is not signal handling, read ahead
- * for more information).
- */
-static void coroutine_bootstrap(CoroutineUContext *self, Coroutine *co)
-{
- /* 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);
- }
-}
-
-/*
- * This is used as the signal handler. This is called with the brand new stack
- * (thanks to sigaltstack). We have to return, given that this is a signal
- * handler and the sigmask and some other things are changed.
- */
-static void coroutine_trampoline(int signal)
-{
- CoroutineUContext *self;
- Coroutine *co;
- CoroutineThreadState *coTS;
-
- /* Get the thread specific information */
- coTS = coroutine_get_thread_state();
- self = coTS->tr_handler;
- coTS->tr_called = 1;
- co = &self->base;
-
- /*
- * Here we have to do a bit of a ping pong between the caller, given that
- * this is a signal handler and we have to do a return "soon". Then the
- * caller can reestablish everything and do a siglongjmp here again.
- */
- if (!sigsetjmp(coTS->tr_reenter, 0)) {
- return;
- }
-
- /*
- * Ok, the caller has siglongjmp'ed back to us, so now prepare
- * us for the real machine state switching. We have to jump
- * into another function here to get a new stack context for
- * the auto variables (which have to be auto-variables
- * because the start of the thread happens later). Else with
- * PIC (i.e. Position Independent Code which is used when PTH
- * is built as a shared library) most platforms would
- * horrible core dump as experience showed.
- */
- coroutine_bootstrap(self, co);
-}
-
-Coroutine *qemu_coroutine_new(void)
-{
- const size_t stack_size = 1 << 20;
- CoroutineUContext *co;
- CoroutineThreadState *coTS;
- struct sigaction sa;
- struct sigaction osa;
- stack_t ss;
- stack_t oss;
- sigset_t sigs;
- sigset_t osigs;
- sigjmp_buf old_env;
-
- /* The way to manipulate stack is with the sigaltstack function. We
- * prepare a stack, with it delivering a signal to ourselves and then
- * put sigsetjmp/siglongjmp where needed.
- * This has been done keeping coroutine-ucontext as a model and with the
- * pth ideas (GNU Portable Threads). See coroutine-ucontext for the basics
- * of the coroutines and see pth_mctx.c (from the pth project) for the
- * sigaltstack way of manipulating stacks.
- */
-
- co = g_malloc0(sizeof(*co));
- co->stack = g_malloc(stack_size);
- co->base.entry_arg = &old_env; /* stash away our jmp_buf */
-
- coTS = coroutine_get_thread_state();
- coTS->tr_handler = co;
-
- /*
- * Preserve the SIGUSR2 signal state, block SIGUSR2,
- * and establish our signal handler. The signal will
- * later transfer control onto the signal stack.
- */
- sigemptyset(&sigs);
- sigaddset(&sigs, SIGUSR2);
- pthread_sigmask(SIG_BLOCK, &sigs, &osigs);
- sa.sa_handler = coroutine_trampoline;
- sigfillset(&sa.sa_mask);
- sa.sa_flags = SA_ONSTACK;
- if (sigaction(SIGUSR2, &sa, &osa) != 0) {
- abort();
- }
-
- /*
- * Set the new stack.
- */
- ss.ss_sp = co->stack;
- ss.ss_size = stack_size;
- ss.ss_flags = 0;
- if (sigaltstack(&ss, &oss) < 0) {
- abort();
- }
-
- /*
- * Now transfer control onto the signal stack and set it up.
- * It will return immediately via "return" after the sigsetjmp()
- * was performed. Be careful here with race conditions. The
- * signal can be delivered the first time sigsuspend() is
- * called.
- */
- coTS->tr_called = 0;
- pthread_kill(pthread_self(), SIGUSR2);
- sigfillset(&sigs);
- sigdelset(&sigs, SIGUSR2);
- while (!coTS->tr_called) {
- sigsuspend(&sigs);
- }
-
- /*
- * Inform the system that we are back off the signal stack by
- * removing the alternative signal stack. Be careful here: It
- * first has to be disabled, before it can be removed.
- */
- sigaltstack(NULL, &ss);
- ss.ss_flags = SS_DISABLE;
- if (sigaltstack(&ss, NULL) < 0) {
- abort();
- }
- sigaltstack(NULL, &ss);
- if (!(oss.ss_flags & SS_DISABLE)) {
- sigaltstack(&oss, NULL);
- }
-
- /*
- * Restore the old SIGUSR2 signal handler and mask
- */
- sigaction(SIGUSR2, &osa, NULL);
- pthread_sigmask(SIG_SETMASK, &osigs, NULL);
-
- /*
- * Now enter the trampoline again, but this time not as a signal
- * handler. Instead we jump into it directly. The functionally
- * redundant ping-pong pointer arithmetic is necessary to avoid
- * type-conversion warnings related to the `volatile' qualifier and
- * the fact that `jmp_buf' usually is an array type.
- */
- if (!sigsetjmp(old_env, 0)) {
- siglongjmp(coTS->tr_reenter, 1);
- }
-
- /*
- * Ok, we returned again, so now we're finished
- */
-
- return &co->base;
-}
-
-void qemu_coroutine_delete(Coroutine *co_)
-{
- CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
-
- 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;
-}
-
Code Review / kvmfornfv.git / blobdiff