| /* |
| * 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; |
| } |
| |