/* * 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 <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 */ static __thread CoroutineUContext leader; static __thread Coroutine *current; /* * 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 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); } /* This function is marked noinline to prevent GCC from inlining it * into coroutine_trampoline(). If we allow it to do that then it * hoists the code to get the address of the TLS variable "current" * out of the while() loop. This is an invalid transformation because * the sigsetjmp() call may be called when running thread A but * return in thread B, and so we might be in a different thread * context each time round the loop. */ CoroutineAction __attribute__((noinline)) qemu_coroutine_switch(Coroutine *from_, Coroutine *to_, CoroutineAction action) { CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_); CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_); int ret; current = to_; ret = sigsetjmp(from->env, 0); if (ret == 0) { siglongjmp(to->env, action); } return ret; } Coroutine *qemu_coroutine_self(void) { if (!current) { current = &leader.base; } return current; } bool qemu_in_coroutine(void) { return current && current->caller; }