343 lines
9.7 KiB
C
343 lines
9.7 KiB
C
/*
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* ucontext coroutine initialization code
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*
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* Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
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* Copyright (C) 2011 Kevin Wolf <kwolf@redhat.com>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.0 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*/
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/* XXX Is there a nicer way to disable glibc's stack check for longjmp? */
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#undef _FORTIFY_SOURCE
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#define _FORTIFY_SOURCE 0
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#include "qemu/osdep.h"
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#include <ucontext.h>
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#include "qemu/coroutine_int.h"
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#include "qemu/coroutine-tls.h"
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#ifdef CONFIG_VALGRIND_H
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#include <valgrind/valgrind.h>
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#endif
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#ifdef QEMU_SANITIZE_ADDRESS
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#ifdef CONFIG_ASAN_IFACE_FIBER
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#define CONFIG_ASAN 1
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#include <sanitizer/asan_interface.h>
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#endif
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#endif
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#ifdef CONFIG_TSAN
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#include <sanitizer/tsan_interface.h>
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#endif
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typedef struct {
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Coroutine base;
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void *stack;
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size_t stack_size;
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#ifdef CONFIG_SAFESTACK
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/* Need an unsafe stack for each coroutine */
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void *unsafe_stack;
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size_t unsafe_stack_size;
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#endif
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sigjmp_buf env;
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#ifdef CONFIG_TSAN
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void *tsan_co_fiber;
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void *tsan_caller_fiber;
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#endif
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#ifdef CONFIG_VALGRIND_H
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unsigned int valgrind_stack_id;
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#endif
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} CoroutineUContext;
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/**
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* Per-thread coroutine bookkeeping
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*/
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QEMU_DEFINE_STATIC_CO_TLS(Coroutine *, current);
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QEMU_DEFINE_STATIC_CO_TLS(CoroutineUContext, leader);
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/*
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* va_args to makecontext() must be type 'int', so passing
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* the pointer we need may require several int args. This
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* union is a quick hack to let us do that
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*/
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union cc_arg {
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void *p;
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int i[2];
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};
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/*
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* QEMU_ALWAYS_INLINE only does so if __OPTIMIZE__, so we cannot use it.
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* always_inline is required to avoid TSan runtime fatal errors.
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*/
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static inline __attribute__((always_inline))
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void on_new_fiber(CoroutineUContext *co)
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{
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#ifdef CONFIG_TSAN
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co->tsan_co_fiber = __tsan_create_fiber(0); /* flags: sync on switch */
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co->tsan_caller_fiber = __tsan_get_current_fiber();
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#endif
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}
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/* always_inline is required to avoid TSan runtime fatal errors. */
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static inline __attribute__((always_inline))
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void finish_switch_fiber(void *fake_stack_save)
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{
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#ifdef CONFIG_ASAN
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CoroutineUContext *leaderp = get_ptr_leader();
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const void *bottom_old;
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size_t size_old;
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__sanitizer_finish_switch_fiber(fake_stack_save, &bottom_old, &size_old);
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if (!leaderp->stack) {
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leaderp->stack = (void *)bottom_old;
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leaderp->stack_size = size_old;
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}
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#endif
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#ifdef CONFIG_TSAN
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if (fake_stack_save) {
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__tsan_release(fake_stack_save);
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__tsan_switch_to_fiber(fake_stack_save, 0); /* 0=synchronize */
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}
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#endif
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}
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/* always_inline is required to avoid TSan runtime fatal errors. */
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static inline __attribute__((always_inline))
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void start_switch_fiber_asan(CoroutineAction action, void **fake_stack_save,
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const void *bottom, size_t size)
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{
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#ifdef CONFIG_ASAN
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__sanitizer_start_switch_fiber(
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action == COROUTINE_TERMINATE ? NULL : fake_stack_save,
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bottom, size);
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#endif
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}
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/* always_inline is required to avoid TSan runtime fatal errors. */
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static inline __attribute__((always_inline))
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void start_switch_fiber_tsan(void **fake_stack_save,
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CoroutineUContext *co,
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bool caller)
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{
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#ifdef CONFIG_TSAN
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void *new_fiber = caller ?
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co->tsan_caller_fiber :
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co->tsan_co_fiber;
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void *curr_fiber = __tsan_get_current_fiber();
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__tsan_acquire(curr_fiber);
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*fake_stack_save = curr_fiber;
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__tsan_switch_to_fiber(new_fiber, 0); /* 0=synchronize */
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#endif
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}
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static void coroutine_trampoline(int i0, int i1)
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{
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union cc_arg arg;
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CoroutineUContext *self;
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Coroutine *co;
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void *fake_stack_save = NULL;
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finish_switch_fiber(NULL);
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arg.i[0] = i0;
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arg.i[1] = i1;
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self = arg.p;
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co = &self->base;
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/* Initialize longjmp environment and switch back the caller */
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if (!sigsetjmp(self->env, 0)) {
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CoroutineUContext *leaderp = get_ptr_leader();
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start_switch_fiber_asan(COROUTINE_YIELD, &fake_stack_save,
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leaderp->stack, leaderp->stack_size);
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start_switch_fiber_tsan(&fake_stack_save, self, true); /* true=caller */
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siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
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}
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finish_switch_fiber(fake_stack_save);
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while (true) {
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co->entry(co->entry_arg);
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qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
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}
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}
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Coroutine *qemu_coroutine_new(void)
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{
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CoroutineUContext *co;
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ucontext_t old_uc, uc;
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sigjmp_buf old_env;
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union cc_arg arg = {0};
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void *fake_stack_save = NULL;
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/* The ucontext functions preserve signal masks which incurs a
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* system call overhead. sigsetjmp(buf, 0)/siglongjmp() does not
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* preserve signal masks but only works on the current stack.
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* Since we need a way to create and switch to a new stack, use
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* the ucontext functions for that but sigsetjmp()/siglongjmp() for
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* everything else.
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*/
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if (getcontext(&uc) == -1) {
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abort();
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}
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co = g_malloc0(sizeof(*co));
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co->stack_size = COROUTINE_STACK_SIZE;
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co->stack = qemu_alloc_stack(&co->stack_size);
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#ifdef CONFIG_SAFESTACK
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co->unsafe_stack_size = COROUTINE_STACK_SIZE;
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co->unsafe_stack = qemu_alloc_stack(&co->unsafe_stack_size);
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#endif
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co->base.entry_arg = &old_env; /* stash away our jmp_buf */
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uc.uc_link = &old_uc;
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uc.uc_stack.ss_sp = co->stack;
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uc.uc_stack.ss_size = co->stack_size;
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uc.uc_stack.ss_flags = 0;
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#ifdef CONFIG_VALGRIND_H
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co->valgrind_stack_id =
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VALGRIND_STACK_REGISTER(co->stack, co->stack + co->stack_size);
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#endif
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arg.p = co;
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on_new_fiber(co);
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makecontext(&uc, (void (*)(void))coroutine_trampoline,
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2, arg.i[0], arg.i[1]);
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/* swapcontext() in, siglongjmp() back out */
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if (!sigsetjmp(old_env, 0)) {
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start_switch_fiber_asan(COROUTINE_YIELD, &fake_stack_save, co->stack,
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co->stack_size);
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start_switch_fiber_tsan(&fake_stack_save,
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co, false); /* false=not caller */
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#ifdef CONFIG_SAFESTACK
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/*
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* Before we swap the context, set the new unsafe stack
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* The unsafe stack grows just like the normal stack, so start from
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* the last usable location of the memory area.
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* NOTE: we don't have to re-set the usp afterwards because we are
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* coming back to this context through a siglongjmp.
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* The compiler already wrapped the corresponding sigsetjmp call with
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* code that saves the usp on the (safe) stack before the call, and
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* restores it right after (which is where we return with siglongjmp).
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*/
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void *usp = co->unsafe_stack + co->unsafe_stack_size;
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__safestack_unsafe_stack_ptr = usp;
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#endif
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swapcontext(&old_uc, &uc);
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}
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finish_switch_fiber(fake_stack_save);
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return &co->base;
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}
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#ifdef CONFIG_VALGRIND_H
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/* Work around an unused variable in the valgrind.h macro... */
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#if !defined(__clang__)
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
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#endif
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static inline void valgrind_stack_deregister(CoroutineUContext *co)
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{
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VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
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}
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#if !defined(__clang__)
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#pragma GCC diagnostic pop
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#endif
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#endif
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void qemu_coroutine_delete(Coroutine *co_)
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{
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CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
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#ifdef CONFIG_VALGRIND_H
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valgrind_stack_deregister(co);
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#endif
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qemu_free_stack(co->stack, co->stack_size);
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#ifdef CONFIG_SAFESTACK
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qemu_free_stack(co->unsafe_stack, co->unsafe_stack_size);
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#endif
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g_free(co);
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}
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/* This function is marked noinline to prevent GCC from inlining it
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* into coroutine_trampoline(). If we allow it to do that then it
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* hoists the code to get the address of the TLS variable "current"
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* out of the while() loop. This is an invalid transformation because
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* the sigsetjmp() call may be called when running thread A but
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* return in thread B, and so we might be in a different thread
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* context each time round the loop.
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*/
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CoroutineAction __attribute__((noinline))
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qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
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CoroutineAction action)
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{
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CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
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CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
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int ret;
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void *fake_stack_save = NULL;
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set_current(to_);
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ret = sigsetjmp(from->env, 0);
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if (ret == 0) {
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start_switch_fiber_asan(action, &fake_stack_save, to->stack,
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to->stack_size);
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start_switch_fiber_tsan(&fake_stack_save,
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to, false); /* false=not caller */
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siglongjmp(to->env, action);
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}
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finish_switch_fiber(fake_stack_save);
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return ret;
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}
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Coroutine *qemu_coroutine_self(void)
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{
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Coroutine *self = get_current();
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CoroutineUContext *leaderp = get_ptr_leader();
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if (!self) {
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self = &leaderp->base;
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set_current(self);
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}
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#ifdef CONFIG_TSAN
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if (!leaderp->tsan_co_fiber) {
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leaderp->tsan_co_fiber = __tsan_get_current_fiber();
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}
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#endif
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return self;
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}
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bool qemu_in_coroutine(void)
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{
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Coroutine *self = get_current();
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return self && self->caller;
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}
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