qemu/util/coroutine-ucontext.c
Thomas Huth 7aa12aa215 Remove the CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE switch
GCC supports "#pragma GCC diagnostic" since version 4.6, and
Clang seems to support it, too, since its early versions 3.x.
That means that our minimum required compiler versions all support
this pragma already and we can remove the test from configure and
all the related #ifdefs in the code.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200710045515.25986-1-thuth@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
2020-07-13 11:40:52 +02:00

333 lines
9.5 KiB
C

/*
* 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 "qemu/osdep.h"
#include <ucontext.h>
#include "qemu/coroutine_int.h"
#ifdef CONFIG_VALGRIND_H
#include <valgrind/valgrind.h>
#endif
#if defined(__SANITIZE_ADDRESS__) || __has_feature(address_sanitizer)
#ifdef CONFIG_ASAN_IFACE_FIBER
#define CONFIG_ASAN 1
#include <sanitizer/asan_interface.h>
#endif
#endif
#ifdef CONFIG_TSAN
#include <sanitizer/tsan_interface.h>
#endif
typedef struct {
Coroutine base;
void *stack;
size_t stack_size;
#ifdef CONFIG_SAFESTACK
/* Need an unsafe stack for each coroutine */
void *unsafe_stack;
size_t unsafe_stack_size;
#endif
sigjmp_buf env;
#ifdef CONFIG_TSAN
void *tsan_co_fiber;
void *tsan_caller_fiber;
#endif
#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];
};
/*
* QEMU_ALWAYS_INLINE only does so if __OPTIMIZE__, so we cannot use it.
* always_inline is required to avoid TSan runtime fatal errors.
*/
static inline __attribute__((always_inline))
void on_new_fiber(CoroutineUContext *co)
{
#ifdef CONFIG_TSAN
co->tsan_co_fiber = __tsan_create_fiber(0); /* flags: sync on switch */
co->tsan_caller_fiber = __tsan_get_current_fiber();
#endif
}
/* always_inline is required to avoid TSan runtime fatal errors. */
static inline __attribute__((always_inline))
void finish_switch_fiber(void *fake_stack_save)
{
#ifdef CONFIG_ASAN
const void *bottom_old;
size_t size_old;
__sanitizer_finish_switch_fiber(fake_stack_save, &bottom_old, &size_old);
if (!leader.stack) {
leader.stack = (void *)bottom_old;
leader.stack_size = size_old;
}
#endif
#ifdef CONFIG_TSAN
if (fake_stack_save) {
__tsan_release(fake_stack_save);
__tsan_switch_to_fiber(fake_stack_save, 0); /* 0=synchronize */
}
#endif
}
/* always_inline is required to avoid TSan runtime fatal errors. */
static inline __attribute__((always_inline))
void start_switch_fiber_asan(CoroutineAction action, void **fake_stack_save,
const void *bottom, size_t size)
{
#ifdef CONFIG_ASAN
__sanitizer_start_switch_fiber(
action == COROUTINE_TERMINATE ? NULL : fake_stack_save,
bottom, size);
#endif
}
/* always_inline is required to avoid TSan runtime fatal errors. */
static inline __attribute__((always_inline))
void start_switch_fiber_tsan(void **fake_stack_save,
CoroutineUContext *co,
bool caller)
{
#ifdef CONFIG_TSAN
void *new_fiber = caller ?
co->tsan_caller_fiber :
co->tsan_co_fiber;
void *curr_fiber = __tsan_get_current_fiber();
__tsan_acquire(curr_fiber);
*fake_stack_save = curr_fiber;
__tsan_switch_to_fiber(new_fiber, 0); /* 0=synchronize */
#endif
}
static void coroutine_trampoline(int i0, int i1)
{
union cc_arg arg;
CoroutineUContext *self;
Coroutine *co;
void *fake_stack_save = NULL;
finish_switch_fiber(NULL);
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)) {
start_switch_fiber_asan(COROUTINE_YIELD, &fake_stack_save, leader.stack,
leader.stack_size);
start_switch_fiber_tsan(&fake_stack_save, self, true); /* true=caller */
siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
}
finish_switch_fiber(fake_stack_save);
while (true) {
co->entry(co->entry_arg);
qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
}
}
Coroutine *qemu_coroutine_new(void)
{
CoroutineUContext *co;
ucontext_t old_uc, uc;
sigjmp_buf old_env;
union cc_arg arg = {0};
void *fake_stack_save = NULL;
/* 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_size = COROUTINE_STACK_SIZE;
co->stack = qemu_alloc_stack(&co->stack_size);
#ifdef CONFIG_SAFESTACK
co->unsafe_stack_size = COROUTINE_STACK_SIZE;
co->unsafe_stack = qemu_alloc_stack(&co->unsafe_stack_size);
#endif
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 = co->stack_size;
uc.uc_stack.ss_flags = 0;
#ifdef CONFIG_VALGRIND_H
co->valgrind_stack_id =
VALGRIND_STACK_REGISTER(co->stack, co->stack + co->stack_size);
#endif
arg.p = co;
on_new_fiber(co);
makecontext(&uc, (void (*)(void))coroutine_trampoline,
2, arg.i[0], arg.i[1]);
/* swapcontext() in, siglongjmp() back out */
if (!sigsetjmp(old_env, 0)) {
start_switch_fiber_asan(COROUTINE_YIELD, &fake_stack_save, co->stack,
co->stack_size);
start_switch_fiber_tsan(&fake_stack_save,
co, false); /* false=not caller */
#ifdef CONFIG_SAFESTACK
/*
* Before we swap the context, set the new unsafe stack
* The unsafe stack grows just like the normal stack, so start from
* the last usable location of the memory area.
* NOTE: we don't have to re-set the usp afterwards because we are
* coming back to this context through a siglongjmp.
* The compiler already wrapped the corresponding sigsetjmp call with
* code that saves the usp on the (safe) stack before the call, and
* restores it right after (which is where we return with siglongjmp).
*/
void *usp = co->unsafe_stack + co->unsafe_stack_size;
__safestack_unsafe_stack_ptr = usp;
#endif
swapcontext(&old_uc, &uc);
}
finish_switch_fiber(fake_stack_save);
return &co->base;
}
#ifdef CONFIG_VALGRIND_H
/* Work around an unused variable in the valgrind.h macro... */
#if !defined(__clang__)
#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);
}
#if !defined(__clang__)
#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
qemu_free_stack(co->stack, co->stack_size);
#ifdef CONFIG_SAFESTACK
qemu_free_stack(co->unsafe_stack, co->unsafe_stack_size);
#endif
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;
void *fake_stack_save = NULL;
current = to_;
ret = sigsetjmp(from->env, 0);
if (ret == 0) {
start_switch_fiber_asan(action, &fake_stack_save, to->stack,
to->stack_size);
start_switch_fiber_tsan(&fake_stack_save,
to, false); /* false=not caller */
siglongjmp(to->env, action);
}
finish_switch_fiber(fake_stack_save);
return ret;
}
Coroutine *qemu_coroutine_self(void)
{
if (!current) {
current = &leader.base;
}
#ifdef CONFIG_TSAN
if (!leader.tsan_co_fiber) {
leader.tsan_co_fiber = __tsan_get_current_fiber();
}
#endif
return current;
}
bool qemu_in_coroutine(void)
{
return current && current->caller;
}