/*
   +----------------------------------------------------------------------+
   | Zend Engine                                                          |
   +----------------------------------------------------------------------+
   | Copyright (c) Zend Technologies Ltd. (http://www.zend.com)           |
   +----------------------------------------------------------------------+
   | This source file is subject to version 2.00 of the Zend license,     |
   | that is bundled with this package in the file LICENSE, and is        |
   | available through the world-wide-web at the following url:           |
   | http://www.zend.com/license/2_00.txt.                                |
   | If you did not receive a copy of the Zend license and are unable to  |
   | obtain it through the world-wide-web, please send a note to          |
   | license@zend.com so we can mail you a copy immediately.              |
   +----------------------------------------------------------------------+
   | Authors: Aaron Piotrowski <aaron@trowski.com>                        |
   |          Martin Schröder <m.schroeder2007@gmail.com>                 |
   +----------------------------------------------------------------------+
*/

#include "zend.h"
#include "zend_API.h"
#include "zend_ini.h"
#include "zend_vm.h"
#include "zend_interfaces.h"
#include "zend_exceptions.h"
#include "zend_builtin_functions.h"
#include "zend_observer.h"

#include "zend_fibers.h"
#include "zend_fibers_arginfo.h"

#ifdef HAVE_VALGRIND
# include <valgrind/valgrind.h>
#endif

#ifndef ZEND_WIN32
# include <unistd.h>
# include <sys/mman.h>
# include <limits.h>

# if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
#  define MAP_ANONYMOUS MAP_ANON
# endif

/* FreeBSD require a first (i.e. addr) argument of mmap(2) is not NULL
 * if MAP_STACK is passed.
 * http://www.FreeBSD.org/cgi/query-pr.cgi?pr=158755 */
# if !defined(MAP_STACK) || defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
#  undef MAP_STACK
#  define MAP_STACK 0
# endif

# ifndef MAP_FAILED
#  define MAP_FAILED ((void * ) -1)
# endif
#endif

#ifdef __SANITIZE_ADDRESS__
# include <sanitizer/common_interface_defs.h>
#endif

ZEND_API zend_class_entry *zend_ce_fiber;
static zend_class_entry *zend_ce_fiber_error;

static zend_object_handlers zend_fiber_handlers;

static zend_function zend_fiber_function = { ZEND_INTERNAL_FUNCTION };

typedef void *fcontext_t;

typedef struct _transfer_t {
	fcontext_t context;
	void *data;
} transfer_t;

extern fcontext_t make_fcontext(void *sp, size_t size, void (*fn)(transfer_t));
extern transfer_t jump_fcontext(fcontext_t to, void *vp);

#define ZEND_FIBER_DEFAULT_PAGE_SIZE 4096

static size_t zend_fiber_get_page_size(void)
{
	static size_t page_size = 0;

	if (!page_size) {
		page_size = zend_get_page_size();
		if (!page_size || (page_size & (page_size - 1))) {
			/* anyway, we have to return a valid result */
			page_size = ZEND_FIBER_DEFAULT_PAGE_SIZE;
		}
	}

	return page_size;
}

static bool zend_fiber_stack_allocate(zend_fiber_stack *stack, size_t size)
{
	void *pointer;
	const size_t page_size = zend_fiber_get_page_size();

	ZEND_ASSERT(size >= page_size + ZEND_FIBER_GUARD_PAGES * page_size);

	stack->size = (size + page_size - 1) / page_size * page_size;
	const size_t msize = stack->size + ZEND_FIBER_GUARD_PAGES * page_size;

#ifdef ZEND_WIN32
	pointer = VirtualAlloc(0, msize, MEM_COMMIT, PAGE_READWRITE);

	if (!pointer) {
		DWORD err = GetLastError();
		char *errmsg = php_win32_error_to_msg(err);
		zend_throw_exception_ex(NULL, 0, "Fiber make context failed: VirtualAlloc failed: [0x%08lx] %s", err, errmsg[0] ? errmsg : "Unknown");
		php_win32_error_msg_free(errmsg);
		return false;
	}

# if ZEND_FIBER_GUARD_PAGES
	DWORD protect;

	if (!VirtualProtect(pointer, ZEND_FIBER_GUARD_PAGES * page_size, PAGE_READWRITE | PAGE_GUARD, &protect)) {
		DWORD err = GetLastError();
		char *errmsg = php_win32_error_to_msg(err);
		zend_throw_exception_ex(NULL, 0, "Fiber protect stack failed: VirtualProtect failed: [0x%08lx] %s", err, errmsg[0] ? errmsg : "Unknown");
		php_win32_error_msg_free(errmsg);
		VirtualFree(pointer, 0, MEM_RELEASE);
		return false;
	}
# endif
#else
	pointer = mmap(NULL, msize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);

	if (pointer == MAP_FAILED) {
		zend_throw_exception_ex(NULL, 0, "Fiber make context failed: mmap failed: %s (%d)", strerror(errno), errno);
		return false;
	}

# if ZEND_FIBER_GUARD_PAGES
	if (mprotect(pointer, ZEND_FIBER_GUARD_PAGES * page_size, PROT_NONE) < 0) {
		zend_throw_exception_ex(NULL, 0, "Fiber protect stack failed: mmap failed: %s (%d)", strerror(errno), errno);
		munmap(pointer, msize);
		return false;
	}
# endif
#endif

	stack->pointer = (void *) ((uintptr_t) pointer + ZEND_FIBER_GUARD_PAGES * page_size);

#ifdef VALGRIND_STACK_REGISTER
	uintptr_t base = (uintptr_t) stack->pointer;
	stack->valgrind = VALGRIND_STACK_REGISTER(base, base + stack->size);
#endif

#ifdef __SANITIZE_ADDRESS__
	stack->prior_pointer = stack->pointer;
	stack->prior_size = stack->size;
#endif

	return true;
}

static void zend_fiber_stack_free(zend_fiber_stack *stack)
{
	if (!stack->pointer) {
		return;
	}

#ifdef VALGRIND_STACK_DEREGISTER
	VALGRIND_STACK_DEREGISTER(stack->valgrind);
#endif

	const size_t page_size = zend_fiber_get_page_size();

	void *pointer = (void *) ((uintptr_t) stack->pointer - ZEND_FIBER_GUARD_PAGES * page_size);

#ifdef ZEND_WIN32
	VirtualFree(pointer, 0, MEM_RELEASE);
#else
	munmap(pointer, stack->size + ZEND_FIBER_GUARD_PAGES * page_size);
#endif

	stack->pointer = NULL;
}

static ZEND_NORETURN void zend_fiber_trampoline(transfer_t transfer)
{
	zend_fiber_context *context = EG(current_fiber);
	zend_fiber_context *from = transfer.data;

	from->handle = transfer.context;

#ifdef __SANITIZE_ADDRESS__
	__sanitizer_finish_switch_fiber(NULL, &from->stack.prior_pointer, &from->stack.prior_size);
#endif

	zend_fiber_context *to = context->function(context);

	context->status = ZEND_FIBER_STATUS_DEAD;

	/* Final context switch, the fiber must not be resumed afterwards! */
	zend_fiber_switch_context(to);

	/* Abort here because we are in an inconsistent program state. */
	abort();
}

ZEND_API bool zend_fiber_init_context(zend_fiber_context *context, void *kind, zend_fiber_coroutine coroutine, size_t stack_size)
{
	if (UNEXPECTED(!zend_fiber_stack_allocate(&context->stack, stack_size))) {
		return false;
	}

	// Stack grows down, calculate the top of the stack. make_fcontext then shifts pointer to lower 16-byte boundary.
	void *stack = (void *) ((uintptr_t) context->stack.pointer + context->stack.size);

	context->handle = make_fcontext(stack, context->stack.size, zend_fiber_trampoline);
	ZEND_ASSERT(context->handle != NULL && "make_fcontext() never returns NULL");

	context->kind = kind;
	context->function = coroutine;

	return true;
}

ZEND_API void zend_fiber_destroy_context(zend_fiber_context *context)
{
	zend_fiber_stack_free(&context->stack);
}

ZEND_API zend_fiber_context *zend_fiber_switch_context(zend_fiber_context *to)
{
	zend_fiber_context *from = EG(current_fiber);
	zend_fiber_vm_state state;

	ZEND_ASSERT(to && to->handle && "Invalid fiber context");
	ZEND_ASSERT(from && "From fiber context must be present");
	ZEND_ASSERT(to != from && "Cannot switch into the running fiber context");

	zend_observer_fiber_switch_notify(from, to);

	zend_fiber_capture_vm_state(&state);

	to->status = ZEND_FIBER_STATUS_RUNNING;

	if (from->status == ZEND_FIBER_STATUS_RUNNING) {
		from->status = ZEND_FIBER_STATUS_SUSPENDED;
	}

	EG(current_fiber) = to;

#ifdef __SANITIZE_ADDRESS__
	void *fake_stack = NULL;
	__sanitizer_start_switch_fiber(
		from->status != ZEND_FIBER_STATUS_DEAD ? &fake_stack : NULL,
		to->stack.prior_pointer,
		to->stack.prior_size);
#endif

	transfer_t transfer = jump_fcontext(to->handle, from);

#ifdef __SANITIZE_ADDRESS__
	__sanitizer_finish_switch_fiber(fake_stack, &to->stack.prior_pointer, &to->stack.prior_size);
#endif

	EG(current_fiber) = from;

	zend_fiber_context *previous = transfer.data;
	previous->handle = transfer.context;

	zend_fiber_restore_vm_state(&state);

	/* Destroy context first to ensure it does not leak if some extension does custom bailout handling. */
	if (previous->status == ZEND_FIBER_STATUS_DEAD) {
		zend_fiber_destroy_context(previous);
	}

	/* Propagate bailout to current fiber / main. */
	if (UNEXPECTED(previous->flags & ZEND_FIBER_FLAG_BAILOUT)) {
		zend_bailout();
	}

	return previous;
}


static zend_always_inline zend_vm_stack zend_fiber_vm_stack_alloc(size_t size)
{
	zend_vm_stack page = emalloc(size);

	page->top = ZEND_VM_STACK_ELEMENTS(page);
	page->end = (zval *) ((uintptr_t) page + size);
	page->prev = NULL;

	return page;
}

static ZEND_STACK_ALIGNED zend_fiber_context *zend_fiber_execute(zend_fiber_context *context)
{
	zend_fiber *fiber = zend_fiber_from_context(context);

	zend_long error_reporting = INI_INT("error_reporting");
	if (!error_reporting && !INI_STR("error_reporting")) {
		error_reporting = E_ALL;
	}

	EG(vm_stack) = NULL;

	zend_first_try {
		zend_vm_stack stack = zend_fiber_vm_stack_alloc(ZEND_FIBER_VM_STACK_SIZE);
		EG(vm_stack) = stack;
		EG(vm_stack_top) = stack->top + ZEND_CALL_FRAME_SLOT;
		EG(vm_stack_end) = stack->end;
		EG(vm_stack_page_size) = ZEND_FIBER_VM_STACK_SIZE;

		fiber->execute_data = (zend_execute_data *) stack->top;
		fiber->stack_bottom = fiber->execute_data;

		memset(fiber->execute_data, 0, sizeof(zend_execute_data));

		fiber->execute_data->func = &zend_fiber_function;
		fiber->stack_bottom->prev_execute_data = EG(current_execute_data);

		EG(current_execute_data) = fiber->execute_data;
		EG(jit_trace_num) = 0;
		EG(error_reporting) = error_reporting;

		fiber->fci.retval = &fiber->value;

		zend_call_function(&fiber->fci, &fiber->fci_cache);

		zval_ptr_dtor(&fiber->fci.function_name);

		if (EG(exception)) {
			if (fiber->flags & ZEND_FIBER_FLAG_DESTROYED) {
				if (EXPECTED(zend_is_graceful_exit(EG(exception)) || zend_is_unwind_exit(EG(exception)))) {
					zend_clear_exception();
				}
			} else {
				fiber->flags = ZEND_FIBER_FLAG_THREW;
			}
		}
	} zend_catch {
		fiber->flags |= ZEND_FIBER_FLAG_BAILOUT;
	} zend_end_try();

	zend_vm_stack_destroy();
	fiber->execute_data = NULL;
	fiber->stack_bottom = NULL;

	zend_fiber_context *caller = fiber->caller;
	fiber->caller = NULL;

	return caller;
}

static zend_object *zend_fiber_object_create(zend_class_entry *ce)
{
	zend_fiber *fiber;

	fiber = emalloc(sizeof(zend_fiber));
	memset(fiber, 0, sizeof(zend_fiber));

	zend_object_std_init(&fiber->std, ce);
	fiber->std.handlers = &zend_fiber_handlers;

	return &fiber->std;
}

static void zend_fiber_object_destroy(zend_object *object)
{
	zend_fiber *fiber = (zend_fiber *) object;

	if (fiber->status != ZEND_FIBER_STATUS_SUSPENDED) {
		return;
	}

	zend_object *exception = EG(exception);
	EG(exception) = NULL;

	fiber->caller = EG(current_fiber);
	fiber->flags |= ZEND_FIBER_FLAG_DESTROYED;

	zend_fiber_switch_context(zend_fiber_get_context(fiber));

	if (EG(exception)) {
		if (!exception && EG(current_execute_data) && EG(current_execute_data)->func
				&& ZEND_USER_CODE(EG(current_execute_data)->func->common.type)) {
			zend_rethrow_exception(EG(current_execute_data));
		}

		zend_exception_set_previous(EG(exception), exception);

		if (!EG(current_execute_data)) {
			zend_exception_error(EG(exception), E_ERROR);
		}
	} else {
		EG(exception) = exception;
	}
}

static void zend_fiber_object_free(zend_object *object)
{
	zend_fiber *fiber = (zend_fiber *) object;

	if (fiber->status == ZEND_FIBER_STATUS_INIT) {
		// Fiber was never started, so we need to release the reference to the callback.
		zval_ptr_dtor(&fiber->fci.function_name);
	}

	zval_ptr_dtor(&fiber->value);

	zend_object_std_dtor(&fiber->std);
}

ZEND_METHOD(Fiber, __construct)
{
	zend_fiber *fiber = (zend_fiber *) Z_OBJ_P(getThis());

	ZEND_PARSE_PARAMETERS_START(1, 1)
		Z_PARAM_FUNC(fiber->fci, fiber->fci_cache)
	ZEND_PARSE_PARAMETERS_END();

	// Keep a reference to closures or callable objects while the fiber is running.
	Z_TRY_ADDREF(fiber->fci.function_name);
}

ZEND_METHOD(Fiber, start)
{
	zend_fiber *fiber = (zend_fiber *) Z_OBJ_P(getThis());
	zval *params;
	uint32_t param_count;
	zend_array *named_params;

	ZEND_PARSE_PARAMETERS_START(0, -1)
		Z_PARAM_VARIADIC_WITH_NAMED(params, param_count, named_params);
	ZEND_PARSE_PARAMETERS_END();

	if (fiber->status != ZEND_FIBER_STATUS_INIT) {
		zend_throw_error(zend_ce_fiber_error, "Cannot start a fiber that has already been started");
		RETURN_THROWS();
	}

	fiber->fci.params = params;
	fiber->fci.param_count = param_count;
	fiber->fci.named_params = named_params;

	zend_fiber_context *context = zend_fiber_get_context(fiber);

	if (!zend_fiber_init_context(context, zend_ce_fiber, zend_fiber_execute, EG(fiber_stack_size))) {
		RETURN_THROWS();
	}

	fiber->caller = EG(current_fiber);

	zend_fiber_switch_context(context);

	if (fiber->status == ZEND_FIBER_STATUS_DEAD) {
		RETURN_NULL();
	}

	RETVAL_COPY_VALUE(&fiber->value);
	ZVAL_UNDEF(&fiber->value);
}

ZEND_METHOD(Fiber, suspend)
{
	zval *value = NULL;

	ZEND_PARSE_PARAMETERS_START(0, 1)
		Z_PARAM_OPTIONAL
		Z_PARAM_ZVAL(value);
	ZEND_PARSE_PARAMETERS_END();

	if (UNEXPECTED(EG(current_fiber)->kind != zend_ce_fiber)) {
		zend_throw_error(zend_ce_fiber_error, "Cannot suspend outside of a fiber");
		RETURN_THROWS();
	}

	zend_fiber *fiber = zend_fiber_from_context(EG(current_fiber));
	zend_fiber_context *caller = fiber->caller;

	if (UNEXPECTED(fiber->flags & ZEND_FIBER_FLAG_DESTROYED)) {
		zend_throw_error(zend_ce_fiber_error, "Cannot suspend in a force-closed fiber");
		RETURN_THROWS();
	}

	ZEND_ASSERT(fiber->status == ZEND_FIBER_STATUS_RUNNING);
	ZEND_ASSERT(caller != NULL);

	if (value) {
		ZVAL_COPY(&fiber->value, value);
	} else {
		ZVAL_NULL(&fiber->value);
	}

	fiber->caller = NULL;
	fiber->execute_data = EG(current_execute_data);
	fiber->stack_bottom->prev_execute_data = NULL;

	zend_fiber_switch_context(caller);

	if (fiber->flags & ZEND_FIBER_FLAG_DESTROYED) {
		// This occurs when the fiber is GC'ed while suspended.
		zend_throw_graceful_exit();
		RETURN_THROWS();
	}

	if (fiber->exception) {
		zval *exception = fiber->exception;
		fiber->exception = NULL;

		zend_throw_exception_object(exception);
		RETURN_THROWS();
	}

	RETVAL_COPY_VALUE(&fiber->value);
	ZVAL_UNDEF(&fiber->value);
}

ZEND_METHOD(Fiber, resume)
{
	zend_fiber *fiber;
	zval *value = NULL;

	ZEND_PARSE_PARAMETERS_START(0, 1)
		Z_PARAM_OPTIONAL
		Z_PARAM_ZVAL(value);
	ZEND_PARSE_PARAMETERS_END();

	fiber = (zend_fiber *) Z_OBJ_P(getThis());

	if (UNEXPECTED(fiber->status != ZEND_FIBER_STATUS_SUSPENDED || fiber->caller != NULL)) {
		zend_throw_error(zend_ce_fiber_error, "Cannot resume a fiber that is not suspended");
		RETURN_THROWS();
	}

	if (value) {
		ZVAL_COPY(&fiber->value, value);
	} else {
		ZVAL_NULL(&fiber->value);
	}

	fiber->caller = EG(current_fiber);
	fiber->stack_bottom->prev_execute_data = EG(current_execute_data);

	zend_fiber_switch_context(zend_fiber_get_context(fiber));

	if (fiber->status == ZEND_FIBER_STATUS_DEAD) {
		RETURN_NULL();
	}

	RETVAL_COPY_VALUE(&fiber->value);
	ZVAL_UNDEF(&fiber->value);
}

ZEND_METHOD(Fiber, throw)
{
	zend_fiber *fiber;
	zval *exception;

	ZEND_PARSE_PARAMETERS_START(1, 1)
		Z_PARAM_OBJECT_OF_CLASS(exception, zend_ce_throwable)
	ZEND_PARSE_PARAMETERS_END();

	fiber = (zend_fiber *) Z_OBJ_P(getThis());

	if (UNEXPECTED(fiber->status != ZEND_FIBER_STATUS_SUSPENDED || fiber->caller != NULL)) {
		zend_throw_error(zend_ce_fiber_error, "Cannot resume a fiber that is not suspended");
		RETURN_THROWS();
	}

	Z_ADDREF_P(exception);
	fiber->exception = exception;

	fiber->caller = EG(current_fiber);
	fiber->stack_bottom->prev_execute_data = EG(current_execute_data);

	zend_fiber_switch_context(zend_fiber_get_context(fiber));

	if (fiber->status == ZEND_FIBER_STATUS_DEAD) {
		RETURN_NULL();
	}

	RETVAL_COPY_VALUE(&fiber->value);
	ZVAL_UNDEF(&fiber->value);
}

ZEND_METHOD(Fiber, isStarted)
{
	zend_fiber *fiber;

	ZEND_PARSE_PARAMETERS_NONE();

	fiber = (zend_fiber *) Z_OBJ_P(getThis());

	RETURN_BOOL(fiber->status != ZEND_FIBER_STATUS_INIT);
}

ZEND_METHOD(Fiber, isSuspended)
{
	zend_fiber *fiber;

	ZEND_PARSE_PARAMETERS_NONE();

	fiber = (zend_fiber *) Z_OBJ_P(getThis());

	RETURN_BOOL(fiber->status == ZEND_FIBER_STATUS_SUSPENDED && fiber->caller == NULL);
}

ZEND_METHOD(Fiber, isRunning)
{
	zend_fiber *fiber;

	ZEND_PARSE_PARAMETERS_NONE();

	fiber = (zend_fiber *) Z_OBJ_P(getThis());

	RETURN_BOOL(fiber->status == ZEND_FIBER_STATUS_RUNNING || fiber->caller != NULL);
}

ZEND_METHOD(Fiber, isTerminated)
{
	zend_fiber *fiber;

	ZEND_PARSE_PARAMETERS_NONE();

	fiber = (zend_fiber *) Z_OBJ_P(getThis());

	RETURN_BOOL(fiber->status == ZEND_FIBER_STATUS_DEAD);
}

ZEND_METHOD(Fiber, getReturn)
{
	zend_fiber *fiber;
	const char *message;

	ZEND_PARSE_PARAMETERS_NONE();

	fiber = (zend_fiber *) Z_OBJ_P(getThis());

	if (fiber->status == ZEND_FIBER_STATUS_DEAD) {
		if (fiber->flags & ZEND_FIBER_FLAG_THREW) {
			message = "The fiber threw an exception";
		} else if (fiber->flags & ZEND_FIBER_FLAG_BAILOUT) {
			message = "The fiber exited with a fatal error";
		} else {
			RETURN_COPY(&fiber->value);
		}
	} else if (fiber->status == ZEND_FIBER_STATUS_INIT) {
		message = "The fiber has not been started";
	} else {
		message = "The fiber has not returned";
	}

	zend_throw_error(zend_ce_fiber_error, "Cannot get fiber return value: %s", message);
	RETURN_THROWS();
}

ZEND_METHOD(Fiber, this)
{
	ZEND_PARSE_PARAMETERS_NONE();

	if (EG(current_fiber)->kind != zend_ce_fiber) {
		RETURN_NULL();
	}

	RETURN_OBJ_COPY(&zend_fiber_from_context(EG(current_fiber))->std);
}

ZEND_METHOD(FiberError, __construct)
{
	zend_throw_error(
		NULL,
		"The \"%s\" class is reserved for internal use and cannot be manually instantiated",
		ZSTR_VAL(Z_OBJCE_P(getThis())->name)
	);
}


void zend_register_fiber_ce(void)
{
	zend_ce_fiber = register_class_Fiber();
	zend_ce_fiber->create_object = zend_fiber_object_create;
	zend_ce_fiber->serialize = zend_class_serialize_deny;
	zend_ce_fiber->unserialize = zend_class_unserialize_deny;

	zend_fiber_handlers = std_object_handlers;
	zend_fiber_handlers.dtor_obj = zend_fiber_object_destroy;
	zend_fiber_handlers.free_obj = zend_fiber_object_free;
	zend_fiber_handlers.clone_obj = NULL;

	zend_ce_fiber_error = register_class_FiberError(zend_ce_error);
	zend_ce_fiber_error->create_object = zend_ce_error->create_object;
}

void zend_fiber_init(void)
{
	zend_fiber_context *context = ecalloc(1, sizeof(zend_fiber_context));

	context->status = ZEND_FIBER_STATUS_RUNNING;

	EG(main_fiber) = context;
	EG(current_fiber) = context;
}

void zend_fiber_shutdown(void)
{
	efree(EG(main_fiber));
}