/*
 * Copyright (c) 2013 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

#include <kern/locks.h>
#include <kern/task.h>
#include <kern/thread.h>
#include <libkern/OSAtomic.h>
#include <vm/vm_pageout.h>

#if defined(__x86_64__) && CONFIG_VMX
#include <i386/vmx/vmx_cpu.h>
#endif

#include <kern/hv_support.h>

int hv_support_available = 0;

/* callbacks for tasks/threads with associated hv objects */
hv_callbacks_t hv_callbacks = {
	.dispatch = NULL,		/* thread is being dispatched for execution */
	.preempt = NULL,		/* thread is being preempted */
	.thread_destroy = NULL,	/* thread is being destroyed */
	.task_destroy = NULL,	/* task is being destroyed */
	.volatile_state = NULL,	/* thread state is becoming volatile */
	.memory_pressure = NULL	/* memory pressure notification */
};

/* trap tables for hv_*_trap syscalls */
static hv_trap_table_t hv_trap_table[] = {
	[HV_TASK_TRAP] = {
		.traps = NULL,
		.trap_count = 0
	},
	[HV_THREAD_TRAP] = {
		.traps = NULL,
		.trap_count = 0
	}
};

static int hv_callbacks_enabled = 0;
static int hv_mp_notify_enabled = 0;
static int hv_mp_notify_destroy = 0;
static lck_grp_t *hv_support_lck_grp = NULL;
static lck_mtx_t *hv_support_lck_mtx = NULL;
static thread_t hv_mp_notify_thread = THREAD_NULL;
static void hv_mp_notify(void);

/* hv_support boot initialization */
void
hv_support_init(void) {
#if defined(__x86_64__) && CONFIG_VMX
	hv_support_available = vmx_hv_support();
#endif

	hv_support_lck_grp = lck_grp_alloc_init("hv_support", LCK_GRP_ATTR_NULL);
	assert(hv_support_lck_grp);

	hv_support_lck_mtx = lck_mtx_alloc_init(hv_support_lck_grp, LCK_ATTR_NULL);
	assert(hv_support_lck_mtx);
}

/* returns true if hv_support is available on this machine */
int
hv_get_support(void) {
	return hv_support_available;
}

/* associate an hv object with the current task */
void
hv_set_task_target(void *target) {
	current_task()->hv_task_target = target;
}

/* associate an hv object with the current thread */
void
hv_set_thread_target(void *target) {
	current_thread()->hv_thread_target = target;
}

/* get hv object associated with the current task */
void*
hv_get_task_target(void) {
	return current_task()->hv_task_target;
}

/* get hv object associated with the current thread */
void*
hv_get_thread_target(void) {
	return current_thread()->hv_thread_target;
}

/* test if a given thread state may be volatile between dispatch
   and preemption */
int
hv_get_volatile_state(hv_volatile_state_t state) {
	int is_volatile = 0;

#if (defined(__x86_64__))
	if (state == HV_DEBUG_STATE) {
		is_volatile = (current_thread()->machine.ids != NULL);
	}
#endif

	return is_volatile;
}

/* memory pressure monitor thread */
static void
hv_mp_notify(void) {
	while (1) {
		mach_vm_pressure_monitor(TRUE, 0, NULL, NULL);

		lck_mtx_lock(hv_support_lck_mtx);
		if (hv_mp_notify_destroy == 1) {
			hv_mp_notify_destroy = 0;
			hv_mp_notify_enabled = 0;
			lck_mtx_unlock(hv_support_lck_mtx);
			break;
		} else {
			hv_callbacks.memory_pressure(NULL);
		}
		lck_mtx_unlock(hv_support_lck_mtx);
	}

	thread_deallocate(current_thread());
}

/* subscribe to memory pressure notifications */
kern_return_t
hv_set_mp_notify(void) {
	kern_return_t kr;

	lck_mtx_lock(hv_support_lck_mtx);
	if (hv_callbacks_enabled == 0) {
		lck_mtx_unlock(hv_support_lck_mtx);
		return KERN_FAILURE;
	}

	if (hv_mp_notify_enabled == 1) {
		hv_mp_notify_destroy = 0;
		lck_mtx_unlock(hv_support_lck_mtx);
		return KERN_SUCCESS;
	}

	kr = kernel_thread_start((thread_continue_t) &hv_mp_notify, NULL,
		&hv_mp_notify_thread);

	if (kr == KERN_SUCCESS) {
		hv_mp_notify_enabled = 1;
	}
	lck_mtx_unlock(hv_support_lck_mtx);

	return kr;
}

/* unsubscribe from memory pressure notifications */
void
hv_release_mp_notify(void) {
	lck_mtx_lock(hv_support_lck_mtx);
	if (hv_mp_notify_enabled == 1) {
		hv_mp_notify_destroy = 1;
	}
	lck_mtx_unlock(hv_support_lck_mtx);
}

/* register a list of trap handlers for the hv_*_trap syscalls */
kern_return_t
hv_set_traps(hv_trap_type_t trap_type, const hv_trap_t *traps,
	unsigned trap_count)
{
	hv_trap_table_t *trap_table = &hv_trap_table[trap_type];
	kern_return_t kr = KERN_FAILURE;

	lck_mtx_lock(hv_support_lck_mtx);
	if (trap_table->trap_count == 0) {	
		trap_table->traps = traps;
		OSMemoryBarrier();
		trap_table->trap_count = trap_count;
		kr = KERN_SUCCESS;
	}
	lck_mtx_unlock(hv_support_lck_mtx);

	return kr;
}

/* release hv_*_trap traps */
void
hv_release_traps(hv_trap_type_t trap_type) {
	hv_trap_table_t *trap_table = &hv_trap_table[trap_type];

	lck_mtx_lock(hv_support_lck_mtx);
	trap_table->trap_count = 0;
	OSMemoryBarrier();
	trap_table->traps = NULL;
	lck_mtx_unlock(hv_support_lck_mtx);
}

/* register callbacks for certain task/thread events for tasks/threads with
   associated hv objects */
kern_return_t
hv_set_callbacks(hv_callbacks_t callbacks) {
	kern_return_t kr = KERN_FAILURE;

	lck_mtx_lock(hv_support_lck_mtx);
	if (hv_callbacks_enabled == 0) {	
		hv_callbacks = callbacks;
		hv_callbacks_enabled = 1;
		kr = KERN_SUCCESS;
	}
	lck_mtx_unlock(hv_support_lck_mtx);

	return kr;
}

/* release callbacks for task/thread events */
void
hv_release_callbacks(void) {
	lck_mtx_lock(hv_support_lck_mtx);	
	hv_callbacks = (hv_callbacks_t) {
		.dispatch = NULL,
		.preempt = NULL,
		.thread_destroy = NULL,
		.task_destroy = NULL,
		.volatile_state = NULL,
		.memory_pressure = NULL
	};

	hv_callbacks_enabled = 0;
	lck_mtx_unlock(hv_support_lck_mtx);
}

/* dispatch hv_task_trap/hv_thread_trap syscalls to trap handlers,
   fail for invalid index or absence of trap handlers, trap handler is
   responsible for validating targets */
#define HV_TRAP_DISPATCH(type, index, target, argument)\
	((__probable(index < hv_trap_table[type].trap_count)) ? \
		hv_trap_table[type].traps[index](target, argument) \
			: KERN_INVALID_ARGUMENT)

kern_return_t hv_task_trap(uint64_t index, uint64_t arg) {
	return HV_TRAP_DISPATCH(HV_TASK_TRAP, index, hv_get_task_target(), arg);
}

kern_return_t hv_thread_trap(uint64_t index, uint64_t arg) {
	return HV_TRAP_DISPATCH(HV_THREAD_TRAP, index, hv_get_thread_target(), arg);
}