schedule.go

package main

import (
	"unsafe"
)

type domain struct {
	next *domain

	pid        uint32
	numThreads uint32
	nextTid    uint32

	Segments    SegmentList
	MemorySpace MemSpace

	runningThreads threadList
	blockedThreads threadList

	programName string
}

func (d *domain) AddThread(t *thread) {
	t.domain = d
	t.next = nil
	t.prev = nil
	d.runningThreads.Enqueue(t)
	t.tid = d.nextTid
	d.nextTid++
	d.numThreads++
}

func (d *domain) RemoveThread(t *thread) {
	if t.domain != d {
		return
	}
	if t.isBlocked {
		d.blockedThreads.Dequeue(t)
	} else {
		d.runningThreads.Dequeue(t)
	}
	t.isRemoved = true
	d.numThreads--
}

type stack struct {
	hi uintptr
	lo uintptr
}

type taskswitchbuf struct {
	sp uintptr
}

type thread struct {
	next *thread
	prev *thread

	domain      *domain
	tid         uint32
	userStack   stack
	kernelStack stack
	isRemoved   bool
	// Currently ignored '^^ I don't have to do it thanks to spurious wakeups
	isBlocked   bool
	waitAddress *uint32

	// flag that shows that this thread would be handled as a new process in linux
	isFork bool

	// Infos to stall a thread when switching
	info InterruptInfo
	regs RegisterState

	kernelInfo InterruptInfo
	kernelRegs RegisterState

	isKernelInterrupt    bool
	interruptedKernelEIP uintptr
	interruptedKernelESP uint32

	// TLS
	tlsSegments [GDT_ENTRIES]GdtEntry

	// fxsave and fxrstor need 512 bytes but 16 byte aligned
	// need space to force alignment if array not aligned
	fpOffset uintptr // should be between 0-15
	fpState  [512 + 16]byte
}

type threadList struct {
	thread *thread
}

func (l *threadList) Next() *thread {
	if l.thread == nil {
		return nil
	}
	l.thread = l.thread.next
	return l.thread
}

func (l *threadList) Enqueue(t *thread) {
	if l.thread == nil {
		l.thread = t
		t.next = t
		t.prev = t
	} else {
		t.next = l.thread
		t.prev = l.thread.prev
		l.thread.prev.next = t
		l.thread.prev = t
	}
}

func (l *threadList) Dequeue(t *thread) {
	if t == l.thread && t.next == t {
		l.thread = nil
	} else if t == l.thread {
		l.thread = t.next
	}
	t.prev.next = t.next
	t.next.prev = t.prev
	t.next = nil
	t.prev = nil
}

type domainList struct {
	head *domain
	tail *domain
}

func (l *domainList) Append(domain *domain) {
	if domain == nil {
		return
	}
	if l.head == nil {
		l.head = domain
		l.tail = l.head
		l.head.next = l.tail
	} else {
		domain.next = l.head
		l.tail.next = domain
		l.tail = domain
	}
	domain.pid = largestPid
	largestPid++
}

func (l *domainList) Remove(d *domain) {
	if d == l.head {
		if d == l.tail {
			l.head = nil
			l.tail = nil
		} else {
			l.head = d.next
			l.tail.next = l.head
		}
		return
	}
	for e := l.head; e.next != l.head; e = e.next {
		if e.next == d {
			e.next = d.next
			if d == l.tail {
				l.tail = e
			}
			break
		}
	}
}

var (
	currentThread  *thread    = &scheduleThread
	currentDomain  *domain    = nil
	allDomains     domainList = domainList{head: nil, tail: nil}
	largestPid     uint32     = 0x0
	kernelHlt      bool       = false
	scheduleThread thread     = thread{}
)

func backupFpRegs(buffer uintptr)
func restoreFpRegs(buffer uintptr)

func AddDomain(d *domain) {
	allDomains.Append(d)
	if ENABLE_DEBUG {
		kdebugln("Added new domain with pid ", d.pid)
	}
	if currentDomain == nil || currentThread == nil {
		currentDomain = allDomains.head
		currentThread = currentDomain.runningThreads.thread
	}
}

func ExitDomain(d *domain) {
	allDomains.Remove(d)

	if allDomains.head == nil {
		currentDomain = nil
	}

	// clean up memory
	scheduleStackArg(func(dom uintptr) {
		doma := (*domain)(unsafe.Pointer(dom))
		cleanUpDomain(doma)
	}, (uintptr)(unsafe.Pointer(d)))
}

// Execute on scheduleStack
func cleanUpDomain(d *domain) {
	// Clean up threads
	for cur := d.runningThreads.thread; d.runningThreads.thread != nil; cur = d.runningThreads.thread {
		//kdebugln("Clean up thread ", cur.tid)
		//kdebugln("t:", (uintptr)(unsafe.Pointer(cur)), " t.n:", (uintptr)(unsafe.Pointer(cur.next)), " t.p:", (uintptr)(unsafe.Pointer(cur.prev)))
		d.runningThreads.Dequeue(cur)
		cleanUpThread(cur)
	}
	for cur := d.blockedThreads.thread; d.blockedThreads.thread != nil; cur = d.blockedThreads.thread {
		cleanUpThread(cur)
		d.blockedThreads.Dequeue(cur)
	}
	// Clean allocated memory
	d.MemorySpace.FreeAllPages()

	// Clean up kernel resources
	if ENABLE_DEBUG {
		kdebugln("Allocated pages ", allocatedPages, " (out of", maxPages, ")")
	}
	Schedule()
	FreePage((uintptr)(unsafe.Pointer(d)))
}

// Execute on scheduleStack
func cleanUpThread(t *thread) {
	// TODO; Adjust when thread control block is no longer a single page
	threadPtr := (uintptr)(unsafe.Pointer(t))
	threadDomain := t.domain
	threadDomain.MemorySpace.UnmapPage(t.kernelStack.lo)
	threadDomain.MemorySpace.UnmapPage(threadPtr)
	if currentThread == t {
		currentThread = nil
	}
}

func ExitThread(t *thread) {
	if t.domain.numThreads <= 1 {
		// we're last thread
		ExitDomain(t.domain) // does not return
	}
	t.domain.RemoveThread(t)
	if ENABLE_DEBUG {
		kdebugln("Removing thread ", t.tid, " from domain ", t.domain.pid)
	}
	scheduleStackArg(func(threadPtr uintptr) {
		thread := (*thread)(unsafe.Pointer(threadPtr))
		cleanUpThread(thread)
		Schedule()
	}, (uintptr)(unsafe.Pointer(t)))
}

func BlockThread(t *thread) {
	t.isBlocked = true
	t.domain.runningThreads.Dequeue(t)
	t.domain.blockedThreads.Enqueue(t)
	PerformSchedule = true
}

func getESP() uintptr
func waitForInterrupt()

func Block() {
	waitForInterrupt()
}

func ResumeThread(t *thread) {
	t.isBlocked = false
	t.domain.blockedThreads.Dequeue(t)
	t.domain.runningThreads.Enqueue(t)
}

func Schedule() {
	if currentDomain == nil {
		kerrorln("No Domains to schedule")
		DisableInterrupts()
		Hlt()
	}
	//kdebug("Scheduling in ")
	//printTid(defaultLogWriter, currentThread)
	nextDomain := currentDomain.next
	newThread := nextDomain.runningThreads.Next()
	if newThread == nil {
		for newDomain := nextDomain.next; newDomain != nextDomain; newDomain = newDomain.next {
			newThread = newDomain.runningThreads.Next()
			if newThread != nil {
				break
			}
		}
	}
	//if currentThread.next == currentThread && currentThread.tid != 0{
	//    kernelPanic("Why no next?")
	//}
	//if newThread.tid == currentThread.tid && currentThread.tid != 0 {
	//    kernelPanic("Why only one thread?")
	//}
	//kprintln("next domain: ", nextDomain.pid)
	//kprintln("next thread: ", newThread.tid)
	//kprintln("domain threads: ", nextDomain.numThreads)

	if newThread == nil {
		if kernelHlt {
			// We are already stalling the kernel
			return
		}
		// All threads blocked or no threads exist anymore.
		kernelHlt = true
		PerformSchedule = false
		//currentThread = nil
		kernelPanic("test")
		return
	}

	kernelHlt = false
	currentDomain = nextDomain
	if newThread == currentThread {
		return
	}

	switchToThread(newThread)

	//kdebug("Now executing: ")
	//printTid(defaultLogWriter, currentThread)
}

func switchToThread(t *thread) {
	// Save state of current thread
	if currentThread != nil {
		addr := uintptr(unsafe.Pointer(&(currentThread.fpState)))
		offset := 16 - (addr % 16)
		currentThread.fpOffset = offset

		backupFpRegs(addr + offset)
	}

	// Load next thread
	//kdebugln("Switching to domain pid", currentDomain.pid, " and thread ", t.tid)
	currentThread = t

	addr := uintptr(unsafe.Pointer(&(currentThread.fpState)))
	offset := currentThread.fpOffset
	if offset != 0xffffffff {
		if (addr+offset)%16 != 0 {
			kprintln(addr, " ", offset)
			kernelPanic("Cannot restore FP state. Not aligned. Did array move?")
		}
		restoreFpRegs(addr + offset)
	}

	// Load TLS
	FlushTlsTable(t.tlsSegments[:])
}

func InitScheduling() {

}