/*******************************************************************************

    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012.

    This file is part of Sortix.

    Sortix is free software: you can redistribute it and/or modify it under the
    terms of the GNU General Public License as published by the Free Software
    Foundation, either version 3 of the License, or (at your option) any later
    version.

    Sortix 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 General Public License for more
    details.

    You should have received a copy of the GNU General Public License along with
    Sortix. If not, see <http://www.gnu.org/licenses/>.

    thread.cpp
    Describes a thread belonging to a process.

*******************************************************************************/

#include <sortix/kernel/platform.h>
#include <sortix/kernel/kthread.h>
#include <sortix/kernel/memorymanagement.h>
#include <sortix/kernel/syscall.h>
#include <sortix/kernel/interrupt.h>
#include <sortix/kernel/time.h>
#include <sortix/kernel/scheduler.h>
#include <sortix/kernel/process.h>
#include <sortix/kernel/thread.h>

#include <sortix/mman.h>
#include <sortix/signal.h>

#include <assert.h>
#include <errno.h>
#include <string.h>

namespace Sortix
{
	Thread::Thread()
	{
		id = 0; // TODO: Make a thread id.
		process = NULL;
		prevsibling = NULL;
		nextsibling = NULL;
		schedulerlistprev = NULL;
		schedulerlistnext = NULL;
		state = NONE;
		memset(&registers, 0, sizeof(registers));
		stackpos = 0;
		stacksize = 0;
		kernelstackpos = 0;
		kernelstacksize = 0;
		kernelstackmalloced = false;
		currentsignal = 0;
		siglevel = 0;
		sighandler = NULL;
		terminated = false;
		fpuinitialized = false;
		// If malloc isn't 16-byte aligned, then we can't rely on offsets in
		// our own class, so we'll just fix ourselves nicely up.
		unsigned long fpuaddr = ((unsigned long) fpuenv+16UL) & ~(16UL-1UL);
		fpuenvaligned = (uint8_t*) fpuaddr;
	}

	Thread::~Thread()
	{
		if ( process )
			process->OnThreadDestruction(this);
		assert(CurrentThread() != this);
		if ( kernelstackmalloced )
			delete[] (uint8_t*) kernelstackpos;
		terminated = true;
	}

	addr_t Thread::SwitchAddressSpace(addr_t newaddrspace)
	{
		bool wasenabled = Interrupt::SetEnabled(false);
		addr_t result = addrspace;
		addrspace = newaddrspace;
		Memory::SwitchAddressSpace(newaddrspace);
		Interrupt::SetEnabled(wasenabled);
		return result;
	}

	// Last chance to clean up user-space things before this thread dies.
	void Thread::LastPrayer()
	{
		Memory::UnmapRange(stackpos, stacksize);
		Memory::Flush();
	}

	extern "C" void BootstrapKernelThread(void* user, ThreadEntry entry)
	{
		entry(user);
		kthread_exit();
	}

	Thread* CreateKernelThread(Process* process, CPU::InterruptRegisters* regs)
	{
		assert(process && regs && process->addrspace);
		Thread* thread = new Thread;
		if ( !thread ) { return NULL; }

		thread->addrspace = process->addrspace;
		thread->SaveRegisters(regs);

		kthread_mutex_lock(&process->threadlock);

		// Create the family tree.
		thread->process = process;
		Thread* firsty = process->firstthread;
		if ( firsty ) { firsty->prevsibling = thread; }
		thread->nextsibling = firsty;
		process->firstthread = thread;

		kthread_mutex_unlock(&process->threadlock);

		return thread;
	}

	Thread* CreateKernelThread(Process* process, ThreadEntry entry, void* user,
	                           size_t stacksize)
	{
		const size_t DEFAULT_KERNEL_STACK_SIZE = 64*8192UL;
		if ( !stacksize ) { stacksize = DEFAULT_KERNEL_STACK_SIZE; }
		uint8_t* stack = new uint8_t[stacksize];
		if ( !stack ) { return NULL; }

		CPU::InterruptRegisters regs;
		SetupKernelThreadRegs(&regs, entry, user, (addr_t) stack, stacksize);

		Thread* thread = CreateKernelThread(process, &regs);
		if ( !thread ) { delete[] stack; }

		thread->kernelstackpos = (addr_t) stack;
		thread->kernelstacksize = stacksize;
		thread->kernelstackmalloced = true;

		return thread;
	}

	Thread* CreateKernelThread(ThreadEntry entry, void* user, size_t stacksize)
	{
		return CreateKernelThread(CurrentProcess(), entry, user, stacksize);
	}

	void StartKernelThread(Thread* thread)
	{
		Scheduler::SetThreadState(thread, ThreadState::RUNNABLE);
	}

	Thread* RunKernelThread(Process* process, CPU::InterruptRegisters* regs)
	{
		Thread* thread = CreateKernelThread(process, regs);
		if ( !thread ) { return NULL; }
		StartKernelThread(thread);
		return thread;
	}

	Thread* RunKernelThread(Process* process, ThreadEntry entry, void* user,
	                        size_t stacksize)
	{
		Thread* thread = CreateKernelThread(process, entry, user, stacksize);
		if ( !thread ) { return NULL; }
		StartKernelThread(thread);
		return thread;
	}

	Thread* RunKernelThread(ThreadEntry entry, void* user, size_t stacksize)
	{
		Thread* thread = CreateKernelThread(entry, user, stacksize);
		if ( !thread ) { return NULL; }
		StartKernelThread(thread);
		return thread;
	}

	void Thread::HandleSignal(CPU::InterruptRegisters* regs)
	{
		int signum = signalqueue.Pop(currentsignal);
		regs->signal_pending = 0;

		if ( !signum )
			return;

		if ( !sighandler )
			return;

		if ( SIG_NUM_LEVELS <= siglevel )
			return;

		// Signals can't return to kernel mode because the kernel stack may have
		// been overwritten by a system call during the signal handler. Correct
		// the return state so it returns to userspace and not the kernel.
		if ( !regs->InUserspace() )
			HandleSignalFixupRegsCPU(regs);

		if ( signum == SIGKILL )
		{
			// We need to run the OnSigKill method here with interrupts enabled
			// and on our own stack. But this method this may have been called
			// from the scheduler on any stack, so we need to do a little
			// bootstrap and switch to our own stack.
			GotoOnSigKill(regs);
			return;
		}

		int level = siglevel++;
		signums[level] = currentsignal = signum;
		memcpy(sigregs + level, regs, sizeof(*regs));

		HandleSignalCPU(regs);
	}

	void Thread::HandleSigreturn(CPU::InterruptRegisters* regs)
	{
		if ( !siglevel )
			return;

		siglevel--;

		currentsignal = siglevel ? signums[siglevel-1] : 0;
		memcpy(regs, sigregs + siglevel, sizeof(*regs));
		regs->signal_pending = 0;

		// Check if a more important signal is pending.
		HandleSignal(regs);
	}

	extern "C" void Thread__OnSigKill(Thread* thread)
	{
		thread->OnSigKill();
	}

	void Thread::OnSigKill()
	{
		LastPrayer();
		kthread_exit();
	}

	int SysRegisterSignalHandler(sighandler_t sighandler)
	{
		CurrentThread()->sighandler = sighandler;
		return 0;
	}

	void Thread::SetHavePendingSignals()
	{
		// TODO: This doesn't really work if Interrupt::IsCPUInterrupted()!
		if ( CurrentThread() == this )
			asm_signal_is_pending = 1;
		else
			registers.signal_pending = 1;
	}

	bool Thread::DeliverSignal(int signum)
	{
		if ( signum <= 0 || 128 <= signum ) { errno = EINVAL; return false; }

		bool wasenabled = Interrupt::SetEnabled(false);
		signalqueue.Push(signum);
		SetHavePendingSignals();
		Interrupt::SetEnabled(wasenabled);

		return true;
	}

	int SysKill(pid_t pid, int signum)
	{
		// Protect the system idle process.
		if ( !pid ) { errno = EPERM; return -1; }

		// If we kill our own process, deliver the signal to this thread.
		Thread* currentthread = CurrentThread();
		if ( currentthread->process->pid == pid )
				return currentthread->DeliverSignal(signum) ? 0 : -1;

		// TODO: Race condition: The process could be deleted while we use it.
		Process* process = Process::Get(pid);
		if ( !process ) { errno = ESRCH; return -1; }

		// TODO: Protect init?
		// TODO: Check for permission.
		// TODO: Check for zombies.

		return process->DeliverSignal(signum) ? 0 : -1;
	}

	int SysRaise(int signum)
	{
		return CurrentThread()->DeliverSignal(signum) ? 0 : -1;
	}

	void Thread::Init()
	{
		Syscall::Register(SYSCALL_KILL, (void*) SysKill);
		Syscall::Register(SYSCALL_RAISE, (void*) SysRaise);
		Syscall::Register(SYSCALL_REGISTER_SIGNAL_HANDLER, (void*) SysRegisterSignalHandler);
	}
}