#pypp 0
// Also declare things which only work during kernel init.
#define INIT
#define ARCH
#include "kernel.hh"
#include "elf.h"

static void init_idle ():
	// initialize idle task as if it is currently running.
	idle.prev_obj = NULL
	idle.next_obj = NULL
	idle.prev = NULL
	idle.next = NULL
	idle.schedule_prev = NULL
	idle.schedule_next = NULL
	idle.address_space = &idle_memory
	// initialize idle_memory.
	idle_memory.prev_obj = NULL
	idle_memory.next_obj = NULL
	idle_memory.prev = NULL
	idle_memory.next = NULL
	idle_memory.pages = &idle_page
	idle_memory.threads = &idle
	idle_memory.memories = NULL
	idle_memory.limit = 0
	idle_memory.used = 0
	idle_memory.arch.directory = (unsigned **)0x80000000
	idle_memory.arch.asid = 0
	// initialize idle_page
	idle_page.prev_obj = NULL
	idle_page.next_obj = NULL
	idle_page.prev = NULL
	idle_page.next = NULL
	idle_page.physical = 0x80000000
	current = &idle

static void init_cp0 ():
	// Set timer to a defined value
	cp0_set (CP0_COMPARE, 1000000)
	// Reset timer
	cp0_set0 (CP0_COUNT)
	// Use the interrupt vector for interrupts
	cp0_set (CP0_CAUSE, 1 << 23)

	// clear the tlb, hardwire page 0 to 0xffffffff
	// and soft-wire it to (0x294 << 20) + (0x290 << 10)
	// (for the idle task).

	cp0_set (CP0_WIRED, 1)
	cp0_set0 (CP0_PAGE_MASK)
	cp0_set0 (CP0_ENTRY_LO0)
	cp0_set0 (CP0_ENTRY_LO1)
	// Get number of tlb entries (is 31).
	unsigned num
	cp0_get (CP0_CONFIG1, num)
	num >>= 25
	num &= 0x3f
	// Clear the tlb.
	for unsigned i = 1; i <= num; ++i:
		// with asid 0, no page faults will be triggered, so it's safe to map memory anywhere.
		cp0_set (CP0_ENTRY_HI, 0x2000 * i)
		cp0_set (CP0_INDEX, i)
		// write the data.
		__asm__ volatile ("tlbwi")
	// Fill the upper page in kseg3.
	cp0_set (CP0_ENTRY_HI, 0xffffe000)
	cp0_set (CP0_ENTRY_LO0, 0x1d)
	cp0_set (CP0_ENTRY_LO1, 0x1f)
	cp0_set0 (CP0_INDEX)
	__asm__ volatile ("tlbwi")
	// Fill the idle task's page in useg.  Set it to non-cachable.
	cp0_set (CP0_ENTRY_HI, 0x284a0000)
	cp0_set (CP0_ENTRY_LO0, 0x16)
	cp0_set (CP0_ENTRY_LO1, 0x14)
	__asm__ volatile ("tlbwr")
	// Allow eret to be used to jump to the idle task.
	cp0_set (CP0_EPC, 0x284a0288)
	// Wait with initializing the status register until the last moment, so that
	// exceptions in the bootup code will fill EPC and friends.

static void init_threads ():
	Thread *previous = NULL
	first_scheduled = NULL
	for unsigned i = 0; i < NUM_THREADS; ++i:
		Memory *mem = top_memory.alloc_memory ()
		Thread *thread = mem->alloc_thread ()
		Page **pages = (Page **)mem->zalloc ()
		Elf32_Ehdr *header = (Elf32_Ehdr *)thread_start[i]
		for unsigned j = 0; j < SELFMAG; ++j:
			if header->e_ident[j] != ELFMAG[j]:
				panic (i * 0x1000 + j, "invalid ELF magic")
		if header->e_ident[EI_CLASS] != ELFCLASS32:
			panic (i * 0x1000 + EI_CLASS, "invalid ELF class")
		if header->e_ident[EI_DATA] != ELFDATA2LSB:
			panic (i * 0x1000 + EI_DATA, "invalid ELF data")
		if header->e_ident[EI_VERSION] != EV_CURRENT:
			panic (i * 0x1000 + EI_VERSION, "invalid ELF version")
		if header->e_type != ET_EXEC:
			panic (i * 0x1000 + 0x10, "invalid ELF type")
		if header->e_machine != EM_MIPS_RS3_LE && header->e_machine != EM_MIPS:
			panic (i * 0x1000 + 0x12, "invalid ELF machine")
		thread->pc = header->e_entry
		thread->sp = 0x80000000
		for unsigned section = 0; section < header->e_shnum; ++section:
			Elf32_Shdr *shdr = (Elf32_Shdr *)(thread_start[i] + header->e_shoff + section * header->e_shentsize)
			if !(shdr->sh_flags & SHF_ALLOC):
				continue
			bool writable = shdr->sh_flags & SHF_WRITE
			//bool executable = shdr->sh_flags & SHF_EXEC_INSTR
			if shdr->sh_type != SHT_NOBITS:
				for unsigned p = (shdr->sh_addr & PAGE_MASK); p <= ((shdr->sh_addr + shdr->sh_size - 1) & PAGE_MASK); p += PAGE_SIZE:
					unsigned idx = (p - (shdr->sh_addr & PAGE_MASK)) >> PAGE_BITS
					if !pages[idx]:
						pages[idx] = mem->alloc_page ()
						pages[idx]->physical = thread_start[i] + (idx << PAGE_BITS)
						++top_memory.limit
					if !mem->map (pages[idx], p, writable):
						panic (0x22446688, "unable to map initial page")
			else:
				for unsigned p = (shdr->sh_addr & PAGE_MASK); p <= ((shdr->sh_addr + shdr->sh_size - 1) & PAGE_MASK); p += PAGE_SIZE:
					Page *page = mem->get_mapping (p)
					if !page:
						page = mem->alloc_page ()
						if !page:
							panic (0x00220022, "out of memory")
						page->physical = mem->zalloc ()
						if !page->physical || !mem->map (page, p, true):
							panic (0x33557799, "unable to map initial bss page")
					else:
						for unsigned a = p; a < p + PAGE_SIZE; a += 4:
							if a >= shdr->sh_addr + shdr->sh_size:
								break
							if a < shdr->sh_addr:
								continue
							((unsigned *)page->physical)[(a & ~PAGE_MASK) >> 2] = 0
		for unsigned p = 0; p <= ((thread_start[i + 1] - thread_start[i] - 1) >> PAGE_BITS); ++p:
			// TODO: this also skips pages where new space is allocated.
			if pages[p]:
				continue
			++top_memory.limit
			top_memory.zfree (thread_start[i] + (p << PAGE_BITS))
		Page *stackpage = mem->alloc_page ()
		stackpage->physical = mem->zalloc ()
		if !stackpage || !mem->map (stackpage, 0x7ffff000, true):
			panic (0x13151719, "unable to map initial stack page")
		thread->arch.a0 = (unsigned)mem->alloc_receiver ()
		thread->arch.a1 = (unsigned)&top_memory
		thread->arch.a2 = (unsigned)mem
		Capability *admin = mem->alloc_capability ((Receiver *)(CAPTYPE_ADMIN | ~PAGE_MASK), &mem->capabilities, ~0)
		thread->arch.a3 = (unsigned)admin
		mem->pfree ((unsigned)pages)
		thread->schedule_next = NULL
		thread->schedule_prev = previous
		if previous:
			previous->schedule_next = thread
		else:
			first_scheduled = thread
		previous = thread

// Initialize the kernel, finish by falling into the idle task.
extern unsigned _end
void init ():
	// Disable interrupts and set interrupt vectors to normal.
	cp0_set0 (CP0_STATUS)
	// Initialize kernel variables to empty.
	sleepers = NULL
	runners = NULL
	zero_pages = NULL
	// Fill junk pages with all memory not currently used.
	junk_pages = (FreePage *)(((unsigned)&_end + (1 << 12) - 1) & ~((1 << 12) - 1))
	FreePage *p, *next
	unsigned count = 1
	for p = junk_pages, next = p; (unsigned)next - 0x80000000 < (1 << 27); p = next, next = (FreePage *)((unsigned)p + (1 << 12)):
		p->next = next
		++count
	p->next = NULL
	// initialize system control coprocessor.
	init_cp0 ()
	// initialize everything about the idle task.
	init_idle ()
	// initialize top_memory.
	top_memory.prev_obj = NULL
	top_memory.next_obj = NULL
	top_memory.prev = NULL
	top_memory.next = NULL
	top_memory.parent = NULL
	top_memory.pages = NULL
	top_memory.threads = NULL
	top_memory.memories = NULL
	top_memory.limit = count
	top_memory.used = 0
	top_memory.arch.directory = NULL
	top_memory.arch.asid = 0
	
	init_threads ()

	// Enable all interrupts and say we're handling an exception.
	// Since we're going to enter the idle task, allow access to cp0.
	cp0_set (CP0_STATUS, 0x1000ff13)

	// Done; return to user space (the idle task).
	__asm__ volatile ("eret")