banan-os/kernel/kernel/APIC.cpp

#include <BAN/ScopeGuard.h>
#include <kernel/Debug.h>
#include <kernel/ACPI.h>
#include <kernel/APIC.h>
#include <kernel/CPUID.h>
#include <kernel/IDT.h>
#include <kernel/Memory/PageTable.h>

#include <string.h>

#define LAPIC_EIO_REG		0xB0
#define LAPIC_SIV_REG		0xF0
#define LAPIC_IS_REG		0x100

#define IOAPIC_MAX_REDIRS	0x01
#define IOAPIC_REDIRS		0x10

#define DEBUG_PRINT_PROCESSORS 0

// https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#multiple-apic-description-table-madt-format

struct MADT : public Kernel::ACPI::SDTHeader
{
	uint32_t local_apic;
	uint32_t flags;
} __attribute__((packed));

struct MADTEntry
{
	uint8_t type;
	uint8_t length;
	union
	{
		struct
		{
			uint8_t acpi_processor_id;
			uint8_t apic_id;
			uint32_t flags;
		} __attribute__((packed)) entry0;
		struct
		{
			uint8_t ioapic_id;
			uint8_t reserved;
			uint32_t ioapic_address;
			uint32_t gsi_base;
		} __attribute__((packed)) entry1;
		struct
		{
			uint8_t bus_source;
			uint8_t irq_source;
			uint32_t gsi;
			uint16_t flags;
		} __attribute__((packed)) entry2;
		struct
		{
			uint16_t reserved;
			uint64_t address;
		} __attribute__((packed)) entry5;
	};
} __attribute__((packed));

union RedirectionEntry
{
	struct
	{
		uint64_t vector				: 8;
		uint64_t delivery_mode		: 3;
		uint64_t destination_mode	: 1;
		uint64_t delivery_status	: 1;
		uint64_t pin_polarity		: 1;
		uint64_t remote_irr			: 1;
		uint64_t trigger_mode		: 1;
		uint64_t mask				: 1;
		uint64_t reserved			: 39;
		uint64_t destination		: 8;
	};
	struct
	{
		uint32_t lo_dword;
		uint32_t hi_dword;
	};
};

using namespace Kernel;

APIC* APIC::create()
{
	uint32_t ecx, edx;
	CPUID::get_features(ecx, edx);
	if (!(edx & CPUID::Features::EDX_APIC))
	{
		dprintln("Local APIC is not available");
		return nullptr;
	}

	const MADT* madt = (const MADT*)Kernel::ACPI::get().get_header("APIC");
	if (madt == nullptr)
	{
		dprintln("Could not find MADT header");
		return nullptr;
	}

	APIC* apic = new APIC;
	apic->m_local_apic = madt->local_apic;
	for (uint32_t i = 0x00; i <= 0xFF; i++)
		apic->m_irq_overrides[i] = i;

	uintptr_t madt_entry_addr = (uintptr_t)madt + sizeof(MADT);
	while (madt_entry_addr < (uintptr_t)madt + madt->length)
	{
		const MADTEntry* entry = (const MADTEntry*)madt_entry_addr;
		switch (entry->type)
		{
			case 0:
				Processor processor;
				processor.processor_id	= entry->entry0.acpi_processor_id;
				processor.apic_id		= entry->entry0.apic_id;
				processor.flags			= entry->entry0.flags & 0x03;
				MUST(apic->m_processors.push_back(processor));
				break;
			case 1:
				IOAPIC ioapic;
				ioapic.id			= entry->entry1.ioapic_id;
				ioapic.address		= entry->entry1.ioapic_address;
				ioapic.gsi_base		= entry->entry1.gsi_base;
				ioapic.max_redirs	= 0;
				MUST(apic->m_io_apics.push_back(ioapic));
				break;
			case 2:
				apic->m_irq_overrides[entry->entry2.irq_source] = entry->entry2.gsi;
				break;
			case 5:
				apic->m_local_apic = entry->entry5.address;
				break;
			default:
				dprintln("Unhandled madt entry, type {}", entry->type);
				break;
		}
		madt_entry_addr += entry->length;
	}

	if (apic->m_local_apic == 0 || apic->m_io_apics.empty())
	{
		dprintln("MADT did not provide necessary information");
		delete apic;
		return nullptr;
	}

	PageTable::kernel().identity_map_page(apic->m_local_apic, PageTable::Flags::ReadWrite | PageTable::Flags::Present);
	for (auto& io_apic : apic->m_io_apics)
	{
		PageTable::kernel().identity_map_page(io_apic.address, PageTable::Flags::ReadWrite | PageTable::Flags::Present);
		io_apic.max_redirs = io_apic.read(IOAPIC_MAX_REDIRS);
	}

	// Mask all interrupts
	uint32_t sivr = apic->read_from_local_apic(LAPIC_SIV_REG);
	apic->write_to_local_apic(LAPIC_SIV_REG, sivr | 0x1FF);

#if DEBUG_PRINT_PROCESSORS
	for (auto& processor : apic->m_processors)
	{
		dprintln("Processor{}", processor.processor_id);
		dprintln("  lapic id: {}", processor.apic_id);
		dprintln("  status:   {}", (processor.flags & Processor::Flags::Enabled) ? "enabled" : (processor.flags & Processor::Flags::OnlineCapable) ? "can be enabled" : "disabled");
	}
#endif

	return apic;
}

uint32_t APIC::read_from_local_apic(ptrdiff_t offset)
{
	return *(uint32_t*)(m_local_apic + offset);
}

void APIC::write_to_local_apic(ptrdiff_t offset, uint32_t data)
{
	*(uint32_t*)(m_local_apic + offset) = data;
}

uint32_t APIC::IOAPIC::read(uint8_t offset)
{
	volatile uint32_t* ioapic = (volatile uint32_t*)address;
	ioapic[0] = offset;
	return ioapic[4];
}

void APIC::IOAPIC::write(uint8_t offset, uint32_t data)
{
	volatile uint32_t* ioapic = (volatile uint32_t*)address;
	ioapic[0] = offset;
	ioapic[4] = data;
}

void APIC::eoi(uint8_t)
{
	write_to_local_apic(LAPIC_EIO_REG, 0);	
}

void APIC::enable_irq(uint8_t irq)
{
	uint32_t gsi = m_irq_overrides[irq];

	IOAPIC* ioapic = nullptr;
	for (IOAPIC& io : m_io_apics)
	{
		if (io.gsi_base <= gsi && gsi <= io.gsi_base + io.max_redirs)
		{
			ioapic = &io;
			break;
		}
	}
	ASSERT(ioapic);

	RedirectionEntry redir;
	redir.lo_dword = ioapic->read(IOAPIC_REDIRS + gsi * 2);
	redir.hi_dword = ioapic->read(IOAPIC_REDIRS + gsi * 2 + 1);

	redir.vector = IRQ_VECTOR_BASE + irq;
	redir.mask = 0;
	redir.destination = m_processors.front().apic_id;

	ioapic->write(IOAPIC_REDIRS + gsi * 2,		redir.lo_dword);
	ioapic->write(IOAPIC_REDIRS + gsi * 2 + 1,	redir.hi_dword);
}

bool APIC::is_in_service(uint8_t irq)
{
	uint32_t dword = (irq + IRQ_VECTOR_BASE) / 32;
	uint32_t bit = (irq + IRQ_VECTOR_BASE) % 32;

	uint32_t isr = read_from_local_apic(LAPIC_IS_REG + dword * 0x10);
	return isr & (1 << bit);
}