banan-os/kernel/kernel/ACPI.cpp

#include <BAN/ScopeGuard.h>
#include <BAN/StringView.h>
#include <kernel/ACPI.h>
#include <kernel/Memory/MMU.h>

#define RSPD_SIZE	20
#define RSPDv2_SIZE	36

namespace Kernel
{

	struct RSDP
	{
		uint8_t signature[8];
		uint8_t checksum;
		uint8_t oemid[6];
		uint8_t revision;
		uint32_t rsdt_address;

		// only in revision >= 2
		uint32_t length;
		uint64_t xsdt_address;
		uint8_t extended_checksum;
		uint8_t reserved[3];
	};

	struct RSDT : public ACPI::SDTHeader
	{
		uint32_t entries[];
	} __attribute__((packed));

	struct XSDT : public ACPI::SDTHeader
	{
		uint64_t entries[];
	} __attribute__((packed));

	static ACPI* s_instance = nullptr;

	BAN::ErrorOr<void> ACPI::initialize()
	{
		ASSERT(s_instance == nullptr);
		s_instance = new ACPI;
		if (s_instance == nullptr)
			return BAN::Error::from_errno(ENOMEM);
		TRY(s_instance->initialize_impl());
		return {};
	}

	ACPI& ACPI::get()
	{
		ASSERT(s_instance != nullptr);
		return *s_instance;
	}

	static bool is_rsdp(uintptr_t rsdp_addr)
	{
		const RSDP* rsdp = (const RSDP*)rsdp_addr;

		if (memcmp(rsdp->signature, "RSD PTR ", 8) != 0)
			return false;

		{
			uint8_t checksum = 0;
			for (uint32_t i = 0; i < RSPD_SIZE; i++)
				checksum += ((const uint8_t*)rsdp)[i];
			if (checksum != 0)
				return false;
		}

		if (rsdp->revision == 2)
		{
			uint8_t checksum = 0;
			for (uint32_t i = 0; i < RSPDv2_SIZE; i++)
				checksum += ((const uint8_t*)rsdp)[i];
			if (checksum != 0)
				return false;
		}

		return true;
	}

	static const RSDP* locate_rsdp()
	{
		// Look in main BIOS area below 1 MB
		for (uintptr_t addr = 0x000E0000; addr < 0x000FFFFF; addr += 16)
			if (is_rsdp(addr))
				return (const RSDP*)addr;
		return nullptr;
	}

	static bool is_valid_std_header(const ACPI::SDTHeader* header)
	{
		uint8_t sum = 0;
		for (uint32_t i = 0; i < header->length; i++)
			sum += ((uint8_t*)header)[i];
		return sum == 0;
	}

	BAN::ErrorOr<void> ACPI::initialize_impl()
	{
		const RSDP* rsdp = locate_rsdp();
		if (rsdp == nullptr)
			return BAN::Error::from_error_code(ErrorCode::ACPI_NoRootSDT);

		if (rsdp->revision >= 2)
		{
			const XSDT* xsdt = (const XSDT*)rsdp->xsdt_address;
			MMU::get().identity_map_page((uintptr_t)xsdt, MMU::Flags::Present);
			BAN::ScopeGuard _([xsdt] { MMU::get().unmap_page((uintptr_t)xsdt); });

			if (memcmp(xsdt->signature, "XSDT", 4) != 0)
				return BAN::Error::from_error_code(ErrorCode::ACPI_RootInvalid);
			if (!is_valid_std_header(xsdt))
				return BAN::Error::from_error_code(ErrorCode::ACPI_RootInvalid);

			m_header_table = (uintptr_t)xsdt->entries;
			m_entry_size = 8;
			m_entry_count = (xsdt->length - sizeof(SDTHeader)) / 8;
		}
		else
		{
			const RSDT* rsdt = (const RSDT*)(uintptr_t)rsdp->rsdt_address;
			MMU::get().identity_map_page((uintptr_t)rsdt, MMU::Flags::Present);
			BAN::ScopeGuard _([rsdt] { MMU::get().unmap_page((uintptr_t)rsdt); });

			if (memcmp(rsdt->signature, "RSDT", 4) != 0)
				return BAN::Error::from_error_code(ErrorCode::ACPI_RootInvalid);
			if (!is_valid_std_header(rsdt))
				return BAN::Error::from_error_code(ErrorCode::ACPI_RootInvalid);

			m_header_table = (uintptr_t)rsdt->entries;
			m_entry_size = 4;
			m_entry_count = (rsdt->length - sizeof(SDTHeader)) / 4;
		}

		MMU::get().identity_map_range(m_header_table, m_entry_count * m_entry_size, MMU::Flags::Present);

		for (uint32_t i = 0; i < m_entry_count; i++)
		{
			auto* header = get_header_from_index(i);
			MMU::get().identity_map_page((uintptr_t)header, MMU::Flags::Present);
			MMU::get().identity_map_range((uintptr_t)header, header->length, MMU::Flags::Present);
		}

		return {};
	}

	const ACPI::SDTHeader* ACPI::get_header(const char signature[4])
	{
		for (uint32_t i = 0; i < m_entry_count; i++)
		{
			const SDTHeader* header = get_header_from_index(i);
			if (is_valid_std_header(header) && memcmp(header->signature, signature, 4) == 0)
				return header;
		}
		return nullptr;
	}

	const ACPI::SDTHeader* ACPI::get_header_from_index(size_t index)
	{
		ASSERT(index < m_entry_count);
		ASSERT(m_entry_size == 4 || m_entry_size == 8);

		uintptr_t header_address = (m_entry_size == 4) ? ((uint32_t*)m_header_table)[index] : ((uint64_t*)m_header_table)[index];
		return (SDTHeader*)header_address;
	}

}