banan-os/kernel/kernel/FS/USTARModule.cpp

#include <BAN/ScopeGuard.h>
#include <kernel/FS/USTARModule.h>

#include <tar.h>

namespace Kernel
{

	bool is_ustar_boot_module(const BootModule& module)
	{
		if (module.start % PAGE_SIZE)
		{
			dprintln("ignoring non-page-aligned module");
			return false;
		}

		if (module.size < 512)
			return false;

		bool has_ustar_signature;
		PageTable::with_fast_page(module.start, [&] {
			has_ustar_signature = memcmp(PageTable::fast_page_as_ptr(257), "ustar", 5) == 0;
		});

		return has_ustar_signature;
	}

	BAN::ErrorOr<void> unpack_boot_module_into_filesystem(BAN::RefPtr<FileSystem> filesystem, const BootModule& module)
	{
		ASSERT(is_ustar_boot_module(module));

		auto root_inode = filesystem->root_inode();

		uint8_t* temp_page = static_cast<uint8_t*>(kmalloc(PAGE_SIZE));
		if (temp_page == nullptr)
			return BAN::Error::from_errno(ENOMEM);
		BAN::ScopeGuard _([temp_page] { kfree(temp_page); });

		size_t offset = 0;
		while (offset + 512 <= module.size)
		{
			size_t file_size = 0;
			mode_t file_mode = 0;
			uid_t file_uid = 0;
			gid_t file_gid = 0;
			uint8_t file_type = 0;
			char file_path[100 + 1 + 155 + 1] {};

			PageTable::with_fast_page((module.start + offset) & PAGE_ADDR_MASK, [&] {
				const size_t page_off = offset % PAGE_SIZE;

				const auto parse_octal =
					[page_off](size_t offset, size_t length) -> size_t
					{
						size_t result = 0;
						for (size_t i = 0; i < length; i++)
						{
							const char ch = PageTable::fast_page_as<char>(page_off + offset + i);
							if (ch == '\0')
								break;
							result = (result * 8) + (ch - '0');
						}
						return result;
					};

				if (memcmp(PageTable::fast_page_as_ptr(page_off + 257), "ustar", 5)) {
					file_size = SIZE_MAX;
					return;
				}

				memcpy(file_path, PageTable::fast_page_as_ptr(page_off + 345), 155);
				const size_t prefix_len = strlen(file_path);
				file_path[prefix_len] = '/';
				memcpy(file_path + prefix_len + 1, PageTable::fast_page_as_ptr(page_off), 100);

				file_mode = parse_octal(100, 8);
				file_uid  = parse_octal(108, 8);
				file_gid  = parse_octal(116, 8);
				file_size = parse_octal(124, 12);
				file_type = PageTable::fast_page_as<char>(page_off + 156);
			});

			if (file_size == SIZE_MAX)
				break;
			if (offset + 512 + file_size > module.size)
				break;

			auto parent_inode = filesystem->root_inode();

			auto file_path_parts = TRY(BAN::StringView(file_path).split('/'));
			for (size_t i = 0; i < file_path_parts.size() - 1; i++)
				parent_inode = TRY(parent_inode->find_inode(file_path_parts[i]));

			switch (file_type)
			{
				case REGTYPE:
				case AREGTYPE: file_mode |= Inode::Mode::IFREG; break;
				case LNKTYPE:                                   break;
				case SYMTYPE:  file_mode |= Inode::Mode::IFLNK; break;
				case CHRTYPE:  file_mode |= Inode::Mode::IFCHR; break;
				case BLKTYPE:  file_mode |= Inode::Mode::IFBLK; break;
				case DIRTYPE:  file_mode |= Inode::Mode::IFDIR; break;
				case FIFOTYPE: file_mode |= Inode::Mode::IFIFO; break;
				default:
					ASSERT_NOT_REACHED();
			}

			auto file_name_sv = file_path_parts.back();

			if (file_type == DIRTYPE)
			{
				TRY(parent_inode->create_directory(file_name_sv, file_mode, file_uid, file_gid));
			}
			else if (file_type == LNKTYPE)
			{
				dwarnln("TODO: hardlink");
			}
			else if (file_type == SYMTYPE)
			{
				TRY(parent_inode->create_file(file_name_sv, file_mode, file_uid, file_gid));

				char link_target[101] {};
				const paddr_t paddr = module.start + offset;
				PageTable::with_fast_page(paddr & PAGE_ADDR_MASK, [&] {
					memcpy(link_target, PageTable::fast_page_as_ptr((paddr % PAGE_SIZE) + 157), 100);
				});

				if (link_target[0])
				{
					auto inode = TRY(parent_inode->find_inode(file_name_sv));
					TRY(inode->set_link_target(link_target));
				}
			}
			else
			{
				TRY(parent_inode->create_file(file_name_sv, file_mode, file_uid, file_gid));

				if (file_size)
				{
					auto inode = TRY(parent_inode->find_inode(file_name_sv));

					size_t nwritten = 0;
					while (nwritten < file_size)
					{
						const paddr_t paddr = module.start + offset + 512 + nwritten;
						PageTable::with_fast_page(paddr & PAGE_ADDR_MASK, [&] {
							memcpy(temp_page, PageTable::fast_page_as_ptr(), PAGE_SIZE);
						});

						const size_t page_off = paddr % PAGE_SIZE;
						const size_t to_write = BAN::Math::min(file_size - nwritten, PAGE_SIZE - page_off);
						TRY(inode->write(nwritten, { temp_page + page_off, to_write }));
						nwritten += to_write;
					}
				}
			}

			offset += 512 + file_size;
			if (auto rem = offset % 512)
				offset += 512 - rem;
		}

		return {};
	}

}