Bootloader: Add .data section

bootloader/bios/a20_line.S

@@ -156,6 +156,8 @@ enable_a20:
 	popw %ax
 	ret
 
+.section .data
+
 a20_line_disabled_msg:
 	.asciz "A20 line disabled. Trying to enable it"
 

bootloader/bios/boot.S

@@ -143,6 +143,8 @@ enter_unreal_mode:
 
 	ret
 
+.section .data
+
 hello_msg:
 	.asciz "This is banan-os bootloader"
 

bootloader/bios/command_line.S

@@ -74,6 +74,8 @@ read_user_command_line:
 	ret
 
 
+.section .data
+
 command_line_enter_msg:
 	.asciz "cmdline: "
 

bootloader/bios/disk.S

@@ -470,6 +470,7 @@ print_root_partition_info:
 	popw %ax
 	ret
 
+.section .data
 
 # These will be patched during bootloader installation
 root_disk_guid:

bootloader/bios/elf.S

@@ -196,6 +196,7 @@ elf_read_kernel_to_memory:
 	movw $elf_read_kernel_to_memory_not_loadable_header_msg, %si
 	jmp print_and_halt
 
+.section .data
 
 elf_validate_file_header_invalid_magic_msg:
 	.asciz "ELF: file has invalid ELF magic"

bootloader/bios/ext2.S

@@ -692,6 +692,7 @@ ext2_find_kernel:
 	movw $ext2_kernel_not_reg_msg, %si
 	jmp print_and_halt
 
+.section .data
 
 kernel_path:
 	.short kernel_path1
@@ -704,7 +705,6 @@ kernel_path2:
 	.short 15
 	.asciz "banan-os.kernel"
 
-
 root_partition_does_not_fit_ext2_filesystem_msg:
 	.asciz "Root partition is too small to contain ext2 filesystem"
 root_partition_has_invalid_ext2_magic_msg:

bootloader/bios/framebuffer.S

@@ -185,6 +185,7 @@ vesa_set_video_mode:
 	popw %ax
 	ret
 
+.section .data
 
 vesa_error_msg:
 	.asciz "VESA error"

bootloader/bios/linker.ld

@@ -8,6 +8,8 @@ SECTIONS
 	. = ALIGN(512);
 	stage2_start = .;
 	.stage2 : { *(.stage2) }
+	. = ALIGN(512);
+	.data : { *(.data) }
 	stage2_end = .;
 
 	. = ALIGN(512);

bootloader/bios/memory_map.S

@@ -114,6 +114,7 @@ print_memory_map:
 
 	ret
 
+.section .data
 
 memory_map_msg:
 	.asciz "memmap:"

bootloader/installer/GPT.cpp

@@ -99,33 +99,33 @@ bool GPTFile::install_stage1(std::span<const uint8_t> stage1)
 	return true;
 }
 
-bool GPTFile::install_stage2(std::span<const uint8_t> stage2, const GUID& root_partition_guid)
+bool GPTFile::install_stage2(std::span<const uint8_t> stage2, std::span<const uint8_t> data, const GUID& root_partition_guid)
 {
-	if (stage2.size() < 16)
+	if (data.size() < 16)
 	{
-		std::cerr << m_path << ": contains invalid .stage2 section, too small for patches" << std::endl;
+		std::cerr << m_path << ": contains invalid .data section, too small for patches" << std::endl;
 		return false;
 	}
 
 	// find GUID patch offsets
 	std::size_t disk_guid_offset(-1);
 	std::size_t part_guid_offset(-1);
-	for (std::size_t i = 0; i < stage2.size() - 16; i++)
+	for (std::size_t i = 0; i < data.size() - 16; i++)
 	{
-		if (memcmp(stage2.data() + i, "root disk guid  ", 16) == 0)
+		if (memcmp(data.data() + i, "root disk guid  ", 16) == 0)
 		{
 			if (disk_guid_offset != std::size_t(-1))
 			{
-				std::cerr << m_path << ": contains invalid .stage2 section, multiple patchable disk guids" << std::endl;
+				std::cerr << m_path << ": contains invalid .data section, multiple patchable disk guids" << std::endl;
 				return false;
 			}
 			disk_guid_offset = i;
 		}
-		if (memcmp(stage2.data() + i, "root part guid  ", 16) == 0)
+		if (memcmp(data.data() + i, "root part guid  ", 16) == 0)
 		{
 			if (part_guid_offset != std::size_t(-1))
 			{
-				std::cerr << m_path << ": contains invalid .stage2 section, multiple patchable partition guids" << std::endl;
+				std::cerr << m_path << ": contains invalid .data section, multiple patchable partition guids" << std::endl;
 				return false;
 			}
 			part_guid_offset = i;
@@ -133,15 +133,14 @@ bool GPTFile::install_stage2(std::span<const uint8_t> stage2, const GUID& root_p
 	}
 	if (disk_guid_offset == std::size_t(-1))
 	{
-		std::cerr << m_path << ": contains invalid .stage2 section, no patchable disk guid" << std::endl;
+		std::cerr << m_path << ": contains invalid .data section, no patchable disk guid" << std::endl;
 		return false;
 	}
 	if (part_guid_offset == std::size_t(-1))
 	{
-		std::cerr << m_path << ": contains invalid .stage2 section, no patchable partition guid" << std::endl;
+		std::cerr << m_path << ": contains invalid .data section, no patchable partition guid" << std::endl;
 		return false;
 	}
-	
 
 	auto partition = find_partition_with_type(bios_boot_guid);
 	if (!partition.has_value())
@@ -152,23 +151,28 @@ bool GPTFile::install_stage2(std::span<const uint8_t> stage2, const GUID& root_p
 
 	const std::size_t partition_size = (partition->ending_lba - partition->starting_lba + 1) * SECTOR_SIZE;
 
-	if (stage2.size() > partition_size)
+	std::size_t data_offset = stage2.size();
+	if (std::size_t rem = data_offset % 512)
+		data_offset += 512 - rem;
+
+	if (data_offset + data.size() > partition_size)
 	{
-		std::cerr << m_path << ": can't fit " << stage2.size() << " bytes of data to partition of size " << partition_size << std::endl;
+		std::cerr << m_path << ": can't fit " << stage2.size() + data.size() << " bytes of data to partition of size " << partition_size << std::endl;
 		return false;
 	}
 
 	uint8_t* partition_start = m_mmap + partition->starting_lba * SECTOR_SIZE;
 	memcpy(partition_start, stage2.data(), stage2.size());
+	memcpy(partition_start + data_offset, data.data(), data.size());
 
 	// patch GUIDs
-	*reinterpret_cast<GUID*>(partition_start + disk_guid_offset) = gpt_header().disk_guid;
+	*reinterpret_cast<GUID*>(partition_start + data_offset + disk_guid_offset) = gpt_header().disk_guid;
-	*reinterpret_cast<GUID*>(partition_start + part_guid_offset) = root_partition_guid;
+	*reinterpret_cast<GUID*>(partition_start + data_offset + part_guid_offset) = root_partition_guid;
 
 	return true;
 }
 
-bool GPTFile::install_bootloader(std::span<const uint8_t> stage1, std::span<const uint8_t> stage2, const GUID& root_partition_guid)
+bool GPTFile::install_bootloader(std::span<const uint8_t> stage1, std::span<const uint8_t> stage2, std::span<const uint8_t> data, const GUID& root_partition_guid)
 {
 	if (!find_partition_with_guid(root_partition_guid).has_value())
 	{
@@ -177,7 +181,7 @@ bool GPTFile::install_bootloader(std::span<const uint8_t> stage1, std::span<cons
 	}
 	if (!install_stage1(stage1))
 		return false;
-	if (!install_stage2(stage2, root_partition_guid))
+	if (!install_stage2(stage2, data, root_partition_guid))
 		return false;
 	return true;
 }

bootloader/installer/GPT.h

@@ -65,7 +65,7 @@ public:
 	GPTFile(std::string_view path);
 	~GPTFile();
 
-	bool install_bootloader(std::span<const uint8_t> stage1, std::span<const uint8_t> stage2, const GUID& root_partition_guid);
+	bool install_bootloader(std::span<const uint8_t> stage1, std::span<const uint8_t> stage2, std::span<const uint8_t> data, const GUID& root_partition_guid);
 
 	const GPTHeader& gpt_header() const;
 
@@ -80,7 +80,7 @@ private:
 	std::optional<GPTPartitionEntry> find_partition_with_type(const GUID& type_guid) const;
 
 	bool install_stage1(std::span<const uint8_t> stage1);
-	bool install_stage2(std::span<const uint8_t> stage2, const GUID& root_partition_guid);
+	bool install_stage2(std::span<const uint8_t> stage2, std::span<const uint8_t> data, const GUID& root_partition_guid);
 
 private:
 	const std::string	m_path;

bootloader/installer/build.sh

@@ -1,3 +0,0 @@
-#!/bin/sh
-
-g++ -O2 -std=c++20 main.cpp crc32.cpp ELF.cpp GPT.cpp GUID.cpp -o install-bootloader

bootloader/installer/main.cpp

@@ -26,9 +26,10 @@ int main(int argc, char** argv)
 
 	auto stage1 = bootloader.find_section(".stage1"sv);
 	auto stage2 = bootloader.find_section(".stage2"sv);
-	if (!stage1.has_value() || !stage2.has_value())
+	auto data = bootloader.find_section(".data"sv);
+	if (!stage1.has_value() || !stage2.has_value() || !data.has_value())
 	{
-		std::cerr << bootloader.path() << " doesn't contain .stage1 and .stage2 sections" << std::endl;
+		std::cerr << bootloader.path() << " doesn't contain .stage1, .stage2 and .data sections" << std::endl;
 		return 1;
 	}
 
@@ -36,7 +37,7 @@ int main(int argc, char** argv)
 	if (!disk_image.success())
 		return 1;
 
-	if (!disk_image.install_bootloader(*stage1, *stage2, *root_partition_guid))
+	if (!disk_image.install_bootloader(*stage1, *stage2, *data, *root_partition_guid))
 		return 1;
 	std::cout << "bootloader installed" << std::endl;