Load ELF file with bootloader instead of flat binary

Makefile

@@ -8,7 +8,7 @@ ARCH_D         := src/arch/$(ARCH)
 VERSION        ?= $(shell git describe --dirty --always)
 GITSHA         ?= $(shell git rev-parse --short HEAD)
 
-KERNEL_FILENAME:= popcorn.bin
+KERNEL_FILENAME:= popcorn.elf
 KERNEL_FONT    := assets/fonts/tamsyn8x16r.psf
 
 MODULES        := kutil
@@ -169,9 +169,6 @@ $(BUILD_D)/boot.debug.efi: $(BUILD_D)/boot.elf
 	-j .debug_aranges -j .debug_line -j .debug_macinfo \
 	--target=efi-app-$(ARCH) $^ $@
 
-$(BUILD_D)/%.bin: $(BUILD_D)/%.elf
-	$(OBJC) $< -O binary $@
-
 $(BUILD_D)/boot.dump: $(BUILD_D)/boot.efi
 	$(OBJD) -D -S $< > $@
 
@@ -201,7 +198,7 @@ $(BUILD_D)/flash.img: $(OVMF)
 $(BUILD_D)/screenfont.psf: $(KERNEL_FONT)
 	cp $^ $@
 
-$(BUILD_D)/fs.img: $(BUILD_D)/boot.efi $(BUILD_D)/kernel.bin $(BUILD_D)/screenfont.psf
+$(BUILD_D)/fs.img: $(BUILD_D)/boot.efi $(BUILD_D)/kernel.elf $(BUILD_D)/screenfont.psf
 	$(eval TEMPFILE := $(shell mktemp --suffix=.img))
 	dd if=/dev/zero of=$@.tmp bs=512 count=93750
 	$(PARTED) $@.tmp -s -a minimal mklabel gpt
@@ -212,7 +209,7 @@ $(BUILD_D)/fs.img: $(BUILD_D)/boot.efi $(BUILD_D)/kernel.bin $(BUILD_D)/screenfo
 	mmd -i $(TEMPFILE) ::/EFI
 	mmd -i $(TEMPFILE) ::/EFI/BOOT
 	mcopy -i $(TEMPFILE) $(BUILD_D)/boot.efi ::/EFI/BOOT/BOOTX64.efi
-	mcopy -i $(TEMPFILE) $(BUILD_D)/kernel.bin ::$(KERNEL_FILENAME)
+	mcopy -i $(TEMPFILE) $(BUILD_D)/kernel.elf ::$(KERNEL_FILENAME)
 	mcopy -i $(TEMPFILE) $(BUILD_D)/screenfont.psf ::screenfont.psf
 	mlabel -i $(TEMPFILE) ::Popcorn_OS
 	dd if=$(TEMPFILE) of=$@.tmp bs=512 count=91669 seek=2048 conv=notrunc

src/boot/elf.h

@@ -0,0 +1,77 @@
+#pragma once
+#include <stdint.h>
+
+#ifndef ELF_VERSION
+#define ELF_VERSION 1
+#endif
+
+#ifndef ELF_WORDSIZE
+#define ELF_WORDSIZE 2
+#endif
+
+#ifndef ELF_ENDIAN
+#define ELF_ENDIAN 1
+#endif
+
+#ifndef ELF_OSABI
+#define ELF_OSABI 0
+#endif
+
+#ifndef ELF_MACHINE
+#define ELF_MACHINE 0x3e
+#endif
+
+const unsigned ELF_PT_LOAD = 1;
+
+struct elf_ident
+{
+	char magic[4];
+
+	uint8_t word_size;
+	uint8_t endianness;
+	uint8_t version;
+	uint8_t os_abi;
+
+	uint64_t reserved;
+} __attribute__ ((packed));
+
+struct elf_header
+{
+	struct elf_ident ident;
+
+	uint16_t type;
+	uint16_t machine;
+
+	uint32_t version;
+
+	uint64_t entrypoint;
+	uint64_t ph_offset;
+	uint64_t sh_offset;
+
+	uint32_t flags;
+
+	uint16_t eh_size;
+
+	uint16_t ph_entsize;
+	uint16_t ph_num;
+
+	uint16_t sh_entsize;
+	uint16_t sh_num;
+
+	uint16_t sh_str_idx;
+} __attribute__ ((packed));
+
+struct elf_program_header
+{
+	uint32_t type;
+	uint32_t flags;
+	uint64_t offset;
+
+	uint64_t vaddr;
+	uint64_t paddr;
+
+	uint64_t file_size;
+	uint64_t mem_size;
+
+	uint64_t align;
+} __attribute__ ((packed));

src/boot/loader.c

@@ -1,3 +1,4 @@
+#include "elf.h"
 #include "guids.h"
 #include "loader.h"
 #include "memory.h"
@@ -13,8 +14,7 @@ loader_alloc_pages(
 	EFI_BOOT_SERVICES *bootsvc,
 	EFI_MEMORY_TYPE mem_type,
 	size_t *length,
-	void **pages,
+	void **pages)
-	void **next)
 {
 	EFI_STATUS status;
 
@@ -33,31 +33,26 @@ loader_alloc_pages(
 
 	*length = page_count * PAGE_SIZE;
 	*pages = (void *)addr;
-	*next = (void*)(addr + *length);
 
 	return EFI_SUCCESS;
 }
 
 EFI_STATUS
-loader_load_file(
+loader_load_font(
 	EFI_BOOT_SERVICES *bootsvc,
 	EFI_FILE_PROTOCOL *root,
-	const CHAR16 *filename,
+	struct loader_data *data)
-	EFI_MEMORY_TYPE mem_type,
-	void **data,
-	size_t *length,
-	void **next)
 {
 	EFI_STATUS status;
 
 	EFI_FILE_PROTOCOL *file = NULL;
-	status = root->Open(root, &file, (CHAR16 *)filename, EFI_FILE_MODE_READ,
+	status = root->Open(root, &file, (CHAR16 *)font_name, EFI_FILE_MODE_READ,
 						EFI_FILE_READ_ONLY | EFI_FILE_HIDDEN | EFI_FILE_SYSTEM);
 
 	if (status == EFI_NOT_FOUND)
 		return status;
 
-	CHECK_EFI_STATUS_OR_RETURN(status, L"Opening file %s", filename);
+	CHECK_EFI_STATUS_OR_RETURN(status, L"Opening file %s", font_name);
 
 	char info[sizeof(EFI_FILE_INFO) + 100];
 	size_t info_length = sizeof(info);
@@ -65,12 +60,16 @@ loader_load_file(
 	status = file->GetInfo(file, &guid_file_info, &info_length, info);
 	CHECK_EFI_STATUS_OR_RETURN(status, L"Getting file info");
 
-	*length = ((EFI_FILE_INFO *)info)->FileSize;
+	data->font_length = ((EFI_FILE_INFO *)info)->FileSize;
 
-	status = loader_alloc_pages(bootsvc, mem_type, length, data, next);
+	status = loader_alloc_pages(
+			bootsvc,
+			KERNEL_FONT_MEMTYPE,
+			&data->font_length,
+			&data->font);
 	CHECK_EFI_STATUS_OR_RETURN(status, L"Allocating pages");
 
-	status = file->Read(file, length, *data);
+	status = file->Read(file, &data->font_length, data->font);
 	CHECK_EFI_STATUS_OR_RETURN(status, L"Reading file");
 
 	status = file->Close(file);
@@ -80,6 +79,95 @@ loader_load_file(
 }
 
 
+EFI_STATUS
+loader_load_elf(
+	EFI_BOOT_SERVICES *bootsvc,
+	EFI_FILE_PROTOCOL *root,
+	struct loader_data *data)
+{
+	EFI_STATUS status;
+
+	EFI_FILE_PROTOCOL *file = NULL;
+	status = root->Open(root, &file, (CHAR16 *)kernel_name, EFI_FILE_MODE_READ,
+						EFI_FILE_READ_ONLY | EFI_FILE_HIDDEN | EFI_FILE_SYSTEM);
+
+	if (status == EFI_NOT_FOUND)
+		return status;
+
+	uint64_t length = 0;
+	data->kernel = 0;
+	data->kernel_entry = 0;
+	data->kernel_length = 0;
+
+	CHECK_EFI_STATUS_OR_RETURN(status, L"Opening file %s", kernel_name);
+
+	struct elf_header header;
+
+	length = sizeof(struct elf_header);
+	status = file->Read(file, &length, &header);
+	CHECK_EFI_STATUS_OR_RETURN(status, L"Reading ELF header");
+
+	if (length < sizeof(struct elf_header))
+		CHECK_EFI_STATUS_OR_RETURN(EFI_LOAD_ERROR, L"Incomplete read of ELF header");
+
+	static const char expected[] = {0x7f, 'E', 'L', 'F'};
+	for (int i = 0; i < sizeof(expected); ++i) {
+		if (header.ident.magic[i] != expected[i])
+			CHECK_EFI_STATUS_OR_RETURN(EFI_LOAD_ERROR, L"Bad ELF magic number");
+	}
+
+	if (header.ident.word_size != ELF_WORDSIZE)
+		CHECK_EFI_STATUS_OR_RETURN(EFI_LOAD_ERROR, L"ELF load error: 32 bit ELF not supported");
+
+	if (header.ph_entsize != sizeof(struct elf_program_header))
+		CHECK_EFI_STATUS_OR_RETURN(EFI_LOAD_ERROR, L"ELF load error: program header size mismatch");
+
+	if (header.ident.version != ELF_VERSION ||
+		header.version != ELF_VERSION)
+		CHECK_EFI_STATUS_OR_RETURN(EFI_LOAD_ERROR, L"ELF load error: wrong ELF version");
+
+	if (header.ident.endianness != 1 ||
+		header.ident.os_abi != 0 ||
+		header.machine != 0x3e)
+		CHECK_EFI_STATUS_OR_RETURN(EFI_LOAD_ERROR, L"ELF load error: wrong machine architecture");
+
+	data->kernel_entry = (void *)header.entrypoint;
+
+	struct elf_program_header prog_header;
+	for (int i = 0; i < header.ph_num; ++i) {
+		status = file->SetPosition(file, header.ph_offset + i * header.ph_entsize);
+		CHECK_EFI_STATUS_OR_RETURN(status, L"Setting ELF file position");
+
+		length = header.ph_entsize;
+		status = file->Read(file, &length, &prog_header);
+		CHECK_EFI_STATUS_OR_RETURN(status, L"Reading ELF program header");
+
+		if (prog_header.type != ELF_PT_LOAD) continue;
+
+		status = file->SetPosition(file, prog_header.offset);
+		CHECK_EFI_STATUS_OR_RETURN(status, L"Setting ELF file position");
+
+		length = prog_header.mem_size;
+		void *addr = (void *)(prog_header.vaddr - KERNEL_VIRT_ADDRESS);
+		status = loader_alloc_pages(bootsvc, KERNEL_MEMTYPE, &length, &addr);
+		CHECK_EFI_STATUS_OR_RETURN(status, L"Allocating kernel pages");
+
+		if (data->kernel == 0)
+			data->kernel = addr;
+		data->kernel_length = (uint64_t)addr + length - (uint64_t)data->kernel;
+
+		length = prog_header.file_size;
+		status = file->Read(file, &length, addr);
+		CHECK_EFI_STATUS_OR_RETURN(status, L"Reading file");
+	}
+
+	status = file->Close(file);
+	CHECK_EFI_STATUS_OR_RETURN(status, L"Closing file handle");
+
+	return EFI_SUCCESS;
+}
+
+
 EFI_STATUS
 loader_load_kernel(
 	EFI_BOOT_SERVICES *bootsvc,
@@ -105,54 +193,26 @@ loader_load_kernel(
 		status = fileSystem->OpenVolume(fileSystem, &root);
 		CHECK_EFI_STATUS_OR_RETURN(status, L"OpenVolume");
 
-		void *next = NULL;
+		status = loader_load_elf(bootsvc, root, data);
-
-		data->kernel = (void *)KERNEL_PHYS_ADDRESS;
-		status = loader_load_file(
-				bootsvc,
-				root,
-				kernel_name,
-				KERNEL_MEMTYPE,
-				&data->kernel,
-				&data->kernel_length,
-				&next);
 		if (status == EFI_NOT_FOUND)
 			continue;
 
 		CHECK_EFI_STATUS_OR_RETURN(status, L"loader_load_file: %s", kernel_name);
 
-		data->font = next;
+		data->font = (void *)((uint64_t)data->kernel + data->kernel_length);
-		status = loader_load_file(
+		status = loader_load_font(bootsvc, root, data);
-				bootsvc,
-				root,
-				font_name,
-				KERNEL_FONT_MEMTYPE,
-				&data->font,
-				&data->font_length,
-				&next);
 
 		CHECK_EFI_STATUS_OR_RETURN(status, L"loader_load_file: %s", font_name);
 
-		data->data = next;
+		data->data = (void *)((uint64_t)data->font + data->font_length);
 		data->data_length += PAGE_SIZE; // extra page for map growth
 		status = loader_alloc_pages(
 				bootsvc,
 				KERNEL_DATA_MEMTYPE,
 				&data->data_length,
-				&data->data,
+				&data->data);
-				&next);
 		CHECK_EFI_STATUS_OR_RETURN(status, L"loader_alloc_pages: kernel data");
 
-		data->log = next;
-		data->log_length = KERNEL_LOG_PAGES * PAGE_SIZE;
-		status = loader_alloc_pages(
-				bootsvc,
-				KERNEL_LOG_MEMTYPE,
-				&data->log_length,
-				&data->log,
-				&next);
-		CHECK_EFI_STATUS_OR_RETURN(status, L"loader_alloc_pages: kernel log");
-
 		return EFI_SUCCESS;
 	}
 

src/boot/loader.h

@@ -28,20 +28,12 @@
 #define KERNEL_DATA_MEMTYPE 0x80000002
 #endif
 
-#ifndef KERNEL_LOG_MEMTYPE
-#define KERNEL_LOG_MEMTYPE 0x80000003
-#endif
-
-#ifndef KERNEL_LOG_PAGES
-#define KERNEL_LOG_PAGES 4
-#endif
-
 #ifndef KERNEL_PT_MEMTYPE
 #define KERNEL_PT_MEMTYPE 0x80000004
 #endif
 
 #ifndef KERNEL_FILENAME
-#define KERNEL_FILENAME L"kernel.bin"
+#define KERNEL_FILENAME L"kernel.elf"
 #endif
 
 #ifndef KERNEL_FONT
@@ -50,6 +42,7 @@
 
 struct loader_data {
 	void *kernel;
+	void *kernel_entry;
 	size_t kernel_length;
 
 	void *font;
@@ -57,9 +50,6 @@ struct loader_data {
 
 	void *data;
 	size_t data_length;
-
-	void *log;
-	size_t log_length;
 };
 
 EFI_STATUS loader_load_kernel(EFI_BOOT_SERVICES *bootsvc, struct loader_data *data);

src/boot/main.c

@@ -27,8 +27,6 @@ struct kernel_header {
 	uint8_t minor;
 	uint16_t patch;
 	uint32_t gitsha;
-
-	void *entrypoint;
 };
 #pragma pack(pop)
 
@@ -77,8 +75,6 @@ efi_main(EFI_HANDLE image_handle, EFI_SYSTEM_TABLE *system_table)
 
 	// Load the kernel image from disk and check it
 	//
-	void *kernel_image = NULL, *kernel_data = NULL;
-	uint64_t kernel_length = 0;
 	con_printf(L"Loading kernel into memory...\r\n");
 
 	struct loader_data load;
@@ -89,7 +85,6 @@ efi_main(EFI_HANDLE image_handle, EFI_SYSTEM_TABLE *system_table)
 	con_printf(L"    %u image bytes at 0x%x\r\n", load.kernel_length, load.kernel);
 	con_printf(L"    %u font bytes at 0x%x\r\n", load.font_length, load.font);
 	con_printf(L"    %u data bytes at 0x%x\r\n", load.data_length, load.data);
-	con_printf(L"    %u log bytes at 0x%x\r\n", load.log_length, load.log);
 
 	struct kernel_header *version = (struct kernel_header *)load.kernel;
 	if (version->magic != KERNEL_HEADER_MAGIC) {
@@ -100,9 +95,9 @@ efi_main(EFI_HANDLE image_handle, EFI_SYSTEM_TABLE *system_table)
 	con_printf(L"    Kernel version %d.%d.%d %x%s\r\n",
 			version->major, version->minor, version->patch, version->gitsha & 0x0fffffff,
 			version->gitsha & 0xf0000000 ? "*" : "");
-	con_printf(L"    Entrypoint 0x%x\r\n", version->entrypoint);
+	con_printf(L"    Entrypoint 0x%x\r\n", load.kernel_entry);
 
-	void (*kernel_main)() = version->entrypoint;
+	void (*kernel_main)() = load.kernel_entry;
 	memory_mark_pointer_fixup((void **)&kernel_main);
 
 	// Set up the kernel data pages to pass to the kernel
@@ -124,10 +119,6 @@ efi_main(EFI_HANDLE image_handle, EFI_SYSTEM_TABLE *system_table)
 	data_header->data_length = load.data_length;
 	memory_mark_pointer_fixup((void **)&data_header->data);
 
-	data_header->log = load.log;
-	data_header->log_length = load.log_length;
-	memory_mark_pointer_fixup((void **)&data_header->log);
-
 	data_header->memory_map = (EFI_MEMORY_DESCRIPTOR *)(data_header + 1);
 	memory_mark_pointer_fixup((void **)&data_header->memory_map);
 

src/boot/memory.c

@@ -192,7 +192,6 @@ memory_virtualize(EFI_RUNTIME_SERVICES *runsvc, struct memory_map *map)
 		case KERNEL_MEMTYPE:
 		case KERNEL_FONT_MEMTYPE:
 		case KERNEL_DATA_MEMTYPE:
-		case KERNEL_LOG_MEMTYPE:
 			d->Attribute |= EFI_MEMORY_RUNTIME;
 
 		default:

src/include/kernel_data.h

@@ -22,9 +22,6 @@ struct popcorn_data {
 	void *data;
 	size_t data_length;
 
-	void *log;
-	size_t log_length;
-
 	void *memory_map;
 	size_t memory_map_length;
 	size_t memory_map_desc_size;

src/kernel/boot.s

@@ -6,12 +6,11 @@ global _header
 _header:
 	dd MAGIC			; Kernel header magic
 	dw 1				; Header version 1
-	dw 1				; Kernel header length
+	dw 16				; Kernel header length
 	db VERSION_MAJOR	; Kernel version
 	db VERSION_MINOR
 	dw VERSION_PATCH
 	dd VERSION_GITSHA
-	dq _start			; Kernel entrypoint
 
 section .text
 align 16