Merge pull request #11 from 0xKSor/feat/elf

Bootloader/CMakeLists.txt

@@ -9,13 +9,13 @@ set(UEFI_COMPILE_OPTIONS
 )
 
 add_executable(BOOTAA64
-    Source/uefi/efi_entry.c
+    Source/modules/uefi/efi_entry.c
     Source/main.c
 )
 target_compile_options(BOOTAA64 PRIVATE ${UEFI_COMPILE_OPTIONS})
 target_include_directories(BOOTAA64 PRIVATE
     ${CMAKE_CURRENT_SOURCE_DIR}/Source
-    ${CMAKE_CURRENT_SOURCE_DIR}/Source/uefi
+    ${CMAKE_CURRENT_SOURCE_DIR}/Source/modules/uefi
 )
 
 target_link_options(BOOTAA64 PRIVATE

Bootloader/Source/main.c

@@ -1,10 +1,11 @@
-#include "uefi/uefi.h"
+#include "modules/uefi/uefi.h"
+#include "modules/elf/elf.h"
 #include "../../Common/bootinfo.h"
 
 #define PAGE_SIZE 0x1000
 #define WSTR(str) ((wchar_t*)L##str)
 
-static wchar_t* kernel_path = WSTR("ksOSKernel.bin");
+static wchar_t* kernel_path = WSTR("ksOSKernel.elf");
 static efi_guid_t dtb_guid = {
     0xb1b621d5, 0xf19c, 0x41a5, {0x83, 0x0b, 0xd9, 0x15, 0x2c, 0x69, 0xaa, 0xe0}
 };
@@ -13,6 +14,14 @@ static void print(const wchar_t* msg) {
     ST->ConOut->OutputString(ST->ConOut, (wchar_t*)msg);
 }
 
+void* memset(void* destination, int value, uint64_t count) {
+    uint8_t* ptr = (uint8_t*)destination;
+    while (count--) {
+        *ptr++ = (uint8_t)value;
+    }
+    return destination;
+}
+
 static efi_status_t die(void) {
     while (1) {
         __asm__ volatile("wfi");
@@ -83,33 +92,73 @@ static efi_status_t read_file_info(efi_file_handle_t* file, efi_file_info_t** fi
     return file->GetInfo(file, &file_info_guid, &file_info_size, *file_info);
 }
 
-static efi_status_t load_kernel(efi_file_handle_t* root, efi_physical_address_t* kernel_addr, uint64_t* kernel_size) {
+static efi_status_t load_kernel(efi_file_handle_t* root, efi_physical_address_t* kernel_addr, uint64_t* kernel_size, efi_file_handle_t** out_handle) {
     efi_file_handle_t* kernel_file = NULL;
-    efi_file_info_t* kernel_info = NULL;
     efi_status_t status = root->Open(root, &kernel_file, kernel_path, EFI_FILE_MODE_READ, 0);
-    if (EFI_ERROR(status)) {
+    if (EFI_ERROR(status)) return status;
-        return status;
-    }
 
+    efi_file_info_t* kernel_info = NULL;
     status = read_file_info(kernel_file, &kernel_info);
-    if (EFI_ERROR(status)) {
+    if (EFI_ERROR(status)) return status;
-        return status;
-    }
 
     *kernel_size = kernel_info->FileSize;
-
-    uintn_t bytes_to_read = (uintn_t)*kernel_size;
     uintn_t kernel_pages = (*kernel_size + PAGE_SIZE - 1) / PAGE_SIZE;
-    *kernel_addr = 0;
 
     status = gBS->AllocatePages(AllocateAnyPages, EfiLoaderData, kernel_pages, kernel_addr);
-    if (EFI_ERROR(status)) {
+    if (EFI_ERROR(status)) return status;
-        return status;
+
+    uintn_t bytes_to_read = (uintn_t)*kernel_size;
+    status = kernel_file->Read(kernel_file, &bytes_to_read, (void*)*kernel_addr);
+    if (EFI_ERROR(status)) return status;
+
+    *out_handle = kernel_file;
+    return EFI_SUCCESS;
+}
+
+static efi_status_t parse_elf_headers(efi_physical_address_t kernel_addr) {
+    Elf64_Ehdr* elf_header = (Elf64_Ehdr*)kernel_addr;
+
+    if (elf_header->e_ident[0] != 0x7f || elf_header->e_ident[1] != 'E' ||
+        elf_header->e_ident[2] != 'L'  || elf_header->e_ident[3] != 'F') {
+        return fail(WSTR("Invalid ELF header\r\n"));
+    }
+    if (elf_header->e_machine != 0xB7) { // AArch64
+        return fail(WSTR("Invalid ELF machine\r\n"));
     }
 
-    status = kernel_file->Read(kernel_file, &bytes_to_read, (void*)*kernel_addr);
+    return EFI_SUCCESS;
-    if (EFI_ERROR(status) || bytes_to_read != (uintn_t)*kernel_size) {
+}
-        return EFI_LOAD_ERROR;
+
+static efi_status_t load_elf_segments(efi_physical_address_t kernel_addr, efi_file_handle_t* kernel_file) {
+    Elf64_Ehdr* elf_header = (Elf64_Ehdr*)kernel_addr;
+
+    for (int i = 0; i < elf_header->e_phnum; i++) {
+        Elf64_Phdr* phdr = (Elf64_Phdr*)(kernel_addr + elf_header->e_phoff + i * elf_header->e_phentsize);
+
+        if (phdr->p_type != PT_LOAD) continue;
+        if (phdr->p_vaddr < 0x40000000) {
+            print(WSTR("Skipping low/weird segment\r\n"));
+            continue;
+        }
+
+        uintn_t pages = (phdr->p_memsz + 0xFFF) / 0x1000;
+        efi_physical_address_t segment_addr = phdr->p_vaddr;
+
+        efi_status_t status = gBS->AllocatePages(AllocateAddress, EfiLoaderData, pages, &segment_addr);
+        if (EFI_ERROR(status)) {
+            if (status == EFI_NOT_FOUND) print(WSTR(" (Range not in RAM) "));
+            if (status == EFI_OUT_OF_RESOURCES) print(WSTR(" (Occupied) "));
+            return fail(WSTR("Address conflict!\r\n"));
+        }
+
+        memset((void*)segment_addr, 0, phdr->p_memsz);
+        kernel_file->SetPosition(kernel_file, phdr->p_offset);
+
+        uintn_t size_to_read = phdr->p_filesz;
+        status = kernel_file->Read(kernel_file, &size_to_read, (void*)segment_addr);
+        if (EFI_ERROR(status) || size_to_read != phdr->p_filesz) {
+            return fail(WSTR("File read error\r\n"));
+        }
     }
 
     return EFI_SUCCESS;
@@ -175,11 +224,20 @@ efi_status_t bootloader_main(void) {
 
     efi_physical_address_t kernel_addr = 0;
     uint64_t kernel_size = 0;
-    status = load_kernel(root, &kernel_addr, &kernel_size);
+    efi_file_handle_t* kernel_file = NULL;
+    status = load_kernel(root, &kernel_addr, &kernel_size, &kernel_file);
     if (EFI_ERROR(status)) {
         return fail(WSTR("Failed to load ksOSKernel.bin\r\n"));
     }
 
+    Elf64_Ehdr* elf_header = (Elf64_Ehdr*)kernel_addr;
+
+    status = parse_elf_headers(kernel_addr);
+    if (EFI_ERROR(status)) return status;
+
+    status = load_elf_segments(kernel_addr, kernel_file);
+    if (EFI_ERROR(status)) return status;
+
     Bootinfo* boot_info = NULL;
     status = gBS->AllocatePool(EfiLoaderData, sizeof(Bootinfo), (void**)&boot_info);
     if (EFI_ERROR(status) || boot_info == NULL) {
@@ -203,7 +261,7 @@ efi_status_t bootloader_main(void) {
     }
 
     typedef void (*kernel_entry_t)(Bootinfo*);
-    kernel_entry_t kernel_main = (kernel_entry_t)kernel_addr;
+    kernel_entry_t kernel_main = (kernel_entry_t)elf_header->e_entry;
     kernel_main(boot_info);
 
     return EFI_SUCCESS;

Bootloader/Source/modules/elf/elf.h

@@ -0,0 +1,32 @@
+#pragma once
+#include "../../modules/uefi/uefi.h" // IWYU pragma: keep
+
+typedef struct {
+    uint8_t  e_ident[16];
+    uint16_t e_type;
+    uint16_t e_machine;
+    uint32_t e_version;
+    uint64_t e_entry;
+    uint64_t e_phoff;
+    uint64_t e_shoff;
+    uint32_t e_flags;
+    uint16_t e_ehsize;
+    uint16_t e_phentsize;
+    uint16_t e_phnum;
+    uint16_t e_shentsize;
+    uint16_t e_shnum;
+    uint16_t e_shstrndx;
+} Elf64_Ehdr;
+
+typedef struct {
+    uint32_t p_type;
+    uint32_t p_flags;
+    uint64_t p_offset;
+    uint64_t p_vaddr;
+    uint64_t p_paddr;
+    uint64_t p_filesz;
+    uint64_t p_memsz;
+    uint64_t p_align;
+} Elf64_Phdr;
+
+#define PT_LOAD 1

Bootloader/Source/modules/uefi/uefi.h

@@ -36,6 +36,8 @@ typedef uint16_t wchar_t;
 #define EFI_LOAD_ERROR EFIERR(1)
 #define EFI_UNSUPPORTED EFIERR(3)
 #define EFI_BUFFER_TOO_SMALL EFIERR(5)
+#define EFI_OUT_OF_RESOURCES EFIERR(9)
+#define EFI_NOT_FOUND EFIERR(14)
 #define EFI_ABORTED EFIERR(21)
 
 #define EFI_OPEN_PROTOCOL_GET_PROTOCOL 0x00000002

Kernel/CMakeLists.txt

@@ -33,14 +33,11 @@ target_link_options(Kernel PRIVATE
     -no-pie
     -T "${CMAKE_CURRENT_SOURCE_DIR}/linker.ld"
     -z max-page-size=0x1000
+    --image-base=0x40100000
+    --no-dynamic-linker
 )
 
 set_target_properties(Kernel PROPERTIES
-    OUTPUT_NAME "Kernel.elf"
+    OUTPUT_NAME "ksOSKernel.elf"
     RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}"
 )
-
-add_custom_command(TARGET Kernel POST_BUILD
-    COMMAND ${LLVM_OBJCOPY} -O binary ${CMAKE_BINARY_DIR}/Kernel.elf ${CMAKE_BINARY_DIR}/Kernel.bin
-    COMMENT "Generating ksOSKernel.bin from Kernel.elf"
-)

Kernel/justfile

@@ -7,8 +7,8 @@ build:
 
     cmake --build {{TEMP_DIR}}/Kernel
 
-    cp {{TEMP_DIR}}/Kernel/Kernel.bin {{BUILD_DIR}}/Kernel/ksOSKernel.bin
+    cp {{TEMP_DIR}}/Kernel/ksOSKernel.elf {{BUILD_DIR}}/Kernel/ksOSKernel.elf
-    @echo "✅ Kernel ready at: {{BUILD_DIR}}/Kernel/ksOSKernel.bin"
+    @echo "✅ Kernel ready at: {{BUILD_DIR}}/Kernel/ksOSKernel.elf"
 
 clean:
     rm -rf {{TEMP_DIR}}/Kernel

Kernel/linker.ld

@@ -1,15 +1,20 @@
-ENTRY(_start)
+PHDRS
+{
+  text PT_LOAD FLAGS(5); /* Read | Execute */
+  data PT_LOAD FLAGS(6); /* Read | Write */
+}
 
-SECTIONS {
+SECTIONS
-    . = 0;
+{
+    . = 0x40100000;
 
     .text : {
         *(.text.boot)
         *(.text*)
-    }
+    } :text
 
-    .rodata : { *(.rodata*) }
+    .rodata : { *(.rodata*) } :text
-    .data   : { *(.data*)   }
+    
-    .bss    : { *(.bss*) *(COMMON) }
+    .data : { *(.data*) } :data
-
+    .bss : { *(.bss*) *(COMMON) } :data
-}
+}

justfile

@@ -28,6 +28,7 @@ DISPLAY_FLAGS := if OS_NAME == "macos" {
 }
 
 ACCEL_INFO := if ACCEL == "" { "none (TCG)" } else { ACCEL }
+RAM := "2G"
 
 export BUILD_DIR := justfile_directory() + "/.build"
 export TEMP_DIR  := BUILD_DIR + "/temp"
@@ -64,14 +65,14 @@ _prep:
     @mkfs.fat -F 32 {{IMG_FILE}} > /dev/null
     @mmd -i {{IMG_FILE}} ::/EFI ::/EFI/BOOT
     @mcopy -i {{IMG_FILE}} {{BOOT_BIN}} ::/EFI/BOOT/BOOTAA64.EFI
-    @mcopy -i {{IMG_FILE}} {{BUILD_DIR}}/Kernel/ksOSKernel.bin ::/ksOSKernel.bin
+    @mcopy -i {{IMG_FILE}} {{BUILD_DIR}}/Kernel/ksOSKernel.elf ::/ksOSKernel.elf
 
 @run: _image
     @echo "🚀 Launching (accel: {{ACCEL_INFO}})..."
     qemu-system-aarch64 {{ACCEL}} \
         -machine virt,acpi=off \
         -cpu {{CPU}} \
-        -m 512M \
+        -m {{RAM}} \
         -device ramfb \
         {{DISPLAY_FLAGS}} \
         -drive if=pflash,format=raw,readonly=on,file={{OVMF_ARM}} \
@@ -85,7 +86,7 @@ _prep:
     qemu-system-aarch64 {{ACCEL}} \
         -machine virt,acpi=off \
         -cpu {{CPU}} \
-        -m 512M \
+        -m {{RAM}} \
         -device ramfb \
         {{DISPLAY_FLAGS}} \
         -drive if=pflash,format=raw,readonly=on,file={{OVMF_ARM}} \