wrote a basic bootloader

2025-02-25 01:14:52 +00:00
commit 012b0454ed
36 changed files with 1667 additions and 0 deletions
@@ -0,0 +1,140 @@
+/* Tell the linker that we want an x86_64 ELF64 output file */
+OUTPUT_FORMAT(elf64-x86-64)
+OUTPUT_ARCH(i386:x86-64)
+
+/* Entry points */
+ENTRY(start)
+
+/* Define the program headers we want in our final kernel executable */
+PHDRS
+{
+    boot    PT_LOAD    FLAGS((1 << 0) | (1 << 2)) ; /* Execute + Read */
+    text    PT_LOAD    FLAGS((1 << 0) | (1 << 2)) ; /* Execute + Read */
+    rodata  PT_LOAD    FLAGS((1 << 2)) ;            /* Read only */
+    data    PT_LOAD    FLAGS((1 << 1) | (1 << 2)) ; /* Write + Read */
+}
+
+/* The kernel is linked to run at -2GB (KERNEL_BASE) */
+KERNEL_BASE = 0xFFFFFFFF80000000;
+
+SECTIONS
+{
+    /* For BIOS boot, start at 1MB physical */
+    . = 1M;
+
+    .boot : {
+        /* BIOS boot sections */
+        KEEP(*(.multiboot))      /* Multiboot header */
+        *(.boottext)             /* BIOS boot code */
+        *(.boottext.*)
+        
+        /* UEFI boot sections */
+        KEEP(*(.pe_header))      /* PE/COFF header for UEFI */
+        *(.efi.header)           /* EFI header */
+        . = ALIGN(4K);
+        *(.efi.text)            /* UEFI boot code */
+        *(.efi.text.*)
+        *(.efi.data)            /* UEFI data */
+        *(.efi.data.*)
+    } :boot
+
+    /* Switch to higher half for kernel proper */
+    . += KERNEL_BASE;
+
+    /* Code section */
+    .text : AT(ADDR(.text) - KERNEL_BASE) {
+        _text_start = .;
+        *(.text)
+        *(.text.*)
+        . = ALIGN(4K);
+        _text_end = .;
+    } :text
+
+    /* Read-only data */
+    .rodata : AT(ADDR(.rodata) - KERNEL_BASE) {
+        _rodata_start = .;
+        *(.rodata)
+        *(.rodata.*)
+        . = ALIGN(4K);
+        _rodata_end = .;
+    } :rodata
+
+    /* Read-write data (initialized) */
+    .data : AT(ADDR(.data) - KERNEL_BASE) {
+        _data_start = .;
+        *(.data)
+        *(.data.*)
+        *(.got)
+        *(.got.*)
+        . = ALIGN(4K);
+        _data_end = .;
+    } :data
+
+    /* Read-write data (uninitialized) */
+    .bss : AT(ADDR(.bss) - KERNEL_BASE) {
+        _bss_start = .;
+        *(COMMON)
+        *(.bss)
+        *(.bss.*)
+        . = ALIGN(4K);
+        _bss_end = .;
+    } :data
+
+    /* Page-aligned data structures */
+    .padata ALIGN(4K) : AT(ADDR(.padata) - KERNEL_BASE) {
+        *(.padata)
+    } :data
+
+    /* Initial stack space */
+    .stack ALIGN(4K) : AT(ADDR(.stack) - KERNEL_BASE) {
+        *(.stack)
+    } :data
+
+    /* Thread-local storage */
+    .tdata ALIGN(4K) : AT(ADDR(.tdata) - KERNEL_BASE) {
+        _tdata_start = .;
+        *(.tdata)
+        *(.tdata.*)
+        . = ALIGN(4K);
+        _tdata_end = .;
+    } :data
+
+    .tbss ALIGN(4K) : AT(ADDR(.tbss) - KERNEL_BASE) {
+        _tbss_start = .;
+        *(.tbss)
+        *(.tbss.*)
+        . = ALIGN(4K);
+        _tbss_end = .;
+    } :data
+
+    /* Debugging information */
+    .debug_info     0 : { *(.debug_info) }
+    .debug_abbrev   0 : { *(.debug_abbrev) }
+    .debug_aranges  0 : { *(.debug_aranges) }
+    .debug_ranges   0 : { *(.debug_ranges) }
+    .debug_line     0 : { *(.debug_line) }
+    .debug_str      0 : { *(.debug_str) }
+    .debug_loc      0 : { *(.debug_loc) }
+
+    /* Discard unused sections */
+    /DISCARD/ : {
+        *(.eh_frame)
+        *(.note.*)
+        *(.comment)
+    }
+}
+
+/* Symbols needed by both BIOS and UEFI boot code */
+PROVIDE(_kernel_start = ADDR(.boot));
+PROVIDE(_kernel_end = ADDR(.tbss) + SIZEOF(.tbss));
+PROVIDE(_kernel_physical_end = ADDR(.tbss) - KERNEL_BASE + SIZEOF(.tbss));
+PROVIDE(_kernel_virtual_base = KERNEL_BASE);
+
+/* UEFI-specific symbols */
+PROVIDE(_efi_start = ADDR(.boot));
+PROVIDE(_efi_text_start = ADDR(.efi.text));
+PROVIDE(_efi_text_end = ADDR(.efi.text) + SIZEOF(.efi.text));
+
+/* BIOS-specific symbols */
+PROVIDE(_multiboot_start = ADDR(.multiboot));
+PROVIDE(_boottext_start = ADDR(.boottext));