| /* |
| * i386 boot code, based on qemu-bmibug. |
| * |
| * Copyright 2019 Doug Gale |
| * Copyright 2019, 2024 Linaro |
| * |
| * This work is licensed under the terms of the GNU GPL, version 2 or later. |
| * See the COPYING file in the top-level directory. |
| * |
| * SPDX-License-Identifier: GPL-2.0-or-later |
| */ |
| |
| .section .head |
| |
| /* Multi-boot header */ |
| multiboot_st: |
| .int 0x1BADB002 |
| .int 0x10000 |
| .int -(0x10000+0x1BADB002) |
| // Load address |
| .int __load_st |
| .int __load_st |
| .int __load_en |
| .int __bss_en |
| .int _start |
| // mode |
| .int 0 |
| // width |
| .int 0 |
| // height |
| .int 0 |
| // depth |
| .int 0 |
| |
| .code32 |
| .section .text |
| |
| /* Kernel Entry Point */ |
| .global _start |
| _start: |
| // Setup stack ASAP |
| mov $stack_end,%esp |
| |
| // Load GDT ASAP |
| lgdt gdtr |
| ljmp $0x8,$.Lloadcs |
| .Lloadcs: |
| mov $0x10,%eax |
| mov %eax,%ds |
| mov %eax,%es |
| mov %eax,%fs |
| mov %eax,%gs |
| mov %eax,%ss |
| |
| // Fixup the IDT to the ridiculous i386 layout |
| xor %ebx,%ebx |
| .Lnextidt: |
| mov idt_00(,%ebx,8),%eax |
| shr $16,%eax |
| movw $0x8,idt_00+2(,%ebx,8) |
| movw $0x8E00,idt_00+4(,%ebx,8) |
| movw %ax,idt_00+6(,%ebx,8) |
| add $1,%ebx |
| cmp $32,%ebx |
| jl .Lnextidt |
| |
| // Load IDTR |
| push $idt_00 |
| push $((32 * 8 - 1) << 16) |
| lidt 2(%esp) |
| add $8,%esp |
| |
| /* |
| * Don't worry about stack frame, assume everything |
| * is garbage when we return, we won't need it. |
| */ |
| call main |
| |
| _exit: /* output any non-zero result in eax to isa-debug-exit device */ |
| test %al, %al |
| jz 1f |
| out %ax, $0xf4 |
| |
| 1: /* QEMU ACPI poweroff */ |
| mov $0x604,%edx |
| mov $0x2000,%eax |
| out %ax,%dx |
| hlt |
| jmp 1b |
| |
| /* |
| * Helper Functions |
| */ |
| |
| /* Output a single character to serial port */ |
| .global __sys_outc |
| __sys_outc: |
| pushl %ebp |
| movl %esp, %ebp |
| out %al,$0xE9 |
| movl %ebp, %esp |
| popl %ebp |
| ret |
| |
| |
| /* Interrupt Descriptor Table */ |
| |
| .section .data |
| .align 16 |
| |
| idt_00: .int 0, 0 |
| idt_01: .int 0, 0 |
| idt_02: .int 0, 0 |
| idt_03: .int 0, 0 |
| idt_04: .int 0, 0 |
| idt_05: .int 0, 0 |
| idt_06: .int 0, 0 /* intr_6_opcode, Invalid Opcode */ |
| idt_07: .int 0, 0 |
| idt_08: .int 0, 0 |
| idt_09: .int 0, 0 |
| idt_0A: .int 0, 0 |
| idt_0B: .int 0, 0 |
| idt_0C: .int 0, 0 |
| idt_0D: .int 0, 0 |
| idt_0E: .int 0, 0 |
| idt_0F: .int 0, 0 |
| idt_10: .int 0, 0 |
| idt_11: .int 0, 0 |
| idt_12: .int 0, 0 |
| idt_13: .int 0, 0 |
| idt_14: .int 0, 0 |
| idt_15: .int 0, 0 |
| idt_16: .int 0, 0 |
| idt_17: .int 0, 0 |
| idt_18: .int 0, 0 |
| idt_19: .int 0, 0 |
| idt_1A: .int 0, 0 |
| idt_1B: .int 0, 0 |
| idt_1C: .int 0, 0 |
| idt_1D: .int 0, 0 |
| idt_1E: .int 0, 0 |
| idt_1F: .int 0, 0 |
| |
| gdt: |
| .short 0 |
| gdtr: |
| .short gdt_en - gdt - 1 |
| .int gdt |
| |
| // Code |
| .short 0xFFFF |
| .short 0 |
| .byte 0 |
| .byte 0x9b |
| .byte 0xCF |
| .byte 0 |
| |
| // Data |
| .short 0xFFFF |
| .short 0 |
| .byte 0 |
| .byte 0x93 |
| .byte 0xCF |
| .byte 0 |
| |
| gdt_en: |
| |
| .section .bss |
| .align 16 |
| |
| stack: .space 65536 |
| stack_end: |
