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|
.file "boot.S"
#define ASM_FILE 1
#include "multiboot.h"
#include "boot/config.h"
#undef ASM_FILE
#define AOUT_KLUDGE MULTIBOOT_AOUT_KLUDGE
#define PHYSADDR(x) (x - 0xffff800000000000)
.global entry, _start, initial_page_table
.code32
.set ARCH, 0
.set CHECKSUM, -(MULTIBOOT2_HEADER_MAGIC + ARCH + (multiboot_header_end - multiboot_header))
/* This header tells GRUB we can be run */
.section .multiboot
.align 8
multiboot_header:
.long MULTIBOOT2_HEADER_MAGIC
.long ARCH
.long multiboot_header_end - multiboot_header
.long CHECKSUM
.align 8
address_tag_start:
.short MULTIBOOT_HEADER_TAG_ADDRESS
.short MULTIBOOT_HEADER_TAG_OPTIONAL
.long address_tag_end - address_tag_start
.long PHYSADDR(multiboot_header) /* header_addr = beginning of MB header */
.long PHYSADDR(k_start) /* load_addr = beginning of .text */
.long PHYSADDR(_edata) /* load_end_addr = end of .data */
.long PHYSADDR(_end) /* bss_end_addr = end of .bss */
address_tag_end:
.align 8
entry_address_tag_start:
.short MULTIBOOT_HEADER_TAG_ENTRY_ADDRESS
.short MULTIBOOT_HEADER_TAG_OPTIONAL
.long entry_address_tag_end - entry_address_tag_start
.long PHYSADDR(_start) /* entry_addr */
entry_address_tag_end:
#if 0
.align 8
framebuffer_tag_start:
.short 5
.short 0
.long frame_buffer_tag_end - framebuffer_tag_start
.long 0 // 1280
.long 0 // 720
.long 0 // 32
frame_buffer_tag_end:
#endif
.align 8
.short MULTIBOOT_HEADER_TAG_END
.short 0
.long 8
multiboot_header_end:
_start:
// disable interrupts during boot
cli
// Take the multiboot information and store it somewhere.
movl $PHYSADDR(sys_stack_bottom), %esp
// reset the stack flags
pushl $0
popf
// set base pointer
movl %esp, %ebp
// pushl %eax
pushl $0x0
pushl %ebx /* Stash the meminfo for later */
// Set up the gdt
lgdt PHYSADDR(GDTPointer)
// set cr3 = start of PML4
mov $PHYSADDR(pml4), %eax
mov %eax, %cr3
// enable PAE
mov %cr4, %eax
or $0x20, %eax
mov %eax, %cr4
// enter long mode
mov $0xC0000080, %ecx
rdmsr
or $0x101, %eax
wrmsr
// Enable paging
movl %cr0, %eax
or $0x80000000, %eax
movl %eax, %cr0
// jump into 64 bit code
ljmp $0x08, $PHYSADDR(_trampoline)
.code64
// for some god-knows why reason, GDB wont set up breakpoints correctly without this trampoline
// even though Weenix still runs if you ljmp directly into _start64 -_-
_trampoline:
// paging is at this point enabled, so no more need more PHYSADDR() wrappers
movabsq $_start64, %rax
jmp *%rax
_start64:
// move the stack pointer to himem so that it is valid once we delete the low map
movq $KERNEL_VMA, %rax
addq %rax, %rsp
addq %rax, %rbp
popq %rbx
movq %rbx, %r11
// set up sregs
movq $0x0, %rax
mov %ax, %ds
mov %ax, %es
mov %ax, %ss
mov %ax, %fs
mov %ax, %gs
mov %r11, %rdi
// now we jump into the C entrypoint.
call entry
cli
hlt // when its done, we are done
// [+] TODO we dont actually set the stack pointer anywhere here???
.align 16
GDT64:
GDTNull:
.quad 0
GDTKernelCode:
// base = 0x0, limit = 0x0
// flags: present, ring 0, executable, readable, 64bit
.word 0, 0
.byte 0, 0x9a, 0x20, 0
GDTEnd:
GDTPointer:
.word GDTEnd - GDT64 - 1 // size of gdt - 1
.long PHYSADDR(GDT64) // pointer to gdt
.code32
.data
sys_stack: // set up 1KB stack
.align 4
.skip 0x1000
sys_stack_bottom:
.align 0x1000
initial_page_table: // maps first 1GB of RAM to both 0x0000000000000000 and 0xffff800000000000
pml4:
.quad PHYSADDR(pdpt) + 3 // 0x0000000000000000
.fill 255,8,0
.quad PHYSADDR(pdpt) + 3 // 0xffff800000000000
.fill 255,8,0
pdpt:
.quad 0x0000000000000083 // 0
.fill 511,8,0
|
