banan-os/kernel/arch/i686/boot.S

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4.6 KiB
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.set PG_PRESENT, 1<<0
.set PG_READ_WRITE, 1<<1
.set PG_PAGE_SIZE, 1<<7
.set FB_WIDTH, 800
.set FB_HEIGHT, 600
.set FB_BPP, 32
#define KERNEL_OFFSET 0xC0000000
#define V2P(vaddr) ((vaddr) - KERNEL_OFFSET)
.code32
# multiboot2 header
.section .multiboot, "aw"
.align 8
multiboot2_start:
.long 0xE85250D6
.long 0
.long multiboot2_end - multiboot2_start
.long -(0xE85250D6 + (multiboot2_end - multiboot2_start))
# framebuffer tag
.align 8
.short 5
.short 0
.long 20
.long FB_WIDTH
.long FB_HEIGHT
.long FB_BPP
# legacy start
.align 8
.short 3
.short 0
.long 12
.long V2P(_start)
.align 8
.short 0
.short 0
.long 8
multiboot2_end:
.section .bananboot, "aw"
.align 8
bananboot_start:
.long 0xBABAB007
.long -(0xBABAB007 + FB_WIDTH + FB_HEIGHT + FB_BPP)
.long FB_WIDTH
.long FB_HEIGHT
.long FB_BPP
bananboot_end:
.section .bss, "aw", @nobits
.align 4096
boot_stack_bottom:
.skip 4096 * 4
boot_stack_top:
.global g_kernel_cmdline
g_kernel_cmdline:
.skip 4096
bootloader_magic:
.skip 8
bootloader_info:
.skip 8
.section .data
# Map first GiB to 0x00000000 and 0xC0000000
.align 32
boot_pdpt:
.long V2P(boot_pd) + (PG_PRESENT)
.long 0
.quad 0
.quad 0
.long V2P(boot_pd) + (PG_PRESENT)
.long 0
.align 4096
boot_pd:
.set i, 0
.rept 512
.long V2P(boot_pts) + i + (PG_READ_WRITE | PG_PRESENT)
.long 0
.set i, i + 0x1000
.endr
boot_pts:
.set i, 0
.rept 512
.rept 512
.long i + (PG_READ_WRITE | PG_PRESENT)
.long 0
.set i, i + 0x1000
.endr
.endr
boot_gdt:
.quad 0x0000000000000000 # null descriptor
.quad 0x00CF9A000000FFFF # kernel code
.quad 0x00CF92000000FFFF # kernel data
boot_gdtr:
.short . - boot_gdt - 1
.long V2P(boot_gdt)
.global g_ap_startup_done
g_ap_startup_done:
.byte 0
.global g_ap_running_count
g_ap_running_count:
.byte 0
.global g_ap_stack_loaded
g_ap_stack_loaded:
.byte 0
.section .text
has_cpuid:
pushfl
pushfl
xorl $0x00200000, (%esp)
popfl
pushfl
popl %eax
xorl (%esp), %eax
popfl
testl $0x00200000, %eax
ret
has_pae:
movl $0, %eax
cpuid
testl $(1 << 6), %edx
ret
has_sse:
movl $1, %eax
cpuid
testl $(1 << 25), %edx
ret
check_requirements:
call has_cpuid
jz .exit
call has_pae
jz .exit
call has_sse
jz .exit
ret
.exit:
jmp system_halt
enable_sse:
movl %cr0, %eax
andw $0xFFFB, %ax
orw $0x0002, %ax
movl %eax, %cr0
movl %cr4, %eax
orw $0x0600, %ax
movl %eax, %cr4
ret
initialize_paging:
# enable PAE
movl %cr4, %ecx
orl $(1 << 5), %ecx
movl %ecx, %cr4
# load page tables
movl $V2P(boot_pdpt), %ecx
movl %ecx, %cr3
# enable paging
movl %cr0, %ecx
orl $(1 << 31), %ecx
movl %ecx, %cr0
ret
.global _start
.type _start, @function
_start:
cli; cld
# save bootloader magic and info
movl %eax, V2P(bootloader_magic)
movl %ebx, V2P(bootloader_info)
# load boot stack
movl $V2P(boot_stack_top), %esp
# load boot GDT
lgdt V2P(boot_gdtr)
ljmpl $0x08, $V2P(gdt_flush)
gdt_flush:
# set correct segment registers
movw $0x10, %ax
movw %ax, %ds
movw %ax, %ss
movw %ax, %es
# do processor initialization
call check_requirements
call enable_sse
call initialize_paging
# load higher half stack pointer
movl $boot_stack_top, %esp
# jump to higher half
leal higher_half, %ecx
jmp *%ecx
higher_half:
# call global constuctors
call _init
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# call to the kernel itself (clear ebp for stacktrace)
xorl %ebp, %ebp
subl $8, %esp
pushl bootloader_info
pushl bootloader_magic
call kernel_main
addl $16, %esp
# call global destructors
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call _fini
system_halt:
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xchgw %bx, %bx
cli
1: hlt
jmp 1b
.section .ap_init, "ax"
.code16
.global ap_trampoline
ap_trampoline:
jmp 1f
.align 8
ap_stack_ptr:
.skip 4
1:
cli; cld
ljmpl $0x00, $ap_cs_clear
ap_cs_clear:
# load ap gdt and enter protected mode
lgdt ap_gdtr
movl %cr0, %eax
orb $1, %al
movl %eax, %cr0
ljmpl $0x08, $ap_protected_mode
.code32
ap_protected_mode:
movw $0x10, %ax
movw %ax, %ds
movw %ax, %ss
movw %ax, %es
movl ap_stack_ptr, %esp
movb $1, V2P(g_ap_stack_loaded)
call V2P(enable_sse)
call V2P(initialize_paging)
# load boot gdt and enter long mode
lgdt V2P(boot_gdtr)
ljmpl $0x08, $ap_flush_gdt
ap_flush_gdt:
# move stack pointer to higher half
movl %esp, %esp
addl $KERNEL_OFFSET, %esp
# jump to higher half
leal ap_higher_half, %ecx
jmp *%ecx
ap_higher_half:
# clear rbp for stacktrace
xorl %ebp, %ebp
1: pause
cmpb $0, g_ap_startup_done
jz 1b
lock incb g_ap_running_count
call ap_main
jmp system_halt
ap_gdt:
.quad 0x0000000000000000 # null descriptor
.quad 0x00CF9A000000FFFF # 32 bit code
.quad 0x00CF92000000FFFF # 32 bit data
ap_gdtr:
.short . - ap_gdt - 1
.long ap_gdt