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|
.set MULTIBOOT_MAGIC, 0x1badb002
.set MULTIBOOT_PAGE_ALIGN, 0x1
.set MULTIBOOT_MEMORY_INFO, 0x2
.set multiboot_flags, MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO
.set multiboot_checksum, -(MULTIBOOT_MAGIC + multiboot_flags)
.section .multiboot
.align 4
.long MULTIBOOT_MAGIC
.long multiboot_flags
.long multiboot_checksum
/* for MULTIBOOT_MEMORY_INFO */
.long 0x00000000 /* header_addr */
.long 0x00000000 /* load_addr */
.long 0x00000000 /* load_end_addr */
.long 0x00000000 /* bss_end_addr */
.long 0x00000000 /* entry_addr */
.section .stack, "aw", @nobits
stack_bottom:
.skip 32768
stack_top:
.section .page_tables, "aw", @nobits
.align 4096
.global boot_pdpt
boot_pdpt:
.skip 4096
.global boot_pd0
boot_pd0:
.skip 4096
.global boot_pd3
boot_pd3:
.skip 4096
.global boot_pd0_pt0
boot_pd0_pt0:
.skip 4096 * 4
.global boot_pd3_pts
boot_pd3_pts:
.skip 4096 * 4
.global boot_pd3_pt1023
boot_pd3_pt1023:
.skip 4096
.section .text
.global start
.type start, @function
.extern init
.type init, @function
.extern multiboot_info_ptr
.type multiboot_info_ptr, @object
/*
construct the following (32-bit PAE) page table layout:
pdpt
0: boot_pd0 (0-1GB)
1: n/a (1-2GB)
2: n/a (2-3GB)
3: boot_pd3 (3-4GB)
boot_pd0 : 512 pde's
0: boot_pd0_pt0 (0-2MB) (id 512 4KB pages)
boot_pd3 : 512 pde's
0: boot_pd3_pts[0] (3072-3074MB) (pseudo 512 4KB pages)
1: boot_pd3_pts[1] (3074-3076MB) (pseudo 512 4KB pages)
2: boot_pd3_pts[2] (3076-3078MB) (pseudo 512 4KB pages)
3: boot_pd3_pts[3] (3078-3080MB) (pseudo 512 4KB pages)
4: boot_pd3_pt1023 (4094-4096MB) (for page table mappings)
the 9 page tables each contain 512 pte's that map individual 4KB pages
*/
start:
cli
cld
/* clear pdpt */
movl $(boot_pdpt - 0xc0000000), %edi
movl $1024, %ecx
xorl %eax, %eax
rep stosl
/* set up pdpt[0] and pdpt[3] */
movl $(boot_pdpt - 0xc0000000), %edi
movl $((boot_pd0 - 0xc0000000) + 1), 0(%edi)
movl $((boot_pd3 - 0xc0000000) + 1), 24(%edi)
/* clear pd0 */
movl $(boot_pd0 - 0xc0000000), %edi
movl $1024, %ecx
xorl %eax, %eax
rep stosl
/* clear pd3 */
movl $(boot_pd3 - 0xc0000000), %edi
movl $1024, %ecx
xorl %eax, %eax
rep stosl
/* clear pd0's pt's */
movl $(boot_pd0_pt0 - 0xc0000000), %edi
movl $(1024 * 4), %ecx
xorl %eax, %eax
rep stosl
/* clear pd3's pt's */
movl $(boot_pd3_pts - 0xc0000000), %edi
movl $(1024 * 5), %ecx
xorl %eax, %eax
rep stosl
/* add boot_pd0_pt0 to boot_pd0 */
movl $(boot_pd0 - 0xc0000000), %edi
movl $(boot_pd0_pt0 - 0xc0000000), %eax
movl %eax, 0(%edi)
/* R/W + Present */
orl $0x3, 0(%edi)
/* add boot_pd3_pts to boot_pd3 */
movl $4, %ecx
movl $(boot_pd3 - 0xc0000000), %edi
movl $(boot_pd3_pts - 0xc0000000), %eax
1:
movl %eax, 0(%edi)
/* R/W + Present */
orl $0x3, 0(%edi)
addl $8, %edi
addl $4096, %eax
loop 1b
/* identity map the 0 to 2MB range */
movl $512, %ecx
movl $(boot_pd0_pt0 - 0xc0000000), %edi
xorl %eax, %eax
1:
movl %eax, 0(%edi)
/* R/W + Present */
orl $0x3, 0(%edi)
addl $8, %edi
addl $4096, %eax
loop 1b
/* pseudo identity map the 3072-3080MB range */
movl $(512 * 4), %ecx
movl $(boot_pd3_pts - 0xc0000000), %edi
xorl %eax, %eax
1:
movl %eax, 0(%edi)
/* R/W + Present */
orl $0x3, 0(%edi)
addl $8, %edi
addl $4096, %eax
loop 1b
/* create an empty page table for the top 2MB at the 4GB mark */
movl $(boot_pd3 - 0xc0000000), %edi
movl $(boot_pd3_pt1023 - 0xc0000000), 4088(%edi)
orl $0x3, 4088(%edi)
movl $0, 4092(%edi)
/* point CR3 to PDPT */
movl $(boot_pdpt - 0xc0000000), %eax
movl %eax, %cr3
/* enable PAE + PSE */
movl %cr4, %eax
orl $0x60, %eax
movl %eax, %cr4
/* enable PG */
movl %cr0, %eax
orl $0x80000000, %eax
movl %eax, %cr0
/* jmp to an address above the 3GB mark */
push %cs
push $1f
retf
1:
movl %cr3, %eax
movl %eax, %cr3
/* unmap the 0-1MB range, which isn't used after jmp-ing up here */
movl $256, %ecx
movl $(boot_pd0_pt0 - 0xc0000000), %edi
xorl %eax, %eax
1:
movl %eax, 0(%edi)
addl $8, %edi
loop 1b
/* set up initial stack and jump into C++ land */
mov $stack_top, %esp
and $-16, %esp
addl $0xc0000000, %ebx
movl %ebx, multiboot_info_ptr
call init
add $4, %esp
pushl $exit_message
call kprintf
add $4, %esp
cli
loop:
hlt
jmp loop
exit_message:
.asciz "Kernel exited."
|
