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Kernel: Create page structures correctly in boot.s

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This commit is contained in:
etaIneLp 2020-05-25 17:19:37 -04:00 • committed by Andreas Kling
parent 4e607192c7
commit 826dc94187
3 changed files with 76 additions and 100 deletions
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104
Kernel/Arch/i386/Boot/boot.S
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@ -42,8 +42,14 @@ boot_pd0:
.global boot_pd3
boot_pd3:
.skip 4096
.global boot_pd3_pde1023_pt
boot_pd3_pde1023_pt:
.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
@ -69,18 +75,18 @@ pdpt
boot_pd0 : 512 pde's
0: (0-2MB) (id 2MB page)
1: (2-4MB) (id 2MB page)
2: (4-6MB) (id 2MB page)
3: (6-8MB) (id 2MB page)
0: boot_pd0_pt0 (0-2MB) (id 512 4KB pages)
boot_pd3 : 512 pde's
0: boot_pd3_pde0 (3072-3074MB) (pseudo)
1: boot_pd3_pde1 (3074-3076MB) (pseudo)
2: boot_pd3_pde2 (3076-3078MB) (pseudo)
3: boot_pd3_pde3 (3078-3080MB) (pseudo)
4: boot_pd3_pde1023_pt (4094-4096MB) (for page table mappings)
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:
@ -104,41 +110,74 @@ start:
xorl %eax, %eax
rep stosl
/* identity map bottom 8MB using 2MB pages (only PDE, no PTE) */
movl $4, %ecx
xorl %eax, %eax
movl $(boot_pd0 - 0xc0000000), %edi
1:
movl %eax, 0(%edi)
/* PS(2MB) + R/W + Present */
orl $0x83, 0(%edi)
addl $8, %edi
addl $(1048576 * 2), %eax
loop 1b
/* clear pd3 */
movl $(boot_pd3 - 0xc0000000), %edi
movl $1024, %ecx
xorl %eax, %eax
rep stosl
/* pseudo-identity map first 8MB above 3GB mark using 2MB pages again */
movl $4, %ecx
/* 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)
/* PS(2MB) + R/W + Present */
orl $0x83, 0(%edi)
/* R/W + Present */
orl $0x3, 0(%edi)
addl $8, %edi
addl $(1048576 * 2), %eax
addl $4096, %eax
loop 1b
/* identity map the 0 to 2MB range */
movl $512, %ecx
movl $(boot_pd0_pt0 - 0xc0000000), %edi
/*movl $0x100000, %eax*/
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_pde1023_pt - 0xc0000000), 4088(%edi)
movl $(boot_pd3_pt1023 - 0xc0000000), 4088(%edi)
orl $0x3, 4088(%edi)
movl $0, 4092(%edi)
@ -158,10 +197,9 @@ start:
/* jmp to an address above the 3GB mark */
push %cs
push $1f
push $1f
retf
1:
movl %cr3, %eax
movl %eax, %cr3