From e8c6577617bffa4402c07c7aa20e3c24f03c1c20 Mon Sep 17 00:00:00 2001
From: Benji Dial <benji6283@gmail.com>
Date: Sun, 6 Sep 2020 00:48:07 -0400
Subject: program loading, others

big kernel additions: paging, elf loading, separate kernel and user page allocation
it now properly loads and runs sd0:bin/init.elf
still need to determine which disk was booted from, and start the init on that disk
---
 src/boot.asm | 49 +++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 39 insertions(+), 10 deletions(-)

(limited to 'src/boot.asm')

diff --git a/src/boot.asm b/src/boot.asm
index c74145c..28d1a89 100644
--- a/src/boot.asm
+++ b/src/boot.asm
@@ -10,6 +10,7 @@ pci_ver       equ 0x4002
 last_pci_bus  equ 0x4004
 
 pci_support equ 0x80
+pae_support equ 0x40
 
   in al, 0x92
   or al, 0x02
@@ -46,6 +47,34 @@ pci_support equ 0x80
   mov byte [last_pci_bus], cl
 
 no_pci:
+  mov eax, 1
+  cpuid
+
+  test dl, 0x40
+  jz no_pae
+
+  or byte [support_flags], pae_support
+
+no_pae:
+  mov ax, 0x1000
+  mov es, ax
+  xor di, di
+
+  mov edx, 0x534d4150
+  xor ebx, ebx
+
+mmap_loop:
+  mov eax, 0xe820
+  mov ecx, 24
+  int 0x15
+
+  jc mmap_end
+  add di, 24
+  test ebx, ebx
+  jnz mmap_loop
+mmap_end:
+  mov word [0x4006], di
+
   cli
 
   lgdt [gdt]
@@ -54,36 +83,36 @@ no_pci:
   or al, 0x01
   mov cr0, eax
 
-  jmp 0x08:pmode
+  jmp 0x10:pmode
 
 bits 32
 
 pmode:
-  mov ax, 0x10
+  mov ax, 0x18
   mov ds, ax
   mov ss, ax
   mov esp, 0x00040000
 
   xor ebp, ebp
+
   call kernel_segment * 16
 
 halt:
   hlt
   jmp halt
 
-times $$ + 0x018a - $ db 0
+times $$ + 510 - 0x3e - $ - (gdt.e - gdt) db 0
 
-;0x7dc8
 gdt:
   dw .e - .t
   dd .t
 .t:
-  dq 0x0000_0000_0000_0000
-  dq 0x00c0_9a00_0000_0037
-  dq 0x00c1_9200_0000_ffff
-  dq 0x0000_0000_0000_0000;TODO: task
-  dq 0x0000_0000_0000_0000
-  dq 0x0000_0000_0000_0000
+  dq 0x0000_0000_0000_0000;0x00: null
+  dq 0x0040_8900_4f98_0068;0x08: tss, 0x4f98
+  dq 0x00cf_9a00_0000_ffff;0x10: kernel code
+  dq 0x00cf_9200_0000_ffff;0x18: kernel data
+  dq 0x00cf_fa00_0000_ffff;0x20: user code
+  dq 0x00cf_f200_0000_ffff;0x28: user data
 .e:
 
 dw 0xaa55
\ No newline at end of file
-- 
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