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c9191444963ce4d0cbafba0113f41e08daec5762
stevia/src/stage2/stage2.nasm
Elaina Claus c919144496 turns out huge unreal mode isn't supported in bochs 
huge unreal mode is 4GiB code in 16bit mode + 4GiB data
we will just use the regular big flat model instead (64KiB code/4GiB data)
2024-10-13 14:50:49 -04:00

492 lines
13 KiB
NASM
Executable File
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; Copyright (c) 2023 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
[BITS 16]
[ORG 0x0500] ; IF YOU CHANGE ORG CHANGE THE SIGN OFFSET AT THE END
[CPU KATMAI]
[map all stage2.map]
[WARNING -reloc-abs-byte]
[WARNING -reloc-abs-word]
[WARNING -reloc-abs-dword] ; Yes, we use absolute addresses. surpress these warnings.
%define __STEVIA_STAGE2
%define __STAGE2_SEGMENT 0x0000
; ###############
; Headers/Includes/Definitions
; ###############
%include "util/bochs_magic.inc"
%include "cdecl16.inc"
%include "entry.inc"
%include "config.inc"
%include "early_mem.inc"
%include "error_codes.inc"
%macro print_string 1
mov ax, %1
push ax
call PrintString
add sp, 0x2
%endmacro
section .text
org 0x0500
begin_text:
jmp short (init - $$)
nop
ALIGN 4, db 0x90
init:
cli ; We do not want to be interrupted
mov cx, (end_bss - begin_bss) ; count = bss length
mov ax, begin_bss
shr ax, 4
mov es, ax ; es = begining of bss section
xor ax, ax
mov di, ax ; dst = 0
cld
rep stosb ; zero bss section
mov ax, __STAGE2_SEGMENT ; configured segment
mov ds, ax ; Set segment registers to 0
mov es, ax ; *
mov fs, ax ; *
mov gs, ax ; *
mov ss, ax ; Set Stack Segment to data segment
mov sp, stack_top ; Set Stack Pointer
mov bp, sp
sub sp, 0x20 ; 32 bytes for local varibles
sti
jmp word __STAGE2_SEGMENT:main
; ###############
; Functions
; ###############
%include "util/kmem_func.nasm"
%include "util/kmemcpy5_func.nasm"
%include "util/kmemset4_func.nasm"
%include "util/error_func.nasm"
; ###############
; FAT32 Driver
; ###############
boot_drive_ptr:
dw 0x0000
partition_offset_ptr:
dw 0x0000
%include 'fat32/FAT32_SYS.inc'
; ###############
; BIOS functions
; ###############
%include 'BIOS/BIOS_SYS.inc'
; structures
struc SteviaInfoStruct_t
.MemoryMapPtr resd 1
.MemoryMapEntries resd 1
endstruc
struc EarlyBootStruct_t
.lba_packet resb LBAPkt_t_size
.partition_table resb partition_table_SIZE
.fat32_bpb resb fat32_bpb_SIZE
.fat32_ebpb resb fat32_ebpb_SIZE
.fat32_nc_data resb fat32_nc_data_SIZE
endstruc
; bp - 2 : uint8_t boot_drive
; bp - 4 : uint16_t part_offset
ALIGN 4, db 0x90
main:
lea ax, [bp - 2]
mov [boot_drive_ptr], ax
lea ax, [bp - 4]
mov [partition_offset_ptr], ax ; setup pointers to boot_drive and partition offset on stack
mov byte [bp - 2], dl ; boot_drive (probably 0x80)
mov word [bp - 4], si ; partition_offset
mov eax, dword [STAGE2_SIG]
cmp eax, 0xDEADBEEF
je main.stage2_main
ERROR STAGE2_SIGNATURE_MISSING
.stage2_main:
call SetTextMode
call disable_cursor
print_string HelloPrompt_cstr
; enable A20 gate
call EnableA20
print_string A20_Enabled_OK_cstr
; enter unreal mode
call EnterUnrealMode
print_string UnrealMode_OK_cstr
; get system memory map
call GetMemoryMap
print_string MemoryMap_OK_cstr
; FAT Driver setup
call InitFATDriver
print_string InitFATSYS_OK_cstr
;
; Find first cluster of bootable file
;
call SearchFATDIR
push dword eax
print_string FileFound_OK_cstr
push dword eax
call PrintDWORD ; void PrintDWORD(uint32_t dword)
add sp, 0x4
print_string NewLine_cstr
hcf:
hlt
jmp short (hcf - $$)
; ##############################
;
; SYSTEM CONFIGURATION FUNCTIONS
;
; ##############################
; Prints a C-Style string (null terminated) using BIOS vga teletype call
; void PrintString(char* buf)
ALIGN 4, db 0x90
PrintString:
__CDECL16_ENTRY
mov di, [bp + 4] ; first arg is char*
.str_len:
xor cx, cx ; ECX = 0
not cx ; ECX = -1 == 0xFFFF
xor ax, ax ; search for al = 0x0
cld
repne scasb ; deincrement cx while searching for al
not cx ; the inverse of a neg number = abs(x) - 1
dec cx ; CX contains the length of the string - nul byte at end
.print:
mov si, [bp + 4] ; source string
.print_L0:
movzx ax, byte [si]
push ax
call PrintCharacter
add sp, 0x2
inc si
dec cx
jcxz PrintString.endp
jmp PrintString.print_L0 ; Fetch next character from string
.endp:
__CDECL16_EXIT
ret ; Return from procedure
; Prints a single character
; void PrintCharacter(char c);
ALIGN 4, db 0x90
PrintCharacter:
__CDECL16_ENTRY
.func:
mov ax, [bp + 4] ; c
mov dx, 0x00ff
and ax, dx
mov ah, 0x0E ; INT 0x10, AH=0x0E call
mov bx, 0x0007 ; BH = page no. BL =Text attribute 0x07 is lightgrey font on black background
int 0x10 ; call video interrupt
.endp:
__CDECL16_EXIT
ret
; TODO: fix the prolog, epilog and stack usage to confirm with cdecl16
; prints the hex representation of of val
; void PrintDWORD(uint32_t val);
ALIGN 4, db 0x90
PrintDWORD:
__CDECL16_ENTRY
.func:
lea si, [IntToHex_table]
mov ebx, 16 ; base-16
mov dword eax, [bp + 4] ;val
xor edx, edx
xor cx, cx
.next_digit:
div ebx ; dividend in edx:eax -> quotient in eax, remainder in edx
push dx ; save remainder
inc cx
xor dx, dx
test eax, eax
jnz PrintDWORD.next_digit
.zero_pad:
cmp cx, 0x0008
je PrintDWORD.print_stack
xor ax, ax
push ax
inc cx
jmp PrintDWORD.zero_pad
.print_stack:
pop bx
dec cx
push cx
movzx ax, byte [bx+si+0] ; bx = index into Hex lookup table
push ax
call PrintCharacter
add sp, 0x2
pop cx
jcxz PrintDWORD.endp
jmp PrintDWORD.print_stack
.endp:
__CDECL16_EXIT
ret
; ##############################
;
; SYSTEM CONFIGURATION FUNCTIONS
;
; ##############################
ALIGN 4, db 0x90
EnterUnrealMode:
__CDECL16_ENTRY
.func:
cli ; no interrupts
push ds ; save real mode data/stack selectors
push es
push fs
push gs
push ss
push cs ; save real mode code selector
xor ax, ax ;
pop ax ; save cs to ax to setup far jump
mov word [__UNREAL_SEGMENT], ax
lgdt [((__STAGE2_SEGMENT << 4) + unreal_gdt_info)] ; load unreal gdt
mov eax, cr0
or al,1 ; set pmode bit
mov cr0, eax ; switch to pmode
jmp short $+2
;jmp far 0x0008:EnterUnrealMode.load_cs
db 0xEA ; jmp far imm16:imm16
dw EnterUnrealMode.load_cs ; error_far_ptr
dw 0x0008 ; error_far_seg
.load_cs:
mov bx, 0x10 ; select descriptor 2
mov ds, bx ; 10h = 0001_0000b
mov ss, bx
mov es, bx
mov fs, bx
mov gs, bx ; other data/stack to index 2 (off 0x10)
and al,0xFE ; toggle bit 1 of cr0
mov cr0, eax ; back to realmode
jmp short $+2
;jmp far 0x0008:EnterUnrealMode.unload_cs
db 0xEA ; jmp far imm16:imm16
dw EnterUnrealMode.unload_cs ; error_far_ptr
__UNREAL_SEGMENT:
dw 0x0000 ; error_far_seg
EnterUnrealMode.unload_cs:
pop ss
pop gs
pop fs
pop es
pop ds ; get back old segments
sti
.endp:
__CDECL16_EXIT
ret
end_text:
section .data follows=.text
align 512
begin_data:
; #############
;
; Strings
;
; #############
%macro define_str 2
ALIGN 4
%1_str:
db %2
%define str_len %strlen(%2) ; string
%1_str_len:
dd str_len
%endmacro
; TODO: technically this is a cstr but it splices a return and newline on the end
; TODO: this probably should be seperated out and the printing functionality should
; TODO: place that newline and return
%macro define_cstr 2
%define CRLF_NUL 0Dh, 0Ah, 00h
ALIGN 4
%1_cstr:
db %2, CRLF_NUL
%endmacro
define_cstr HelloPrompt, "Hello from Stevia Stage2!"
define_cstr A20_Enabled_OK, "A20 Enabled OK"
define_cstr MemoryMap_OK, "Memory map OK"
define_cstr UnrealMode_OK, "Unreal mode OK"
define_cstr FileFound_OK, "Found SFN entry for bootable binary, first cluster -> "
define_cstr InitFATSYS_OK, "FAT32 Driver Init..."
define_cstr NewLine, ""
define_str BootTarget, "BOOT BIN"
ALIGN 4
IntToHex_table:
db '0123456789ABCDEF'
; see docs/gdt.txt for a quick refresher on GDT
ALIGN 16, db 0
unreal_gdt_info:
unreal_gdt_size: dw (unreal_gdt_end - unreal_gdt_start) - 1
unreal_gdt_ptr: dd ((__STAGE2_SEGMENT << 4) + unreal_gdt_start)
unreal_gdt_start:
; entry 0 (null descriptor)
dq 0 ; first entry is null
; entry 1 (16bit code 64KiB limit)
dd 0x0000FFFF ; Base Address(15:0) 31:16, Segment Limit(15:0) 15:0
db 0x00 ; Base Address 23:16
db 1001_1010b ; Access Byte: Present, ring0, S = 1, executable (1), non-conforming, readable, Accessed
db 0000_0000b ; Flags: GR = 4KiB, attr = <DB/L/Avl>, Granularity = 4KiB & 16:19 of limit
db 0x00 ; Base Address 31:24
; entry 2 (16bit data segment with 4 GiB flat mapping)
dd 0x0000FFFF ; Base Address(15:0) 31:16, Segment Limit(15:0) 15:0
db 0x00 ; Base Address(23:16)
db 1001_0010b ; Access Byte: Present, ring0, S = 1, data (0), non-confirming, writable, present
db 1000_1111b ; Flags: GR = 4KiB, attr = <16-bit/?/?>, Granularity = 4KiB & 16:19 of limit
db 0x00 ; Base Address(31:24)
unreal_gdt_end:
ALIGN 16, db 0
gdt32_info:
gdt32_size: dw (gdt32_end - gdt32_start) - 1
gdt32_ptr: dd ((__STAGE2_SEGMENT << 4) + gdt32_start)
gdt32_start:
dq 0
.gdt32_code:
dw 0xFFFF ; code segment (RX)
dw 0x0000
db 0x00
db 1001_1000b ; Access: readable, executable
db 1100_1111b ; 4KB granularity, 32-bit
db 0x00
.gdt32_data: ; data segment (RW)
dw 0xFFFF
dw 0x0000
db 0x00
db 1001_0010b ; Access: readable, writable
db 1100_1111b ; 4KB granularity, 32-bit
db 0x00
.gdt32_stack: ; Stack segment (RW)
dw 0xFFFF
dw 0x0000
db 0x00
db 1001_0010b ; Access: readable, writable
db 1100_1111b ; 4KB granularity, 32-bit
db 0x00
.gdt32_ro_data: ; Read-only data segment (RO)
dw 0xFFFF
dw 0x0000
db 0x00
db 1001_0000b ; Access: readable, not writable
db 1100_1111b ; 4KB granularity, 32-bit
db 0x00
gdt32_end:
ALIGN 8
version_magic:
db "Stevia Stage2 built with NASM - ", __NASM_VER__, 00h
ALIGN 8
datetime_magic:
db 'Assembled - ', __DATE__, ' ', __TIME__, 00h
end_data:
%assign bytes_remaining ((MAX_STAGE2_BYTES - 4) - ($ - $$))
%warning STAGE2 has bytes_remaining bytes remaining for code/data (MAX: MAX_STAGE2_BYTES)
; section start location needs to be a 'critical expression'
; i.e resolvable at build time, we are setting 0x7E00 as the offset since
section .sign start=((MAX_STAGE2_BYTES - 512) + 0x0500)
times ((512 - 4) - ($ -$$) ) db 0x90 ; nop
STAGE2_SIG: dd 0xDEADBEEF ; Signature to mark the end of the stage2
section .bss follows=.sign
align 512
begin_bss:
stack_bottom:
stack resb 4096
stack_top:
stage2_main_redzone resb 32
SteviaInfo resd 4
fat32_state resb FAT32_State_t_size
disk_buffer resb 512
fat_buffer resb 512
dir_buffer resb 512
fat_fsinfo resb 512
%define BIOSMemoryMap_SIZE 4096
BIOSMemoryMap resb 4096
end_bss:
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