cutting out everything from miniboot
this file has always just been a place holder to get some code to load from the disk I wanted to cut out all the extra stuff in it just to simplify things down.
This commit is contained in:
@@ -21,131 +21,30 @@
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[BITS 32]
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[ORG 0x100000]
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[CPU KATMAI]
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jmp short start32
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jmp short init32
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nop
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; Unless noted otherwise, functions will be the standard x86 cdecl used in GCC
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; In cdecl, subroutine arguments are passed on the stack.
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; Integer values and memory addresses are returned in the EAX register,
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; floating point values in the ST0 x87 register.
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; Registers EAX, ECX, and EDX are caller-saved,
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; and the rest are callee-saved.
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; The x87 floating point registers ST0 to ST7 must be empty (popped or freed)
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; when calling a new function, and ST1 to ST7 must be empty on exiting a function.
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; ST0 must also be empty when not used for returning a value.
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;
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; EXAMPLE: to call uint8_t* kmemset(uint8_t* dest, uint8_t val, uint8_t size);
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; => kmemset(*((char*) 0xb8000), 'F', (80*25))
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;
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; push ebp ; save old call frame pointer
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; mov ebp, esp ; new call frame pointer
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; push 0x000007D0 ; push args RTL, EBP - 4
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; push 'F' ; * EBP - 8
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; push 0x000b8000 ; * EBP - 12
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; call kmemset ; call function, this also places a return pointer on stack
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; add esp, 12 ; remove call arguments from stack frame
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; mov esp, ebp ; restore stack frame pointer (callee saves EBP)
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; pop ebp ; restore call frame pointer
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;
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;
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; 33 bytes BPB + 26 Byte EBPB
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struc BPBStruct
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.OemName resb 8
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.BytesPerSect resw 1
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.SecsPerClust resb 1
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.ResSectors resw 1
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.FATs resb 1
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.RootDirEnts resw 1
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.Sectors resw 1
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.Media resb 1
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.SectPerFAT resw 1
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.SectPerTrack resw 1
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.Heads resw 1
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.Hidden resd 1
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.SectorHuge resd 1
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; begin EBPB
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.DriveNumber resb 1
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.NTReserved resb 1
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.Signature resb 1
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.VolumeID resd 1
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.VolumeLabel resb 11
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.SysIdent resb 8
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endstruc
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; 12 bytes
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struc FSInfoStruct
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.first_root_dir_sector resw 1
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.last_root_dir_sector resw 1
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.root_dir_len resw 1
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.first_data_sector resw 1
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.active_cluster resw 1
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.active_FAT_cluster resw 1
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endstruc
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; 20 bytes
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struc KInfoStruct
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.load_address resd 1
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.file_len resd 1
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.file_name resb 8
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.file_ext resb 3
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.reserved1 resb 1
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endstruc
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; Address Range Descriptor Structure
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;
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; Offset in Bytes Name Description
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; 0 BaseAddrLow u32 - Low 32 Bits of Base Address
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; 4 BaseAddrHigh u32 - High 32 Bits of Base Address
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; 8 LengthLow u32 - Low 32 Bits of Length in Bytes
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; 12 LengthHigh u32 - High 32 Bits of Length in Bytes
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; 16 Type u32 - Address type of this range.
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; 20 ExtType u32 - ACPI 3.0 extended type
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struc AddressRangeDescStruct
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.BaseAddrLow resd 1
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.BaseAddrHigh resd 1
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.LengthLow resd 1
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.LengthHigh resd 1
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.Type resd 1
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.ExtType resd 1
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endstruc
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; 20 bytes, passed to loaded kernel
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struc CBootInfoStruct
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.MemoryMapPtr resd 1
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.MemoryMapEntries resd 1
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.BPBDataPtr resd 1
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.FSInfoPtr resd 1
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.KInfoPtr resd 1
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endstruc
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;;;
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; Errors
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; 0 = unused
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; 1 = No CPUID support on this platform (VM or some very old hardware?)
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; 2 = magic signature not found at end of file
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; 3 = Unexpected/unhandled artithmetic overflow/carry
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; E = General Error
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; S = magic signature not found at end of file
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; O = OK
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;;;
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%define MAX_BYTES (1024 * 8)
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%define VGA_BUF 0xb8000
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;black BG/Green FG
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%define TTY_COLOR 0x0200
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;black BG/Red FG
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%define TTY_ERR_CLR 0x0400
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;subtract 1 for max array values
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%define VGA_MAX_Y 25
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%define VGA_MAX_X 80
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; VGA memory is row-major => offset = (row * MAX_Colums) + colum
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; macro array is counted from 0,0 = 1,1 => 79,24 is the last usable space in a page
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%define VGA_OFFSET(x,y) (((y*VGA_MAX_X) + x)*2)
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;subtract 1 for max array values
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%define VGA_MAX_Y 25
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%define VGA_MAX_X 80
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start32:
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mov ax, 0x10
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ALIGN 16, db 0
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init32:
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mov ax, 0x10 ; 0x10 selector segment
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mov ds, ax
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mov es, ax
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mov fs, ax
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@@ -154,394 +53,35 @@ start32:
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mov esp, stack_top
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mov ebp, esp
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; debugger hack because gdb doesn't like to switch register sizes
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; issue a set $eax = 1 to continue
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%ifdef DEBUG_HACK
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mov eax, 0
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.gdb_hack:
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test eax, eax
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jz start32.gdb_hack
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%endif
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mov eax, dword [BOOT_SIG]
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cmp eax, 0xA0B0C0D0
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jz start32.signature_present
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mov al, "2"
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call error
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jz .signature_present
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mov dl, "S"
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jmp .result
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.signature_present:
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call check_cpuid
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push ebp
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mov ebp, esp
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lea eax, [welcome_cstr]
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push eax
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call vga_puts
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leave
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push ebp
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mov ebp, esp
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lea eax, [version_cstr]
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push eax
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call vga_puts
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leave
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push ebp
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mov ebp, esp
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lea eax, [datetime_cstr]
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push eax
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call vga_puts
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leave
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mov eax, VGA_BUF
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add eax, VGA_OFFSET(78, 24)
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mov dword [eax], 0x2f4b2f4f
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hlt
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; Early error printer. Prints 'ERR: X' where X is an error code in al
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error:
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mov dl, "O"
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.result:
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mov eax, VGA_BUF
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add eax, VGA_OFFSET(73, 24)
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mov dword [eax], 0x1f451f52
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add eax, 0x4
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mov dword [eax], 0x1f3e1f53
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add eax, 0x4
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; RES> in white-on-blue
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mov dword [eax], 0x4f524f45
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add eax, 0x2
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mov dword [eax], 0x4f3a4f52
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add eax, 0x2
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mov dword [eax], 0x4f204f20
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add eax, 0x2
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mov byte [eax], al
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mov ecx, 0x1f201f20
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and cl, dl ; 0x1f201f(dl)
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ror ecx, 16 ; 0x1f(dl)1f20 = ' (dl)'
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mov dword [eax], ecx ; should be a space and contents of dl
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.endp:
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hlt
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check_cpuid:
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; flip cpuid id bit (bit 21) to check for cpuid support
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; copy flags to eax via stack
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pushfd
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pop eax
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mov ecx, eax ; copy to ecx for compare
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xor eax, 1 << 21 ; xor eax with the 21st bit set
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push eax ; push new flags and pop to flags register
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popfd
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pushfd
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pop eax
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cmp eax, ecx ; can we change the bit?
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je .no_cpuid
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ret
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.no_cpuid:
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mov al, "1"
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call error
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; int vga_puts(char* str)
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;
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; INPUT:
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; str: C-Sytle string
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;
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; OUTPUT:
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; EAX = characters printed
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;
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vga_puts:
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; prolog, EBP = SFP (Stack frame pointer), [EBP-4] = char* str
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push edi
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push esi
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push ebx
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.get_str_len:
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mov edi, [ebp - 4]
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xor ecx, ecx ; ECX = 0
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not ecx ; ECX = -1 == 0xFFFFFFFF
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xor eax, eax ; search for al = 0x0
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cld
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repne scasb ; deincrement ecx while searching for al
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not ecx ; the inverse of a neg number = abs(x) - 1
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dec ecx ; ECX contains the length of the string - nul byte at end
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mov edi, VGA_BUF ; load dest index with VGA buffer + calculated offset
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mov esi, [ebp -4] ; load source index with src string
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; ECX = string length
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; ESI = source string to print
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; EDI = destination in the VGA buffer
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.print_char:
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cmp ecx, 0x0
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jle vga_puts.endf
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cmp byte [vga_buf_pos_x], 80
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je vga_puts.end_of_line
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cmp byte [vga_buf_pos_y], 25
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je vga_puts.scroll_up
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cmp byte [esi], 0x20
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jl vga_puts.special_character_switch
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push ebp
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mov ebp, esp
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xor eax, eax
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mov al, [vga_buf_pos_y]
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push eax ; vga_pos_y
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xor eax, eax
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mov al, [vga_buf_pos_x]
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push eax ; vga_pos_x
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; uint16_t vga_calc_offset(uint8_t vga_pos_x, uint8_t vga_pos_y)
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call vga_calc_offset
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leave
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xor bx, bx
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mov bl, byte [esi]
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or bx, TTY_COLOR ; create VGA character
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mov [edi+eax], bx
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inc esi
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inc byte [vga_buf_pos_x]
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dec ecx
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jmp vga_puts.print_char ; loop until ECX == 0
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.end_of_line:
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; advance to next row
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inc byte [vga_buf_pos_y]
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mov byte [vga_buf_pos_x], 0
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jmp vga_puts.print_char
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.scroll_up:
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; after 25 rows, move to next page (either swap pages [memcpy] or erase page 0)
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mov byte [vga_buf_pos_x], 0
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mov byte [vga_buf_pos_y], 0
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push ebp
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mov ebp, esp
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mov eax, 0x7D0
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push eax ; 1 VGA page = 0x7D0 elements
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xor eax, eax
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push eax ; we want to blank the page with 0x0000
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mov eax, VGA_BUF
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push eax ; load vga buffer base (0xb8000)
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; uint16_t* kmemset_word(void* dest, uint16_t val, size_t len);
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call kmemset_byte
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leave
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jmp vga_puts.print_char
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.special_character_switch:
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cmp byte[esi], 0xA
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je vga_puts.handle_LF
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cmp byte[esi], 0xD
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je vga_puts.handle_CR
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; Default case
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.special_character_endp:
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dec ecx
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inc esi
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jmp vga_puts.print_char
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.handle_LF:
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; advance to next row
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inc byte [vga_buf_pos_y]
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jmp vga_puts.special_character_endp
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.handle_CR:
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mov byte [vga_buf_pos_x], 0
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jmp vga_puts.special_character_endp
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.endf:
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pop ebx
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pop esi
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pop edi
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ret
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; short vga_get_xy(void)
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;
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; INPUT:
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;
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; OUTPUT:
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; EAX = xy_pos
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; > x = xy_pos && 0xFF00
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; y = xy_pos && 0x00FF
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; 2 MSB of EAX are 0.
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;
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vga_get_xy:
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.endf:
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ret
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; void vga_set_xy(short xy_pos)
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; xy_pos is a byte packed word (16bit value), MSB is x, LSB is y
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; => x = xy_pos && 0xFF00
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; y = xy_pos && 0x00FF
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||||
;
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; INPUT:
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; xy_pos
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||||
;
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; OUTPUT:
|
||||
; NONE
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;
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vga_set_xy:
|
||||
.endf:
|
||||
ret
|
||||
|
||||
; uint16_t vga_calc_offset(uint8_t vga_pos_x, uint8_t vga_pos_y)
|
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; VGA_OFFSET(x,y) == (((y*VGA_MAX_X) + x)*2)
|
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vga_calc_offset:
|
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xor eax, eax
|
||||
xor edx, edx
|
||||
|
||||
mov edx, [ebp-4]
|
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mov ax, VGA_MAX_X
|
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mul dx ; DX:AX contains (y*VGA_MAX_X)
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jc vga_calc_offset.artithmetic_error
|
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mov edx, [ebp-8]
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add ax, dx
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jc vga_calc_offset.artithmetic_error
|
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|
||||
mov dx, 0x02
|
||||
mul dx ; DX:AX contains (y*VGA_MAX_X) + x) * 2
|
||||
jnc vga_calc_offset.endf
|
||||
|
||||
.artithmetic_error:
|
||||
mov al, '3'
|
||||
call error
|
||||
|
||||
.endf:
|
||||
; (e)AX contains the offset
|
||||
ret
|
||||
|
||||
; uint32_t* kmemset(void* dest, uint32_t val, size_t len);
|
||||
kmemset_dword:
|
||||
push edi ; function uses edi, so save it.
|
||||
; [ebp] = previous call frame
|
||||
mov ecx, [ebp - 4] ; size_t len
|
||||
|
||||
mov eax, [ebp - 8] ; uint32_t val
|
||||
|
||||
mov edi, [ebp - 12] ; void * ptr
|
||||
; [ebp - 16] = return adress
|
||||
; [ebp - 20] = saved EDI
|
||||
rep stosd
|
||||
.endf:
|
||||
mov eax, [ebp - 12] ; return pointer to dest
|
||||
pop edi ; restore edi
|
||||
ret
|
||||
|
||||
; uint16_t* kmemset(void* dest, uint16_t val, size_t len);
|
||||
kmemset_word:
|
||||
push edi ; function uses edi, so save it.
|
||||
; [ebp] = previous call frame
|
||||
mov ecx, [ebp - 4] ; size_t len
|
||||
|
||||
mov ax, [ebp - 8] ; uint16_t val
|
||||
|
||||
mov edi, [ebp - 12] ; void * ptr
|
||||
; [ebp - 16] = return adress
|
||||
; [ebp - 20] = saved EDI
|
||||
rep stosw
|
||||
.endf:
|
||||
mov eax, [ebp - 12] ; return pointer to dest
|
||||
pop edi ; restore edi
|
||||
ret
|
||||
|
||||
; uint8_t* kmemset(void* dest, uint8_t val, size_t len);
|
||||
kmemset_byte:
|
||||
push edi ; function uses edi, so save it.
|
||||
; [ebp] = previous call frame
|
||||
mov ecx, [ebp - 4] ; size_t len
|
||||
|
||||
mov al, [ebp - 8] ; uint8_t val
|
||||
|
||||
mov edi, [ebp - 12] ; void * ptr
|
||||
; [ebp - 16] = return adress
|
||||
; [ebp - 20] = saved EDI
|
||||
rep stosb
|
||||
.endf:
|
||||
mov eax, [ebp - 12] ; return pointer to dest
|
||||
pop edi ; restore edi
|
||||
ret
|
||||
|
||||
; uint32_t* kmemset(uint32_t* dest, uint32_t* src, size_t len);
|
||||
kmemcpy_dword:
|
||||
push edi
|
||||
push esi ; edi, esi are callee save
|
||||
|
||||
mov edi, [ebp-12] ; dest
|
||||
mov esi, [ebp-8] ; source
|
||||
mov ecx, [ebp-4] ; length
|
||||
|
||||
cld ; ensure we are incrementing
|
||||
rep movsd
|
||||
|
||||
.endf:
|
||||
mov eax, [ebp-12] ; return pointer to dest
|
||||
pop esi
|
||||
pop edi
|
||||
ret
|
||||
|
||||
; uint16_t* kmemset(uint16_t* dest, uint16_t* src, size_t len);
|
||||
kmemcpy_word:
|
||||
push edi
|
||||
push esi ; edi, esi are callee save
|
||||
|
||||
mov edi, [ebp-12] ; dest
|
||||
mov esi, [ebp-8] ; source
|
||||
mov ecx, [ebp-4] ; length
|
||||
|
||||
cld ; ensure we are incrementing
|
||||
rep movsw
|
||||
|
||||
.endf:
|
||||
mov eax, [ebp-12] ; return pointer to dest
|
||||
pop esi
|
||||
pop edi
|
||||
ret
|
||||
|
||||
; uint8_t* kmemset(uint8_t* dest, uint8_t* src, size_t len);
|
||||
; not overlap safe
|
||||
kmemcpy_byte:
|
||||
push edi
|
||||
push esi ; edi, esi are callee save
|
||||
|
||||
mov edi, [ebp-12] ; dest
|
||||
mov esi, [ebp-8] ; source
|
||||
mov ecx, [ebp-4] ; length
|
||||
|
||||
cld ; ensure we are incrementing
|
||||
rep movsb
|
||||
|
||||
.endf:
|
||||
mov eax, [ebp-12] ; return pointer to dest
|
||||
pop esi
|
||||
pop edi
|
||||
ret
|
||||
|
||||
; Static Values
|
||||
vga_buf_pos_x:
|
||||
db 0x00
|
||||
vga_buf_pos_y:
|
||||
db 0x00
|
||||
jmp .endp - $$
|
||||
|
||||
; Strings
|
||||
ALIGN 16, db 0
|
||||
%define StrCRLF_NUL 0Dh, 0Ah, 00h
|
||||
welcome_cstr:
|
||||
db 'CBoot Stage3', StrCRLF_NUL
|
||||
version_cstr:
|
||||
db 'CBoot v0.0.3 ', 'NASM - ', __NASM_VER__, StrCRLF_NUL
|
||||
datetime_cstr:
|
||||
|
||||
Reference in New Issue
Block a user