208 lines
6.6 KiB
PHP
Executable File
208 lines
6.6 KiB
PHP
Executable File
; Copyright (C) 2020 Bradley Claus
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;
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; This program is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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;
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with this program. If not, see <https://www.gnu.org/licenses/>.
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; ## Generic Low mem map (from osdev wiki) ##
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; start end size type description
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; Low Memory (the first MiB)
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; 0x00000000 0x000003FF 1 KiB RAM - partially unusable Real Mode IVT (Interrupt Vector Table)
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; 0x00000400 0x000004FF 256 bytes RAM - partially unusable BDA (BIOS data area)
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; 0x00000500 0x00007BFF almost 30 KiB RAM - free for use Conventional memory
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; 0x00007C00 0x00007DFF 512 bytes RAM - partially unusable OS BootSector
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; 0x00007E00 0x0007FFFF 480.5 KiB RAM - free for use Conventional memory
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; 0x00080000 0x0009FFFF 128 KiB RAM - partially unusable EBDA (Extended BIOS Data Area)
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; 0x000A0000 0x000FFFFF 384 KiB various (unusable) Video memory, ROM Area
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; ## A rough overview of high mem ##
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; Idealy this needs to be probed with the E820 functions
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; # Start # End # size # description
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;
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; 0x00100000 0x00EFFFFF 0x00E00000 (14 MiB) RAM -- free for use (if it exists) Extended memory
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; 0x00F00000 0x00FFFFFF 0x00100000 (1 MiB) Possible memory mapped hardware ISA Memory Hole 15-16MB
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; 0x01000000 ???????? ??? (whatever exists) RAM -- free for use More Extended memory
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; 0xC0000000 (sometimes) 0xFFFFFFFF 0x40000000 (1 GiB) Memory mapped PCI devices, PnP NVRAM?, IO APIC/s, local APIC/s, BIOS, ...
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; 0x0000000100000000 ??? ??? (whatever exists) RAM -- free for use (PAE/64bit)/More Extended memory
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; ???????????????? ??? ??? Potentially usable for memory mapped PCI devices in modern hardware (but typically not, due to backward compatibility)
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; 0x2700 -> 0x28FF
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%define disk_buffer 0x2700
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; 0x2900 -> 0x2AFF
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%define fat_buffer 0x2900
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; 0x2B00 -> 0x2CFF
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%define dir_buffer 0x2B00
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; copy of partition table, 72 bytes
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%define partition_table 0x3000
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%define partition_table_SIZE 72
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; copy of FAT32 BPB, 33 bytes (+1 to the next value to align to uint16_t)
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;0x3048
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%define fat32_bpb 0x3050
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%define fat32_bpb_SIZE 33
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; copy of FAT32 EBPB, 54 bytes
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;0x306A
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%define fat32_ebpb 0x3070
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%define fat32_ebpb_SIZE 54
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; FAT32 FSInfo, 512 bytes
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;0x30A2
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%define fat32_fsinfo 0x30B0
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%define fat32_fsinfo_SIZE 512
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; some stored state for the fat32 driver
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;0x32A2
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%define fat32_state 0x32B0
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%define fat32_state_SIZE 32
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; next free space is 0x32D0
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%define fat32_nc_data 0x32D0
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%define fat32_nc_data_size 16
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; lba_packet for raw_disk_read
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%define lba_packet 0x4000
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%define BIOSMemoryMap 0x4200
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%define SteviaInfo 0x4400
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; High memory addresses for loading kernel (for use with unreal mode and 32bit override)
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; file load buffer at 16MB
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%define HMEM_load_buffer 0x1000000
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;PhysicalAddress = Segment * 16 + Offset
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%define SEG_TO_LINEAR(s,o) ((s << 4) + o)
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; Offset = physical / (Segment * 16)
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%define LINEAR_TO_OFFSET(p,s) ((p / (s << 4)))
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; Seg = (physical - offset) / 16
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%define LINEAR_TO_SEGMENT(p,o) ((p - o) >> 4)
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; create normalized linear addres from seg:off (16:4)
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; Segement = linear >> 4 (top 16 bits)
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; offset = linear & 0x0F (low 4 bits)
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; 20 bytes, passed to loaded kernel
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struc SteviaInfoStruct_t
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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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.EBPBDataPtr resd 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_t
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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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; moves argument into eax then pushes lower 16bits then upper 16 bits of of argument to stack
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; eax is clobbered
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%macro PUSH_DWORD 1
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mov eax, %1
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push ax
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shr eax, 16
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push ax
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%endmacro
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; same as PUSH_DWORD except no arguments, pushes EAX directly
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%macro PUSH_DWORD_EAX 0
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push ax
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shr eax, 16
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push ax
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%endmacro
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; pops upper 16bits then lower 16bits into eax
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; eax is clobbered
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%macro POP_DWORD_EAX 0
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xor eax, eax
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pop ax
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shl eax, 16
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pop ax
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%endmacro
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; moves data on stack referenced by bp to eax
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; stack must be organized as follows (tl;dr push lower 16bits first ie. PUSH_DWORD macro)
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; MOV_DWORD_EAX 2
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; STACK TOP (0x0)
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; upper_uint16 [bp-4]
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; lower_uint16 [bp-2]
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; --- [bp] ---
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; ...
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; STACK BOTTOM
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;
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; first argument == starting offset from bp for lower 16bits
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%macro MOV_DWORD_EAX 1
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mov ax, [bp-(%1+2)]
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shl eax, 16
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mov ax, [bp-%1]
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; eax contains dword from stack
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%endmacro
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%macro DEBUG_HCF 0
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DEBUG_LOOP:
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hlt
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jmp short DEBUG_LOOP
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%endmacro
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; uint8_t* kmemset(void* dest, uint8_t val, size_t len);
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kmemset:
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push di ; function uses di, so save it.
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mov cx, [bp - 2] ; size_t len
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mov al, [bp - 4] ; uint8_t val
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mov di, [bp - 6] ; void * ptr
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cld
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rep stosb
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.endf:
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mov ax, [bp - 6] ; return pointer to dest
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pop di ; restore di
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ret
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; uint8_t* kmemset(uint8_t* dest, uint8_t* src, size_t len);
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; not overlap safe
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kmemcpy:
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push di
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push si ; di, si are callee save
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mov cx, [bp - 2] ; length
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mov si, [bp - 4] ; source
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mov di, [bp - 6] ; dest
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cld ; ensure we are incrementing
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rep movsb
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.endf:
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mov ax, [bp - 6] ; return pointer to dest
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pop si
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pop di
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ret |