14b109ea24
modified: compiler/create_crosscompiler.sh deleted: notes modified: src/.gdb_history deleted: src/amd64_vol2.pdf modified: src/bootloader/bios_functions/bios_disk.asm modified: src/bootloader/bios_functions/print.asm modified: src/bootloader/bootloader.asm modified: src/bootloader/cpu_check.asm modified: src/bootloader/enter_kernel.asm deleted: src/bootloader/enter_kernel_backup modified: src/bootloader/gdt.asm deleted: src/bootloader/multicore.asm deleted: src/bootloader/notes new file: src/debug/gdbinit.gdb deleted: src/indigo_os modified: src/kernel/include/libc.h modified: src/kernel/include/paging.h modified: src/kernel/include/video.h modified: src/kernel/kernel.c modified: src/kernel/libs/acpi.c modified: src/kernel/libs/drivers/serial.c modified: src/kernel/libs/drivers/video.c modified: src/kernel/libs/libc.c modified: src/kernel/libs/page.c modified: src/link.ld modified: src/makefile new file: tools/README.md modified: tools/page/page.py
69 lines
1.3 KiB
NASM
69 lines
1.3 KiB
NASM
protected_gdt:
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.gdt_start: ; we need to start with a null gdt
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dd 0
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dd 0
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.gdt_code:
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dw 0xffff
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dw 0x0000
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db 0x00
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db 10011010b
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db 11001111b
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db 0x0000
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.gdt_data:
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dw 0xffff
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dw 0x0000
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db 0x00
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db 10010010b
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db 11001111b
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db 0x0000
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.gdt_end:
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.descriptor:
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dw .gdt_end - .gdt_start - 1
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dq .gdt_start
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PROTECTED_CODE_SEGMENT equ .gdt_code - .gdt_start
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PROTECTED_DATA_SEGMENT equ .gdt_data - .gdt_start
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long_gdt:
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.gdt_start:
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;and now we set up a temporary GDT creating a 1:1 mapping
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dw 0xffff
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dw 0
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db 0 ;this is the invalid GDT
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db 0
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db 1
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db 0
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;now for the code GDT:
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.gdt_code:
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dw 0 ; segment limit 15:00 (I don't think this matters in 64 bit mode!)
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dw 0 ; base address 15:00
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db 0 ; base address 23:16
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db 10011010b ;1st flags and type. The first four bits (1010) are type, and the last are flags. See https://www.cs.bham.ac.uk/~exr/lectures/opsys/10_11/lectures/os-dev.pdf
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db 10101111b ;1111 is segment limit continued. 0: available, 0: 64 bit (change?), 1: 32 bit segment, 1: granularity (shifts 3 hex didgets to get all of memory)
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db 0
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.gdt_data:
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dw 0
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dw 0
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db 0
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db 10010010b
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db 00000000b
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db 0
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.gdt_end: ; later calculates offset in defs below
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.descriptor:
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dw .gdt_end - .gdt_start - 1
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dq .gdt_start
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LONG_CODE_SEGMENT equ .gdt_code - .gdt_start
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LONG_DATA_SEGMENT equ .gdt_data - .gdt_start
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