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Various bug fixes as well as a change to provide our own GDT. #4

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Various bug fixes as well as a change to provide our own GDT. #4

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d4c0a6c
Remove stdio.h include
mkilgore May 8, 2015
234f40a
Add a simple Makefile - Rename kernel.asm to fix conflict
mkilgore May 8, 2015
642fe51
Remove redundent cli in 'start'
mkilgore May 8, 2015
deb6b7a
Fix possiblity of code continuing on if `kmain` returns
mkilgore May 8, 2015
7b99635
Apply attribute packed to IDT_entry
mkilgore May 8, 2015
87e796e
Create our own GDT on startup
mkilgore May 8, 2015
d2b959a
Implement idt_ptr struct to simplify code
mkilgore May 8, 2015
ea847eb
Insert hlt instruction into kmain loop
mkilgore May 8, 2015
63c1629
Back-up register values in keyboard interrupt handler
mkilgore May 8, 2015
9d4c881
Update README.md
mkilgore May 8, 2015
cade471
Add .gitignore file
mkilgore May 8, 2015
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12 changes: 12 additions & 0 deletions head.asm
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Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,19 @@ load_gdt:
ret

keyboard_handler:
push ds
push es
push fs
push gs
pushad

call keyboard_handler_main

popad
pop ds
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@andpar83 andpar83 Dec 29, 2016

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Shouldn't be in reverse order?

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@mkilgore mkilgore Dec 29, 2016 •
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I'd say you would be right. I'm guessing I never noticed this bug because all of those segments probably contain the same value everywhere in the program. but obviously it's still a bug and it would easily blow things up if/when features are added that make use of the segment registers (Such as using them for CPU-local data).

On that note it also appears the segments are also never assigned, so it's quite likely this code got lucky in other areas. A while back I had an issue stemming from something similar in my kernel, it's fixed here. The code in this PR doesn't reload the segments after the lgdt, but that's necessary to ensure they actually contain the correct values and also to ensure they start utilizing the newly defined segments.

pop es
pop fs
pop gs
iretd

start:
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