Use a low address to store GDT and E820 #20
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I move INITSEG to 0x0050. it is the lowest address for useable. this area about 30KB. it is enough to store GDT and E820.
coolgw
reviewed
Feb 13, 2020
| @@ -3,7 +3,7 @@ | |||
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| CYLS = 10 | |||
| BOOTSEG = 0x07C0 | |||
| INITSEG = 0x7000 | |||
| INITSEG = 0x0050 | |||
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use #include <common.h> and remove INITSEG here.
BTW: the file name bootsector.s to bootsector.S.
coolgw
reviewed
Feb 13, 2020
| @@ -93,7 +93,8 @@ _lowlevel_init: | |||
| # Type 4: ACPI NVS memory | |||
| # Type 5: Area containing bad memory | |||
| #Set register base https://wiki.osdev.org/Detecting_Memory_(x86) | |||
| mov $0x8004, %di | |||
| E820_OFFSET=0x1004 | |||
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same comment, move E820_OFFSET to common.h
coolgw
reviewed
Feb 13, 2020
| @@ -185,7 +184,7 @@ fin: | |||
| hlt | |||
| jmp fin | |||
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| INITSEG = 0x7000 | |||
| INITSEG = 0x0050 | |||
coolgw
reviewed
Feb 13, 2020
| @@ -43,7 +44,8 @@ unsigned int memtest(unsigned int start, unsigned int end); | |||
| #define COL8_840084 13 | |||
| #define COL8_008484 14 | |||
| #define COL8_848484 15 | |||
| #define MEM_MAP_ADDR (char *)((0x00078004)-(SYSSEG << 4)) | |||
| #define E820_OFFSET 0x1004 | |||
| #define MEM_MAP_ADDR (char *)((INITSEG << 4)+(E820_OFFSET)-(SYSSEG << 4)) | |||
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I suppose this is the address after paging? so this PR depend on the paging PR?
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I have no idea the point of move this to the lower memory, could you help explain it? |
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I move INITSEG to 0x0050. it is the lowest address for useable.
this area about 30KB. it is enough to store GDT and E820.
https://wiki.osdev.org/Memory_Map_(x86)#Overview