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Made getgdt more descriptive

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This commit is contained in:
Robbe Van Herck 2020-01-10 10:05:19 +01:00
parent 95c0371065
commit 9536ddd3d3
No known key found for this signature in database
GPG key ID: A66F76F7B81BD784
3 changed files with 38 additions and 12 deletions
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4
bootloader/main.asm
View file

@ -327,14 +327,14 @@ dd 0x00000000
dw 0xffff
dw 0x0000
db 0x00
db 0b10011010
db 0b10011110
db 0b11001111
db 0x00
dw 0xffff
dw 0x0000
db 0x00
db 0b10010010
db 0b10010110
db 0b11001111
db 0x00
.gdt_end:

4
docs/bootloader.md
View file

@ -50,8 +50,8 @@
| Entry | Base | Limit | Flags | Access | Purpose |
|-------|-------------|---------|--------|------------|--------------|
| 0x0 | 0x00000000 | 0x00000 | 0b0000 | 0b00000000 | Null Segment |
| 0x8 | 0x00000000 | 0xfffff | 0b1100 | 0b10011010 | Code Segment |
| 0x10 | 0x00000000 | 0xfffff | 0b1100 | 0b10010010 | Data Segment |
| 0x8 | 0x00000000 | 0xfffff | 0b1100 | 0b10011110 | Code Segment |
| 0x10 | 0x00000000 | 0xfffff | 0b1100 | 0b10010110 | Data Segment |
## Known issues

42
kernel/shell.c
View file

@ -44,6 +44,7 @@ int get_gdt(char* unused) {
uint32_t base = entry.base_lower | entry.base_middle << 16 | entry.base_higher << 24;
uint32_t limit = entry.limit_lower | (entry.flags_limit_higher & 0x0f) << 16;
uint8_t flags = (entry.flags_limit_higher >> 4);
bool is_data = ((entry.access_byte & 0b00001000) >> 3) == 0;
//terminal_writestring("\nEntry ");
//terminal_writeint(entry_num, 10);
@ -70,14 +71,39 @@ int get_gdt(char* unused) {
terminal_writeint(entry.access_byte, 2);
terminal_writestring(" (ring ");
terminal_writeint((entry.access_byte & 0b01100000) >> 5, 10);
terminal_writestring(", S = ");
terminal_writeint((entry.access_byte & 0b00010000) >> 4, 2);
terminal_writestring(", EX = ");
terminal_writeint((entry.access_byte & 0b00001000) >> 3, 2);
terminal_writestring(", DC = ");
terminal_writeint((entry.access_byte & 0b00000100) >> 2, 2);
terminal_writestring(", RW = ");
terminal_writeint((entry.access_byte & 0b00000010) >> 1, 2);
if ((entry.access_byte & 0b00010000) == 0) {
terminal_writestring(", System");
}
if (is_data) {
terminal_writestring(", Data");
if((entry.access_byte & 0b00000100) == 0) {
terminal_writestring(" (growing up, ");
} else {
terminal_writestring(" (growing down, ");
}
if((entry.access_byte & 0b00000010) == 0) {
terminal_writestring("r--)");
} else {
terminal_writestring("rw-)");
}
} else {
terminal_writestring(", Code");
if((entry.access_byte & 0b00000100) == 0) {
terminal_writestring(" (non-conforming, ");
} else {
terminal_writestring(" (conforming, ");
}
if((entry.access_byte & 0b00000010) == 0) {
terminal_writestring("--x)");
} else {
terminal_writestring("r-x)");
}
}
terminal_writestring(")\n");
}
return 0;