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Made getgdt more descriptive

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 0xffff
dw 0x0000 dw 0x0000
db 0x00 db 0x00
db 0b10011010 db 0b10011110
db 0b11001111 db 0b11001111
db 0x00 db 0x00
dw 0xffff dw 0xffff
dw 0x0000 dw 0x0000
db 0x00 db 0x00
db 0b10010010 db 0b10010110
db 0b11001111 db 0b11001111
db 0x00 db 0x00
.gdt_end: .gdt_end:

4
docs/bootloader.md
View File

@ -50,8 +50,8 @@
| Entry | Base | Limit | Flags | Access | Purpose | | Entry | Base | Limit | Flags | Access | Purpose |
|-------|-------------|---------|--------|------------|--------------| |-------|-------------|---------|--------|------------|--------------|
| 0x0 | 0x00000000 | 0x00000 | 0b0000 | 0b00000000 | Null Segment | | 0x0 | 0x00000000 | 0x00000 | 0b0000 | 0b00000000 | Null Segment |
| 0x8 | 0x00000000 | 0xfffff | 0b1100 | 0b10011010 | Code Segment | | 0x8 | 0x00000000 | 0xfffff | 0b1100 | 0b10011110 | Code Segment |
| 0x10 | 0x00000000 | 0xfffff | 0b1100 | 0b10010010 | Data Segment | | 0x10 | 0x00000000 | 0xfffff | 0b1100 | 0b10010110 | Data Segment |
## Known issues ## 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 base = entry.base_lower | entry.base_middle << 16 | entry.base_higher << 24;
uint32_t limit = entry.limit_lower | (entry.flags_limit_higher & 0x0f) << 16; uint32_t limit = entry.limit_lower | (entry.flags_limit_higher & 0x0f) << 16;
uint8_t flags = (entry.flags_limit_higher >> 4); uint8_t flags = (entry.flags_limit_higher >> 4);
bool is_data = ((entry.access_byte & 0b00001000) >> 3) == 0;
//terminal_writestring("\nEntry "); //terminal_writestring("\nEntry ");
//terminal_writeint(entry_num, 10); //terminal_writeint(entry_num, 10);
@ -70,14 +71,39 @@ int get_gdt(char* unused) {
terminal_writeint(entry.access_byte, 2); terminal_writeint(entry.access_byte, 2);
terminal_writestring(" (ring "); terminal_writestring(" (ring ");
terminal_writeint((entry.access_byte & 0b01100000) >> 5, 10); terminal_writeint((entry.access_byte & 0b01100000) >> 5, 10);
terminal_writestring(", S = "); if ((entry.access_byte & 0b00010000) == 0) {
terminal_writeint((entry.access_byte & 0b00010000) >> 4, 2); terminal_writestring(", System");
terminal_writestring(", EX = "); }
terminal_writeint((entry.access_byte & 0b00001000) >> 3, 2); if (is_data) {
terminal_writestring(", DC = "); terminal_writestring(", Data");
terminal_writeint((entry.access_byte & 0b00000100) >> 2, 2);
terminal_writestring(", RW = "); if((entry.access_byte & 0b00000100) == 0) {
terminal_writeint((entry.access_byte & 0b00000010) >> 1, 2); 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"); terminal_writestring(")\n");
} }
return 0; return 0;