shockrah/jankos
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

trying out a new version of gdt initialization

Browse Source
This commit is contained in:
shockrah 2019-10-14 00:45:40 -07:00
parent c94252c3f2
commit d68f4b5264
4 changed files with 14 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
gdt.c
View File

@ -28,12 +28,16 @@ void gdt_configure() {
// Granularity: 4KB // Granularity: 4KB
// 32-bit opcodes // 32-bit opcodes
// Code segment selector // Code segment selector
gdt_configure_entry(1, 0, 0xffffffff, 0x9a, 0xcf); gdt_configure_entry(1, 0, 0xffffffff, 0x9a, 0xcf); // code segment
// Finally the data segment // Finally the data segment
// All the same except the desriptor type specifies that its data // All the same except the desriptor type specifies that its data
gdt_configure_entry(2, 0, 0xffffffff, 0x92, 0xcf); gdt_configure_entry(2, 0, 0xffffffff, 0x92, 0xcf); // data segment
// user mode segments
gdt_configure_entry(3, 0, 0xffffffff, 0xfa, 0xcf);
gdt_configure_entry(4, 0, 0xffffffff, 0xf2, 0xcf);
// Load in the new changes to the gdt // Load in the new changes to the gdt
load_gdt(); load_gdt(&gdt_ptr);
} }

4
gdt.h
View File

@ -1,7 +1,7 @@
#include "types.h" #include "types.h"
#define NO_GDT_ENTRIES 3 #define NO_GDT_ENTRIES 5
struct GDT_Entry { struct GDT_Entry {
u16 low_limit; u16 low_limit;
@ -22,7 +22,7 @@ struct GDT_Entry gdt_entries[NO_GDT_ENTRIES];
struct GDT_PTR gdt_ptr; struct GDT_PTR gdt_ptr;
// this func is actually taken care of in gdt_seg.s // this func is actually taken care of in gdt_seg.s
extern void load_gdt(); extern void load_gdt(struct GDT_PTR* ptr);
void gdt_configure_entry(u32 entry, u32 base, u32 limit, u8 access, u8 gran); void gdt_configure_entry(u32 entry, u32 base, u32 limit, u8 access, u8 gran);

8
gdt_seg.s
View File

@ -2,16 +2,16 @@ global load_gdt
extern gdt_ptr extern gdt_ptr
load_gdt: load_gdt:
lgdt [gdt_ptr] lgdt [esp+4]
mov ax, 0x10 ; offset in the gdt to our data segment mov ax, 0x10 ; offset in the gdt to our data segment
mov ds, ax mov ds, ax
mov es, ax mov es, ax
mov fs, ax mov fs, ax
mov gs, ax mov gs, ax
mov ss, ax mov ss, ax
jmp 0x08:flush_cs ; far jump to the code segment jmp 0x08:.flush_cs ; far jump to the code segment
flush_cs: .flush_cs:
ret ; here we go back to the caller code but with our segments configured ret

4
loader.s
View File

@ -23,9 +23,7 @@ align 4
; sets up our gdt and segment selectors for later use ; sets up our gdt and segment selectors for later use
loader: loader:
; load the gdt that I setup call gdt_configure
call load_gdt
;call gdt_configure
call test_dispatcher call test_dispatcher
.loop: .loop: