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GDT Rewritten to be slightly more stable

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This commit is contained in:
Benjamin Kyd
2019-04-28 00:10:47 +01:00
parent 6be1414484
commit fe0a4a6d3b
7 changed files with 44 additions and 34 deletions
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build/OwOS.bin
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build/OwOS.iso
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iso/boot/OwOS.bin
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2
kernel.cpp
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@@ -8,8 +8,6 @@
#include <lib/std/memory.h> #include <lib/std/memory.h>
#include <lib/kernel/logger/logger.h> #include <lib/kernel/logger/logger.h>
#define BochsBreak() outw(0x8A00,0x8A00); outw(0x8A00,0x08AE0);
extern "C" { extern "C" {
extern void INIT_FPU(void); extern void INIT_FPU(void);
} }

63
kernel/gdt.cpp
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@@ -4,47 +4,58 @@
#include <lib/std/memory.h> #include <lib/std/memory.h>
struct SegmentDescriptor_t { struct SegmentDescriptor_t {
uint16_t limit_0; uint16_t limit_low;
uint16_t base_0; uint16_t base_low;
uint8_t base_1; uint8_t base_middle;
uint8_t access; uint8_t access;
uint8_t limit_1:4; uint8_t granularity0:4;
uint8_t flags:4; uint8_t granularity1:4;
uint8_t base_2; uint8_t base_high;
} __attribute__((packed)); } __attribute__((packed));
SegmentDescriptor_t _GDT[256]; struct GDT_t {
uint16_t limit;
uint32_t base;
} __attribute__((packed));
void lgdt(void* GDT, uint16_t size) { SegmentDescriptor_t _GDT[5];
GDT_t _GDTptr;
void lgdt(void* base, uint16_t size) {
struct { struct {
uint16_t size; uint16_t length;
void* GDT; void* base;
} __attribute__((packed)) GDTR = { size, GDT }; } __attribute__((packed)) GDTR = { size, base };
asm ( "lgdt %0" : : "m"(GDTR) ); asm ( "lgdt %0" : : "m"(GDTR) );}
}
void initGDT() { void initGDT() {
memset(&_GDT, 0, sizeof(_GDT)); #define BochsBreak() outw(0x8A00,0x8A00); outw(0x8A00,0x08AE0);
_GDTptr.limit = (sizeof(SegmentDescriptor_t) * 5) - 1;
_GDTptr.base = (uint32_t)&_GDT;
// Leave 0 blank for null segment // Null segment
setGDTGate(0, 0, 0, 0, 0);
// Code Base 0 limit 32 Access EXEC + RW // Code Base 0 limit 32 Access EXEC + RW
setGDT(1, 0x00000000, 0xFFFFFFFF, GDT_ACCESS_PRESENT | GDT_ACCESS_EXEC | GDT_ACCESS_RW, GDT_FLAG_GR_PAGE | GDT_FLAG_SZ_32B); setGDTGate(1, 0x00000000, 0xFFFFFFFF, GDT_ACCESS_PRESENT | GDT_ACCESS_EXEC | GDT_ACCESS_RW, GDT_FLAG_GR_PAGE | GDT_FLAG_SZ_32B);
// Data Base 0 Limit 32 Access RW // Data Base 0 Limit 32 Access RW
setGDT(2, 0x00000000, 0xFFFFFFFF, GDT_ACCESS_PRESENT | GDT_ACCESS_RW, GDT_FLAG_GR_PAGE | GDT_FLAG_SZ_32B); setGDTGate(2, 0x00000000, 0xFFFFFFFF, GDT_ACCESS_PRESENT | GDT_ACCESS_RW, GDT_FLAG_GR_PAGE | GDT_FLAG_SZ_32B);
lgdt(&_GDT, sizeof(_GDT)); lgdt(&_GDT, sizeof(_GDT));
BochsBreak();
SEGMENTS_RELOAD(); SEGMENTS_RELOAD();
} }
void setGDT(uint32_t index, uint32_t baseAddr, uint32_t limitAddr, uint8_t accessLvl, uint8_t flags) { void setGDTGate(uint32_t index, uint32_t baseAddr, uint32_t limitAddr, uint8_t accessLvl, uint8_t flags) {
if (index > 256) return; if (index > 5) return;
_GDT[index].base_0 = (baseAddr >> 0) & 0xFFFF; _GDT[index].base_low = (baseAddr & 0xFFFF);
_GDT[index].base_1 = (baseAddr >> 16) & 0xFF; _GDT[index].base_middle = (baseAddr >> 16) & 0xFF;
_GDT[index].base_2 = (baseAddr>> 24) & 0xFF; _GDT[index].base_high = (baseAddr >> 24) & 0xFF;
_GDT[index].limit_0 = (limitAddr >> 0) & 0xFFFF;
_GDT[index].limit_1 = (limitAddr >> 16) & 0x0F; _GDT[index].limit_low = (limitAddr >> 0) & 0xFFFF;
_GDT[index].access = accessLvl; _GDT[index].granularity0 = (limitAddr >> 16) & 0x0F;
_GDT[index].flags = flags & 0x0F;
_GDT[index].granularity1 = flags & 0x0F;
_GDT[index].access = accessLvl;
} }

2
kernel/gdt.h
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@@ -20,4 +20,4 @@ extern "C" {
} }
void initGDT(); void initGDT();
void setGDT(uint32_t index, uint32_t baseAddr, uint32_t limitAddr, uint8_t accessLvl, uint8_t flags); void setGDTGate(uint32_t index, uint32_t baseAddr, uint32_t limitAddr, uint8_t accessLvl, uint8_t flags);

11
kernel/segment.asm
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@@ -1,13 +1,14 @@
.global SEGMENTS_RELOAD .global SEGMENTS_RELOAD
SEGMENTS_RELOAD: SEGMENTS_RELOAD:
ljmp $0x08, $reloadCS
reloadCS:
movw $0x10, %ax movw $0x10, %ax
movw %ax, %es
movw %ax, %ss
movw %ax, %ds movw %ax, %ds
movw %ax, %es
movw %ax, %fs movw %ax, %fs
movw %ax, %gs movw %ax, %gs
movw %ax, %ss
ljmp $0x08, $flush2
flush2:
ret ret