PoliEcho/kern
1
0
Fork 0
forked from PoliEcho-holding-org/kern
Code Pull Requests Activity

Got GDT working

Browse Source
This commit is contained in:
Tom-on
2025-03-21 12:30:04 +01:00
parent 5076d1c56b
commit 05c8ee8f67
6 changed files with 71 additions and 104 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/include/gdt.h
+30 -37
View File
@@ -3,24 +3,6 @@
#include <kernel.h>
/*
* Entries:
* 0 Null desc.
* 1 Kernel code desc.
* 2 Kernel data desc.
* 3 SYSENTER
* 4 SYSEXIT
* 5 User code desc.
* 6 User data desc.
* 7 Task State Segment
*/
#define GDT_ENTRIES 8
#define GDT_KERNEL_CODE 0x28
#define GDT_KERNEL_DATA 0x30
#define GDT_USER_CODE 0x50
#define GDT_USER_DATA 0x48
#define GDT_TSS 0x50
/*
* Segment selector explanation (why kcode is 0x08?)
*
@@ -47,13 +29,39 @@
#define SEGMENT_SEL(_priv, _tab, _i)\
(uint16_t)(((_i) << 3) | ((_tab) << 2) | (_priv))
/*
* Entries:
* 0 Null desc.
* 1 Kernel code desc.
* 2 Kernel data desc.
* 3 User code desc.
* 4 User data desc.
* 5 Task State Segment
*/
#define GDT_ENTRIES 6
#define GDT_NULL SEGMENT_SEL(0, 0, 0)
#define GDT_KERNEL_CODE SEGMENT_SEL(0, 0, 1)
#define GDT_KERNEL_DATA SEGMENT_SEL(0, 0, 2)
#define GDT_USER_CODE SEGMENT_SEL(3, 0, 3)
#define GDT_USER_DATA SEGMENT_SEL(3, 0, 4)
#define GDT_TSS SEGMENT_SEL(0, 0, 5)
#define GDT_DESC(_lim, _base, _acc, _flag) (struct gdt_entry){\
.limit = (_lim) & 0xffff,\
.baseLow = (uint16_t)(_base),\
.baseMid = (uint8_t)((_base) >> 16),\
.access = (_acc),\
.flags = (_flag << 4) | (((_lim) >> 16) & 0x0f),\
.baseHigh = (uint8_t)((_base) >> 24),\
}
struct gdt_entry {
uint16_t limit;
uint16_t baseLow;
uint8_t baseMid;
uint8_t access;
uint8_t granulatiry;
uint8_t baseHigh;
uint8_t baseMid;
uint8_t access;
uint8_t flags; // low 4 bits are 4 msbs of limit, high 4 bits are flags
uint8_t baseHigh;
} __packed;
struct gdt_pointer {
@@ -61,15 +69,6 @@ struct gdt_pointer {
uint32_t base;
} __packed;
struct tss_entry {
uint16_t length;
uint16_t baseLow;
uint8_t baseMid;
uint8_t flags1;
uint8_t flags2;
uint8_t baseHigh;
} __packed;
struct tss_pointer {
uint16_t link;
uint16_t __reserved0;
@@ -90,7 +89,6 @@ struct tss_pointer {
uint32_t edx;
uint32_t ebx;
uint32_t esp;
uint32_t ebs;
uint32_t ebp;
uint32_t esi;
uint32_t edi;
@@ -112,11 +110,6 @@ struct tss_pointer {
uint32_t ssp;
} __packed;
struct gdt_entries {
struct gdt_entry descriptors[GDT_ENTRIES - 1]; // Subtract one for TSS
struct tss_entry tss;
};
int gdt_init(void);
#endif
kernel/include/kernel.h
+5 -1
View File
@@ -73,6 +73,7 @@ typedef int32_t intptr_t;
* Linker defined values
*/
extern uint32_t __kernel_start, __kernel_end;
extern uint32_t __kernel_stack_top, __kernel_stack_bottom;
/*
* Logging and errors
@@ -82,7 +83,10 @@ extern uint32_t __kernel_start, __kernel_end;
#define pr_dbg(_s) printk("[debug] %s\n", (_s))
#define pr_wrn(_s) printk("[warning] %s\n", (_s))
#define pr_err(_s) printk("[error] %s\n", (_s))
#define panic(_s) printk("[panic] %s\n", (_s))
#define panic(_s) do {\
printk("[panic] %s\n", (_s));\
while (1) __asm__ volatile ("cli; hlt");\
} while (0)
#define BUG() panic("BUG()")
#define WARN() pr_wrn("WARN()")
#define BUG_ON(_e) ((_e) ? BUG() : NULL)
kernel/linker.ld
+7
View File
@@ -32,6 +32,13 @@ SECTIONS {
*(COMMON)
*(.bss)
} : data
/* Stack */
. = ALIGN(16);
__kernel_stack_bottom = .;
. += 16K;
__kernel_stack_top = .;
__kernel_end = .;
/DISCARD/ : {
kernel/src/entry.s
+7 -5
View File
@@ -17,20 +17,22 @@ multiboot:
dd FLAGS
dd CHECK
section .bss
align 16
; Initialize stack
stack_bottom:
section .bss
align 16
global __kernel_stack_top
global __kernel_stack_bottom
__kernel_stack_bottom:
resb 16384
stack_top:
__kernel_stack_top:
; Entry point
section .text
global _start
extern kmain
_start:
mov esp, stack_top ; Setup stack
mov esp, __kernel_stack_top
push eax
push ebx
call kmain ; Call kernel main
kernel/src/gdt.c
+22 -60
View File
@@ -2,22 +2,9 @@
#include <string.h>
#include <gdt.h>
static struct gdt_entries gdt;
static struct gdt_entry gdt[GDT_ENTRIES];
static struct gdt_pointer gdtp;
static struct tss_pointer tss;
struct tss_pointer* tssp = &tss;
void gdt_loadTss(struct tss_pointer* ptr) {
size_t addr = (size_t)ptr;
gdt.tss.baseLow = (uint16_t)addr;
gdt.tss.baseMid = (uint8_t)(addr >> 16);
gdt.tss.flags1 = 0x89;
gdt.tss.flags2 = 0;
gdt.tss.baseHigh = (uint8_t)(addr >> 24);
__asm__ volatile ("ltr %0" : : "rm"(SEGMENT_SEL(0, 0, 7)));
}
void gdt_reload(void) {
__asm__ volatile (
@@ -37,66 +24,41 @@ void gdt_reload(void) {
);
}
void tss_reload(void) {
__asm__ volatile ("ltr %0" : : "rm"(GDT_TSS));
gdt[5].access |= 0x02;
}
int gdt_init(void) {
// Null descriptor (0)
gdt.descriptors[0].limit = 0;
gdt.descriptors[0].baseLow = 0;
gdt.descriptors[0].baseMid = 0;
gdt.descriptors[0].access = 0;
gdt.descriptors[0].granulatiry = 0;
gdt.descriptors[0].baseHigh = 0;
gdt[0] = GDT_DESC(0, 0, 0, 0);
// Kernel code (8)
gdt.descriptors[1].limit = 0xffff;
gdt.descriptors[1].baseLow = 0;
gdt.descriptors[1].baseMid = 0;
gdt.descriptors[1].access = 0x9a;
gdt.descriptors[1].granulatiry = 0xcf;
gdt.descriptors[1].baseHigh = 0;
gdt[1] = GDT_DESC(0xfffff, 0, 0x9a, 0xc);
// Kernel data (16)
gdt.descriptors[2].limit = 0xffff;
gdt.descriptors[2].baseLow = 0;
gdt.descriptors[2].baseMid = 0;
gdt.descriptors[2].access = 0x90;
gdt.descriptors[2].granulatiry = 0xcf;
gdt.descriptors[2].baseHigh = 0;
gdt[2] = GDT_DESC(0xfffff, 0, 0x92, 0xc);
// SYSENTER/SYSEXIT
gdt.descriptors[3] = (struct gdt_entry){ 0 }; // (24)
gdt.descriptors[4] = (struct gdt_entry){ 0 }; // (32)
// User code (24)
gdt[3] = GDT_DESC(0xfffff, 0, 0xfa, 0xc);
// User code (40)
gdt.descriptors[5].limit = 0;
gdt.descriptors[5].baseLow = 0;
gdt.descriptors[5].baseMid = 0;
gdt.descriptors[5].access = 0xfa;
gdt.descriptors[5].granulatiry = 0x20;
gdt.descriptors[5].baseHigh = 0;
// User data (32)
gdt[4] = GDT_DESC(0xfffff, 0, 0xf2, 0xc);
// User data (48)
gdt.descriptors[6].limit = 0;
gdt.descriptors[6].baseLow = 0;
gdt.descriptors[6].baseMid = 0;
gdt.descriptors[6].access = 0xf2;
gdt.descriptors[6].granulatiry = 0;
gdt.descriptors[6].baseHigh = 0;
// TSS (40)
memset(&tss, 0, sizeof(tss));
gdt[5] = GDT_DESC(sizeof(tss) - 1, (uint32_t)&tss, 0x89, 0x00);
tss.iopb = sizeof(struct tss_pointer);
tss.esp0 = __kernel_stack_top;
tss.ss0 = GDT_KERNEL_DATA;
// TSS (56)
gdt.tss.length = 104;
gdt.tss.baseLow = 0;
gdt.tss.baseMid = 0;
gdt.tss.flags1 = 0x89;
gdt.tss.flags2 = 0;
gdt.tss.baseHigh = 0;
gdtp.limit = sizeof(struct gdt_entries) - 1;
// GDT Pointer
gdtp.limit = sizeof(gdt) - 1;
gdtp.base = (uint32_t)&gdt;
gdt_reload();
tss_reload();
memset(tssp, 0, sizeof(struct tss_pointer));
gdt_loadTss(tssp);
return 0;
}
kernel/src/kernel.c
-1
View File
@@ -27,7 +27,6 @@ void kmain(void* ptr, uint32_t magic) {
gdt_init();
// isr_init();
// pag_init();
while (1);
debugf("Basic initialization complete!\n");