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working on task switching

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This commit is contained in:
rami 2024-07-06 03:51:46 -04:00
parent 766596ef98
commit 1b7474095b
8 changed files with 196 additions and 98 deletions
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46
include/kernel/elf.h Normal file
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@ -0,0 +1,46 @@
#ifndef HAZEL_ELF_H_
#define HAZEL_ELF_H_
#include <stdint.h>
#define EI_NIDENT 16
typedef uint16_t Elf32_Half;
typedef uint32_t Elf32_Addr;
typedef uint32_t Elf32_Off;
typedef uint32_t Elf32_Word;
typedef int32_t Elf32_Sword;
typedef struct {
uint8_t e_ident[EI_NIDENT];
Elf32_Half e_type;
Elf32_Half e_machine;
Elf32_Word e_version;
Elf32_Addr e_entry;
Elf32_Off e_phoff;
Elf32_Off e_shoff;
Elf32_Word e_flags;
Elf32_Half e_ehsize;
Elf32_Half e_phentsize;
Elf32_Half e_phnum;
Elf32_Half e_shentsize;
Elf32_Half e_shnum;
Elf32_Half e_shstrndx;
} elf_t;
typedef struct {
Elf32_Word sh_name;
Elf32_Word sh_type;
Elf32_Word sh_flags;
Elf32_Addr sh_addr;
Elf32_Off sh_offset;
Elf32_Word sh_size;
Elf32_Word sh_link;
Elf32_Word sh_info;
Elf32_Word sh_addralign;
Elf32_Word sh_entsize;
} section_t;
section_t *elf_find_section(elf_t *elf, const char *name);
#endif

46
include/kernel/kernel.h
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@ -3,16 +3,11 @@
#include <kernel/multiboot.h>
#include <kernel/log.h>
#include <kernel/task.h>
#define cpu_relax asm volatile ("pause" ::)
#define CHECK_FLAG(x, n) (x & (1<<n))
typedef struct {
uint32_t eip;
uint32_t esp;
uint32_t cr3;
} task_t;
#define KERNEL_VMA 0xC0000000
typedef struct {
@ -22,6 +17,7 @@ typedef struct {
uint32_t mmap_size;
log_method_t log_method;
uint64_t ticks;
task_t *current_task;
} kernel_ctx_t;
#define GDT_NULL 0
@ -84,42 +80,4 @@ struct tss_entry {
} __attribute__((packed));
typedef struct tss_entry tss_t;
#define EI_NIDENT 16
typedef uint16_t Elf32_Half;
typedef uint32_t Elf32_Addr;
typedef uint32_t Elf32_Off;
typedef uint32_t Elf32_Word;
typedef int32_t Elf32_Sword;
typedef struct {
uint8_t e_ident[EI_NIDENT];
Elf32_Half e_type;
Elf32_Half e_machine;
Elf32_Word e_version;
Elf32_Addr e_entry;
Elf32_Off e_phoff;
Elf32_Off e_shoff;
Elf32_Word e_flags;
Elf32_Half e_ehsize;
Elf32_Half e_phentsize;
Elf32_Half e_phnum;
Elf32_Half e_shentsize;
Elf32_Half e_shnum;
Elf32_Half e_shstrndx;
} elf_t;
typedef struct {
Elf32_Word sh_name;
Elf32_Word sh_type;
Elf32_Word sh_flags;
Elf32_Addr sh_addr;
Elf32_Off sh_offset;
Elf32_Word sh_size;
Elf32_Word sh_link;
Elf32_Word sh_info;
Elf32_Word sh_addralign;
Elf32_Word sh_entsize;
} section_t;
#endif

17
include/kernel/task.h Normal file
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@ -0,0 +1,17 @@
#ifndef HAZEL_TASK_H_
#define HAZEL_TASK_H_
#include <stdint.h>
#include <kernel/elf.h>
typedef struct {
uint32_t eip;
uint32_t esp;
uint32_t cr3;
uint32_t *next;
} task_t;
int task_init(task_t *task, elf_t *elf);
void schedule(void);
#endif

16
kernel/elf.c Normal file
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@ -0,0 +1,16 @@
#include <kernel/elf.h>
#include <strcmp.h>
section_t *elf_find_section(elf_t *elf, const char *name) {
section_t *str = (section_t *)((uint32_t)elf + elf->e_shoff + elf->e_shstrndx*elf->e_shentsize);
section_t *found = 0;
for (int i = 0; i < elf->e_shnum; i++) {
section_t *sec = (section_t *)((uint32_t)elf + elf->e_shoff + i*elf->e_shentsize);
const char *n = (char *)((uint32_t)elf + str->sh_offset + sec->sh_name);
if (!strcmp(n, name)) {
found = sec;
}
}
return found;
}

25
kernel/init.asm
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@ -115,6 +115,31 @@ flush_tss:
ltr [esp+4]
ret
extern ctx
global task_switch
task_switch:
push ebx
push esi
push edi
push ebp
mov esi, [ctx+28]
; Return if only one process is running
mov eax, [esi+12]
cmp eax, 0
je ret
; Check if using same virtual memory
cmp [esi+8], [eax+8]
je .ret
mov ecx, [eax+8]
mov cr3, ecx
.ret:
pop ebp
pop edi
pop esi
pop ebx
ret
extern exception_handler
%macro isr_err_stub 1
isr_stub_%+%1:

91
kernel/kernel.c
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@ -5,6 +5,8 @@
#include <kernel/idt.h>
#include <kernel/pic.h>
#include <kernel/pit.h>
#include <kernel/elf.h>
#include <kernel/task.h>
#include <stdint.h>
kernel_ctx_t ctx = {0};
@ -33,42 +35,41 @@ void sleep(int delay) {
cpu_relax;
}
int strcmp(const char *str1, const char *str2) {
while (*str1 && (*str1 == *str2)) {
str1++;
str2++;
}
return *(uint8_t *)str1 - *(uint8_t *)str2;
}
void kernel(multiboot_info_t *info) {
if (!CHECK_FLAG(info->flags, 3)) goto halt; // Modules
if (!CHECK_FLAG(info->flags, 6)) goto halt; // Memory map
if (!CHECK_FLAG(info->flags, 12)) goto halt; // VBE data
ctx.multi_mmap = (multi_mmap_t *)(info->memmapaddress + KERNEL_VMA);
ctx.multi_mmap_size = info->memmaplength;
if (serial_port_init(COM1)) ctx.log_method = LOG_COM1;
LOG("Kernel log being sent to COM1\n");
if (!mmap_init()) goto halt;
LOG("%d bytes of RAM detected\nCreated a %d byte large physical memory map at 0x%08X\n", ctx.mmap_size*BLOCK_SIZE*8, ctx.mmap_size, (uint32_t)ctx.mmap);
void idt_init() {
for (int i = 0; i < 32; i++) {
idt_encode_entry(idt, i, isr_stub_table[i], GDT_SEGMENT_SELECTOR(1, 0), TRAP_GATE_32 | INT_RING0 | INT_PRESENT);
idt_encode_entry(idt, i, isr_stub_table[i], GDT_SEGMENT_SELECTOR(GDT_KERNEL_CODE, RING0), TRAP_GATE_32 | INT_RING0 | INT_PRESENT);
}
idt_encode_entry(idt, 32, (uint32_t)pit_isr, GDT_SEGMENT_SELECTOR(1, 0), INT_GATE_32 | INT_RING0 | INT_PRESENT);
idt_encode_entry(idt, 32, (uint32_t)pit_isr, GDT_SEGMENT_SELECTOR(GDT_KERNEL_CODE, RING0), INT_GATE_32 | INT_RING0 | INT_PRESENT);
idtr.size = (sizeof(struct idt_entry) * 256) - 1;
idtr.base = (uint32_t) idt;
asm volatile ("lidt %0" :: "m"(idtr));
}
void kernel(multiboot_info_t *info) {
if (!CHECK_FLAG(info->flags, 3)) goto halt; // Modules
if (!CHECK_FLAG(info->flags, 6)) goto halt; // Memory map
if (!CHECK_FLAG(info->flags, 12)) goto halt; // VBE data
if (serial_port_init(COM1)) ctx.log_method = LOG_COM1;
LOG("Kernel log being sent to COM1\n");
ctx.multi_mmap = (multi_mmap_t *)(info->memmapaddress + KERNEL_VMA);
ctx.multi_mmap_size = info->memmaplength;
if (!mmap_init()) goto halt;
LOG("%d bytes of RAM detected\nCreated a %d byte large physical memory map at 0x%08X\n", ctx.mmap_size*BLOCK_SIZE*8, ctx.mmap_size, (uint32_t)ctx.mmap);
idt_init();
/*
pic_remap(PIC_1_START, PIC_2_START);
//asm volatile ("sti" ::);
//ctx.ticks = 0;
//pit_init();
asm volatile ("sti" ::);
ctx.ticks = 0;
pit_init();
*/
// Setup TSS
uint32_t base = (uint32_t)&tss;
uint32_t limit = base + sizeof(tss_t);
gdt[5].base_low = base & 0xFFFF;
@ -78,42 +79,24 @@ void kernel(multiboot_info_t *info) {
gdt[5].granularity = (limit >> 16) & 0x0F;
gdt[5].granularity |= 0x40;
gdt[5].access = 0x89;
tss.ss0 = GDT_SEGMENT_SELECTOR(2, RING0);
tss.ss0 = GDT_SEGMENT_SELECTOR(GDT_KERNEL_DATA, RING0);
uint32_t esp0 = 0;
asm volatile ("mov %%esp, %0" : "=r" (esp0));
tss.esp0 = esp0;
tss.cs = GDT_SEGMENT_SELECTOR(3, RING3);
tss.ss = tss.ds = tss.es = tss.fs = tss.gs = GDT_SEGMENT_SELECTOR(4, RING3);
tss.cs = GDT_SEGMENT_SELECTOR(GDT_USER_CODE, RING3);
tss.ss = tss.ds = tss.es = tss.fs = tss.gs = GDT_SEGMENT_SELECTOR(GDT_USER_DATA, RING3);
flush_tss(GDT_SEGMENT_SELECTOR(5, RING3));
multi_mod_t *init = (multi_mod_t *)(info->moduleaddress + KERNEL_VMA);
elf_t *elf = (elf_t *)(init->mod_start+KERNEL_VMA);
section_t *str = (section_t *)((uint32_t)elf + elf->e_shoff + elf->e_shstrndx*elf->e_shentsize);
section_t *text = 0;
for (int i = 0; i < elf->e_shnum; i++) {
section_t *sec = (section_t *)((uint32_t)elf + elf->e_shoff + i*elf->e_shentsize);
//LOG("Pingas: %d\n", elf->e_shstrndx);
const char *name = (char *)((uint32_t)elf + str->sh_offset + sec->sh_name);
if (!strcmp(name, ".text")) {
text = sec;
}
}
task_t task = {0};
if (!task_init(&task, elf)) goto halt;
uint32_t elf_phys = (uint32_t)elf - KERNEL_VMA;
LOG("0x%08X\n", elf_phys);
uint32_t *elf_page_dir = mmap_find_first_free_block();
uint32_t *elf_page_tab = mmap_find_first_free_block();
elf_page_dir[768] = ((uint32_t)boot_page_tab - KERNEL_VMA) | 3;
elf_page_dir[PAGE_DIR_INDEX(elf->e_entry)] = ((uint32_t)elf_page_tab - KERNEL_VMA) | 7;
for (int i = 0; i < 1024; i++) {
elf_page_tab[i] = (elf_phys + 0x1000*i) | 7;
}
ctx.current_task = &task;
asm volatile ("mov %0, %%cr3" :: "r"(task.cr3));
asm volatile ("mov %0, %%cr3" :: "r"((uint32_t)elf_page_dir - KERNEL_VMA));
uint32_t stack = (uint32_t)mmap_find_first_free_block();
LOG("Switching to ring 3... EIP: 0x%08X ESP: 0x%08X\n", elf->e_entry+text->sh_offset, stack+0x1000);
jmp_user_mode(stack+0x1000, elf->e_entry+text->sh_offset);
LOG("Switching to ring 3... EIP: 0x%08X ESP: 0x%08X\n", task.eip, task.esp);
jmp_user_mode(task.esp, task.eip);
halt:
for (;;) {}

39
kernel/task.c Normal file
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@ -0,0 +1,39 @@
#include <kernel/task.h>
#include <kernel/mem.h>
extern uint32_t boot_page_tab[1024];
extern kernel_ctx_t ctx;
int task_init(task_t *task, elf_t *elf) {
section_t *text = elf_find_section(elf, ".text");
if (!text) return 0;
task->eip = elf->e_entry + text->sh_offset;
// Allocate a page for a stack
task->esp = (uint32_t)mmap_find_first_free_block() + 0x1000;
uint32_t *page_dir = mmap_find_first_free_block();
task->cr3 = (uint32_t)page_dir - KERNEL_VMA;
uint32_t *page_tab = mmap_find_first_free_block();
for (int i = 0; i < 1024; i++) {
// Map kernel to 3GiB
if (i == 768) page_dir[i] = ((uint32_t)boot_page_tab - KERNEL_VMA) | 3;
// Map 3.4GiB-4GiB as non-present kernel entries
else if (i > 768) page_dir[i] = 4;
// Map remaining entries as non-present u/s
else page_dir[i] = 6;
}
// Map the ELF image to its specified entry
// This will cause problems if the ELF image is larger than 4 MiB so I need to fix this
page_dir[PAGE_DIR_INDEX(elf->e_entry)] = ((uint32_t)page_tab - KERNEL_VMA) | 7;
uint32_t elf_phys = (uint32_t)elf - KERNEL_VMA;
for (int i = 0; i < 1024; i++) {
page_tab[i] = (elf_phys + 0x1000*i) | 7;
}
return 1;
}
void schedule(void) {
// If there's only one task running
if (!ctx.current_task->next) return;
}

14
lib/strcmp.h Normal file
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@ -0,0 +1,14 @@
#ifndef HAZEL_STRCMP_H_
#define HAZEL_STRCMP_H_
#include <stdint.h>
int strcmp(const char *str1, const char *str2) {
while (*str1 && (*str1 == *str2)) {
str1++;
str2++;
}
return *(uint8_t *)str1 - *(uint8_t *)str2;
}
#endif