Yoooooo userland execution :3

Makefile

@@ -51,7 +51,7 @@ clean:
 	rm -f isodir/boot/myos.kernel
 
 $(ARCHDIR)/interrupt.o: CFLAGS += -mgeneral-regs-only
-kernel/elf.o: CFLAGS += -masm=intel
+# kernel/elf.o: CFLAGS += -masm=intel
 
 %.o : %.c
 	i686-elf-gcc -c $< -o $@ $(CFLAGS)
@@ -71,7 +71,7 @@ debug: CFLAGS += -g -O0
 debug: ASFLAGS += -g
 debug: all
 
-run: myos.iso
+run: all
 	qemu-system-i386 myos.iso
 
 run-debug: debug

arch/i686/bootstrap.s

@@ -70,7 +70,7 @@ _start:
 
     call gdt_init
 
-    movw 0x10, %ax
+    movw $0x10, %ax
     movw %ax, %ds
     movw %ax, %es
     movw %ax, %fs

arch/i686/gdt.c

@@ -3,7 +3,7 @@
 #include <stdint.h>
 #include <stddef.h>
 
-#define NUM_ENTRIES 6
+#define NUM_ENTRIES 256
 
 struct SegmentDescriptor {
     uint32_t limit;
@@ -101,7 +101,7 @@ static void add_entry(struct SegmentDescriptor entry)
 
 static void load_gdt() 
 {
-    gdt.size = NUM_ENTRIES * 8 - 1;
+    gdt.size = NUM_ENTRIES * sizeof(struct SegmentDescriptor) - 1;
     gdt.base = entries;
 
     asm ( "lgdt %0" : : "m"(gdt) );
@@ -125,7 +125,7 @@ void gdt_init()
     terminal_putchar('\n');
 
     struct SegmentDescriptor kernel_code;
-    kernel_code.limit = 0x000003FF;
+    kernel_code.limit = 0xFFFFF;
     kernel_code.base =  0x00000000;
     kernel_code.access_byte = 0b10011010;
     kernel_code.flags = 0b1100;
@@ -136,8 +136,8 @@ void gdt_init()
     terminal_putchar('\n');
 
     struct SegmentDescriptor kernel_data;
-    kernel_data.limit = 0x000003FF;
+    kernel_data.limit = 0xFFFFF;
-    kernel_data.base =  0x00400000;
+    kernel_data.base =  0x00000000;
     kernel_data.access_byte = 0b10010010;
     kernel_data.flags = 0b1100;
 
@@ -146,8 +146,8 @@ void gdt_init()
     terminal_putchar('\n');
 
     struct SegmentDescriptor user_code;
-    user_code.limit = 0x000003FF;
+    user_code.limit = 0xFFFFF;
-    user_code.base =  0x00800000;
+    user_code.base =  0x00000000;
     user_code.access_byte = 0b11111010;
     user_code.flags = 0b1100;
 
@@ -157,8 +157,8 @@ void gdt_init()
     terminal_putchar('\n');
 
     struct SegmentDescriptor user_data;
-    user_data.limit = 0x000FFFFF;
+    user_data.limit = 0xFFFFF;
-    user_data.base =  0x00c00000;
+    user_data.base =  0x00000000;
     user_data.access_byte = 0b11110010;
     user_data.flags = 0b1100;
 
@@ -179,4 +179,9 @@ void gdt_init()
     terminal_putchar('\n');
 
     load_gdt();
+
+    tss.ss0 = 0x10;
+    asm("mov %%esp, %0" : "=r" (tss.esp0));
+
+    asm ("ltr %%ax" : : "a"(0x28));
 }

arch/i686/idt.c

@@ -1,9 +1,10 @@
-#include <kernel/tty.h>
 #include <kernel/gdt.h>
+#include <kernel/tty.h>
 #include <debugging.h>
 #include "interrupt.h"
 #include <stdint.h>
 #include <stddef.h>
+#include "io.h"
 
 #define NUM_ENTRIES 0x100
 
@@ -101,20 +102,9 @@ struct InterruptDescriptor generate_entry(bool present, void isr(struct interrup
     return entry;
 }
 
-static inline void outb(uint16_t port, uint8_t val)
-{
-    __asm__ volatile ( "outb %b0, %w1" : : "a"(val), "Nd"(port) : "memory");
-    /* There's an outb %al, $imm8 encoding, for compile-time constant port numbers that fit in 8b. (N constraint).
-     * Wider immediate constants would be truncated at assemble-time (e.g. "i" constraint).
-     * The  outb  %al, %dx  encoding is the only option for all other cases.
-     * %1 expands to %dx because  port  is a uint16_t.  %w1 could be used if we had the port number a wider C type */
-}
-
 void idt_init()
 {
-    outb(0x21,0xfd);
+    terminal_initialize();
-    outb(0xa1,0xff);
-
     struct InterruptDescriptor entry;
 
     entry = generate_entry(true, exception, 0xF, 0, 0x8);
@@ -123,12 +113,6 @@ void idt_init()
         add_entry(entry, i);
     }
 
-    entry = generate_entry(true, irq, 0xF, 0, 0x8);
-    for (int i = 0x20; i < 0x28; i++)
-    {
-        add_entry(entry, i);
-    }
-
     entry = generate_entry(true, divide_by_zero, 0xF, 0, 0x8);
     add_entry(entry, DivisionByZero);
 
@@ -138,11 +122,18 @@ void idt_init()
     entry = generate_entry(true, double_fault, 0xF, 0, 0x8);
     add_entry(entry, DoubleFault);
 
+    outb(0x21,0x20); // Tell the PIC to use interrupts 0x20 - 0x27
+    entry = generate_entry(true, irq, 0xE, 0, 0x8);
+    for (int i = 0x20; i < 0x28; i++)
+    {
+        add_entry(entry, i);
+    }
+
     struct InterruptDescriptor print_entry;
     print_entry.present = true;
     print_entry.offset = (uint32_t)print;
     print_entry.gate_type = 0xE;
-    print_entry.ring = 3;
+    print_entry.ring = 0;
     print_entry.selector = 0x8;
 
     add_entry(print_entry, 0x80);
@@ -157,9 +148,4 @@ void idt_init()
     add_entry(input_entry, 0x81);
 
     load_idt();
-
-    tss.ss0 = 0x10;
-    asm("mov %%esp, %0" : "=r" (tss.esp0));
-    asm("mov $0x28, %ax");
-    asm("ltr %ax");
 }

arch/i686/interrupt.c

@@ -1,6 +1,7 @@
 #include <kernel/tty.h>
 #include <stddef.h>
 #include <debugging.h>
+#include "io.h"
 
 struct interrupt_frame {
     uint32_t eflags;
@@ -25,35 +26,26 @@ static void stack_trace()
 
 __attribute__((interrupt)) void divide_by_zero(struct interrupt_frame* frame) 
 {
-    terminal_initialize();
-    stack_trace();
     terminal_writestring("Yo dude u cant divide by zero yao\n");
     while (1) { }
 }
 
 __attribute__((interrupt)) void general_protection_fault(struct interrupt_frame* frame)
 {
-    /* terminal_initialize();
+    terminal_writestring("GPF handler called\n");
-    stack_trace();
-    terminal_writestring("General protection fault\n");
-    terminal_writestring("Error code:\n");
-    print_hex_bytes(frame, sizeof(frame));
-    terminal_putchar('\n'); */
     while (1) { }
 }
 
 __attribute__((interrupt)) void double_fault(struct interrupt_frame* frame) 
 {
-    // terminal_writestring("2 Errors in a row, u better behave naughty naughty\n");
+    terminal_writestring("2 Errors in a row, u better behave naughty naughty\n");
-    // while (1) { }
+    while (1) { }
 }
 
 __attribute__((interrupt)) void exception(struct interrupt_frame* frame)
 {
-    /* terminal_initialize();
-    stack_trace();
     terminal_writestring("Some weird error code stuff\n");
-    terminal_writestring("Error code:\n");
+    /* terminal_writestring("Error code:\n");
     print_hex_bytes(frame, sizeof(frame));
     terminal_putchar('\n'); */
     while (1) { }
@@ -109,6 +101,7 @@ __attribute__((interrupt)) void input(struct interrupt_frame* frame)
 
 __attribute__((interrupt)) void irq(struct interrupt_frame* frame) 
 {
-
+    terminal_writestring("Test");
+    outb(0x20, 0x20);
 }
 

arch/i686/io.h

@@ -0,0 +1,19 @@
+#include <stdint.h>
+
+static inline void outb(uint16_t port, uint8_t val)
+{
+    __asm__ volatile ( "outb %b0, %w1" : : "a"(val), "Nd"(port) : "memory");
+    /* There's an outb %al, $imm8 encoding, for compile-time constant port numbers that fit in 8b. (N constraint).
+     * Wider immediate constants would be truncated at assemble-time (e.g. "i" constraint).
+     * The  outb  %al, %dx  encoding is the only option for all other cases.
+     * %1 expands to %dx because  port  is a uint16_t.  %w1 could be used if we had the port number a wider C type */
+}
+
+static inline void inb(uint16_t port, uint8_t val)
+{
+    __asm__ volatile ( "inb %b0, %w1" : : "a"(val), "Nd"(port) : "memory");
+    /* There's an outb %al, $imm8 encoding, for compile-time constant port numbers that fit in 8b. (N constraint).
+     * Wider immediate constants would be truncated at assemble-time (e.g. "i" constraint).
+     * The  outb  %al, %dx  encoding is the only option for all other cases.
+     * %1 expands to %dx because  port  is a uint16_t.  %w1 could be used if we had the port number a wider C type */
+}

arch/i686/pic.c

@@ -0,0 +1,17 @@
+#include "io.h"
+
+#define ICW1_ICW4	0x01		/* Indicates that ICW4 will be present */
+#define ICW1_SINGLE	0x02		/* Single (cascade) mode */
+#define ICW1_INTERVAL4	0x04		/* Call address interval 4 (8) */
+#define ICW1_LEVEL	0x08		/* Level triggered (edge) mode */
+#define ICW1_INIT	0x10		/* Initialization - required! */
+
+#define ICW4_8086	0x01		/* 8086/88 (MCS-80/85) mode */
+#define ICW4_AUTO	0x02		/* Auto (normal) EOI */
+#define ICW4_BUF_SLAVE	0x08		/* Buffered mode/slave */
+#define ICW4_BUF_MASTER	0x0C		/* Buffered mode/master */
+#define ICW4_SFNM	0x10		/* Special fully nested (not) */
+
+void init_pic() {
+    
+}

kernel/elf.c

@@ -3,43 +3,35 @@
 #include <debugging.h>
 #include <kernel/tty.h>
 #include <kernel/gdt.h>
+#include <debugging.h>
+
+static void* memcpy(void* restrict dstptr, const void* restrict srcptr, size_t size) {
+	unsigned char* dst = (unsigned char*) dstptr;
+	const unsigned char* src = (const unsigned char*) srcptr;
+	for (size_t i = 0; i < size; i++)
+		dst[i] = src[i];
+	return dstptr;
+}
 
 void run_program(uint8_t* program, size_t length)
 {
-    uint8_t* userland_code = (uint8_t*) 0x00800004;
+    uint8_t* userland_code = (uint8_t*) 0x0;
+    memcpy(userland_code, program, length);
 
-    for (size_t i = 0; i < length; i++) {
+    print_hex_bytes(userland_code, 1);
-        userland_code[i] = program[i];
+    terminal_putchar('\n');
-    }
 
-    tss.ss0 = 0x10;
+    asm ("\
-
+    mov $0x20 | 0x3, %%ax;\
-    asm("sti");
+    movw %%ax, %%ds;\
-    asm("int 0x80");
+    movw %%ax, %%es;\
-
+    movw %%ax, %%fs;\
-    asm("mov %0, esp" : "=r" (tss.esp0));
+    movw %%ax, %%gs;\
-
+    pushl $0x20 | 0x3;  /* SS  selector */ \
-    // Generates segfault
+    pushl $0x00c00100;      /* ESP */ \
-    // asm("mov esp, %0" : "=r" (tss.esp0));
+    pushf;              /* EFLAGS */    \
-
+    popl %%eax; orl $0x200, %%eax; pushl %%eax; /* Set interrupts in USERPACE */\
-    asm("mov ax, 0x23 # Load registers with the correct GDT segments values");
+    pushl $0x18 | 0x3;  /* CS selector */\
-	asm("mov ds, ax");
+    pushl $0x0;         /* EIP */ \
-	asm("mov es, ax");
+    iret;":::"eax");
-	asm("mov fs, ax");
-	asm("mov gs, ax");
-
-    asm("push 0x23");
-    asm("push 0x00c00100");
-
-    asm("pushfd");
-    asm("pop eax");
-    asm("or eax, 0x200");
-    asm("push eax");
-
-    asm("push 0x1b");
-    asm("push 0x00800000");
-
-    asm("iret");
-
-    asm("int 0x21");
 }

kernel/kernel.c

@@ -9,30 +9,8 @@
 #endif
 
 uint8_t program[] = {
-/*     0xcd,
+    0xB8, 0x00, 0x00, 0x00, 0x00, // mov eax, 0x0 (Just a simple NOP-like instruction)
-    0x80,
+    0xF4                          // hlt (halts the CPU, should trap to kernel if interrupts enabled)
-    0xc6,
-    0x05,
-    0x00,
-    0x80,
-    0x0b,
-    0x00,
-    0x62,
-    0xeb,
-    0xfe, */
-/*     0x90,
-    0xe9,
-    0xfa,
-    0x7f,
-    0x7b,
-    0xf8, */
-/*     0x90,
-    0xeb,
-    0xfd, */
-    0x6a,
-    0x69,
-    0xeb,
-    0xfc,
 };
 
 void kernel_main(void) 
@@ -42,6 +20,12 @@ void kernel_main(void)
 
     idt_init();
 
+    // asm("int $13");
+    // asm("ljmp $0x18, $0x00c00100");  // Example: Far jump to user code segment with selector 0x18
+
+    print_hex_bytes(idt_init, 4);
+    terminal_putchar('\n');
+
     run_program(program, 15);
 
     /*