separate the source code from object files; more modular Makefile

16 files changed, 422 insertions, 0 deletions

diff --git a/src/kernel/gdt.c b/src/kernel/gdt.c
new file mode 100644
index 0000000..b0d6320
--- /dev/null
+++ b/src/kernel/gdt.c
@@ -0,0 +1,121 @@
+#include <kernel/gdt.h>
+#include <kernel/util.h>
+#include <stdint.h>
+
+extern void stack_top; // platform/boot.s
+
+struct gdt_entry {
+	uint64_t limit_low  : 16;
+	uint64_t base_low   : 24;
+	uint64_t accessed   :  1; // set by the processor
+	                          // CODE        | DATA
+	uint64_t rw         :  1; // readable?   | writeable?
+	uint64_t conforming :  1; // conforming? | expands down?
+	uint64_t code       :  1; // 1           | 0
+
+	uint64_t codeordata :  1; // 1 for everything other than TSS and LDT
+	uint64_t ring       :  2;
+	uint64_t present    :  1; // always 1
+	uint64_t limit_high :  4;
+	uint64_t available  :  1; // ???
+	uint64_t long_mode  :  1;
+	uint64_t x32        :  1;
+	uint64_t gran       :  1; // 1 - 4kb, 0 - 1b
+	uint64_t base_high  :  8;
+} __attribute__((packed));
+
+struct tss_entry {
+	uint32_t prev_tss; // unused
+	uint32_t esp0; // kernel mode stack pointer
+	uint32_t ss0;  // kernel mode stack segment
+	// total size = 0x68 (?) - 3 * sizeof(uint32_t) = 5c
+	uint8_t  _unused[0x5c];
+} __attribute__((packed));
+
+struct lgdt_arg {
+	uint16_t limit;
+	uint32_t base;
+} __attribute__((packed));
+
+static struct gdt_entry GDT[SEG_end];
+static struct tss_entry TSS;
+static struct lgdt_arg lgdt_arg; // probably doesn't need to be global
+
+static void gdt_prepare();
+static void gdt_load();
+
+
+static void gdt_prepare() {
+	GDT[SEG_null].present = 0;
+
+	GDT[SEG_r0data].limit_low  = 0xFFFF;
+	GDT[SEG_r0data].limit_high = 0xF;
+	GDT[SEG_r0data].gran       = 1; // 4KB * 0xFFFFF = (almost) 4GB
+	GDT[SEG_r0data].base_low   = 0;
+	GDT[SEG_r0data].base_high  = 0;
+	GDT[SEG_r0data].accessed   = 0;
+	GDT[SEG_r0data].rw         = 1;
+	GDT[SEG_r0data].conforming = 0;
+	GDT[SEG_r0data].code       = 0;
+	GDT[SEG_r0data].codeordata = 1;
+	GDT[SEG_r0data].ring       = 0;
+	GDT[SEG_r0data].present    = 1;
+	GDT[SEG_r0data].long_mode  = 0; // ???
+	GDT[SEG_r0data].available  = 1; // ???
+	GDT[SEG_r0data].x32        = 1;
+
+	// copy to r0 code
+	GDT[SEG_r0code] = GDT[SEG_r0data];
+	GDT[SEG_r0code].code = 1;
+
+	GDT[SEG_r3data] = GDT[SEG_r0data];
+	GDT[SEG_r3data].ring = 3;
+	GDT[SEG_r3code] = GDT[SEG_r0code];
+	GDT[SEG_r3code].ring = 3;
+
+	// tss
+	memset(&TSS, 0, sizeof(TSS));
+	TSS.ss0 = SEG_r0data << 3; // kernel data segment
+	TSS.esp0 = (uint32_t) &stack_top;
+
+	GDT[SEG_TSS].limit_low  = sizeof(TSS);
+	GDT[SEG_TSS].base_low   = (uint32_t) &TSS;
+	GDT[SEG_TSS].accessed   = 1; // 1 for TSS
+	GDT[SEG_TSS].rw         = 0; // 1 busy / 0 not busy
+	GDT[SEG_TSS].conforming = 0; // 0 for TSS
+	GDT[SEG_TSS].code       = 1; // 32bit
+	GDT[SEG_TSS].codeordata = 0; // is a system entry
+	GDT[SEG_TSS].ring       = 3;
+	GDT[SEG_TSS].present    = 1;
+	GDT[SEG_TSS].limit_high = (sizeof(TSS) >> 16) & 0xf;
+	GDT[SEG_TSS].available  = 0; // 0 for TSS
+	GDT[SEG_TSS].long_mode  = 0;
+	GDT[SEG_TSS].x32        = 0; // idk
+	GDT[SEG_TSS].gran       = 0;
+	GDT[SEG_TSS].base_high  = (((uint32_t) &TSS) >> 24) & 0xff;
+}
+
+void change_cs(int seg); // temporary
+
+static void gdt_load() {
+	lgdt_arg.limit = sizeof(GDT) - 1;
+	lgdt_arg.base = (uint32_t) &GDT;
+	asm("lgdt (%0)" 
+	    : : "r" (&lgdt_arg) : "memory");
+	asm("ltr %%ax"
+	    : : "a" (SEG_TSS << 3 | 3) : "memory");
+
+	// update all segment registers
+	change_cs(SEG_r0code << 3);
+	asm("mov %0, %%ds;"
+	    "mov %0, %%ss;"
+	    "mov %0, %%es;"
+	    "mov %0, %%fs;"
+	    "mov %0, %%gs;"
+	    : : "r" (SEG_r0data << 3) : "memory");
+}
+
+void gdt_init() {
+	gdt_prepare();
+	gdt_load();
+}
diff --git a/src/kernel/gdt.h b/src/kernel/gdt.h
new file mode 100644
index 0000000..9e5a6a5
--- /dev/null
+++ b/src/kernel/gdt.h
@@ -0,0 +1,15 @@
+#pragma once
+
+enum {
+	SEG_null,
+	// order dictated by SYSENTER
+	SEG_r0code,
+	SEG_r0data,
+	SEG_r3code,
+	SEG_r3data,
+	SEG_TSS,
+
+	SEG_end
+};
+
+void gdt_init();
diff --git a/src/kernel/idt.c b/src/kernel/idt.c
new file mode 100644
index 0000000..65f511f
--- /dev/null
+++ b/src/kernel/idt.c
@@ -0,0 +1,75 @@
+#include <kernel/gdt.h>
+#include <kernel/idt.h>
+#include <kernel/isr.h>
+#include <kernel/panic.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+struct idt_entry {
+	uint16_t offset_low   ;
+	uint16_t code_seg     ;
+	uint8_t  zero         ; // unused, has to be 0
+	uint8_t  type      : 4; // 16/32 bit, task/interrupt/task gate
+	uint8_t  storage   : 1; // 0 for interrupt/trap gates
+	uint8_t  ring      : 2;
+	uint8_t  present   : 1;
+	uint16_t offset_high  ;
+} __attribute__((packed));
+
+// is exactly the same as lgdt_arg, i should combine them into a single struct
+// later
+struct lidt_arg {
+	uint16_t limit;
+	uint32_t base;
+} __attribute__((packed));
+
+
+static struct idt_entry IDT[256];
+static struct lidt_arg lidt_arg;
+
+static inline void idt_add(uint8_t num, bool user, void (*isr));
+static void idt_prepare();
+static void idt_load();
+static void idt_test();
+
+
+static inline void idt_add(uint8_t num, bool user, void (*isr)) {
+	uintptr_t offset = (uintptr_t) isr;
+
+	IDT[num] = (struct idt_entry) {
+		.offset_low  = offset,
+		.offset_high = offset >> 16,
+		.code_seg    = SEG_r0code << 3,
+		.zero        = 0,
+		.present     = 1,
+		.ring        = user ? 3 : 0,
+		.storage     = 0,
+		.type        = 0xE, // 32-bit interrupt gate
+	};
+}
+
+static void idt_prepare() {
+	for (int i = 0; i < 256; i++)
+		IDT[i].present = 0;
+
+	idt_add(0x08, false, isr_double_fault);
+	idt_add(0x0d, false, isr_general_protection_fault);
+	idt_add(0x34, false, isr_test_interrupt);
+}
+
+static void idt_load() {
+	lidt_arg.limit = sizeof(IDT) - 1;
+	lidt_arg.base = (uintptr_t) &IDT;
+	asm("lidt (%0)" : : "r" (&lidt_arg) : "memory");
+}
+
+static void idt_test() {
+	asm("int $0x34" : : : "memory");
+	if (!isr_test_interrupt_called) panic();
+}
+
+void idt_init() {
+	idt_prepare();
+	idt_load();
+	idt_test();
+}
diff --git a/src/kernel/idt.h b/src/kernel/idt.h
new file mode 100644
index 0000000..5627657
--- /dev/null
+++ b/src/kernel/idt.h
@@ -0,0 +1,3 @@
+#pragma once
+
+void idt_init();
diff --git a/src/kernel/isr.c b/src/kernel/isr.c
new file mode 100644
index 0000000..b715de0
--- /dev/null
+++ b/src/kernel/isr.c
@@ -0,0 +1,24 @@
+#include <kernel/isr.h>
+#include <kernel/panic.h>
+#include <kernel/tty.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+bool isr_test_interrupt_called = false;
+
+__attribute__((interrupt))
+void isr_double_fault(struct interrupt_frame *frame) {
+	tty_const("#DF");
+	panic();
+}
+
+__attribute__((interrupt))
+void isr_general_protection_fault(struct interrupt_frame *frame) {
+	tty_const("#GP");
+	panic();
+}
+
+__attribute__((interrupt))
+void isr_test_interrupt(struct interrupt_frame *frame) {
+	isr_test_interrupt_called = true;
+}
diff --git a/src/kernel/isr.h b/src/kernel/isr.h
new file mode 100644
index 0000000..150fc46
--- /dev/null
+++ b/src/kernel/isr.h
@@ -0,0 +1,15 @@
+#pragma once
+#include <stdbool.h>
+
+struct interrupt_frame;
+
+extern bool isr_test_interrupt_called; // used in the self-test in idt.c
+
+__attribute__((interrupt))
+void isr_double_fault(struct interrupt_frame *frame);
+
+__attribute__((interrupt))
+void isr_general_protection_fault(struct interrupt_frame *frame);
+
+__attribute__((interrupt))
+void isr_test_interrupt(struct interrupt_frame *frame);
diff --git a/src/kernel/main.c b/src/kernel/main.c
new file mode 100644
index 0000000..0193514
--- /dev/null
+++ b/src/kernel/main.c
@@ -0,0 +1,33 @@
+#include <kernel/gdt.h>
+#include <kernel/idt.h>
+#include <kernel/mem.h>
+#include <kernel/panic.h>
+#include <kernel/proc.h>
+#include <kernel/tty.h>
+#include <platform/asm.h>
+
+void r3_test();
+
+void kmain()
+{
+	tty_clear();
+	tty_const("gdt...");
+	gdt_init();
+	tty_const("idt...");
+	idt_init();
+	tty_const("sysenter...");
+	sysenter_setup();
+	tty_const("mem...");
+	mem_init();
+
+	tty_const("creating process...");
+	struct process *proc = process_new(r3_test);
+	tty_const("switching...");
+	process_switch(proc);
+}
+
+void r3_test() {
+	tty_const("ok");
+	asm("cli");
+	panic();
+}
diff --git a/src/kernel/mem.c b/src/kernel/mem.c
new file mode 100644
index 0000000..08eb285
--- /dev/null
+++ b/src/kernel/mem.c
@@ -0,0 +1,19 @@
+#include <kernel/mem.h>
+
+extern void *_kernel_end;
+static void *highest_page;
+
+void mem_init() {
+	highest_page = &_kernel_end;
+}
+
+void *page_alloc(size_t pages) {
+	void *bottom = highest_page;
+	highest_page += pages * PAGE_SIZE;
+	return bottom;
+}
+
+// frees `pages` consecutive pages starting from *first
+void page_free(void *first, size_t pages) {
+	// not implemented
+}
diff --git a/src/kernel/mem.h b/src/kernel/mem.h
new file mode 100644
index 0000000..e8e6a4f
--- /dev/null
+++ b/src/kernel/mem.h
@@ -0,0 +1,12 @@
+#pragma once
+#include <stddef.h>
+
+#define PAGE_SIZE 4096
+
+void mem_init();
+
+// allocates `pages` consecutive pages
+void *page_alloc(size_t pages);
+
+// frees `pages` consecutive pages starting from *first
+void page_free(void *first, size_t pages);
diff --git a/src/kernel/panic.h b/src/kernel/panic.h
new file mode 100644
index 0000000..7d2ea5f
--- /dev/null
+++ b/src/kernel/panic.h
@@ -0,0 +1,14 @@
+#pragma once
+#include <kernel/tty.h>
+#include <platform/asm.h>
+
+// dumb c shit
+#define panic_tostr2(x) #x
+#define panic_tostr(x)  panic_tostr2(x)
+
+#define panic() do { \
+	tty_const(" PANIC! at the "); \
+	tty_const(__func__); \
+	tty_const(" (" __FILE__ ":" panic_tostr(__LINE__) ") "); \
+	halt_cpu(); \
+} while (0)
diff --git a/src/kernel/proc.c b/src/kernel/proc.c
new file mode 100644
index 0000000..776238c
--- /dev/null
+++ b/src/kernel/proc.c
@@ -0,0 +1,19 @@
+#include <kernel/mem.h>
+#include <kernel/proc.h>
+#include <platform/asm.h>
+
+struct process *process_current;
+
+struct process *process_new(void *eip) {
+	struct process *proc;
+	proc = page_alloc(1); // TODO kmalloc
+	proc->stack_top = proc->esp = page_alloc(1) + 1 * PAGE_SIZE;
+	proc->eip = eip;
+
+	return proc;
+}
+
+void process_switch(struct process *proc) {
+	process_current = proc;
+	sysexit(proc->eip, proc->esp);
+}
diff --git a/src/kernel/proc.h b/src/kernel/proc.h
new file mode 100644
index 0000000..976b275
--- /dev/null
+++ b/src/kernel/proc.h
@@ -0,0 +1,13 @@
+#pragma once
+
+struct process {
+	void *stack_top;
+	void *esp;
+
+	void *eip;
+};
+
+extern struct process *process_current;
+
+struct process *process_new(void *eip);
+void process_switch(struct process *proc);
diff --git a/src/kernel/tty.c b/src/kernel/tty.c
new file mode 100644
index 0000000..5c4c47d
--- /dev/null
+++ b/src/kernel/tty.c
@@ -0,0 +1,38 @@
+/* will be moved to userspace later on */
+
+#include <kernel/tty.h>
+
+struct vga_cell {
+	unsigned char c;
+	unsigned char style;
+} __attribute__((__packed__));
+
+static const size_t     vga_len = 80 * 25;
+static struct vga_cell *vga     = (void*) 0xB8000;
+static size_t           vga_pos = 0;
+
+static void tty_scroll() {
+	for (int i = 0; i < vga_len - 80; i++) {
+		vga[i] = vga[i + 80];
+	}
+	vga_pos -= 80;
+}
+
+void tty_putchar(char c)
+{
+	if (vga_pos >= vga_len - 80) tty_scroll();
+	vga[vga_pos++].c = c;
+}
+
+void tty_write(const char *buf, size_t len)
+{
+	for (size_t i = 0; i < len; i++) {
+		tty_putchar(buf[i]);
+	}
+}
+
+void tty_clear() {
+	for (size_t i = 0; i < vga_len; i++)
+		vga[i].c = ' ';
+	vga_pos = 0;
+}
diff --git a/src/kernel/tty.h b/src/kernel/tty.h
new file mode 100644
index 0000000..3dc1525
--- /dev/null
+++ b/src/kernel/tty.h
@@ -0,0 +1,8 @@
+#pragma once
+#include <stddef.h>
+
+void tty_putchar(char c);
+void tty_write(const char *buf, size_t len);
+void tty_clear();
+
+#define tty_const(str) tty_write(str, sizeof(str) - 1)
diff --git a/src/kernel/util.c b/src/kernel/util.c
new file mode 100644
index 0000000..da3ac9d
--- /dev/null
+++ b/src/kernel/util.c
@@ -0,0 +1,9 @@
+#include <kernel/util.h>
+#include <stdint.h>
+
+void *memset(void *s, int c, size_t n) {
+	uint8_t *s2 = s;
+	for (size_t i = 0; i < n; n++)
+		s2[i] = c;
+	return s;
+}
diff --git a/src/kernel/util.h b/src/kernel/util.h
new file mode 100644
index 0000000..688ac63
--- /dev/null
+++ b/src/kernel/util.h
@@ -0,0 +1,4 @@
+#pragma once
+#include <stddef.h>
+
+void *memset(void *s, int c, size_t n);