Implemented a basic syscall handler

TODO

@@ -18,7 +18,8 @@ TODO
 [x] PIT
 [ ] RTC
 [ ] HPET
-[ ] System calls
+[x] System calls
+[ ] Separate syscall sources into individual files
 [ ] Userspace
 [x] Processes/Tasks
 [x] Scheduler

docs/syscalls.txt

@@ -1,6 +1,21 @@
 System Calls 
 ============
 
+System calls are a way of interfacing with the kernel from userspace.
+
+Calling
+-------
+System calls are called via interrupt 0x80. Arguments can be passed through
+registers in this order with EAX containing the system call number (see [Table](#Table))
+and arguments in EBX, ECX, EDX, ESI, EDI and EBP respectively.
+
+Table
+-----
+
+
+Syscalls
+--------
+
 pid_t fork(void);
 Creates a child process.
 

kernel/include/isr.h

@@ -17,7 +17,7 @@ typedef void (*isr_handler_ptr)(struct isr_int_frame* iframe);
 
 int isr_init(void);
 void isr_register(uint8_t i, isr_handler_ptr handler);
-int isr_handle_interrupt(struct isr_int_frame iframe);
+void isr_handle_interrupt(struct isr_int_frame iframe);
 
 // Assembly definitions (isr.s)
 extern void isr_return(void);

kernel/include/syscall.h

@@ -1,8 +1,15 @@
 #ifndef _SYSCALL_H
 #define _SYSCALL_H
 
+#include <kernel.h>
 #include <isr.h>
 
-int syscall_handler(struct isr_int_frame* iframe) { (void)iframe; return 1; }
+#define SYSCALL_MAX	2
+#define SYS_EXIT	0
+#define SYS_TEST	1
+
+int syscall_init(void);
+void syscall_register(size_t idx, void* handler);
+void syscall_handler(struct isr_int_frame* iframe);
 
 #endif

kernel/src/bootloader.c

@@ -80,6 +80,8 @@ int boot_init_mb1(void* ptr, uint32_t magic) {
 	// TODO: VBE table
 	// TODO: Framebuffer
 	
+	debugf("[boot] Initiated with MultiBoot 1\n");
+
 	return 0;
 }
 

kernel/src/isr.c

@@ -85,7 +85,7 @@ void isr_send_eoi(uint8_t irq) {
 }
 
 // TODO: Write fault handlers and make this more robust 
-int isr_handle_interrupt(struct isr_int_frame iframe) {
+void isr_handle_interrupt(struct isr_int_frame iframe) {
 	if (iframe.interrupt < 32) { 
 		// ISRs 0-31 - Exceptions
 		if (iframe.error) debugf("[kernel] Error code: 0x%08x\n", iframe.error);
@@ -97,9 +97,7 @@ int isr_handle_interrupt(struct isr_int_frame iframe) {
 		if (irq_handlers[irq]) irq_handlers[irq](&iframe);
 	} else if (iframe.interrupt == 128) { 
 		// ISR 128 - System call
-		return syscall_handler(&iframe);
+		syscall_handler(&iframe);
 	}
-
-	return 0;
 }
 

kernel/src/kernel.c

@@ -1,5 +1,6 @@
 #include <bootloader.h>
 #include <kmalloc.h>
+#include <syscall.h>
 #include <kernel.h>
 #include <paging.h>
 #include <serial.h>
@@ -10,20 +11,16 @@
 #include <pmm.h>
 #include <tty.h>
 
-void test(void);
-
 __noreturn
 void kmain(void* ptr, uint32_t magic) {
-	if (boot_init_mb1(ptr, magic) != 0) panic("Unsupported bootloader.");
-
 	// Serial console for debugging
 	if (serial_init(COM1) != 0) panic("Failed to initialize Serial driver.");
-	debugf("\x1b[H\x1b[J\x1b[0mkern. \x1b[36m(serial console)\x1b[0m\n\n");
+
+	// Load structures from bootloader
+	if (boot_init_mb1(ptr, magic) != 0) panic("Unsupported bootloader.");
 
 	// System init
 	if (gdt_init() != 0) panic("Failed to initalize GDT.");
-	debugf("[gdt] Segment selectors: NULL: 0x%04x, KCODE: 0x%04x, KDATA: 0x%04x, UCODE: 0x%04x, UDATA: 0x%04x, TSS: 0x%04x\n",
-		GDT_NULL, GDT_KERNEL_CODE, GDT_KERNEL_DATA, GDT_USER_CODE, GDT_USER_DATA, GDT_TSS);
 	if (isr_init() != 0) panic("Failed to initalize ISRs.");
 	if (pag_init() != 0) panic("Failed to initalize Paging.");
 
@@ -36,38 +33,16 @@ void kmain(void* ptr, uint32_t magic) {
 	tty_puts("kern.\n\n");
 
 	if (timer_init() != 0) panic("Failed to initialize timer.");
+	if (syscall_init() != 0) panic("Failed to initialize syscalls.");
 	if (task_init() != 0) panic("Failed to initialize tasking.");
 
-	// Create a temporary test task
+	char* s = "Hello, World!";
-	task_create(task_create_id(), (uint32_t)test, 1, pag_get_pagedir(), 0, NULL);
+	__asm__ volatile("int $0x80" :: "a"(SYS_TEST), "b"(s));
 
-	size_t delay = 0;
-	while (1) {
-		delay++;
-
-		if (delay < 0x1FFFFFF) continue;
-		delay = 0;
-
-		tty_puts("[kernel] Hello!\n");
-	}
-	
-	// TODO: Syscalls
 	// TODO: Interprocess communication
 	// TODO: Load & run /sbin/init
 
-	panic("kmain() reached end.");
+	// We don't want to halt
-}
+	while (1);
-
-// An imaginary second task
-void test(void) {
-	size_t delay = 0;
-	while (1) {
-		delay++;
-
-		if (delay < 0x2FFFFFF) continue;
-		delay = 0;
-
-		tty_puts("[test] Hello!\n");
-	}
 }
 

kernel/src/serial.c

@@ -17,6 +17,8 @@ int serial_init(int dev) {
 	if (inb(dev + 0) != 0xAE) return 1;
 	outb(dev + 4, 0x0F);	// non-loopback, IRQs enabled, OUT#1 and OUT#2 bits enabled
 	
+	debugf("\x1b[H\x1b[JSerial display initiated!\n\n");
+	
 	return 0;
 }
 

kernel/src/syscall.c

@@ -0,0 +1,66 @@
+#include <kernel.h>
+#include <task.h>
+#include <tty.h>
+
+#include <syscall.h>
+
+// Syscall table
+void* syscalls[SYSCALL_MAX] = { 0 };
+
+void sys_exit(int code) {
+	debugf("[syscall] Task #%d exited with code %d.\n", task_current->id, code);
+	task_kill(task_current->id);
+}
+
+void sys_test(char* msg) {
+	debugf("[syscall] Test: %s\n", msg);
+}
+
+int syscall_init(void) {
+	syscall_register(SYS_EXIT, (void*)sys_exit);
+	syscall_register(SYS_TEST, (void*)sys_test);
+
+	debugf("[syscall] Initiated syscalls!\n");
+
+	return 0;
+}
+
+void syscall_register(size_t idx, void* handler) {
+	if (idx > SYSCALL_MAX) {
+		debugf("[syscall] Failed to register syscall #%d.\n", idx);
+		return;
+	}
+
+	syscalls[idx] = handler;
+}
+
+void syscall_handler(struct isr_int_frame* iframe) {
+	size_t nr = iframe->eax;
+	if (nr > SYSCALL_MAX || !syscalls[nr]) {
+		iframe->eax = -1;
+		debugf("[syscall] Tried to call syscall #%d which doesn't exist.\n", nr);
+		return;
+	}
+
+	void* handler = syscalls[nr];
+
+	int ret;
+	debugf("0x%08x\n", &ret);
+	__asm__ volatile(
+		"push %1\n"
+		"push %2\n"
+		"push %3\n"
+		"push %4\n"
+		"push %5\n"
+		"push %6\n"
+		"call *%7\n"
+		"add $24, %%esp\n"
+		"mov %%eax, %0\n"
+		: "=a"(ret)
+		: "g"(iframe->ebp), "g"(iframe->edi), "g"(iframe->esi),
+		  "g"(iframe->edx), "g"(iframe->ecx), "g"(iframe->ebx),
+		  "g"(handler)
+	);
+	iframe->eax = ret;
+}
+

kernel/src/timer.c

@@ -34,7 +34,7 @@ void pit_phase(uint8_t ch, uint8_t mode, uint32_t hz) {
 	uint32_t div = PIT_DIV / hz;
 	outb(PIT_CH0 + ch, div & 0xFF);
 	outb(PIT_CH0 + ch, div >> 8);
-	debugf("[PIT] Set PIT divisor to %d (%d Hz).\n", div, hz);
+	debugf("[pit] Set PIT divisor to %d (%d Hz).\n", div, hz);
 
 	sti();
 }

kernel/src/tty.c

@@ -28,6 +28,8 @@ int tty_init(void) {
 	tty_ctx.buf = (uint8_t*)KERNEL_FRAMEBUF;
 	tty_clear();
 
+	debugf("[tty] Initiated %dx%d VGA display to TTY.\n", VGA_WIDTH, VGA_HEIGHT);
+
 	return 0;
 }