[serial] Serial logging.

Makefile

@@ -19,7 +19,7 @@ install: kernel initrd
 	@${ECHO} "\r\033[34;1m   --   Kernel and ramdisk installed.\033[0m"
 
 run: kernel initrd
-	${EMU} -kernel kernel -initrd initrd
+	${EMU} -kernel kernel -initrd initrd -serial stdio
 
 kernel: start.o link.ld main.o ${MODULES} ${FILESYSTEMS}
 	@${ECHO} -n "\033[32m   LD   $<\033[0m"

core/serial.c

@@ -0,0 +1,43 @@
+/**
+ * Serial Port Driver
+ */
+#include <system.h>
+
+#define SERIAL_PORT_A 0x3F8
+#define SERIAL_PORT_B 0x2F8
+#define SERIAL_PORT_C 0x3E8
+#define SERIAL_PORT_D 0x2E8
+
+void
+serial_install() {
+	/* We will initialize the first serial port */
+	outportb(SERIAL_PORT_A + 1, 0x00);
+	outportb(SERIAL_PORT_A + 3, 0x80);
+	outportb(SERIAL_PORT_A + 0, 0x03);
+	outportb(SERIAL_PORT_A + 1, 0x00);
+	outportb(SERIAL_PORT_A + 3, 0x03);
+	outportb(SERIAL_PORT_A + 2, 0xC7);
+	outportb(SERIAL_PORT_A + 4, 0x0B);
+}
+
+int
+serial_rcvd() {
+	return inportb(SERIAL_PORT_A + 5) & 1;
+}
+
+char
+serial_recv() {
+	while (serial_rcvd() == 0);
+	return inportb(SERIAL_PORT_A);
+}
+
+int
+serial_transmit_empty() {
+	return inportb(SERIAL_PORT_A + 5) & 0x20;
+}
+
+void
+serial_send(char out) {
+	while (serial_transmit_empty() == 0);
+	outportb(SERIAL_PORT_A, out);
+}

core/shell.c

@@ -157,6 +157,33 @@ start_shell() {
 				kprintf(" From here, you have access to the virtual file system layer and \n");
 				kprintf(" can read files, list files in directories, dump memory, registers,\n");
 				kprintf(" and a few other things.\n");
+			} else if (!strcmp(cmd, "out")) {
+				if (tokenid < 3) {
+					kprintf("Need a port and a character (both as numbers, please) to write...\n");
+				} else {
+					int port;
+					port = atoi(argv[1]);
+					int val;
+					val  = atoi(argv[2]);
+					kprintf("Writing %d (%c) to port %d\n", val, (unsigned char)val, port);
+					outportb((short)port, (unsigned char)val);
+				}
+			} else if (!strcmp(cmd, "serial")) {
+				if (tokenid < 2) {
+					kprintf("Need some arguments.\n");
+				} else {
+					int i = 1;
+					for (i = 1; i < tokenid; ++i) {
+						int j = 0;
+						for (j = 0; j < strlen(argv[i]); ++j) {
+							serial_send(argv[i][j]);
+							writech(argv[i][j]);
+						}
+						writech(' ');
+					}
+					serial_send('\n');
+					writech('\n');
+				}
 			} else {
 				kprintf("Unrecognized command: %s\n", cmd);
 			}

core/system.c

@@ -91,6 +91,25 @@ strlen(
 	return i;
 }
 
+/*
+ * atoi
+ * Naïve implementation thereof.
+ */
+int
+atoi(
+		const char *str
+	) {
+	uint32_t len = strlen(str);
+	uint32_t out = 0;
+	uint32_t i;
+	uint32_t pow = 1;
+	for (i = len; i > 0; --i) {
+		out += (str[i-1] - 48) * pow;
+		pow *= 10;
+	}
+	return out;
+}
+
 /*
  * inportb
  * Read from an I/O port.

core/vga.c

@@ -131,6 +131,7 @@ writech(
 		*where = c | att;
 		csr_x++;
 	}
+	serial_send(c);
 
 	if (csr_x >= 80) {
 		csr_x = 0;

include/system.h

@@ -27,6 +27,7 @@ extern void *memcpy(void *restrict dest, const void *restrict src, size_t count)
 extern void *memset(void *dest, int val, size_t count);
 extern unsigned short *memsetw(unsigned short *dest, unsigned short val, int count);
 extern int strlen(const char *str);
+extern int atoi(const char *str);
 extern unsigned char inportb(unsigned short _port);
 extern void outportb(unsigned short _port, unsigned char _data);
 extern int strcmp(const char *a, const char *b);
@@ -146,4 +147,10 @@ void free(void *ptr);
 /* shell */
 extern void start_shell();
 
+/* Serial */
+extern void serial_install();
+extern char serial_recv();
+extern void serial_send(char out);
+
+
 #endif

main.c

@@ -82,6 +82,7 @@ int main(struct multiboot *mboot_ptr, uint32_t mboot_mag)
 	/* Hardware drivers */
 	timer_install();
 	keyboard_install();
+	serial_install();
 
 	/* Memory management */
 	paging_install(mboot_ptr->mem_upper);