From bcea9313266aa0ab453dec93af391eebee70c649 Mon Sep 17 00:00:00 2001
From: Fabian Freyer <fabian.freyer@physik.tu-berlin.de>
Date: Thu, 22 Feb 2018 20:20:03 +0100
Subject: [PATCH] tests: allow test kernels to print to serial

---
 tests/data/multiboot/Makefile |  3 ++-
 tests/data/multiboot/libc.c   | 22 +++++++++++++++++++++-
 tests/data/multiboot/libc.h   | 18 ++++++++++++++++++
 3 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/tests/data/multiboot/Makefile b/tests/data/multiboot/Makefile
index 2e89b56..53dea42 100644
--- a/tests/data/multiboot/Makefile
+++ b/tests/data/multiboot/Makefile
@@ -1,5 +1,6 @@
 CCFLAGS=-m32 -Wall -Wextra -Werror -fno-stack-protector -nostdinc -fno-builtin
 ASFLAGS=-m32
+OUTPUT=COM1
 
 UNAME_S!=uname -s
 LIBGCC!=$(CC) ${CCFLAGS} -print-libgcc-file-name
@@ -27,7 +28,7 @@ modules.elf: start.o modules.o libc.o
 	$(LD) $(LDFLAGS) -o $@ $> $(LIBGCC)
 
 .c.o:
-	$(CC) $(CCFLAGS) -c -o $@ $<
+	$(CC) -DOUTPUT=$(COM1) $(CCFLAGS) -c -o $@ $<
 
 .S.o:
 	$(CC) $(ASFLAGS) -c -o $@ $<
diff --git a/tests/data/multiboot/libc.c b/tests/data/multiboot/libc.c
index 43502f5..2cc4414 100644
--- a/tests/data/multiboot/libc.c
+++ b/tests/data/multiboot/libc.c
@@ -22,6 +22,8 @@
 
 #include "libc.h"
 
+static char serial_set_up = 0;
+
 void* memcpy(void *dest, const void *src, int n)
 {
     char *d = dest;
@@ -46,7 +48,25 @@ void* memset(void *b, int c, unsigned len)
 
 static void print_char(char c)
 {
-    outb(0xe9, c);
+    #if (OUTPUT != DEBUGCON)
+    /* Check if serial is set up */
+    if (!serial_set_up) {
+        outb(OUTPUT + 1, 0x00);    // Disable all interrupts
+        outb(OUTPUT + 3, 0x80);    // Enable DLAB (set baud rate divisor)
+        outb(OUTPUT + 0, 0x03);    // Set divisor to 3 (lo byte) 38400 baud
+        outb(OUTPUT + 1, 0x00);    //                  (hi byte)
+        outb(OUTPUT + 3, 0x03);    // 8 bits, no parity, one stop bit
+        outb(OUTPUT + 2, 0xC7);    // Enable FIFO, clear them, with 14-byte threshold
+        outb(OUTPUT + 4, 0x0B);    // IRQs enabled, RTS/DSR set
+        serial_set_up = 1;
+    }
+    /* Check if transmit is empty */
+    while ( (inb(OUTPUT + 5) & 0x20) == 0 );
+    if ( c == '\n' )
+	    print_char('\r');
+    #endif
+
+    outb(OUTPUT, c);
 }
 
 static void print_str(char *s)
diff --git a/tests/data/multiboot/libc.h b/tests/data/multiboot/libc.h
index b16cf64..d9b943c 100644
--- a/tests/data/multiboot/libc.h
+++ b/tests/data/multiboot/libc.h
@@ -23,6 +23,17 @@
 #ifndef LIBC_H
 #define LIBC_H
 
+/* Serial Ports */
+#define DEBUGCON 0xe9
+#define COM1 0x3f8
+#define COM2 0x2F8
+#define COM3 0x3E8
+#define COM4 0x2E8
+
+#ifndef OUTPUT
+#define OUTPUT DEBUGCON
+#endif
+
 /* Integer types */
 
 typedef unsigned long long uint64_t;
@@ -53,6 +64,13 @@ static inline void outb(uint16_t port, uint8_t data)
     asm volatile ("outb %0, %1" : : "a" (data), "Nd" (port));
 }
 
+static inline uint8_t inb(uint16_t port)
+{
+    uint8_t ret;
+    asm volatile ( "inb %1, %0" : "=a"(ret) : "Nd"(port) );
+    return ret;
+}
+
 
 /* Misc functions */