stos+amd64: Add serial logging + trace facility

Signed-off-by: Chloe M. <chloe@mensia.org>

paw/stos/arch/amd64/Makefile

@@ -12,23 +12,34 @@ include ../../../mk/stos.mk
 ASMFILES = $(shell find . -name "*.S")
 ASMOFILES = $(ASMFILES:.S=.S.o)
 
+CFILES = $(shell find . -name "*.c")
+OFILES = $(CFILES:.c=.o)
+
 MISC_OFILES = $(ASMOFILES)
+MISC_OFILES += $(OFILES)
 MISC_OFILES += $(shell find $(ST_PROJECT_ROOT)/paw/spkg/ -name "*.o")
 MISC_OFILES += $(shell find $(ST_PROJECT_ROOT)/paw/stos/ -name "*.o" | grep -v "arch")
 
 KERNEL_PATH =       \
 	$(ST_PROJECT_ROOT)/artifacts/stoskrnl.sys
-CFLAGS =			\
-	$(SYS_CFLAGS)
+CFLAGS =				\
+	$(SYS_CFLAGS)		\
+	-I../../target		\
+	-I../../head/		\
+	-I$(ST_PROJECT_ROOT)/sdk/head
 
 .PHONY: all
 all: bin
 
 .PHONY: bin
-bin:  $(ASMOFILES)
+bin: $(OFILES) $(ASMOFILES)
 	$(PROMPT) "LD" $(KERNEL_PATH)
 	$(SYS_LD) -Tdevel/link.ld $(MISC_OFILES) -o $(KERNEL_PATH)
 
+%.o: %.c
+	$(PROMPT) "CC" $<
+	$(SYS_CC) -c $< $(CFLAGS) -o $@
+
 %.S.o: %.S
 	$(PROMPT) "AS" $<
 	$(SYS_CC) -c $< $(CFLAGS) -o $@

paw/stos/arch/amd64/platform/uart.c

@@ -0,0 +1,105 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: serial interface
+ * Author:      Chloe M.
+ */
+
+#include <hal/serial.h>
+#include <machine/pio.h>
+#include <stdef.h>
+
+/* Channel port numbers */
+#define UART_COM1 0x3F8
+#define UART_COM2 0x2F8
+#define UART_COM3 0x3E8
+#define UART_COM4 0x2E8
+#define UART_COM5 0x5F8
+#define UART_COM6 0x4F8
+#define UART_COM7 0x5E8
+#define UART_COM8 0x4E8
+
+/* Register offsets */
+#define UART_REG(OFFSET) (UART_COM1 + OFFSET)
+#define UART_REG_FCR UART_REG(2) /* FIFO Control Register */
+#define UART_REG_LCR UART_REG(3) /* Line Control Register */
+#define UART_REG_MCR UART_REG(4) /* MODEM Control Register */
+#define UART_REG_LSR UART_REG(5) /* Line Status Register */
+#define UART_REG_MSR UART_REG(6) /* MODEM Status Register */
+#define UART_REG_SR  UART_REG(7) /* Scratch Register */
+
+/* Registers when LCR.DLAB=0 */
+#define UART_REG_RBR UART_REG(0) /* Receiver Buffer Register */
+#define UART_REG_THR UART_REG(0) /* Transmitter Holding Register */
+#define UART_REG_IER UART_REG(1) /* Interrupt Enable Register */
+
+/* Registers when LCR.DLAB=1 */
+#define UART_REG_DLL UART_REG(0) /* Divisor Latch Low */
+#define UART_REG_DLH UART_REG(1) /* Divisor Latch High */
+
+#define UART_LCR_WLS0 BIT(0) /* Word Length Select Bit 0 */
+#define UART_LCR_WLS1 BIT(1) /* Word Length Select Bit 1 */
+#define UART_LCR_DLAB BIT(7) /* Divisor Latch Access Bit*/
+
+#define UART_MCR_DTR  BIT(0) /* Data Terminal Ready*/
+#define UART_MCR_LOOP BIT(4) /* Loop */
+
+#define UART_LSR_THRE BIT(5) /* Transmitter Holding Register */
+
+#define UART_DIVISOR(RATE) (115200 / RATE)
+
+static inline BOOLEAN
+UartTxEmpty(VOID)
+{
+    return ISSET(UART_REG_LSR, UART_LSR_THRE) != 0;
+}
+
+VOID
+HalSerialWrite(const CHAR *Data, USIZE Length)
+{
+    if (Data == NULL) {
+        return;
+    }
+
+    while (!UartTxEmpty()) {
+        ASMV("pause");
+    }
+
+    for (USIZE Index = 0; Index < Length; ++Index) {
+        MdOutb(UART_REG_THR, Data[Index]);
+    }
+}
+
+ST_STATUS
+HalSerialInit(VOID)
+{
+    /* Disable interrupts */
+    MdOutb(UART_REG_IER, 0x00);
+
+    /* Set DLAB to set baud rate */
+    MdOutb(UART_REG_LCR, UART_LCR_DLAB);
+
+    /* Set speed to 57600 baud */
+    MdOutb(UART_REG_DLL, UART_DIVISOR(57600));
+    MdOutb(UART_REG_IER, 0x00);
+
+    /* Set word size to 8 bits and clear DLAB */
+    MdOutb(UART_REG_LCR, UART_LCR_WLS0 | UART_LCR_WLS1);
+
+    /* Disable FIFOs for now... (TODO: Use them) */
+    MdOutb(UART_REG_FCR, 0x00);
+
+    /* Test chip in loopback mode */
+    MdOutb(UART_REG_MCR, UART_MCR_LOOP);
+    MdOutb(UART_REG_THR, 0xF0);
+    if (MdInb(UART_REG_RBR != 0xF0))
+        return -1;
+
+    /*
+     * Mark the data terminal ready and clear
+     * loopback mode.
+     */
+    MdOutb(UART_REG_MCR, UART_MCR_DTR);
+    return 0;
+}

paw/stos/head/ex/trace.h

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Trace facility
+ * Author:      Chloe M.
+ */
+
+#ifndef _EX_TRACE_H_
+#define _EX_TRACE_H_ 1
+
+#include <lib/printf.h>
+
+#define TRACE       printf
+#define FmtPrintf   vsnprintf
+
+#endif  /* !_EX_TRACE_H_ */

paw/stos/head/hal/serial.h

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: HAL serial interface
+ * Author:      Chloe M.
+ */
+
+#ifndef _HAL_SERIAL_H_
+#define _HAL_SERIAL_H_ 1
+
+#include <stapi/status.h>
+
+/*
+ * Initialize the serial driver
+ */
+ST_STATUS HalSerialInit(VOID);
+
+/*
+ * Transmit data over serial
+ *
+ * @Data:   Data to transmit
+ * @Length: Length of data to transmit
+ */
+VOID HalSerialWrite(const CHAR *Data, USIZE Length);
+
+#endif  /* !_HAL_SERIAL_H_ */

paw/stos/init/init.c

@@ -6,9 +6,26 @@
  * Author:       Chloe M.
  */
 
+#include <ex/trace.h>
+#include <hal/serial.h>
 #include <stdef.h>
 
+/*
+ * Display a boot banner
+ */
+static VOID
+BootBanner(VOID)
+{
+    TRACE("Machine has been turned on~\n");
+    TRACE("Booting SystemPaw3 !! <3\n");
+}
+
 VOID
 KiKernelEntry(VOID)
 {
+    /* Initialize the serial driver */
+    HalSerialInit();
+
+    /* Write the boot banner */
+    BootBanner();
 }

paw/stos/lib/_printf.c

@@ -6,7 +6,10 @@
  * Author:      Chloe M.
  */
 
+#include <hal/serial.h>
+
 void
 _putchar(char c)
 {
+    HalSerialWrite(&c, 1);
 }