From e6aaa1a83c321a1cdad11cfc11d829ff51929ba3 Mon Sep 17 00:00:00 2001
From: belliash <belliash@codingworkshop.eu.org>
Date: Wed, 10 Aug 2022 17:56:41 +0200
Subject: [PATCH] Mark serial port as fully initialized and always check that
 before printing anything to the serial console

---
 sdk/xtdk/hltypes.h    |  5 +++--
 sdk/xtklib/hl/cport.c |  7 ++++++-
 xtldr/efiutil.c       | 24 ++++++++++++++++--------
 3 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/sdk/xtdk/hltypes.h b/sdk/xtdk/hltypes.h
index a72cebb..cb5ef83 100644
--- a/sdk/xtdk/hltypes.h
+++ b/sdk/xtdk/hltypes.h
@@ -21,8 +21,9 @@
 #define COMPORT_DIV_DLM             0x01 /* Divisor Latch Most */
 
 /* Serial port control flags */
-#define COMPORT_FLAG_DBR            0x01 /* Default Baud Rate */
-#define COMPORT_FLAG_MC             0x02 /* Modem Control */
+#define COMPORT_FLAG_INIT           0x01 /* Port Initialized */
+#define COMPORT_FLAG_DBR            0x02 /* Default Baud Rate */
+#define COMPORT_FLAG_MC             0x04 /* Modem Control */
 
 /* Serial port Fifo Control Register (FCR) access masks */
 #define COMPORT_FCR_DISABLE         0x00 /* Disable */
diff --git a/sdk/xtklib/hl/cport.c b/sdk/xtklib/hl/cport.c
index 2fe354b..58aa879 100644
--- a/sdk/xtklib/hl/cport.c
+++ b/sdk/xtklib/hl/cport.c
@@ -212,6 +212,7 @@ HlInitializeComPort(IN OUT PCPPORT Port,
 {
     PUCHAR Address;
     UCHAR Byte = 0;
+    USHORT Flags = 0;
     ULONG Mode;
 
     /* Check if serial port is set */
@@ -233,7 +234,7 @@ HlInitializeComPort(IN OUT PCPPORT Port,
     {
         /* Use default baud (clock) rate if not set */
         BaudRate = COMPORT_CLOCK_RATE;
-        Port->Flags = COMPORT_FLAG_DBR;
+        Flags |= COMPORT_FLAG_DBR;
     }
 
     /* Store COM pointer */
@@ -288,10 +289,14 @@ HlInitializeComPort(IN OUT PCPPORT Port,
         return STATUS_IO_DEVICE_ERROR;
     }
 
+    /* Mark port as fully initialized */
+    Flags |= COMPORT_FLAG_INIT;
+
     /* Disable loopback mode and use port normally */
     HlIoPortOutByte(PtrToUshort(Address + (ULONG)COMPORT_REG_MCR), COMPORT_MCR_NOM);
     Port->Address = Address;
     Port->Baud = BaudRate;
+    Port->Flags = Flags;
 
     /* Return success */
     return STATUS_SUCCESS;
diff --git a/xtldr/efiutil.c b/xtldr/efiutil.c
index 755a2c2..cb41c4a 100644
--- a/xtldr/efiutil.c
+++ b/xtldr/efiutil.c
@@ -28,14 +28,18 @@ BlDbgPrint(IN PUINT16 Format,
 {
     VA_LIST Arguments;
 
-    /* Initialise the va_list */
-    VA_START(Arguments, Format);
+    /* Check if EFI serial port is fully initialized */
+    if(EfiSerialPort.Flags & COMPORT_FLAG_INIT)
+    {
+        /* Initialise the va_list */
+        VA_START(Arguments, Format);
 
-    /* Format and print the string to the serial console */
-    BlStringPrint(BlComPortPutChar, Format, Arguments);
+        /* Format and print the string to the serial console */
+        BlStringPrint(BlComPortPutChar, Format, Arguments);
 
-    /* Clean up the va_list */
-    VA_END(Arguments);
+        /* Clean up the va_list */
+        VA_END(Arguments);
+    }
 }
 
 /**
@@ -65,8 +69,12 @@ BlEfiPrint(IN PUINT16 Format,
     /* Format and print the string to the stdout */
     BlStringPrint(BlConsolePutChar, Format, Arguments);
 
-    /* Format and print the string to the serial console */
-    BlStringPrint(BlComPortPutChar, Format, Arguments);
+    /* Check if EFI serial port is fully initialized */
+    if(EfiSerialPort.Flags & COMPORT_FLAG_INIT)
+    {
+        /* Format and print the string to the serial console */
+        BlStringPrint(BlComPortPutChar, Format, Arguments);
+    }
 
     /* Clean up the va_list */
     VA_END(Arguments);