Created ECHO system call for testing purposes.

Furthermore, a quick way to get one's own process number.

kernel/Makefile

@@ -103,6 +103,7 @@ proc.o:	$a
 proc.o:	$h/callnr.h
 proc.o:	$h/com.h
 proc.o:	proc.h
+proc.o:	ipc.h
 proc.o:	sendmask.h
 
 protect.o:	$a

kernel/ipc.h

@@ -0,0 +1,14 @@
+/* Masks and flags for system calls. */
+#define SYSCALL_FUNC	0x0F	/* mask for system call function */
+#define SYSCALL_FLAGS   0xF0    /* mask for system call flags */
+#define NON_BLOCKING    0x10	/* prevent blocking, return error */
+#define FRESH_ANSWER    0x20	/* ignore pending notifications as answer */
+				/* (default behaviour for SENDREC calls) */
+
+/* System calls (numbers passed when trapping to the kernel) */
+#define ECHO		 0	/* function code for echoing messages */
+#define SEND		 1	/* function code for sending messages */
+#define RECEIVE		 2	/* function code for receiving messages */
+#define SENDREC	 	 3  	/* function code for SEND + RECEIVE */
+#define NOTIFY		 4	/* function code for notifications */
+

kernel/proc.c

@@ -29,6 +29,7 @@
 #include <minix/callnr.h>
 #include <minix/com.h>
 #include "proc.h"
+#include "ipc.h"
 #include "sendmask.h"
 
 
@@ -99,7 +100,7 @@ message *m_ptr;			/* pointer to message in the caller's space */
   	return(ECALLDENIED);			/* SENDREC was required */
   
   /* Verify that requested source and/ or destination is a valid process. */
-  if (! isoksrc_dst(src_dst)) 
+  if (! isoksrc_dst(src_dst) && function != ECHO) 
   	return(EBADSRCDST);
 
   /* Check validity of message pointer. */
@@ -153,6 +154,11 @@ message *m_ptr;			/* pointer to message in the caller's space */
   case NOTIFY:
       result = mini_notify(caller_ptr, src_dst, m_ptr);
       break;
+  case ECHO:
+      kprintf("Echo message from process %s\n", proc_nr(caller_ptr));
+      CopyMess(caller_ptr->p_nr, caller_ptr, m_ptr, caller_ptr, m_ptr);
+      result = OK;
+      break;
   default:
       result = EBADCALL;			/* illegal system call */
   }