//-------------------------------------------------------------------
//	courseid.cpp
//
//	This program employs inline assembly language to make direct 
//	system-calls to the Linux kernel, and so it does not need to 
//	be linked to any routines in the standard C runtime library.
//	
//	We will use this program in illustrating some concepts about
//	'memory-mapping' of files (using the UNIX 'mmap()' function)
//	and about linking and loading of a binary-format executable.
//
//	    	compile using:  $ gcc -c courseid.cpp
//	   
//	Then link the object-file (using our special linker-script):
//
//	        $ ld courseid.o -T ldscript -o courseid.b
//
//	We have designed a special application (named 'launch.cpp') 
//	that can 'map' the executable file 'courseid.b' into memory
//	and then execute it by making an indirect C function-call. 
//
//	NOTE: In the 'asm' constructs which are used below:
//	      -- the "i" constraint denotes an immediate operand
//	      -- the "m" constraint denotes a memory operand
//
//	Reference: Richard M. Stallman, "Using and Porting GNU CC,"
//	Boston: The Free Software Foundation (1999), pages 337-338.
//
//	programmer: ALLAN CRUSE
//	written on: 19 OCT 2004
//	revised on: 20 OCT 2004
//-------------------------------------------------------------------

#define sys_write  4	// system-call ID-number
#define dev_stdout 1	// device-file ID-number

int main( void )
{
	char	msg[] = "\nComputer Science 326: Operating Systems\n\n";	
	int	len = sizeof( msg ) - 1;
	
	asm(" movl  %0, %%eax " : : "i" (sys_write) );
	asm(" movl  %0, %%ebx " : : "i" (dev_stdout) );
	asm(" leal  %0, %%ecx " : : "m" (msg[0]) );
	asm(" movl  %0, %%edx " : : "m" (len) );	
	asm(" int  $0x80 ");
}