CS307 Assignment, due on paper at class time, Friday, 4/28/00

1. Describe in as much detail as you can the layout of the virtual address space as it is used by the versions of Linux and gcc/g++ in our labs. You can print out addresses:

   
   	#include 
   	...
   	cout << "0x" << hex << (unsigned int)(ptrofsomekind) << endl;
   

   or

   
   	#include 
   	...
   	printf( "0x%x\n", (unsigned int)(&i) );
   

   You can also use the gnu debugger gdb to get a better look at where the stack pointer points, where global variables are located, etc.

   I'm particularly interested in knowing

   • Where (i.e. in what range of virtual addresses) are global variables located? Does there seem to be a limit to the size of global variables allowed?
   • Where are literal strings stored?
   • Where is the program text stored? Try modifying program instructions at run-time (you can get a function's address by "char *p = (char *)(FunctionName)"). What happens?
   • Where is the stack? Is there a limit to the stack size? Is that limit configurable?
   • Where is the heap (a.k.a. "free store" or "place where memory allocated by malloc or new comes from")? Which way does it grow?

   But please tell me about anything else you learn.
   
   

2. If a Linux process is blocked and it receives a signal for which it has registered a handler, does the handler get called? If so, does the process return to blocked state after the handler is done, or does the signal unblock the process permanently? Give me a printout of the code you used to answer this question (make it as simple as you can).
   
   
3. Do the semaphores available with our version of Linux collect blocked processes in a first-in-first-out fashion, first-in-last-out, or some other more random way?
   
   
4. Using what you learned in the previous question, write the simplest program you can that will do the following:
   • The parent forks two children.
   • The parent and children print out "Hi, I'm process #" messages in this sequence: parent, child A, parent, child B, parent, child A, parent, child B, etc.
   • When you hit CTRL-C, all three processes should terminate. (Use "ps x" or "ps ax" to see whether the processes are still running after you try to get rid of them--if not, "kill -9 processID" should do the job.)
   • The synchronization between the parent and children should use as few local variables as possible (zero would be dandy), and no shared memory--only semaphores.

   You may use the Up and Down functions from norace.c if you wish.

   Hand this program in via HSP.