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List:       linux-kernel
Subject:    Stack
From:       Christos Ricudis <ricudis () paiko ! the ! forthnet ! gr>
Date:       1996-07-31 18:00:55
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Hello, 

I'm trying to port University of Wisconsin Condor to Linux-ELF. Condor 
is a package that does job batching, process migration and process 
checkpoint/restore in user level. 

In order to checkpoint a running process, condor needs to save its stack
and data segments. 

In an earlier port to a.out, there are two methods of finding the 
address of the stack: 

1) Stack end address : Always assumed to be 0xc0000000;

2) Stack start address : 

a. Looking up proc/pid/stat, tsk->mm->start_stack, or
b. Using SETJMP : 

	jmp_buf         env;

        (void)SETJMP( env );
        return JMP_BUF_SP(env) & ~1023;

The two methods give different results, that differ by around 2084 bytes.
(why should they?).

There is some test code that  checks if a typical stack address (the address
of a local data object) is located inside the bounds of the addresses 
previously found. 

Using method a., I get a stack_start address that is higher than the typical
stack address (strange?). Which is the correct way of finding the stack
addresses?

Also. I need nlist() for ELF. nlist() in libc is commented out. Somebody
mentioned somewhat called elflib, however I couldn't find anything related. 

Christos Ricudis
ricudis@paiko.the.forthnet.gr


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