[LV-kern-commit] CVS: kernel-2.4/Documentation/vax ptrace.txt,NONE,1.1

[Dave A. <ai...@us...>]

Update of /cvsroot/linux-vax/kernel-2.4/Documentation/vax
In directory usw-pr-cvs1:/tmp/cvs-serv16947/Documentation/vax

Added Files:
	ptrace.txt 
Log Message:
DA: ptrace info


--- NEW FILE ---
ptrace implementation for VAX
(c) Dave Airlie 2001
=============================

Howto get the PC?

The PC of the programming under debugging is stored on its kernel stack when
it is context switched. The PC stored in the PCB is the vax_switch_to PC, not the user space codes current position.

getreg/putreg use the stack top value to work out the pt_regs structures 
location and point into this.  the calculation is taken from the process.c
code for creating the stack.

SINGLESTEP

The single step code enables the T bit in the PSL for tracing, and the 
trace pending handler causes a SIGTRAP.