[openib-general] RE: ptrace peektext failure for Mellanox IBGD 1.7.0 based cluster

[David Lecomber]

On Mon, 2005-10-10 at 15:22 +0200, Eli Cohen wrote:
> David, 
> IBGD 1.7 does not support kernel 2.6.11 so I assume you have made
> changes to IBGD to make it compile. 
> In the files you sent I can't see a call to ptrace with
> PTRACE_PEEKTEXT but I can see a call to PTRACE_PEEKDATA. Note that in
> the IBGD stack, registered buffers are not inherited by a child
> process when a the parent forks. This is accomplished by setting the
> VM_DONTCOPY flag on the vma. It is so done to retain the virtual to
> physical translation of a page at the parent by disabling COW on the
> pages. So the child may not even have these buffers in its address
> space and this could be the reason why ptrace fails.
> 
> Note also that IBGD 1.8 is the latest release and it does support
> kernel 2.6.11 so you may consider using it, though the description
> above holds also for IBGD 1.8
> 
> Eli

Hi Eli,

Thanks for looking at this.

Peektext/peekdata are synonymous, at least in Linux (c.f. the man page
for ptrace).  Do you happen to have a 1.8 based machine you could try
the example on for me (please!)?

Do you have any suggestions for a way to work around this.  All
debuggers need to be able to read memory locations, and even write to
them (for breakpoints) - so it's kind of essential!

Regards
David