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Re: [Xen-devel] [PATCH] gdbserver-xen: fix corefile access

On Fri, Mar 03, 2006 at 10:20:21AM +0900, Horms wrote:
> On Thu, Mar 02, 2006 at 01:24:41PM +0000, Keir Fraser wrote:
> > 
> > On 2 Mar 2006, at 12:19, Horms wrote:
> > 
> > >>The correct fix is to update the xc_ptrace_core() interface to match
> > >>the xc_ptrace() interface. Kip Macy made the latter SMP aware, but
> > >>didn't fix up the former.
> > >>
> > >>It should be easy to do -- note how xc_ptrace() takes a domid on
> > >>PTRACE_ATTACH, and vcpuid at all other times. xc_ptrace_core() should
> > >>take a fd on PTRACE_ATTACH, and vcpuid at all other times. Since we
> > >>don't dump SMP core files right now, vcpuid should either be ignored
> > >>for the time being, or fail the call if vcpuid!=0.
> > >
> > >I didn't notice that, but I should have.
> > >
> > >Are you suggesting that xc_ptrace_core() should record the fd passed
> > >to it on PTRACE_ATTACH and use that later, presumably in current_domid?
> > >If so, yes that does look very easy. If not, can you explain a little
> > >further? In any case, I'll look into it tomorrow.
> > 
> > Yeah, you should record it the same way that xc_ptrace() records the 
> > domid. Really the two calls (xc_ptrace and xc_ptrace_core) should 
> > probably be merged -- we could pass an extra flag to PTRACE_ATTACH to 
> > indicate whether we are attaching to a coredump or to a live domain. 
> > Then we could get rid of xc_ptrace_core altogether.
> That sounds reasonable to me. Though internally the do different things,
> so would the idea be to something like:
>   rename xc_ptrace xc_ptrace_thread
>   make xc_ptrace a wapper for xc_ptrace_thread and xc_ptrace_core

Sorry, scratch that. I think they can just be merged into one
function, I'll try and get a patch together.

Do you think it would be better to pass the isfile flag in the form
of PTRACE_ATTACH|XC_PTRACE_FILE as the third argument to xc_ptrace,
or parhaps use the last argument to xc_ptrace, edata (or perhaps the
second last one, eaddr), which are unused for ATTACH.


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