lkml.org 
[lkml]   [2010]   [Feb]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [patch] x86: ptrace and core-dump extensions for xstate
From
Date
On Thu, 2010-02-04 at 12:55 -0800, Roland McGrath wrote:
> Just proofread it. I really did mean "obvious typos", i.e. spelling,
> whitespace, punctuation, nothing more.

Roland, All I found after double checking is:

> For now, only first 8 bytes of the sw_usable_bytes[464..467]

should be

> For now, only first 8 bytes of the sw_usable_bytes[464..471]

Let me know if I am overlooking something.

>
> > This issue is not new and gets handled in the same way as for existing
> > fxsave/fxrstor, as they don't specify page alignment restrictions.
>
> I didn't suggest it was new. I was looking for some confirmation that
> there is in fact no permanent (i.e. compile-time) size limit.

Yes. No size limit as of now.

> I don't think this is the right way to think about it. The regset code
> does not need to do anything different at all. There will in future be
> other callers of the regset hooks, that's what the whole interface is there
> for. Regardless of whether modification is full or partial, you just
> enforce the various bitmasks on the resultant buffer as you already do, and
> that's all there is to it. If userland stores partial contents with a
> bogus format, that's its problem. It's just like the program itself had
> used xrstor in user mode with the same bogus buffer contents.

Ok. I think I can agree, if we are ok with giving room for the ptrace
(or any other user of the API) to make a mistake and corrupt reg-state
of the process under debug, if it doesn't follow rules.

> > We probably have to extend regset infrastructure to track which NT_*
> > types are part of PTRACE_[GET|SET]REGSET and which are not.
>
> I don't understand what you mean. The point of the generic requests is
> that they apply to any user_regset you want. user_regset does not need
> anything new.

Thought some of them might be only relevant to core-dump or based on
permissions etc. But I guess get/set routines of the regset should be
able to take care of this?

> > Also, I am not sure if pushing the ptrace interpretation of the user
> > pointer into the regset routines is a good idea.
>
> I don't understand what you mean here at all. I did not suggest anything
> that affects what the regset routines themselves do in any way at all.
>
> It is an unacceptably bad idea to have any new ptrace interfaces for regset
> access that do anything different than exactly let you get/set all or part
> of a regset exactly as the arch's user_regset provides it.

So in the example you provided before:

struct iovec iov = { mybuffer, mylength };
ret = ptrace(PTRACE_GETREGSET, NT_X86_XSTATE, &iov);

You wanted to propose common data format (iov) for all of the NT_* ?

thanks,
suresh



\
 
 \ /
  Last update: 2010-02-04 23:09    [W:0.084 / U:0.524 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site