Re: [PATCH] ptrace RSE bug

David Mosberger-Tang
2007-09-07T15:11:20Z

Anything that avoids complicating the kernel exit path is worth doing!
The exit path is complicated enough as it is.

--david

On 9/7/07, Petr Tesarik <ptesarik@suse.cz> wrote:
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> Shaohua Li wrote:
> > On Thu, 2007-09-06 at 15:59 +0200, Petr Tesarik wrote:
> >>[...]
> >> So, what happens if upon syscall entry notification the debugger
> >> modifies the part of the RBS (in user-space) which corresponds to the
> >> arguments of that syscall? Currently, the syscall takes the modified
> >> arguments, but with your change it would still take the stale data
> >> from
> >> the kernel RBS.
> > The patch does sync from user RBS to kernel RBS just after syscall trace
> > enter. this is an exception I said doing sync just before syscall
> > return. I thought this covers your case, no?
>
> Ah, I'm sorry, I missed that part of the patch. Well, if we have to do a
> sync on every syscall_trace_enter() and syscall_trace_leave(), then the
> only cases where introducing TIF_RESTORE_RSE saves us a duplicate sync
> seems to be in the clone/fork and exit paths. In other words, it's
> probably not worth the added complexity. But since you have written the
> whole complex thing already, I have no objections against it.
>
> Regards,
> Petr Tesarik
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