resending this mail, since my earlier email did not reach lkml. On Wed, Nov 09, 2005 at 03:07:55PM +0530, Prasanna S Panchamukhi wrote: > Zach, > > Thanks for doing this. > > On Tue, Nov 08, 2005 at 05:36:53AM -0800, Zachary Amsden wrote: > > Andi Kleen wrote: > > > > >On Tuesday 08 November 2005 05:39, Zachary Amsden wrote: > > > > > > > > >>IA-32 linear address translation is loads of fun. > > >> > > >> > > > > > >Thanks for doing that audit work. Can you please double check x86-64 code > > >is > > >ok? > > > > > >Actually giving all that complexity maybe it would be better to just > > >stop handling the case and remove all that. I'm not sure what kprobes > > >needs it for - it doesn't even handle user space yet and even if it ever > > >does it is unlikely that handling 16bit code makes much sense. And the > > > The code was added to address the problem related to stealing of interrupts from > VM86. Please see the discussion thread for more details from the URL below > http://lkml.org/lkml/2004/11/9/214 > > > But were kprobes even inteneded for userspace? There are races here > > that are difficult to close without some heavy machinery, and I would > > rather not put the machinery in place if simplifying the code is the > > right answer. > > Presently kprobes supports only kernel space probes. Work is in progress > for user space probes support. > > >+ addr = (kprobe_opcode_t *)convert_eip_to_linear(regs, > >+ regs->eip - > >sizeof(kprobe_opcode_t), > >+ ¤t->mm->context, &limit); > >+ > > Instead you can check if it is in kernel mode and calculate the address directly > first, since it is in the fast path. > addr = regs->eip - sizeof(kprobe_opcode_t); > else > addr = convert_eip_to_linear(..); > > there by avoiding calling convert_eip_to_linear () in case of every kernel probes. > > > >+ /* Don't let userspace races re-address into kernel space */ > >+ if ((unsigned long)addr > limit) > >+ return 0; > > there is no need for this check here in the fast path, because kprobes handles this > case by checking if the address is on the kprobes hash list and later returning > from that point. > > Please make sure it pass the test case discussed in the thread, URL is below. > http://lkml.org/lkml/2004/11/9/214 > > Thanks > -Prasanna > -- > Prasanna S Panchamukhi > Linux Technology Center > India Software Labs, IBM Bangalore > Ph: 91-80-25044636 > <prasanna@xxxxxxxxxx> -- Have a Nice Day! Thanks & Regards Prasanna S Panchamukhi Linux Technology Center India Software Labs, IBM Bangalore Ph: 91-80-25044636 <prasanna@xxxxxxxxxx>
