On Fri, Jun 08, 2012 at 04:17:44PM +1000, Michael Ellerman wrote: > On Fri, 2012-06-08 at 11:31 +0530, Ananth N Mavinakayanahalli wrote: > > On Fri, Jun 08, 2012 at 03:51:54PM +1000, Michael Ellerman wrote: > > > On Fri, 2012-06-08 at 10:06 +0530, Ananth N Mavinakayanahalli wrote: > > > > On Wed, Jun 06, 2012 at 11:08:04AM -0700, Jim Keniston wrote: > > > > > On Wed, 2012-06-06 at 15:05 +0530, Ananth N Mavinakayanahalli wrote: > > > > > > On Wed, Jun 06, 2012 at 11:27:02AM +0200, Peter Zijlstra wrote: > > > > > > > On Wed, 2012-06-06 at 14:51 +0530, Ananth N Mavinakayanahalli > > > > > > > wrote: > > > > > > > > ... > > > > > > > > > > For the kernel, the only ones that are off limits are rfi (return > > > > > > from > > > > > > interrupt), mtmsr (move to msr). All other instructions can be > > > > > > probed. > > > > > > > > > > > > Both those instructions are supervisor level, so we won't see them > > > > > > in > > > > > > userspace at all; so we should be able to probe all user level > > > > > > instructions. > > > > > > > > > > Presumably rfi or mtmsr could show up in the instruction stream via an > > > > > erroneous or mischievous asm statement. It'd be good to verify that > > > > > you > > > > > handle that gracefully. > > > > > > > > That'd be flagged elsewhere, by the architecture itself -- you'd get a > > > > privileged instruciton exception if you try execute any instruction not > > > > part of the UISA. I therefore don't think its a necessary check in the > > > > uprobes code. > > > > > > But you're not executing the instruction, you're passing it to > > > emulate_step(). Or am I missing something? > > > > But MSR_PR=1 and hence emulate_step() will return -1 and hence we will > > end up single-stepping using user_enable_single_step(). Same with rfid. > > Right. But that was exactly Jim's point, you may be asked to emulate > those instructions even though you wouldn't expect to see them in > userspace code, so you need to handle it. > > Luckily it looks like emulate_step() will do the right thing for you. > It'd be good to test it to make 100% sure.
Sure. Will add that check and send v2. Ananth _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
