On Tue, Feb 28, 2017 at 11:22:27AM +0000, Abel Vesa wrote: > On Tue, Feb 28, 2017 at 11:58:49AM +0100, Nicolai Stange wrote: > > Hi Abel, > > > > On Tue, Feb 28 2017, Abel Vesa wrote: > > > > > On Mon, Feb 27, 2017 at 04:52:06PM +0100, Nicolai Stange wrote: > > >> On Fri, Feb 24 2017, Abel Vesa wrote: > > >> Wouldn't it be better (and more consistent with other archs) to have > > >> > > >> pt_regs->ARM_lr = original lr > > >> pt_refs->ARM_pc = current lr > > >> > > >> instead? > > > > The stack would look like this then > > > > @ ... | ARM_ip | ARM_sp | ARM_lr | ARM_pc | ... > > | > > @ 0 4 48 52 56 60 64 68 > > 72 > > @ R0 | R1 | ... | LR | SP + 4 | original LR | original PC | PSR | > > OLD_R0 | original LR | > > > > I.e. the pt_regs would capture almost the full context of the > > instrumented function (except for ip). > > > So basicly what you are saying is: > - instead of current LR save original LR (previous one saved in instrumented > function epilog) > - instead of current PC save original PC (previous one saved in instrumented > function epilog) > > I still don't see the point of saving the actual value of PC since nobody > will ever > restore it. In case of livepatch it will get overwritten anyway. As for LR, I > agree, > it could be the original one in pt_regs. > > I'll look into this sometime today or tomorrow and get back with updates.
Which is exactly what I proposed, with code, on one of the previous iterations of this patch... -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
