On Wed, Oct 16, 2019 at 11:36:10AM +0200, Jessica Yu wrote: > +++ Peter Zijlstra [16/10/19 11:23 +0200]: > > On Wed, Oct 16, 2019 at 08:51:27AM +0200, Miroslav Benes wrote: > > > On Tue, 15 Oct 2019, Joe Lawrence wrote: > > > > > > > On 10/15/19 10:13 AM, Miroslav Benes wrote: > > > > > Yes, it does. klp_module_coming() calls module_disable_ro() on all > > > > > patching modules which patch the coming module in order to call > > > > > apply_relocate_add(). New (patching) code for a module can be relocated > > > > > only when the relevant module is loaded. > > > > > > > > FWIW, would the LPC blue-sky2 model (ie, Steve's suggestion @ plumber's where > > > > livepatches only patch a single object and updates are kept on disk to handle > > > > coming module updates as they are loaded) eliminate those outstanding > > > > relocations and the need to perform this late permission flipping? > > > > > > Yes, it should, but we don't have to wait for it. PeterZ proposed a > > > different solution to this specific issue in > > > https://lore.kernel.org/lkml/20191015141111.GP2359@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > > > > > It should not be a problem to create a live patch module like that and the > > > code in kernel/livepatch/ is almost ready. Something like > > > module_section_disable_ro(mod, section) (and similar for X protection) > > > should be enough. Module reloads would still require juggling with the > > > protections, but I think it is all feasible. > > > > Just had a browse around the module code, and while the section info is > > in load_info, it doesn't get retained for active modules. > > > > So I suppose I'll go add that for KLP enabled things. > > Elf section info does get saved for livepatch modules though, see > mod->klp_info. And wouldn't this only be needed for livepatch modules? Right, I just found that, but it is x86 only for some mysterious reason. And yes, it's KLP only. I was thikning of adding a KLP only list of {name,addr,size} sections that start with ".klp" in layout_sections(). Would that not work across architectures?
