On Thu, Apr 14, 2022 at 11:35:42AM +0200 Petr Mladek wrote: > On Wed 2022-02-16 11:39:30, Joe Lawrence wrote: > > From: Joao Moreira <jmoreira@xxxxxxx> > > > > For automatic resolution of livepatch relocations, a file called > > symbols.klp is used. This file maps symbols within every compiled kernel > > object allowing the identification of symbols whose name is unique, thus > > relocation can be automatically inferred, or providing information that > > helps developers when code annotation is required for solving the > > matter. > > > > Add support for creating symbols.klp in the main Makefile. First, ensure > > that built-in is compiled when CONFIG_LIVEPATCH is enabled (as required > > to achieve a complete symbols.klp file). Define the command to build > > symbols.klp (cmd_klp_map) and hook it in the modules rule. > > > > As it is undesirable to have symbols from livepatch objects inside > > symbols.klp, make livepatches discernible by modifying > > scripts/Makefile.build to create a .livepatch file for each livepatch in > > $(MODVERDIR). This file then used by cmd_klp_map to identify and bypass > > livepatches. > > > > For identifying livepatches during the build process, a flag variable > > LIVEPATCH_$(basetarget).o is considered in scripts/Makefile.build. This > > way, set this flag for the livepatch sample Makefile in > > samples/livepatch/Makefile. > > I do not see the related code in scripts/Makefile.build. > > > Finally, Add a clean rule to ensure that symbols.klp is removed during > > clean. > > > > Notes: > > > > To achieve a correct symbols.klp file, all kernel objects must be > > considered, thus, its construction require these objects to be priorly > > built. On the other hand, invoking scripts/Makefile.modpost without > > having a complete symbols.klp in place would occasionally lead to > > in-tree livepatches being post-processed incorrectly. > > Honestly, I do not understand what it exactly means that "in-tree > livepatches would occasionally be post-processed incorrectly". > > Is it the problem that modpost is not able to handle the unresolved > symbols that have to be updated by klp-convert? > > > To prevent this > > from becoming a circular dependency, the construction of symbols.klp > > uses non-post-processed kernel objects and such does not cause harm as > > the symbols normally referenced from within livepatches are visible at > > this stage. Also due to these requirements, the spot in-between modules > > compilation and the invocation of scripts/Makefile.modpost was picked > > for hooking cmd_klp_map. > > > > The approach based on .livepatch files was proposed as an alternative to > > using MODULE_INFO statements. This approach was originally proposed by > > Miroslav Benes as a workaround for identifying livepathes without > > depending on modinfo during the modpost stage. It was moved to this > > patch as the approach also shown to be useful while building > > symbols.klp. > > All the tricky code is removed in the 5th patch. My understanding is > that the problem causing the cyclic dependency is solved by modifying > modpost. > > It looks like this patch is outdated and mostly obsoleted. On the > other hand, the commit message in 5th patch is too short. > > What about merging the two patches and updating the commit message? +1 Yes, please merge those patches. These '$(shell ...)' side-effect lines in the definition of 'cmd_klp_map' are quite confusing. Kind regards, Nicolas
