On Tue, Aug 29, 2017 at 04:01:32PM -0300, Joao Moreira wrote: > Livepatches may use symbols which are not contained in its own scope, > and, because of that, may end up compiled with relocations that will > only be resolved during module load. Yet, when the referenced symbols are > not exported, solving this relocation requires information on the object > that holds the symbol (either vmlinux or modules) and its position inside > the object, as an object may contain multiple symbols with the same name. > Providing such information must be done accordingly to what is specified > in Documentation/livepatch/module-elf-format.txt. > > Currently, there is no trivial way to embed the required information as > requested in the final livepatch elf object. klp-convert solves this > problem in two different forms: (i) by relying on a symbol map, which is > built during kernel compilation, to automatically infers the relocation > targeted symbol, and, when such inference is not possible (ii) by using > annotations in the elf object to convert the relocation accordingly to > the specification, enabling it to be handled by the livepatch loader. > > Given the above, add support for symbol mapping in the form of > Symbols.list file; add klp-convert tool; integrate klp-convert tool into > kbuild; make livepatch modules discernible during kernel compilation > pipeline; add data-structure and macros to enable users to annotate > livepatch source code; make modpost stage compatible with livepatches; > update livepatch-sample and update documentation. > > The patch was tested under three use-cases: > > use-case 1: There is a relocation in the lp that can be automatically > resolved by klp-convert (tested by removing the annotations from > samples/livepatch/livepatch-annotated-sample.c) > > use-case 2: There is a relocation in the lp that cannot be automatically > resolved, as the name of the respective symbol appears in multiple > objects. The livepatch contains an annotation to enable a correct > relocation - reproducible with this livepatch sample: > www.livewire.com.br/suse/klp/livepatch-sample.1.c > > use-case 3: There is a relocation in the lp that cannot be automatically > resolved similarly as 2, but no annotation was provided in the livepatch, > triggering an error during compilation - reproducible with this livepatch > sample: www.livewire.com.br/suse/klp/livepatch-sample.2.c > > Joao Moreira (2): > kbuild: Support for Symbols.list creation > documentation: Update on livepatch elf format > > Josh Poimboeuf (5): > livepatch: Create and include UAPI headers > livepatch: Add klp-convert tool > livepatch: Add klp-convert annotation helpers > modpost: Integrate klp-convert > livepatch: Add sample livepatch module > > Miroslav Benes (1): > modpost: Add modinfo flag to livepatch modules Thanks a lot for picking these patches up and improving them. I've only glanced at the code, but so far it's looking good. It may be a few weeks before a I get a chance to do a proper review. One quick question, possibly for Miroslav. Do we have a plan yet for dealing with GCC optimizations? https://lkml.kernel.org/r/20161110161053.heua3abuaekz4yy7@treble I still like the '-fpreserve-function-abi' idea, but maybe it's not realistic. -- Josh -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
