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 .gitignore | 1 + Documentation/livepatch/module-elf-format.txt | 47 +- MAINTAINERS | 2 + Makefile | 29 +- include/linux/livepatch.h | 12 + include/uapi/linux/livepatch.h | 33 ++ kernel/livepatch/core.c | 4 +- samples/livepatch/Makefile | 5 +- samples/livepatch/livepatch-annotated-sample.c | 128 +++++ samples/livepatch/livepatch-sample.c | 1 - scripts/Kbuild.include | 4 +- scripts/Makefile | 1 + scripts/Makefile.build | 6 + scripts/Makefile.modpost | 24 +- scripts/livepatch/.gitignore | 1 + scripts/livepatch/Makefile | 7 + scripts/livepatch/elf.c | 696 +++++++++++++++++++++++++ scripts/livepatch/elf.h | 84 +++ scripts/livepatch/klp-convert.c | 567 ++++++++++++++++++++ scripts/livepatch/list.h | 389 ++++++++++++++ scripts/mod/modpost.c | 80 ++- scripts/mod/modpost.h | 1 + 22 files changed, 2104 insertions(+), 18 deletions(-) create mode 100644 include/uapi/linux/livepatch.h create mode 100644 samples/livepatch/livepatch-annotated-sample.c create mode 100644 scripts/livepatch/.gitignore create mode 100644 scripts/livepatch/Makefile create mode 100644 scripts/livepatch/elf.c create mode 100644 scripts/livepatch/elf.h create mode 100644 scripts/livepatch/klp-convert.c create mode 100644 scripts/livepatch/list.h -- 2.12.0
