Re: [PATCH v7 00/10] livepatch: klp-convert tool

Marcos Paulo de Souza
2023-03-14T20:24:08Z

On Mon, Mar 06, 2023 at 09:08:14AM -0500, Joe Lawrence wrote:
> Summary
> -------
>
> 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 infer 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 a
> symbols.klp 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. For example. see the saved_command_line
> variable in lib/livepatch/test_klp_convert2.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. See the KLP_MODULE_RELOC / KLP_SYMPOS annotation sections
> in lib/livepatch/test_klp_convert{1,2}.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 by
> removing the KLP_MODULE_RELOC / KLP_SYMPOS annotation sections in
> lib/livepatch/test_klp_convert{1,2}.c.
>
> Selftests have been added to exercise these klp-convert use-cases
> through several tests.
>
>
> Testing
> -------
>
> The patchset selftests build and execute on x86_64, s390x, and ppc64le
> for both default config (with added livepatch dependencies) and a larger
> RHEL-9-ish config.
>
> Using the Intel's Linux Kernel Performance tests's make.cross,
> klp-convert builds and processes livepatch .ko's for x86_64 ppc64le
> ppc32 s390 arm64 arches.
>
>
> Summary of changes in v7
> ------------------------
>
> - rebase for v6.2
> - combine ("livepatch: Add klp-convert tool") with ("livepatch: Add
> klp-convert annotation helpers")
> - combine ("kbuild: Support for symbols.klp creation") with ("modpost:
> Integrate klp-convert") to simplify Kbuild magic [Petr, Nicolas]
> - klp-convert: add safe_snprintf() (-Wsign-compare)
> - klp-convert: fix -Wsign-compare warnings
> - klp-convert: use calloc() where appropriate
> - klp-convert: copy ELF e_flags
> - selftests: fix various build warnings
> - klp-convert: WARN msg simplification, failed sanity checks, and sympos
> comment [Marcos]
> - klp-convert: fix elf_write_file() error paths [Petr]

Thanks for the new version Joe. I've run the ksefltests on my x86 laptop, and it
succeed as expected, so

Tested-by: Marcos Paulo de Souza <mpdesouza@suse.com>

>
>
> Previous versions
> -----------------
>
> RFC:
> https://lore.kernel.org/lkml/cover.1477578530.git.jpoimboe@redhat.com/
> v2:
> https://lore.kernel.org/lkml/f52d29f7-7d1b-ad3d-050b-a9fa8878faf2@redhat.com/
> v3:
> https://lore.kernel.org/lkml/20190410155058.9437-1-joe.lawrence@redhat.com/
> v4:
> https://lore.kernel.org/lkml/20190509143859.9050-1-joe.lawrence@redhat.com/
> v5:
> (not posted)
> https://github.com/joe-lawrence/klp-convert-tree/tree/klp-convert-v5-devel
> v6:
> https://lore.kernel.org/live-patching/20220216163940.228309-1-joe.lawrence@redhat.com/
>
>
> Joe Lawrence (10):
> livepatch: Create and include UAPI headers
> livepatch: Add klp-convert tool
> kbuild/modpost: create symbols.klp and integrate klp-convert
> livepatch: Add sample livepatch module
> documentation: Update on livepatch elf format
> livepatch/selftests: add klp-convert
> livepatch/selftests: test multiple sections
> livepatch/selftests: add __asm__ symbol renaming examples
> livepatch/selftests: add data relocations test
> livepatch/selftests: add static keys test
>
> .gitignore | 2 +
> Documentation/dontdiff | 1 +
> Documentation/livepatch/livepatch.rst | 3 +
> Documentation/livepatch/module-elf-format.rst | 42 +-
> MAINTAINERS | 2 +
> Makefile | 16 +-
> include/linux/livepatch.h | 13 +
> include/uapi/linux/livepatch.h | 25 +
> kernel/livepatch/core.c | 4 +-
> lib/livepatch/Makefile | 12 +
> lib/livepatch/test_klp_convert.h | 45 +
> lib/livepatch/test_klp_convert1.c | 121 +++
> lib/livepatch/test_klp_convert2.c | 110 +++
> lib/livepatch/test_klp_convert_data.c | 190 ++++
> lib/livepatch/test_klp_convert_keys.c | 91 ++
> lib/livepatch/test_klp_convert_keys_mod.c | 52 +
> lib/livepatch/test_klp_convert_mod_a.c | 31 +
> lib/livepatch/test_klp_convert_mod_b.c | 19 +
> lib/livepatch/test_klp_convert_mod_c.c | 36 +
> lib/livepatch/test_klp_convert_sections.c | 120 +++
> samples/livepatch/Makefile | 1 +
> .../livepatch/livepatch-annotated-sample.c | 93 ++
> scripts/Makefile | 1 +
> scripts/Makefile.modfinal | 33 +
> scripts/Makefile.modpost | 5 +
> scripts/livepatch/.gitignore | 1 +
> scripts/livepatch/Makefile | 5 +
> scripts/livepatch/elf.c | 817 ++++++++++++++++
> scripts/livepatch/elf.h | 74 ++
> scripts/livepatch/klp-convert.c | 893 ++++++++++++++++++
> scripts/livepatch/klp-convert.h | 47 +
> scripts/livepatch/list.h | 391 ++++++++
> scripts/mod/modpost.c | 28 +-
> scripts/mod/modpost.h | 1 +
> .../selftests/livepatch/test-livepatch.sh | 403 ++++++++
> 35 files changed, 3716 insertions(+), 12 deletions(-)
> create mode 100644 include/uapi/linux/livepatch.h
> create mode 100644 lib/livepatch/test_klp_convert.h
> create mode 100644 lib/livepatch/test_klp_convert1.c
> create mode 100644 lib/livepatch/test_klp_convert2.c
> create mode 100644 lib/livepatch/test_klp_convert_data.c
> create mode 100644 lib/livepatch/test_klp_convert_keys.c
> create mode 100644 lib/livepatch/test_klp_convert_keys_mod.c
> create mode 100644 lib/livepatch/test_klp_convert_mod_a.c
> create mode 100644 lib/livepatch/test_klp_convert_mod_b.c
> create mode 100644 lib/livepatch/test_klp_convert_mod_c.c
> create mode 100644 lib/livepatch/test_klp_convert_sections.c
> 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/klp-convert.h
> create mode 100644 scripts/livepatch/list.h
>
> --
> 2.39.2
>