On Wed, Apr 10, 2019 at 11:50:49AM -0400, Joe Lawrence wrote: > Hi folks, > > This is the third installment of the klp-convert tool for generating and > processing livepatch symbols for livepatch module builds. For those > following along at home, archive links to previous versions: > > RFC: > https://lore.kernel.org/lkml/cover.1477578530.git.jpoimboe@xxxxxxxxxx/ > v2: > https://lore.kernel.org/lkml/f52d29f7-7d1b-ad3d-050b-a9fa8878faf2@xxxxxxxxxx/ > > (Note that I don't see v2 archived at lore, but that is a link to the > most recent subthread that lore did catch.) > > > 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. > Could we get some details with examples or a sample, sorry I might be dense and missing simple information. The problem being solved is not clear to me from the changelog. > 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 > 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. 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. > Are these a part of the series? Balbir Singh > > Branches > -------- > > Since I spent some time tinkering with v2 and accumulated a bunch of > fixes, I collected them up and am posting this new version. For review > purposes, I posted two branches up to github: > > 1 - an expanded branch that with changes separate from the original > https://github.com/joe-lawrence/linux/commits/klp-convert-v3-expanded > > 2 - a squashed branch of (1) that comprises v3: > https://github.com/joe-lawrence/linux/commits/klp-convert-v3 > > Non-trivial commits in the expanded branch have some extra commentary > and details for debugging in the commit message that were dropped when > squashing into their respective parent commits. > > > TODO > ---- > > There are a few outstanding items that I came across while reviewing v2, > but as changes started accumulating, it made sense to defer those to a > later version. I'll reply to this thread individual topics to start > discussion sub-threads for those. > > > Changelogs > ---------- > > The commit changelogs were getting long, so I've moved them here for > posterity and review purposes: > > livepatch: Create and include UAPI headers > v2: > - jmoreira: split up and changelog > v3: > - joe: convert to SPDX license tags > > kbuild: Support for Symbols.list creation > v3: > - jmoreira: adjust for multiobject livepatch > - joe: add klpclean to PHONY > - joe: align KLP prefix > > livepatch: Add klp-convert tool > v2: > - khlebnikov: use HOSTLOADLIBES_ instead of HOSTLDFLAGS: -lelf must be > at the end > - jmoreira: add support to automatic relocation conversion in > klp-convert.c, changelog > v3: > - joe: convert to SPDX license tags > - jmoreira: add rela symbol name to WARNs > - jmoreira: ignore relocations to .TOC and symbols with index 0 > - joe: separate and fix valid_sympos() sympos=0 and sympos=1..n checks > - joe: fix symbol use-after-frees > - joe: fix remaining valgrind leak complaints (non-error paths only) > - joe: checkpatch nits > > livepatch: Add klp-convert annotation helpers > v2: > - jmoreira: split up: move KLP_MODULE_RELOC from previous patch to > here, add KLP_SYMPOS, move macros from include/uapi/livepatch.h to > include/linux/livepatch.h > v3: > - joe: suggested by jpoimboe, KLP_MODULE_RELOC macro should 4-byte > align klp_module_reloc structures > > modpost: Integrate klp-convert > v2: > - khlebnikov: save cmd_ld_ko_o into .module.cmd, if_changed_rule > doesn't do that.f > - khlebnikov: fix bashisms for debian where /bin/sh is a symlink to > /bin/dash > - khlebnikov: rename rule_link_module to rule_ld_ko_o, otherwise > arg-check inside if_changed_rule compares cmd_link_module and > cmd_ld_ko_o. > - khlebnikov: check modinfo -F livepatch only if CONFIG_LIVEPATCH is > true. > - mbenes: remove modinfo call. LIVEPATCH_ in Makefile > - jmoreira: split up: move the .livepatch file-based scheme for > identifying livepatches to a previous patch, as it was required for > correctly building Symbols.list there. > v3: > - joe: adjust rule_ld_ko_o to call echo-cmd > - joe: rebase for v5.1 > - joe: align KLP prefix > > modpost: Add modinfo flag to livepatch modules > v2: > - jmoreira: fix modpost.c (add_livepatch_flag) to update module > structure with livepatch flag and prevent modpost from breaking due to > unresolved symbols > v3: > - joe: adjust modpost.c::get_modinfo() call for v5.0 version > > livepatch: Add sample livepatch module > v3: > - joe: update all in-tree livepatches with LIVEPATCH_* modinfo flag > > documentation: Update on livepatch elf format > v2: > - jmoreira: update module to use KLP_SYMPOS > - jmoreira: Comments on symbol resolution scheme > - jmoreira: Update Makefile > - jmoreira: Remove MODULE_INFO statement > - jmoreira: Changelog > v3: > - joe: rebase for v5.1 > - joe: code shuffle to better match original source file > > livepatch/selftests: add klp-convert > v3: > - joe: clarify sympos=0 and sympos=1..n > > > And now the usual git cover-letter boilerplate... > > Joao Moreira (2): > kbuild: Support for Symbols.list creation > documentation: Update on livepatch elf format > > Joe Lawrence (1): > livepatch/selftests: add klp-convert > > 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/livepatch.txt | 3 + > Documentation/livepatch/module-elf-format.txt | 50 +- > MAINTAINERS | 2 + > Makefile | 30 +- > include/linux/livepatch.h | 13 + > include/uapi/linux/livepatch.h | 22 + > kernel/livepatch/core.c | 4 +- > lib/livepatch/Makefile | 15 + > lib/livepatch/test_klp_atomic_replace.c | 1 - > lib/livepatch/test_klp_callbacks_demo.c | 1 - > lib/livepatch/test_klp_callbacks_demo2.c | 1 - > lib/livepatch/test_klp_convert1.c | 106 +++ > lib/livepatch/test_klp_convert2.c | 103 +++ > lib/livepatch/test_klp_convert_mod_a.c | 25 + > lib/livepatch/test_klp_convert_mod_b.c | 13 + > lib/livepatch/test_klp_livepatch.c | 1 - > samples/livepatch/Makefile | 7 + > .../livepatch/livepatch-annotated-sample.c | 102 +++ > samples/livepatch/livepatch-sample.c | 1 - > scripts/Kbuild.include | 4 +- > scripts/Makefile | 1 + > scripts/Makefile.build | 7 + > scripts/Makefile.modpost | 24 +- > scripts/livepatch/.gitignore | 1 + > scripts/livepatch/Makefile | 7 + > scripts/livepatch/elf.c | 753 ++++++++++++++++++ > scripts/livepatch/elf.h | 72 ++ > scripts/livepatch/klp-convert.c | 692 ++++++++++++++++ > scripts/livepatch/klp-convert.h | 39 + > scripts/livepatch/list.h | 391 +++++++++ > scripts/mod/modpost.c | 82 +- > scripts/mod/modpost.h | 1 + > .../selftests/livepatch/test-livepatch.sh | 64 ++ > 34 files changed, 2616 insertions(+), 23 deletions(-) > create mode 100644 include/uapi/linux/livepatch.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_mod_a.c > create mode 100644 lib/livepatch/test_klp_convert_mod_b.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 > > -- > 2.20.1
