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. 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. 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
