Hi all, Thanks for the feedback to v3, I've incorporated a few more bug fixes and style/spelling nitpicks for the series. v4 is a bit of a resting place to collect loose ends before considering some heavier future work, namely arch-specific special section support. See the TODO section below for more details. 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/ v3: https://lore.kernel.org/lkml/20190410155058.9437-1-joe.lawrence@xxxxxxxxxx/ 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 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 -------- For review purposes, I posted two branches up to github: 1 - an expanded branch with changes separate from the original https://github.com/joe-lawrence/linux/tree/klp-convert-v4-expanded 2 - a squashed branch of (1) that comprises v4: https://github.com/joe-lawrence/linux/tree/klp-convert-v4 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 ---- Summarized from the v3 thread, thanks to Miroslav, Joao and Josh for feedback and parsing my long braindumps. - Special (architecture specific) section support: .altinstructions, .altinst_replacement .parainstructions __jump_table We want to apply livepatch relocations *before* these sections are processed. Or more precisely, the special section data structures entries which directly or indirectly involve livepatch relocations. Those need to be extracted into "klp.arch" sections, a corresponding rela section generated, and the kernel needs supporting code to handle deferred processing. Note that there is already x86-arch code present for handling .altinstruction and .parainstructions sections in arch/x86/kernel/livepatch.c. - Support for multiple homonym <object, name> symbols with unique <position> values. Consider a target module with symbol table that looks like: 29: ... FILE LOCAL DEFAULT ABS test_klp_convert_mod_a.c 32: ... FUNC LOCAL DEFAULT 3 get_homonym_string 33: ... OBJECT LOCAL DEFAULT 5 homonym_string 37: ... FILE LOCAL DEFAULT ABS test_klp_convert_mod_b.c 38: ... FUNC LOCAL DEFAULT 3 get_homonym_string 39: ... OBJECT LOCAL DEFAULT 11 homonym_string - The BFD library is incapable of handling two rela sections with identical sh_info values *as relocation sections*. This affects binutils and related programs like gdb, objdump, crash utility, etc. which fail to process klp-converted .ko files. https://sourceware.org/bugzilla/show_bug.cgi?id=24456 https://sourceware.org/ml/binutils/2019-04/msg00194.html Changelogs ---------- livepatch: Create and include UAPI headers v2: - jmoreira: split up and changelog v3: - joe: convert to SPDX license tags v4: - joe: from Masahiro, update UAPI headers with "GPL-2.0 WITH Linux-syscall-note" - joe: from Masahiro, types.h isn't needed by UAPI header kbuild: Support for Symbols.list creation v3: - jmoreira: adjust for multiobject livepatch - joe: add klpclean to PHONY - joe: align KLP prefix - joe: update all in-tree livepatches with LIVEPATCH_* modinfo flag v4: - joe: from Miroslav, update the samples and self-test Makefiles with the LIVEPATCH_ build prefix. - joe: from Artem, use $(SLIST) in klpclean and $(call cmd,livepatch) instead of $(call cmd_livepatch) 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 v4: - joe: spelling nits s/Insuficient/Insufficient and s/clasic/classic - joe: from Miroslav, tweak klp-convert usage msg - joe: don't move multiple list elements in convert_rela() - joe: relax duplicate user symbol check 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: from Josh, KLP_MODULE_RELOC macro should 4-byte align klp_module_reloc structures v4: - joe: remove the ',' struct array delimiter from KLP_SYMPOS 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 v4: - joe: rule_ld_ko_o should include $(Q) to honor build verbosity 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 - joe: from Miroslav: remove MODULE_INFO(livepatch, "Y") from samples livepatch: Add sample livepatch module 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 documentation: Update on livepatch elf format v3: - joe: clarify sympos=0 and sympos=1..n livepatch/selftests: add klp-convert v3 (new) v4: - joe: Add a ',' struct array delimiter after KLP_SYMPOS livepatch/klp-convert: abort on special sections v4 (new) Git boilerplate --------------- Joao Moreira (2): kbuild: Support for Symbols.list creation documentation: Update on livepatch elf format Joe Lawrence (2): livepatch/selftests: add klp-convert livepatch/klp-convert: abort on special sections 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 | 20 + 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 | 6 + .../livepatch/livepatch-annotated-sample.c | 102 +++ samples/livepatch/livepatch-callbacks-demo.c | 1 - samples/livepatch/livepatch-sample.c | 1 - samples/livepatch/livepatch-shadow-fix1.c | 1 - samples/livepatch/livepatch-shadow-fix2.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 | 73 ++ scripts/livepatch/klp-convert.c | 731 +++++++++++++++++ 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 ++ 37 files changed, 2653 insertions(+), 26 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
