This series introduces new objtool features and a klp-build script to
generate livepatch modules using a source .patch as input.
This builds on concepts from the longstanding out-of-tree kpatch [1]
project which began in 2012 and has been used for many years to generate
livepatch modules for production kernels. However, this is a complete
rewrite which incorporates hard-earned lessons from 12+ years of
maintaining kpatch.
Key improvements compared to kpatch-build:
- Integrated with objtool: Leverages objtool's existing control-flow
graph analysis to help detect changed functions.
- Works on vmlinux.o: Supports late-linked objects, making it
compatible with LTO, IBT, and similar.
- Simplified code base: ~3k fewer lines of code.
- Upstream: No more out-of-tree #ifdef hacks, far less cruft.
- Cleaner internals: Vastly simplified logic for symbol/section/reloc
inclusion and special section extraction.
- Robust __LINE__ macro handling: Avoids false positive binary diffs
caused by the __LINE__ macro by introducing a fix-patch-lines script
which injects #line directives into the source .patch to preserve
the original line numbers at compile time.
The primary user interface is the klp-build script which does the
following:
- Builds an original kernel with -function-sections and
-fdata-sections, plus objtool function checksumming.
- Applies the .patch file and rebuilds the kernel using the same
options.
- Runs 'objtool klp diff' to detect changed functions and generate
intermediate binary diff objects.
- Builds a kernel module which links the diff objects with some
livepatch module init code (scripts/livepatch/init.c).
- Finalizes the livepatch module (aka work around linker wreckage)
using 'objtool klp post-link'.
I've tested with a variety of patches on defconfig and Fedora-config
kernels with both GCC and Clang.
These patches can also be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git klp-build-v2
Please test!
[1] https://github.com/dynup/kpatch
Changes since the RFC:
https://lore.kernel.org/cover.1725334260.git.jpoim...@kernel.org
- Too many to list. Doubled the patch count exactly ;-)
Josh Poimboeuf (62):
s390/vmlinux.lds.S: Prevent thunk functions from getting placed with
normal text
vmlinux.lds: Unify TEXT_MAIN, DATA_MAIN, and related macros
x86/module: Improve relocation error messages
x86/kprobes: Remove STACK_FRAME_NON_STANDARD annotation
compiler: Tweak __UNIQUE_ID() naming
compiler.h: Make addressable symbols less of an eyesore
elfnote: Change ELFNOTE() to use __UNIQUE_ID()
kbuild: Remove 'kmod_' prefix from __KBUILD_MODNAME
modpost: Ignore unresolved section bounds symbols
x86/alternative: Refactor INT3 call emulation selftest
objtool: Make find_symbol_containing() less arbitrary
objtool: Speed up SHT_GROUP reindexing
objtool: Fix broken error handling in read_symbols()
objtool: Propagate elf_truncate_section() error in elf_write()
objtool: Add empty symbols to the symbol tree again
objtool: Fix interval tree insertion for zero-length symbols
objtool: Fix weak symbol detection
objtool: Fix x86 addend calculation
objtool: Fix __pa_symbol() relocation handling
objtool: Fix "unexpected end of section" warning for alternatives
objtool: Check for missing annotation entries in read_annotate()
objtool: Const string cleanup
objtool: Clean up compiler flag usage
objtool: Remove .parainstructions reference
objtool: Convert elf iterator macros to use 'struct elf'
objtool: Add section/symbol type helpers
objtool: Mark .cold subfunctions
objtool: Fix weak symbol hole detection for .cold functions
objtool: Mark prefix functions
objtool: Simplify reloc offset calculation in unwind_read_hints()
objtool: Avoid emptying lists for duplicate sections
objtool: Suppress section skipping warnings with --dryrun
objtool: Rename --Werror to --werror
objtool: Reindent check_options[]
objtool: Refactor add_jump_destinations()
objtool: Simplify special symbol handling in elf_update_symbol()
objtool: Generalize elf_create_symbol()
objtool: Generalize elf_create_section()
objtool: Add elf_create_data()
objtool: Introduce elf_create_reloc() and elf_init_reloc()
objtool: Add elf_create_file()
kbuild,x86: Fix module permissions for __jump_table and __bug_table
x86/alternative: Define ELF section entry size for alternatives
x86/jump_label: Define ELF section entry size for jump table
x86/extable: Define ELF section entry size for exception tables
x86/bug: Define ELF section entry size for the bug table
x86/orc: Define ELF section entry size for unwind hints
objtool: Make STACK_FRAME_NON_STANDARD consistent
kbuild,objtool: Defer objtool validation step for CONFIG_LIVEPATCH
objtool/klp: Add --checksum option to generate per-function checksums
objtool/klp: Add --debug-checksum=<funcs> to show per-instruction
checksums
objtool/klp: Introduce klp diff subcommand for diffing object files
objtool/klp: Add --debug option to show cloning decisions
objtool/klp: Add post-link subcommand to finalize livepatch modules
objtool: Disallow duplicate prefix symbols
objtool: Add base objtool support for livepatch modules
livepatch/klp-build: Introduce fix-patch-lines script to avoid
__LINE__ diff noise
livepatch/klp-build: Add stub init code for livepatch modules
livepatch/klp-build: Introduce klp-build script for generating
livepatch modules
livepatch/klp-build: Add --debug option to show cloning decisions
livepatch/klp-build: Add --show-first-changed option to show function
divergence
livepatch: Introduce source code helpers for livepatch modules
MAINTAINERS | 3 +-
arch/Kconfig | 3 +
arch/s390/include/asm/nospec-insn.h | 2 +-
arch/s390/kernel/vmlinux.lds.S | 2 +-
arch/x86/Kconfig | 1 +
arch/x86/include/asm/alternative.h | 7 +-
arch/x86/include/asm/asm.h | 20 +-
arch/x86/include/asm/bug.h | 44 +-
arch/x86/include/asm/jump_label.h | 32 +-
arch/x86/kernel/alternative.c | 53 +-
arch/x86/kernel/kprobes/opt.c | 4 -
arch/x86/kernel/module.c | 15 +-
arch/x86/kernel/unwind_orc.c | 2 +
include/asm-generic/vmlinux.lds.h | 40 +-
include/linux/compiler.h | 8 +-
include/linux/elfnote.h | 13 +-
include/linux/init.h | 3 +-
include/linux/jump_label.h | 20 +-
include/linux/livepatch.h | 25 +-
include/linux/livepatch_external.h | 76 +
include/linux/livepatch_helpers.h | 68 +
include/linux/objtool.h | 16 +-
kernel/extable.c | 2 +
kernel/livepatch/core.c | 8 +-
scripts/Makefile.lib | 6 +-
scripts/Makefile.modfinal | 18 +-
scripts/Makefile.vmlinux_o | 2 +-
scripts/link-vmlinux.sh | 3 +-
scripts/livepatch/fix-patch-lines | 79 +
scripts/livepatch/init.c | 108 ++
scripts/livepatch/klp-build | 781 +++++++++
scripts/mod/modpost.c | 5 +
scripts/module.lds.S | 26 +-
tools/include/linux/interval_tree_generic.h | 2 +-
tools/include/linux/livepatch_external.h | 76 +
tools/objtool/Build | 4 +-
tools/objtool/Makefile | 48 +-
tools/objtool/arch/loongarch/decode.c | 6 +-
tools/objtool/arch/powerpc/decode.c | 6 +-
tools/objtool/arch/x86/decode.c | 68 +-
tools/objtool/arch/x86/special.c | 2 +-
tools/objtool/builtin-check.c | 70 +-
tools/objtool/builtin-klp.c | 53 +
tools/objtool/check.c | 690 +++++---
tools/objtool/elf.c | 812 ++++++---
tools/objtool/include/objtool/arch.h | 5 +-
tools/objtool/include/objtool/builtin.h | 6 +-
tools/objtool/include/objtool/check.h | 6 +-
tools/objtool/include/objtool/checksum.h | 43 +
.../objtool/include/objtool/checksum_types.h | 25 +
tools/objtool/include/objtool/elf.h | 186 +-
tools/objtool/include/objtool/klp.h | 35 +
tools/objtool/include/objtool/objtool.h | 6 +-
tools/objtool/include/objtool/warn.h | 40 +
tools/objtool/klp-diff.c | 1504 +++++++++++++++++
tools/objtool/klp-post-link.c | 165 ++
tools/objtool/objtool.c | 42 +-
tools/objtool/orc_gen.c | 8 +-
tools/objtool/special.c | 4 +-
tools/objtool/sync-check.sh | 1 +
tools/objtool/weak.c | 7 +
61 files changed, 4687 insertions(+), 728 deletions(-)
create mode 100644 include/linux/livepatch_external.h
create mode 100644 include/linux/livepatch_helpers.h
create mode 100755 scripts/livepatch/fix-patch-lines
create mode 100644 scripts/livepatch/init.c
create mode 100755 scripts/livepatch/klp-build
create mode 100644 tools/include/linux/livepatch_external.h
create mode 100644 tools/objtool/builtin-klp.c
create mode 100644 tools/objtool/include/objtool/checksum.h
create mode 100644 tools/objtool/include/objtool/checksum_types.h
create mode 100644 tools/objtool/include/objtool/klp.h
create mode 100644 tools/objtool/klp-diff.c
create mode 100644 tools/objtool/klp-post-link.c
--
2.49.0
