linux-next.git/scripts/livepatch, branch master

objtool/klp: Fix symbol resolution for duplicate data symbols

2026-08-03T05:12:39+00:00

find_sympos() calculates a sympos used by livepatch to disambiguate duplicately-named symbols. For function symbols, there's a hack which counts .text.unlikely symbols before other .text symbols, matching the linker script's section ordering. Not only is the hack fragile, data symbols can have the same problem. So for example, adding a reference to pwq_cache in ep_unregister_pollwait() can trigger a corrupt sympos and a relocation to the wrong pwq_cache symbol in the livepatch module, resulting in a crash or undefined behavior. Remove the existing hack in favor of a fully deterministic solution, using the new .klp.symid table to derive the symbol-to-id mapping from the original vmlinux.o and the id-to-address mapping from the corresponding vmlinux, which can then be used to determine the exact sympos associated with the original vmlinux. Modules don't need any special treatment: the .ko has the same section/symbol ordering as the original whole-archive symbol table. Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files") Reported-by: Ben Procknow Reported-by: Joe Lawrence Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: live-patching@vger.kernel.org Link: https://lore.kernel.org/20260710153042.3156788-1-joe.lawrence@redhat.com Link: https://lore.kernel.org/20260724221730.3126529-1-joe.lawrence@redhat.com Link: https://patch.msgid.link/919785e3bf2245db02ff6391e735d9cb139170b1.1785727106.git.jpoimboe@kernel.org

objtool/klp: Add .klp.symid for sympos disambiguation

2026-08-03T05:12:39+00:00

Livepatch identifies a duplicate-named symbol by its position (sympos) among same-named kallsyms entries, which for vmlinux are counted in ascending address order in the final linked kernel. That order can't be reliably derived from vmlinux.o: the final link reorders sub-sections (.text.unlikely*, .data..*, etc). Bridge the gap with a new .klp.symid section which can be used to correlate symbols between vmlinux.o and vmlinux so that klp-diff can reliably determine the sympos. The table can't survive --gc-sections: keeping it alive would keep every duplicate-named symbol's section alive, so the reference kernel would stop matching the one which ships. klp-build rejects CONFIG_LD_DEAD_CODE_DATA_ELIMINATION instead. Nothing is lost today: x86_64 is the only HAVE_KLP_BUILD arch and doesn't select HAVE_LD_DEAD_CODE_DATA_ELIMINATION, arm64 and s390 have never selected it either, and on powerpc, it's still EXPERIMENTAL and disabled by every distro kernel. This is the build-time half of reliable vmlinux sympos computation; "objtool klp diff" will consume the table in a subsequent commit. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: live-patching@vger.kernel.org Link: https://patch.msgid.link/64d50f077b569f47883c015cdb7079edb068efe8.1785727106.git.jpoimboe@kernel.org

objtool/klp: Skip hidden directories when finding objects

2026-08-03T05:12:39+00:00

klp-build's find_objects() scans the whole tree for vmlinux.o and .ko files, pruning only klp-tmp/ and .git/. Development tools can leave other dot-directories in the tree. Kernel objects never live under hidden directories, so prune them all. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: live-patching@vger.kernel.org Link: https://patch.msgid.link/6c8eaa9feb17e3811f4ef7733fd7288b7f489183.1785727106.git.jpoimboe@kernel.org

klp-build: Validate short-circuit prerequisites

2026-05-05T04:16:06+00:00

The --short-circuit option implicitly requires that certain directories are already in klp-tmp. Enforce that to prevent confusing errors. Acked-by: Song Liu Signed-off-by: Josh Poimboeuf

objtool/klp: Remove "objtool --checksum"

2026-05-05T04:16:05+00:00

The checksum functionality has been moved to "objtool klp checksum" which is now used by klp-build. Remove the now-dead --checksum and --debug-checksum options from the default objtool command. Acked-by: Song Liu Signed-off-by: Josh Poimboeuf

klp-build: Use "objtool klp checksum" subcommand

2026-05-05T04:16:05+00:00

Use the new "objtool klp checksum" subcommand instead of injecting --checksum into every objtool invocation via OBJTOOL_ARGS during the kernel build. This decouples checksum generation from the build, running it in separate post-build passes, making the code (and the patch generation pipeline itself) more modular. Acked-by: Song Liu Signed-off-by: Josh Poimboeuf

klp-build: Remove redundant SRC and OBJ variables

2026-05-05T04:16:04+00:00

SRC and OBJ are both set to $(pwd) and are always identical. The script already enforces that klp-build runs from the kernel root directory, and builds are done in-place, making these variables unnecessary. Suggested-by: Song Liu Acked-by: Song Liu Signed-off-by: Josh Poimboeuf

klp-build: Print "objtool klp diff" command in verbose mode

2026-05-05T04:16:04+00:00

Print the full objtool command line when '--verbose' is given to help with debugging. Acked-by: Song Liu Signed-off-by: Josh Poimboeuf

klp-build: Reject patches to realmode

2026-05-05T04:16:03+00:00

Realmode code is compiled as a separate 16-bit binary and embedded into the kernel image via rmpiggy.S. It can't be livepatched. Acked-by: Song Liu Signed-off-by: Josh Poimboeuf

klp-build: Reject patches to vDSO

2026-05-05T04:16:03+00:00

vDSO code runs in userspace and can't be livepatched. Such patches also cause spurious "new function" errors due to generated files like vdso*-image.c having unstable line numbers across builds. Acked-by: Song Liu Signed-off-by: Josh Poimboeuf