When computing klp checksums, instructions with non-relocated jump/call
destination offsets are problematic because the offset values can change
when surrounding code has moved, causing the function to be incorrectly
marked as changed.
Specifically, that includes jumps from alternatives to the end of the
alternative, which from objtool's perspective are jumps to the end of
the alternative instruction block in the original function.
Note that 'jump_dest' jumps don't include sibling calls (those use
call_dest), nor do they include jumps to/from .cold sub functions (those
are cross-section and need a reloc).
Fix it by hashing the opcode bytes (excluding the immediate operand)
along with a position-independent representation of the destination.
For calls, use the function name, and for jumps, use the destination's
offset within its function.
[Note the "9 bit hole" comment was wrong: it has been 8 bits since
commit 70589843b36f ("objtool: Add option to trace function validation")
added the 'trace' field. Adding the 4-bit 'immediate_len' field now
leaves a 4-bit hole.]
Fixes: 0d83da43b1e1 ("objtool/klp: Add --checksum option to generate per-function checksums")
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Pull objtool updates from Ingo Molnar: - KLP support updates and fixes (Song Liu) - KLP-build script updates and fixes (Joe Lawrence) - Support Clang RAX DRAP sequence, to address clang false positive (Josh Poimboeuf) - Reorder ORC register numbering to match regular x86 register numbering (Josh Poimboeuf) - Misc cleanups (Wentong Tian, Song Liu) * tag 'objtool-core-2026-04-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: objtool/x86: Reorder ORC register numbering objtool: Support Clang RAX DRAP sequence livepatch/klp-build: report patch validation fuzz livepatch/klp-build: add terminal color output livepatch/klp-build: provide friendlier error messages livepatch/klp-build: improve short-circuit validation livepatch/klp-build: fix shellcheck complaints livepatch/klp-build: add Makefile with check target livepatch/klp-build: add grep-override function livepatch/klp-build: switch to GNU patch and recountdiff livepatch/klp-build: support patches that add/remove files objtool/klp: Correlate locals to globals objtool/klp: Match symbols based on demangled_name for global variables objtool/klp: Remove .llvm suffix in demangle_name() objtool/klp: Also demangle global objects objtool/klp: Use sym->demangled_name for symbol_name hash objtool/klp: Remove trailing '_' in demangle_name() objtool/klp: Remove redundant strcmp() in correlate_symbols() objtool: Use section/symbol type helpers
Reorder the ORC register values so their ordering matches the x86 instruction set register encodings. No functional change intended. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Recent Clang can use RAX as a temporary register for the DRAP stack alignment sequence. Add support for that. Fixes the following warning: vmlinux.o: error: objtool: vmw_host_printf+0xd: unknown CFA base reg 0 Closes: https://lore.kernel.org/cefefdd1-7b82-406d-8ff4-e4b167e45ee6@app.fastmail.com Reported-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://patch.msgid.link/3f33dc720b83dc6d3a2b7094f75a5c90a0b1cbc5.1773708458.git.jpoimboe@kernel.org
For no apparent reason (possibly related to CONFIG_KMSAN), Clang can randomly pass the value of RSP to other registers and then back again to RSP. Handle that accordingly. Fixes the following warnings: drivers/input/misc/uinput.o: warning: objtool: uinput_str_to_user+0x165: undefined stack state drivers/input/misc/uinput.o: warning: objtool: uinput_str_to_user+0x165: unknown CFA base reg -1 Reported-by: Arnd Bergmann <arnd@arndb.de> Closes: https://lore.kernel.org/90956545-2066-46e3-b547-10c884582eb0@app.fastmail.com Link: https://patch.msgid.link/240e6a172cc73292499334a3724d02ccb3247fc7.1772818491.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Having a single large pv_ops array has the main disadvantage of needing all prototypes of the single array members in one header file. This is adding up to the need to include lots of otherwise unrelated headers. In order to allow multiple smaller pv_ops arrays dedicated to one area of the kernel each, allow multiple arrays in objtool. For better performance limit the possible names of the arrays to start with "pv_ops". Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://patch.msgid.link/20260105110520.21356-19-jgross@suse.com
Add a function to get the name of a CPU feature. The function is architecture dependent and currently only implemented for x86. The feature names are automatically generated from the cpufeatures.h include file. Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Link: https://patch.msgid.link/20251121095340.464045-27-alexandre.chartre@oracle.com
When tracing function validation, instruction state changes can report changes involving registers. These registers are reported with the name "r<num>" (e.g. "r3"). Print the CPU specific register name instead of a generic name (e.g. print "rbx" instead of "r3" on x86). Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Link: https://patch.msgid.link/20251121095340.464045-13-alexandre.chartre@oracle.com
objtool executes the objdump command to disassemble code. Use libopcodes instead to have more control about the disassembly scope and output. If libopcodes is not present then objtool is built without disassembly support. Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Link: https://patch.msgid.link/20251121095340.464045-4-alexandre.chartre@oracle.com
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.