linux-toradex.git/tools/objtool/Makefile, branch v6.19

objtool: Fix libopcodes linking with static libraries

2026-01-21T19:25:14+00:00

Commit 436326bc525d ("objtool: fix build failure due to missing libopcodes
check") tests for libopcodes using an empty main(), which passes even when
static libraries lack their dependencies. This causes undefined reference
errors (xmalloc, bfd_get_bits, etc.) when linking against static libopcodes
without its required libbfd and libiberty.

Fix by testing with an actual libopcodes symbol and trying increasingly
complete library combinations until one succeeds.

Fixes: 436326bc525d ("objtool: fix build failure due to missing libopcodes check")
Reported-by: Rafael J. Wysocki 
Signed-off-by: Sasha Levin 
Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: Rafael J. Wysocki (Intel) 
Link: https://patch.msgid.link/20260121162532.1596238-1-sashal@kernel.org

objtool: fix build failure due to missing libopcodes check

2026-01-13T10:37:51+00:00

Commit 59953303827e ("objtool: Disassemble code with libopcodes instead
of running objdump") added support for using libopcodes for disassembly.
However, the feature detection checks for libbfd availability but then
unconditionally links against libopcodes:

  ifeq ($(feature-libbfd),1)
      OBJTOOL_LDFLAGS += -lopcodes
  endif

This causes build failures in environments where libbfd is installed but
libopcodes is not, since the test-libbfd.c feature test only links
against -lbfd and -ldl, not -lopcodes:

  /usr/bin/ld: cannot find -lopcodes: No such file or directory
  collect2: error: ld returned 1 exit status
  make[4]: *** [Makefile:109: objtool] Error 1

Additionally, the shared feature framework uses $(CC) which is the
cross-compiler in cross-compilation builds. Since objtool is a host tool
that links with $(HOSTCC) against host libraries, the feature detection
can falsely report libopcodes as available when the cross-compiler's
sysroot has it but the host system doesn't.

Fix this by replacing the feature framework check with a direct inline
test that uses $(HOSTCC) to compile and link a test program against
libopcodes, similar to how xxhash availability is detected.

Fixes: 59953303827e ("objtool: Disassemble code with libopcodes instead of running objdump")
Assisted-by: claude-opus-4-5-20251101
Signed-off-by: Sasha Levin 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://patch.msgid.link/20251223120357.2492008-1-sashal@kernel.org

objtool: Build with disassembly can fail when including bdf.h

2025-11-27T08:32:46+00:00

Building objtool with disassembly support can fail when including
the bdf.h file:

  In file included from tools/objtool/include/objtool/arch.h:108,
                   from check.c:14:
  /usr/include/bfd.h:35:2: error: #error config.h must be included before this header
     35 | #error config.h must be included before this header
        |  ^~~~~

This check is present in the bfd.h file generated from the binutils
source code, but it is not necessarily present in the bfd.h file
provided in a binutil package (for example, it is not present in
the binutil RPM).

The solution to this issue is to define the PACKAGE macro before
including bfd.h. This is the solution suggested by the binutil
developer in bug 14243, and it is used by other kernel tools
which also use bfd.h (perf and bpf).

Fixes: 59953303827ec ("objtool: Disassemble code with libopcodes instead of running objdump")
Closes: https://lore.kernel.org/all/3fa261fd-3b46-4cbe-b48d-7503aabc96cb@oracle.com/
Reported-by: Nathan Chancellor 
Suggested-by: Nathan Chancellor 
Signed-off-by: Alexandre Chartre 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://sourceware.org/bugzilla/show_bug.cgi?id=14243
Link: https://patch.msgid.link/20251126134519.1760889-1-alexandre.chartre@oracle.com

objtool: Add Function to get the name of a CPU feature

2025-11-24T19:39:47+00:00

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 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Josh Poimboeuf 
Link: https://patch.msgid.link/20251121095340.464045-27-alexandre.chartre@oracle.com

objtool: Disassemble code with libopcodes instead of running objdump

2025-11-21T14:30:07+00:00

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 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Josh Poimboeuf 
Link: https://patch.msgid.link/20251121095340.464045-4-alexandre.chartre@oracle.com

objtool: Set minimum xxhash version to 0.8

2025-11-18T08:59:25+00:00

XXH3 is only supported starting with xxhash 0.8.  Enforce that.

Fixes: 0d83da43b1e1 ("objtool/klp: Add --checksum option to generate per-function checksums")
Closes: https://lore.kernel.org/SN6PR02MB41579B83CD295C9FEE40EED6D4FCA@SN6PR02MB4157.namprd02.prod.outlook.com
Reported-by: Michael Kelley 
Signed-off-by: Josh Poimboeuf 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Michael Kelley 
Tested-by: Michael Kelley 
Link: https://patch.msgid.link/7227c94692a3a51840278744c7af31b4797c6b96.1762990139.git.jpoimboe@kernel.org

objtool/klp: Introduce klp diff subcommand for diffing object files

2025-10-14T21:50:18+00:00

Add a new klp diff subcommand which performs a binary diff between two
object files and extracts changed functions into a new object which can
then be linked into a livepatch module.

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
    (coming in a later patch) which injects #line directives into the
    source .patch to preserve the original line numbers at compile time.

Note the end result of this subcommand is not yet functionally complete.
Livepatch needs some ELF magic which linkers don't like:

  - Two relocation sections (.rela*, .klp.rela*) for the same text
    section.

  - Use of SHN_LIVEPATCH to mark livepatch symbols.

Unfortunately linkers tend to mangle such things.  To work around that,
klp diff generates a linker-compliant intermediate binary which encodes
the relevant KLP section/reloc/symbol metadata.

After module linking, a klp post-link step (coming soon) will clean up
the mess and convert the linked .ko into a fully compliant livepatch
module.

Note this subcommand requires the diffed binaries to have been compiled
with -ffunction-sections and -fdata-sections, and processed with
'objtool --checksum'.  Those constraints will be handled by a klp-build
script introduced in a later patch.

Without '-ffunction-sections -fdata-sections', reliable object diffing
would be infeasible due to toolchain limitations:

  - For intra-file+intra-section references, the compiler might
    occasionally generated hard-coded instruction offsets instead of
    relocations.

  - Section-symbol-based references can be ambiguous:

    - Overlapping or zero-length symbols create ambiguity as to which
      symbol is being referenced.

    - A reference to the end of a symbol (e.g., checking array bounds)
      can be misinterpreted as a reference to the next symbol, or vice
      versa.

A potential future alternative to '-ffunction-sections -fdata-sections'
would be to introduce a toolchain option that forces symbol-based
(non-section) relocations.

Acked-by: Petr Mladek 
Tested-by: Joe Lawrence 
Signed-off-by: Josh Poimboeuf

objtool/klp: Add --checksum option to generate per-function checksums

2025-10-14T21:50:17+00:00

In preparation for the objtool klp diff subcommand, add a command-line
option to generate a unique checksum for each function.  This will
enable detection of functions which have changed between two versions of
an object file.

Acked-by: Petr Mladek 
Tested-by: Joe Lawrence 
Signed-off-by: Josh Poimboeuf

objtool: Clean up compiler flag usage

2025-10-14T21:45:24+00:00

KBUILD_HOSTCFLAGS and KBUILD_HOSTLDFLAGS aren't defined when objtool is
built standalone.  Also, the EXTRA_WARNINGS flags are rather arbitrary.

Make things simpler and more consistent by specifying compiler flags
explicitly and tweaking the warnings.  Also make a few code tweaks to
make the new warnings happy.

Acked-by: Petr Mladek 
Tested-by: Joe Lawrence 
Signed-off-by: Josh Poimboeuf

objtool: Hide unnecessary compiler error message

2025-03-12T22:43:38+00:00

The check for using old libelf prints an error message when libelf.h is
not available but does not abort. This may confuse so hide the compiler
error message.

Signed-off-by: David Engraf 
Link: https://lore.kernel.org/r/20250203073610.206000-1-david.engraf@sysgo.com
Signed-off-by: Josh Poimboeuf