objtool/klp: Add test for instruction operand checksums

checksum_update_insn() hashes an instruction's bytes and then what any
relocation on it refers to: a string section contributes the string's
contents, anything else the target symbol's name and adjusted addend, with
a reference to a static resolved through its section symbol first.

None of that shows up in the bytes.  A rel32 operand is zero in the object
and supplied by the relocation, so calling a different function, editing a
literal the code passes, or reading a different index of an array all leave
the encoded instruction byte-identical.  A checksum stopping at the bytes
reports the function unchanged and the patch silently does not contain the
fix.

test-checksum-position is the other half: what must *not* change the
checksum when a function merely moves.

Each of the four is verified by sabotaging the line it covers.  The static
case needed a writer the compiler cannot see through -- without one it
proves the array is never written, folds every read to zero, and emits no
relocation at all, so the reference under test does not exist and the
variant passes having compared two identical objects.

Assisted-by: Claude:claude-opus-4
Based-on-test-by: Joe Lawrence <joe.lawrence@redhat.com>
Assisted-by: Claude:claude-opus-5
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/20260916184351.2720310-52-song@kernel.org

0 files changed, 0 insertions, 0 deletions