[PATCH v2 35/58] objtool/klp: Add test for recorded checksum values
From: Song Liu <song@kernel.org>
Date: 2026-09-14 06:28:35
Subsystem:
objtool, the rest · Maintainers:
Josh Poimboeuf, Peter Zijlstra, Linus Torvalds
Whether klp diff treats a function as changed is decided by its checksum, and until now nothing looked at one. A test asserting only that the right functions were cloned cannot tell a correct checksum from one that happens to differ. Asserts both directions -- the changed function's checksum moves, the untouched one's does not -- and that checksumming identical input twice gives the same answer, since otherwise every rebuild reports spurious changes. Assisted-by: Claude:claude-opus-4 Based-on-test-by: Joe Lawrence [off-list ref] Assisted-by: Claude:claude-opus-5 Signed-off-by: Song Liu <song@kernel.org> --- .../tests/generic/test-checksum-value.sh | 37 +++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100755 tools/objtool/tests/generic/test-checksum-value.sh
diff --git a/tools/objtool/tests/generic/test-checksum-value.sh b/tools/objtool/tests/generic/test-checksum-value.sh
new file mode 100755
index 000000000000..feae6a12e98d
--- /dev/null
+++ b/tools/objtool/tests/generic/test-checksum-value.sh@@ -0,0 +1,37 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# The per-function checksums klp checksum records are what klp diff uses to +# decide which functions changed. A checksum covering too little misses a real +# change and the patch silently omits the function; one covering too much, or +# unstable across identical input, clones functions nobody patched and drags +# their dependencies in with them. +# +# test-basic covers which functions got cloned, which is downstream of this and +# passes for either kind of wrong checksum as long as the two errors do not +# happen to cancel. This checks the checksums themselves. + +. "$(dirname "$0")/../lib.sh" + +setup +build_pair basic.c + +assert_input_symbol changed +assert_input_symbol untouched + +run_checksum + +# The edited function's checksum has to move, the untouched one's must not. +assert_checksum_differs changed +assert_checksum_matches untouched + +# And it has to be a function of the code, not of the build: checksumming the +# same input twice has to give the same answer, or every rebuild reports +# spurious changes. +first="$(checksum_of orig.o changed)" +build_pair basic.c +run_checksum +[ "$(checksum_of orig.o changed)" = "$first" ] || + fail "checksum for 'changed' differs between builds of identical source" + +pass "checksums track the changed function and are stable across rebuilds"
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2.53.0-Meta