[tip: objtool/core] objtool/klp: Add test for a static call introduced by the patch

[tip-bot2 for Song Liu]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     b2747b54e136f5c4d897a31f6d8aa8891ad30379
Gitweb:        https://git.kernel.org/tip/b2747b54e136f5c4d897a31f6d8aa8891ad30379
Author:        Song Liu <song@xxxxxxxxxx>
AuthorDate:    Wed, 16 Sep 2026 11:43:43 -07:00
Committer:     Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
CommitterDate: Wed, 16 Sep 2026 17:21:46 -07:00

objtool/klp: Add test for a static call introduced by the patch

The counterpart to the static branch case: a patch may add a static call to
a function which had none, so the .static_call_sites entry is new and there
is nothing in the original to correlate it against.

Where the key lives still decides whether that is allowed.  A vmlinux key
is reachable; a module-owned one is not, for the same reason an existing
module key is not -- late module patching lets the livepatch load first and
the unresolved entry is dereferenced when the module arrives.  Both halves
are here because they fail in opposite directions: dropping the new entry
leaves a static call the kernel never patches, and accepting a new
module-owned one is the corruption the check exists to prevent.

Both halves are one test over one fixture: built with -DNEW_CALL the key is
vmlinux's and the new entry has to be carried in; built with -DMODNAME as
well the key belongs to a module, klp diff has to reject it, and no output
object may be left behind.  The premise is asserted first -- the original
must have no .static_call_sites at all -- since otherwise this is a second
copy of test-static-call-module-key.

Covers the same ground as corpus/x86_64/static-call-vmlinux-new and
corpus/x86_64/static-call-module-new in Joe Lawrence's klp-build unit test
corpus.

Assisted-by: Claude:claude-opus-4
Based-on-test-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
Assisted-by: Claude:claude-opus-5
Signed-off-by: Song Liu <song@xxxxxxxxxx>
Link: https://patch.msgid.link/20260916184351.2720310-51-song@xxxxxxxxxx
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 tools/objtool/tests/generic/test-static-call-new.sh | 45 ++++++++++++-
 1 file changed, 45 insertions(+)
 create mode 100755 tools/objtool/tests/generic/test-static-call-new.sh

diff --git a/tools/objtool/tests/generic/test-static-call-new.sh b/tools/objtool/tests/generic/test-static-call-new.sh
new file mode 100755
index 0000000..f7d2b39
--- /dev/null
+++ b/tools/objtool/tests/generic/test-static-call-new.sh
@@ -0,0 +1,45 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# A patch may introduce a static call where the original function had none.
+#
+# The .static_call_sites entry is then new, with nothing in the original to
+# correlate it against, so klp diff has to carry it into the patch from
+# scratch.  Where the key lives still decides whether that is allowed: a
+# vmlinux key is reachable, and a module-owned one is not, for the same reason
+# an existing module key is not -- late module patching lets the livepatch load
+# first, and the unresolved entry is dereferenced when the module arrives.
+#
+# Both halves are here because they fail in opposite directions.  Dropping the
+# new entry leaves a static call the kernel never patches; accepting a new
+# module-owned one is the corruption the check exists to prevent.
+#
+# Covers the same ground as corpus/x86_64/static-call-vmlinux-new and
+# static-call-module-new in Joe Lawrence's klp-build unit test corpus.
+
+. "$(dirname "$0")/../lib.sh"
+
+setup
+build_pair static_call.c -DNEW_CALL
+
+# The premise: the original really has no static call, the patched one does.
+has_input_section orig.o .static_call_sites &&
+	fail "fixture put a .static_call_sites in the original; nothing new to add"
+has_input_section patched.o .static_call_sites ||
+	probe_skip "compiler produced no .static_call_sites on this arch"
+
+run_diff
+assert_patched target
+assert_section .static_call_sites
+assert_reloc_sym .static_call_sites target
+
+# The same new call, with the key owned by a module: not reachable, so the
+# build has to stop rather than emit a relocation nothing will resolve.
+rm -f "$workdir/out.o"
+build_pair static_call.c -DNEW_CALL -DMODNAME='"klp_testmod"'
+run_diff 255
+assert_diff_log 'unsupported static call key __SCK__klp_test_call'
+[ -e "$workdir/out.o" ] &&
+	fail "output object produced for a rejected input"
+
+pass "static call introduced by the patch carried in, or rejected for a module key"