[PATCH v2 24/58] objtool/klp: Add test for correlation across ThinLTO name mangling

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Two translation units (TU_B selects the second) linked with ThinLTO.
+ * Importing bump() promotes the file-local counter, renaming it
+ * counter.llvm.<hash>.  The hash is content derived, so it differs between the
+ * original and patched builds.
+ */
+
+#ifdef TU_B
+
+extern int bump(void);
+
+int other_entry(void)
+{
+	return bump() + bump();
+}
+
+#else
+
+static const char __modinfo[]
+	__attribute__((section(".modinfo"), used, aligned(1))) = "\0name=vmlinux";
+
+static int counter;
+
+int bump(void)
+{
+	return ++counter;
+}
+
+int target(void)
+{
+#ifdef PATCHED
+	return counter + 1;
+#else
+	return counter;
+#endif
+}
+
+#endif

@@ -0,0 +1,48 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Correlating ThinLTO-promoted locals requires demangling the .llvm.<hash>
+# suffix, and the resulting klp relocation must name the original symbol: that
+# is the one in the running kernel's kallsyms.
+
+. "$(dirname "$0")/../lib.sh"
+
+setup
+clang_only "ThinLTO requires clang"
+
+find_thinlto_toolchain ||
+	probe_skip "no matching clang/lld pair for a ThinLTO link; set THIN_LD to one"
+
+build_thinlto()		# $1 output object, $2 extra flags
+{
+	$THIN_CC -flto=thin -O2 -ffunction-sections -fdata-sections $2 \
+		-c "$FIXTURES_DIR/thinlto_local.c" -o "$workdir/tu_a.o" 2>/dev/null || return 1
+	$THIN_CC -flto=thin -O2 -ffunction-sections -fdata-sections $2 -DTU_B \
+		-c "$FIXTURES_DIR/thinlto_local.c" -o "$workdir/tu_b.o" 2>/dev/null || return 1
+	"$THIN_LD" -r "$workdir/tu_a.o" "$workdir/tu_b.o" -o "$1" 2>/dev/null || return 1
+}
+
+build_thinlto "$workdir/orig.o" "" ||
+	probe_skip "ThinLTO build failed ($THIN_CC, $THIN_LD)"
+build_thinlto "$workdir/patched.o" -DPATCHED ||
+	probe_skip "ThinLTO build failed ($THIN_CC, $THIN_LD)"
+
+orig_sym="$(in_symbols orig.o    | grep -o 'counter\.llvm\.[0-9]*' | head -1)"
+new_sym="$( in_symbols patched.o | grep -o 'counter\.llvm\.[0-9]*' | head -1)"
+
+[ -n "$orig_sym" ] && [ -n "$new_sym" ] ||
+	probe_skip "$THIN_CC did not promote the local symbol"
+
+# Equal hashes would make plain name matching work, testing nothing.
+[ "$orig_sym" != "$new_sym" ] ||
+	probe_skip "$THIN_CC gave the same ThinLTO hash for both builds"
+
+run_diff
+assert_patched target
+
+out_symbols | grep -q "\.klp\.sym\.vmlinux\.$orig_sym," ||
+	fail "expected a klp relocation naming $orig_sym"
+out_symbols | grep -q "\.klp\.sym\.vmlinux\.$new_sym," &&
+	fail "klp relocation names $new_sym, which the running kernel does not have"
+
+pass "ThinLTO-mangled local correlated across differing hashes ($THIN_CC, $THIN_LD)"