[PATCH v2 53/58] objtool/klp: Add test for the alignment of cloned data sections

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Data with an alignment stricter than its size.
+ *
+ * A cloned data section has to keep its sh_addralign.  The kernel has plenty
+ * of data whose alignment is a correctness property rather than an
+ * optimisation -- per-CPU variables, anything touched by an aligned SSE move,
+ * cacheline-aligned locks -- and a clone that lands under-aligned faults or
+ * silently shares a cacheline it was written to avoid.
+ *
+ * The object is new in the patched build, so klp diff has to clone it rather
+ * than reference the kernel's copy.
+ */
+
+static const char __modinfo[]
+	__attribute__((section(".modinfo"), used, aligned(1))) = "\0name=vmlinux";
+
+#ifdef PATCHED
+int aligned_data[2] __attribute__((aligned(64))) = { 1, 2 };
+#endif
+
+int target(int x)
+{
+#ifdef PATCHED
+	return x + aligned_data[0];
+#else
+	return x;
+#endif
+}

@@ -0,0 +1,40 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# A cloned data section keeps its alignment.
+#
+# Plenty of kernel data is aligned for correctness rather than speed: per-CPU
+# variables, anything touched by an aligned vector move, structures padded to
+# own a cacheline. A clone that lands under-aligned either faults on first use
+# or silently shares a line it was laid out to avoid, and neither shows up
+# until the patch is loaded on hardware that cares.
+#
+# Fixed by 2f2600decb30 ("objtool/klp: Fix alignment of cloned data
+# sections").
+#
+# Covers the same ground as corpus/x86_64/cloned-data-alignment in Joe
+# Lawrence's klp-build unit test corpus.
+
+. "$(dirname "$0")/../lib.sh"
+
+setup
+build_pair data_alignment.c
+
+# The premise: the compiler really did over-align it, and the object is new in
+# the patch so it has to be cloned rather than referenced.
+want="$(in_sections patched.o | sed 's/^ *\[[ 0-9]*\] *//' |
+	awk '$1 == ".data.aligned_data" { print $NF }')"
+[ "$want" = 64 ] ||
+	probe_skip "compiler gave .data.aligned_data alignment '$want', not 64"
+has_input_section orig.o .data.aligned_data &&
+	fail "fixture put aligned_data in the original; nothing to clone"
+
+run_diff
+assert_section .data.aligned_data
+
+got="$(out_sections | sed 's/^ *\[[ 0-9]*\] *//' |
+       awk '$1 == ".data.aligned_data" { print $NF }')"
+[ "$got" = "$want" ] ||
+	fail "cloned .data.aligned_data has alignment $got, expected $want"
+
+pass "cloned data section keeps its alignment"