[PATCH v3 22/58] objtool/klp: Add test for symids in discarded sections

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Compiled twice and partially linked so the result has duplicate locals,
+ * which is what symid_needed() requires.  dup_normal is in a live section,
+ * dup_discarded in one the vmlinux link throws away.  DISCARDED_SEC selects
+ * which discarded section, since there is more than one and each was its own
+ * bug.
+ */
+
+#ifndef DISCARDED_SEC
+#define DISCARDED_SEC ".exitcall.exit"
+#endif
+
+static const char __modinfo[]
+	__attribute__((section(".modinfo"), used, aligned(1))) = "\0name=vmlinux";
+
+static int dup_normal = 1;
+
+static void *dup_discarded
+	__attribute__((section(DISCARDED_SEC), used)) = &dup_normal;
+
+int FUNC_NAME(void)
+{
+	return dup_normal + (dup_discarded != (void *)0);
+}

@@ -0,0 +1,44 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# .klp.symid must not reference symbols in sections the vmlinux link discards.
+# Each such section has been its own bug, found only when someone built a
+# config where a duplicate happened to land there, so cover the whole list
+# rather than whichever one was reported last.
+
+. "$(dirname "$0")/../lib.sh"
+
+setup
+
+# Allocated sections which vmlinux.lds.h discards unconditionally.  A symid
+# referencing one of these fails the vmlinux link outright:
+#
+#   `__exitcall_hid_exit' referenced in section `.klp.symid' of vmlinux.o:
+#   defined in discarded section `.exitcall.exit' of vmlinux.o
+for sec in .exitcall.exit .no_trim_symbol; do
+	build_one symid_discarded.c a.o \
+		-DFUNC_NAME=use_a -DDISCARDED_SEC="\"$sec\""
+	build_one symid_discarded.c b.o \
+		-DFUNC_NAME=use_b -DDISCARDED_SEC="\"$sec\""
+
+	# --klp-symids only runs on a file named vmlinux.o
+	rm -f "$workdir/vmlinux.o"
+	partial_link "$workdir/vmlinux.o" "$workdir/a.o" "$workdir/b.o" ||
+		probe_skip "partial link unavailable"
+
+	"$OBJTOOL" --klp-symids --link "$workdir/vmlinux.o" ||
+		fail "objtool --klp-symids failed"
+
+	symids="$(in_relocs vmlinux.o |
+		  awk '/rela.klp.symid/,/^$/')"
+
+	# Without this the test would also pass if symid generation stopped
+	# entirely.
+	echo "$symids" | grep -q 'dup_normal' ||
+		fail "$sec: no symid for the duplicate in a live section"
+
+	echo "$symids" | grep -q 'dup_discarded' &&
+		fail "symid emitted for a symbol in discarded section $sec"
+done
+
+pass "no symids for symbols in discarded sections"