selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/tools/objtool/weak.c b/tools/objtool/weak.c
new file mode 100644
index 000000000..d6562f292
--- /dev/null
+++ b/tools/objtool/weak.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2020 Matt Helsley <mhelsley@vmware.com>
+ * Weak definitions necessary to compile objtool without
+ * some subcommands (e.g. check, orc).
+ */
+
+#include <stdbool.h>
+#include <errno.h>
+#include <objtool/objtool.h>
+#include <objtool/arch.h>
+#include <objtool/builtin.h>
+
+#define UNSUPPORTED(name)						\
+({									\
+	fprintf(stderr, "error: objtool: " name " not implemented\n");	\
+	return ENOSYS;							\
+})
+
+int __weak orc_dump(const char *_objname)
+{
+	UNSUPPORTED("ORC");
+}
+
+int __weak orc_create(struct objtool_file *file)
+{
+	UNSUPPORTED("ORC");
+}
+
+int __weak cmd_klp(int argc, const char **argv)
+{
+	UNSUPPORTED("klp");
+}