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, 41 insertions, 0 deletions

diff --git a/arch/arm/mach-shmobile/timer.c b/arch/arm/mach-shmobile/timer.c
new file mode 100644
index 000000000..2335311b5
--- /dev/null
+++ b/arch/arm/mach-shmobile/timer.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SH-Mobile Timer
+ *
+ * Copyright (C) 2010  Magnus Damm
+ * Copyright (C) 2002 - 2009  Paul Mundt
+ */
+#include <linux/platform_device.h>
+#include <linux/clocksource.h>
+#include <linux/delay.h>
+#include <linux/of_address.h>
+
+#include "common.h"
+
+void __init shmobile_init_delay(void)
+{
+	struct device_node *np;
+	u32 max_freq = 0;
+
+	for_each_of_cpu_node(np) {
+		u32 freq;
+
+		if (!of_property_read_u32(np, "clock-frequency", &freq))
+			max_freq = max(max_freq, freq);
+	}
+
+	if (!max_freq)
+		return;
+
+	/*
+	 * Calculate a worst-case loops-per-jiffy value
+	 * based on maximum cpu core hz setting and the
+	 * __delay() implementation in arch/arm/lib/delay.S.
+	 *
+	 * This will result in a longer delay than expected
+	 * when the cpu core runs on lower frequencies.
+	 */
+
+	if (!preset_lpj)
+		preset_lpj = max_freq / HZ;
+}