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/mips/cobalt/time.c b/arch/mips/cobalt/time.c
new file mode 100644
index 000000000..1b6fa6649
--- /dev/null
+++ b/arch/mips/cobalt/time.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Cobalt time initialization.
+ *
+ *  Copyright (C) 2007  Yoichi Yuasa <yuasa@linux-mips.org>
+ */
+#include <linux/i8253.h>
+#include <linux/init.h>
+
+#include <asm/gt64120.h>
+#include <asm/time.h>
+
+#define GT641XX_BASE_CLOCK	50000000	/* 50MHz */
+
+void __init plat_time_init(void)
+{
+	u32 start, end;
+	int i = HZ / 10;
+
+	setup_pit_timer();
+
+	gt641xx_set_base_clock(GT641XX_BASE_CLOCK);
+
+	/*
+	 * MIPS counter frequency is measured during a 100msec interval
+	 * using GT64111 timer0.
+	 */
+	while (!gt641xx_timer0_state())
+		;
+
+	start = read_c0_count();
+
+	while (i--)
+		while (!gt641xx_timer0_state())
+			;
+
+	end = read_c0_count();
+
+	mips_hpt_frequency = (end - start) * 10;
+	printk(KERN_INFO "MIPS counter frequency %dHz\n", mips_hpt_frequency);
+}