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>

2 files changed, 73 insertions, 0 deletions

diff --git a/drivers/soc/gemini/Makefile b/drivers/soc/gemini/Makefile
new file mode 100644
index 000000000..8cbd1e45d
--- /dev/null
+++ b/drivers/soc/gemini/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-y	+= soc-gemini.o
diff --git a/drivers/soc/gemini/soc-gemini.c b/drivers/soc/gemini/soc-gemini.c
new file mode 100644
index 000000000..642b96c91
--- /dev/null
+++ b/drivers/soc/gemini/soc-gemini.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017 Linaro Ltd.
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ */
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+#include <linux/of.h>
+
+#define GLOBAL_WORD_ID				0x00
+#define GEMINI_GLOBAL_ARB1_CTRL			0x2c
+#define GEMINI_ARB1_BURST_MASK			GENMASK(21, 16)
+#define GEMINI_ARB1_BURST_SHIFT			16
+/* These all define the priority on the BUS2 backplane */
+#define GEMINI_ARB1_PRIO_MASK			GENMASK(9, 0)
+#define GEMINI_ARB1_DMAC_HIGH_PRIO		BIT(0)
+#define GEMINI_ARB1_IDE_HIGH_PRIO		BIT(1)
+#define GEMINI_ARB1_RAID_HIGH_PRIO		BIT(2)
+#define GEMINI_ARB1_SECURITY_HIGH_PRIO		BIT(3)
+#define GEMINI_ARB1_GMAC0_HIGH_PRIO		BIT(4)
+#define GEMINI_ARB1_GMAC1_HIGH_PRIO		BIT(5)
+#define GEMINI_ARB1_USB0_HIGH_PRIO		BIT(6)
+#define GEMINI_ARB1_USB1_HIGH_PRIO		BIT(7)
+#define GEMINI_ARB1_PCI_HIGH_PRIO		BIT(8)
+#define GEMINI_ARB1_TVE_HIGH_PRIO		BIT(9)
+
+#define GEMINI_DEFAULT_BURST_SIZE		0x20
+#define GEMINI_DEFAULT_PRIO			(GEMINI_ARB1_GMAC0_HIGH_PRIO | \
+						 GEMINI_ARB1_GMAC1_HIGH_PRIO)
+
+static int __init gemini_soc_init(void)
+{
+	struct regmap *map;
+	u32 rev;
+	u32 val;
+	int ret;
+
+	/* Multiplatform guard, only proceed on Gemini */
+	if (!of_machine_is_compatible("cortina,gemini"))
+		return 0;
+
+	map = syscon_regmap_lookup_by_compatible("cortina,gemini-syscon");
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+	ret = regmap_read(map, GLOBAL_WORD_ID, &rev);
+	if (ret)
+		return ret;
+
+	val = (GEMINI_DEFAULT_BURST_SIZE << GEMINI_ARB1_BURST_SHIFT) |
+		GEMINI_DEFAULT_PRIO;
+
+	/* Set up system arbitration */
+	regmap_update_bits(map,
+			   GEMINI_GLOBAL_ARB1_CTRL,
+			   GEMINI_ARB1_BURST_MASK | GEMINI_ARB1_PRIO_MASK,
+			   val);
+
+	pr_info("Gemini SoC %04x revision %02x, set arbitration %08x\n",
+		rev >> 8, rev & 0xff, val);
+
+	return 0;
+}
+subsys_initcall(gemini_soc_init);