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, 65 insertions, 0 deletions

diff --git a/arch/powerpc/boot/mpc52xx-psc.c b/arch/powerpc/boot/mpc52xx-psc.c
new file mode 100644
index 000000000..c2c08633e
--- /dev/null
+++ b/arch/powerpc/boot/mpc52xx-psc.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * MPC5200 PSC serial console support.
+ *
+ * Author: Grant Likely <grant.likely@secretlab.ca>
+ *
+ * Copyright (c) 2007 Secret Lab Technologies Ltd.
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ *
+ * It is assumed that the firmware (or the platform file) has already set
+ * up the port.
+ */
+
+#include "types.h"
+#include "io.h"
+#include "ops.h"
+
+/* Programmable Serial Controller (PSC) status register bits */
+#define MPC52xx_PSC_SR		0x04
+#define MPC52xx_PSC_SR_RXRDY		0x0100
+#define MPC52xx_PSC_SR_RXFULL		0x0200
+#define MPC52xx_PSC_SR_TXRDY		0x0400
+#define MPC52xx_PSC_SR_TXEMP		0x0800
+
+#define MPC52xx_PSC_BUFFER	0x0C
+
+static void *psc;
+
+static int psc_open(void)
+{
+	/* Assume the firmware has already configured the PSC into
+	 * uart mode */
+	return 0;
+}
+
+static void psc_putc(unsigned char c)
+{
+	while (!(in_be16(psc + MPC52xx_PSC_SR) & MPC52xx_PSC_SR_TXRDY)) ;
+	out_8(psc + MPC52xx_PSC_BUFFER, c);
+}
+
+static unsigned char psc_tstc(void)
+{
+	return (in_be16(psc + MPC52xx_PSC_SR) & MPC52xx_PSC_SR_RXRDY) != 0;
+}
+
+static unsigned char psc_getc(void)
+{
+	while (!(in_be16(psc + MPC52xx_PSC_SR) & MPC52xx_PSC_SR_RXRDY)) ;
+	return in_8(psc + MPC52xx_PSC_BUFFER);
+}
+
+int mpc5200_psc_console_init(void *devp, struct serial_console_data *scdp)
+{
+	/* Get the base address of the psc registers */
+	if (dt_get_virtual_reg(devp, &psc, 1) < 1)
+		return -1;
+
+	scdp->open = psc_open;
+	scdp->putc = psc_putc;
+	scdp->getc = psc_getc;
+	scdp->tstc = psc_tstc;
+
+	return 0;
+}