selftests/bpf: Test rhtab kptr cancellation semanticsgrafted

Resizable hash-map updates and deletions must not perform full special-field
destruction in their caller context. In particular, a referenced kptr must
remain attached to the allocation until the memory allocator destructor can
release it safely.

Add separate coverage for both affected paths. The update test stores a task
kptr, replaces the ordinary value bytes with BPF_EXIST, and verifies that the
kptr survived. The delete test removes an element and exchanges its kptr
through the still-valid map-value pointer before the allocation is reclaimed.

Both cases observe a NULL kptr when rhtab uses bpf_obj_free_fields(). They
recover and release the reference after rhtab switches to cancellation
semantics.

Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
[ kkd: Split update and delete coverage and rewrote the commit log ]
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904104203.345917-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-probe.c b/drivers/clocksource/timer-probe.c
new file mode 100644
index 000000000..b7860bc0d
--- /dev/null
+++ b/drivers/clocksource/timer-probe.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.
+ */
+
+#include <linux/acpi.h>
+#include <linux/init.h>
+#include <linux/of.h>
+#include <linux/clocksource.h>
+
+extern struct of_device_id __timer_of_table[];
+
+static const struct of_device_id __timer_of_table_sentinel
+	__used __section("__timer_of_table_end");
+
+void __init timer_probe(void)
+{
+	struct device_node *np;
+	const struct of_device_id *match;
+	of_init_fn_1_ret init_func_ret;
+	unsigned timers = 0;
+	int ret;
+
+	for_each_matching_node_and_match(np, __timer_of_table, &match) {
+		if (!of_device_is_available(np))
+			continue;
+
+		init_func_ret = match->data;
+
+		ret = init_func_ret(np);
+		if (ret) {
+			if (ret != -EPROBE_DEFER)
+				pr_err("Failed to initialize '%pOF': %d\n", np,
+				       ret);
+			continue;
+		}
+
+		timers++;
+	}
+
+	timers += acpi_probe_device_table(timer);
+
+	if (!timers)
+		pr_crit("%s: no matching timers found\n", __func__);
+}