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, 82 insertions, 0 deletions

diff --git a/tools/perf/tests/mem2node.c b/tools/perf/tests/mem2node.c
new file mode 100644
index 000000000..7ce1ad7b6
--- /dev/null
+++ b/tools/perf/tests/mem2node.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compiler.h>
+#include <linux/bitmap.h>
+#include <linux/kernel.h>
+#include <linux/zalloc.h>
+#include <perf/cpumap.h>
+#include <internal/cpumap.h>
+#include "debug.h"
+#include "env.h"
+#include "mem2node.h"
+#include "tests.h"
+
+static struct node {
+	int		 node;
+	const char 	*map;
+} test_nodes[] = {
+	{ .node = 0, .map = "0"     },
+	{ .node = 1, .map = "1-2"   },
+	{ .node = 3, .map = "5-7,9" },
+};
+
+#define T TEST_ASSERT_VAL
+
+static unsigned long *get_bitmap(const char *str, int nbits)
+{
+	struct perf_cpu_map *map = perf_cpu_map__new(str);
+	unsigned long *bm = NULL;
+
+	bm = bitmap_zalloc(nbits);
+
+	if (map && bm) {
+		struct perf_cpu cpu;
+		unsigned int i;
+
+		perf_cpu_map__for_each_cpu(cpu, i, map)
+			__set_bit(cpu.cpu, bm);
+	}
+
+	if (map)
+		perf_cpu_map__put(map);
+	else
+		free(bm);
+
+	return bm && map ? bm : NULL;
+}
+
+static int test__mem2node(struct test_suite *t __maybe_unused, int subtest __maybe_unused)
+{
+	struct mem2node map;
+	struct memory_node nodes[3];
+	struct perf_env env = {
+		.memory_nodes    = (struct memory_node *) &nodes[0],
+		.nr_memory_nodes = ARRAY_SIZE(nodes),
+		.memory_bsize    = 0x100,
+	};
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(nodes); i++) {
+		nodes[i].node = test_nodes[i].node;
+		nodes[i].size = 10;
+
+		T("failed: alloc bitmap",
+		  (nodes[i].set = get_bitmap(test_nodes[i].map, 10)));
+	}
+
+	T("failed: mem2node__init", !mem2node__init(&map, &env));
+	T("failed: mem2node__node",  0 == mem2node__node(&map,   0x50));
+	T("failed: mem2node__node",  1 == mem2node__node(&map,  0x100));
+	T("failed: mem2node__node",  1 == mem2node__node(&map,  0x250));
+	T("failed: mem2node__node",  3 == mem2node__node(&map,  0x500));
+	T("failed: mem2node__node",  3 == mem2node__node(&map,  0x650));
+	T("failed: mem2node__node", -1 == mem2node__node(&map,  0x450));
+	T("failed: mem2node__node", -1 == mem2node__node(&map, 0x1050));
+
+	for (i = 0; i < ARRAY_SIZE(nodes); i++)
+		zfree(&nodes[i].set);
+
+	mem2node__exit(&map);
+	return 0;
+}
+
+DEFINE_SUITE("mem2node", mem2node);