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, 36 insertions, 0 deletions

diff --git a/tools/include/nolibc/assert.h b/tools/include/nolibc/assert.h
new file mode 100644
index 000000000..84ff8ad9a
--- /dev/null
+++ b/tools/include/nolibc/assert.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * Assert for NOLIBC
+ * Copyright (C) 2026 Thomas Weißschuh <linux@weissschuh.net>
+ */
+
+/* make sure to include all global symbols */
+#include "nolibc.h"
+
+#ifndef _NOLIBC_ASSERT_H
+#define _NOLIBC_ASSERT_H
+
+#include "errno.h"
+#include "stdio.h"
+#include "stdlib.h"
+
+#endif /* _NOLIBC_ASSERT_H */
+
+/* NDEBUG needs to be evaluated on *each* inclusion */
+#ifdef assert
+#undef assert
+#endif
+
+#ifndef NDEBUG
+#define assert(expr)									\
+({											\
+	if (!(expr)) {									\
+		fprintf(stderr, "%s: %s:%d: %s: Assertion `%s' failed.\n",		\
+			program_invocation_short_name, __FILE__, __LINE__, __func__,	\
+			#expr);								\
+		abort();								\
+	}										\
+})
+#else
+#define assert(expr) ((void)0)
+#endif