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, 37 insertions, 0 deletions

diff --git a/tools/testing/shared/shared.h b/tools/testing/shared/shared.h
new file mode 100644
index 000000000..13fb4d399
--- /dev/null
+++ b/tools/testing/shared/shared.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __SHARED_H__
+#define __SHARED_H__
+
+#include <linux/types.h>
+#include <linux/bug.h>
+#include <linux/kernel.h>
+#include <linux/bitops.h>
+
+#include <linux/gfp.h>
+#include <linux/rcupdate.h>
+
+#ifndef module_init
+#define module_init(x)
+#endif
+
+#ifndef module_exit
+#define module_exit(x)
+#endif
+
+#ifndef MODULE_AUTHOR
+#define MODULE_AUTHOR(x)
+#endif
+
+#ifndef MODULE_LICENSE
+#define MODULE_LICENSE(x)
+#endif
+
+#ifndef MODULE_DESCRIPTION
+#define MODULE_DESCRIPTION(x)
+#endif
+
+#ifndef dump_stack
+#define dump_stack()	assert(0)
+#endif
+
+#endif /* __SHARED_H__ */