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, 74 insertions, 0 deletions

diff --git a/include/trace/events/initcall.h b/include/trace/events/initcall.h
new file mode 100644
index 000000000..5282afdf3
--- /dev/null
+++ b/include/trace/events/initcall.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM initcall
+
+#if !defined(_TRACE_INITCALL_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_INITCALL_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(initcall_level,
+
+	TP_PROTO(const char *level),
+
+	TP_ARGS(level),
+
+	TP_STRUCT__entry(
+		__string(level, level)
+	),
+
+	TP_fast_assign(
+		__assign_str(level);
+	),
+
+	TP_printk("level=%s", __get_str(level))
+);
+
+TRACE_EVENT(initcall_start,
+
+	TP_PROTO(initcall_t func),
+
+	TP_ARGS(func),
+
+	TP_STRUCT__entry(
+		/*
+		 * Use field_struct to avoid is_signed_type()
+		 * comparison of a function pointer
+		 */
+		__field_struct(initcall_t, func)
+	),
+
+	TP_fast_assign(
+		__entry->func = func;
+	),
+
+	TP_printk("func=%pS", __entry->func)
+);
+
+TRACE_EVENT(initcall_finish,
+
+	TP_PROTO(initcall_t func, int ret),
+
+	TP_ARGS(func, ret),
+
+	TP_STRUCT__entry(
+		/*
+		 * Use field_struct to avoid is_signed_type()
+		 * comparison of a function pointer
+		 */
+		__field_struct(initcall_t,	func)
+		__field(int,			ret)
+	),
+
+	TP_fast_assign(
+		__entry->func = func;
+		__entry->ret = ret;
+	),
+
+	TP_printk("func=%pS ret=%d", __entry->func, __entry->ret)
+);
+
+#endif /* if !defined(_TRACE_GPIO_H) || defined(TRACE_HEADER_MULTI_READ) */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>