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, 92 insertions, 0 deletions

diff --git a/tools/perf/util/debug.h b/tools/perf/util/debug.h
new file mode 100644
index 000000000..6b737e195
--- /dev/null
+++ b/tools/perf/util/debug.h
@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* For debugging general purposes */
+#ifndef __PERF_DEBUG_H
+#define __PERF_DEBUG_H
+
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <linux/compiler.h>
+
+extern int verbose;
+extern int debug_kmaps;
+extern int debug_peo_args;
+extern bool quiet, dump_trace;
+extern int debug_ordered_events;
+extern int debug_data_convert;
+extern int debug_type_profile;
+
+#ifndef pr_fmt
+#define pr_fmt(fmt) fmt
+#endif
+
+#define pr_err(fmt, ...) \
+	eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_warning(fmt, ...) \
+	eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_warning_once(fmt, ...) ({		\
+	static int __warned;			\
+	if (unlikely(!__warned)) {		\
+		pr_warning(fmt, ##__VA_ARGS__); \
+		__warned = 1;			\
+	}					\
+})
+#define pr_info(fmt, ...) \
+	eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debug(fmt, ...) \
+	eprintf(1, verbose, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debugN(n, fmt, ...) \
+	eprintf(n, verbose, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debug2(fmt, ...) pr_debugN(2, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debug3(fmt, ...) pr_debugN(3, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debug4(fmt, ...) pr_debugN(4, pr_fmt(fmt), ##__VA_ARGS__)
+
+/* Special macro to print perf_event_open arguments/return value. */
+#define pr_debug2_peo(fmt, ...) {				\
+	if (debug_peo_args)						\
+		pr_debugN(0, pr_fmt(fmt), ##__VA_ARGS__);	\
+	else							\
+		pr_debugN(2, pr_fmt(fmt), ##__VA_ARGS__);	\
+}
+
+#define pr_time_N(n, var, t, fmt, ...) \
+	eprintf_time(n, var, t, fmt, ##__VA_ARGS__)
+
+#define pr_oe_time(t, fmt, ...)  pr_time_N(1, debug_ordered_events, t, pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_oe_time2(t, fmt, ...) pr_time_N(2, debug_ordered_events, t, pr_fmt(fmt), ##__VA_ARGS__)
+
+#define STRERR_BUFSIZE	128	/* For the buffer size of str_error_r */
+
+union perf_event;
+
+int dump_printf(const char *fmt, ...) __printf(1, 2);
+void trace_event(union perf_event *event);
+
+int ui__error(const char *format, ...) __printf(1, 2);
+int ui__warning(const char *format, ...) __printf(1, 2);
+#define ui__warning_once(format, ...) ({		\
+	static int __warned;				\
+	if (unlikely(!__warned)) {			\
+		ui__warning(format, ##__VA_ARGS__);	\
+		__warned = 1;				\
+	}						\
+})
+
+void pr_stat(const char *fmt, ...);
+
+int eprintf(int level, int var, const char *fmt, ...) __printf(3, 4);
+int eprintf_time(int level, int var, u64 t, const char *fmt, ...) __printf(4, 5);
+int veprintf(int level, int var, const char *fmt, va_list args);
+
+int perf_debug_option(const char *str);
+FILE *debug_file(void);
+void debug_set_file(FILE *file);
+void debug_set_display_time(bool set);
+void perf_debug_setup(void);
+int perf_quiet_option(void);
+
+void __dump_stack(FILE *file, void **stackdump, size_t stackdump_size);
+void dump_stack(void);
+void sighandler_dump_stack(int sig);
+
+#endif	/* __PERF_DEBUG_H */