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/lib/subcmd/help.h b/tools/lib/subcmd/help.h
new file mode 100644
index 000000000..355c066c8
--- /dev/null
+++ b/tools/lib/subcmd/help.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __SUBCMD_HELP_H
+#define __SUBCMD_HELP_H
+
+#include <sys/types.h>
+#include <stdio.h>
+
+struct cmdnames {
+	size_t alloc;
+	size_t cnt;
+	struct cmdname {
+		size_t len; /* also used for similarity index in help.c */
+		char name[];
+	} **names;
+};
+
+static inline void mput_char(char c, unsigned int num)
+{
+	while(num--)
+		putchar(c);
+}
+
+void load_command_list(const char *prefix,
+		struct cmdnames *main_cmds,
+		struct cmdnames *other_cmds);
+void add_cmdname(struct cmdnames *cmds, const char *name, size_t len);
+void clean_cmdnames(struct cmdnames *cmds);
+int cmdname_compare(const void *a, const void *b);
+void uniq(struct cmdnames *cmds);
+/* Here we require that excludes is a sorted list. */
+void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes);
+int is_in_cmdlist(struct cmdnames *c, const char *s);
+void list_commands(const char *title, struct cmdnames *main_cmds,
+		   struct cmdnames *other_cmds);
+
+#endif /* __SUBCMD_HELP_H */