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, 33 insertions, 0 deletions

diff --git a/tools/objtool/weak.c b/tools/objtool/weak.c
new file mode 100644
index 000000000..d6562f292
--- /dev/null
+++ b/tools/objtool/weak.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2020 Matt Helsley <mhelsley@vmware.com>
+ * Weak definitions necessary to compile objtool without
+ * some subcommands (e.g. check, orc).
+ */
+
+#include <stdbool.h>
+#include <errno.h>
+#include <objtool/objtool.h>
+#include <objtool/arch.h>
+#include <objtool/builtin.h>
+
+#define UNSUPPORTED(name)						\
+({									\
+	fprintf(stderr, "error: objtool: " name " not implemented\n");	\
+	return ENOSYS;							\
+})
+
+int __weak orc_dump(const char *_objname)
+{
+	UNSUPPORTED("ORC");
+}
+
+int __weak orc_create(struct objtool_file *file)
+{
+	UNSUPPORTED("ORC");
+}
+
+int __weak cmd_klp(int argc, const char **argv)
+{
+	UNSUPPORTED("klp");
+}