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, 100 insertions, 0 deletions

diff --git a/scripts/atomic/gen-atomic-long.sh b/scripts/atomic/gen-atomic-long.sh
new file mode 100755
index 000000000..9826be3ba
--- /dev/null
+++ b/scripts/atomic/gen-atomic-long.sh
@@ -0,0 +1,100 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+ATOMICDIR=$(dirname $0)
+
+. ${ATOMICDIR}/atomic-tbl.sh
+
+#gen_cast(arg, int, atomic)
+gen_cast()
+{
+	local arg="$1"; shift
+	local int="$1"; shift
+	local atomic="$1"; shift
+
+	[ "${arg%%:*}" = "p" ] || return
+
+	printf "($(gen_param_type "${arg}" "${int}" "${atomic}"))"
+}
+
+#gen_args_cast(int, atomic, arg...)
+gen_args_cast()
+{
+	local int="$1"; shift
+	local atomic="$1"; shift
+
+	while [ "$#" -gt 0 ]; do
+		local cast="$(gen_cast "$1" "${int}" "${atomic}")"
+		local arg="$(gen_param_name "$1")"
+		printf "${cast}${arg}"
+		[ "$#" -gt 1 ] && printf ", "
+		shift;
+	done
+}
+
+#gen_proto_order_variant(meta, pfx, name, sfx, order, arg...)
+gen_proto_order_variant()
+{
+	local meta="$1"; shift
+	local pfx="$1"; shift
+	local name="$1"; shift
+	local sfx="$1"; shift
+	local order="$1"; shift
+
+	local atomicname="${pfx}${name}${sfx}${order}"
+
+	local ret="$(gen_ret_type "${meta}" "long")"
+	local params="$(gen_params "long" "atomic_long" "$@")"
+	local argscast_32="$(gen_args_cast "int" "atomic" "$@")"
+	local argscast_64="$(gen_args_cast "s64" "atomic64" "$@")"
+	local retstmt="$(gen_ret_stmt "${meta}")"
+
+	gen_kerneldoc "raw_" "${meta}" "${pfx}" "${name}" "${sfx}" "${order}" "atomic_long" "long" "$@"
+
+cat <<EOF
+static __always_inline ${ret}
+raw_atomic_long_${atomicname}(${params})
+{
+#ifdef CONFIG_64BIT
+	${retstmt}raw_atomic64_${atomicname}(${argscast_64});
+#else
+	${retstmt}raw_atomic_${atomicname}(${argscast_32});
+#endif
+}
+
+EOF
+}
+
+cat << EOF
+// SPDX-License-Identifier: GPL-2.0
+
+// Generated by $0
+// DO NOT MODIFY THIS FILE DIRECTLY
+
+#ifndef _LINUX_ATOMIC_LONG_H
+#define _LINUX_ATOMIC_LONG_H
+
+#include <linux/compiler.h>
+#include <asm/types.h>
+
+#ifdef CONFIG_64BIT
+typedef atomic64_t atomic_long_t;
+#define ATOMIC_LONG_INIT(i)		ATOMIC64_INIT(i)
+#define atomic_long_cond_read_acquire	atomic64_cond_read_acquire
+#define atomic_long_cond_read_relaxed	atomic64_cond_read_relaxed
+#else
+typedef atomic_t atomic_long_t;
+#define ATOMIC_LONG_INIT(i)		ATOMIC_INIT(i)
+#define atomic_long_cond_read_acquire	atomic_cond_read_acquire
+#define atomic_long_cond_read_relaxed	atomic_cond_read_relaxed
+#endif
+
+EOF
+
+grep '^[a-z]' "$1" | while read name meta args; do
+	gen_proto "${meta}" "${name}" ${args}
+done
+
+cat <<EOF
+#endif /* _LINUX_ATOMIC_LONG_H */
+EOF