tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
selftests/bpf: Add test for bpftool access to read-only protected maps
Add selftest cases that validate bpftool's expected behavior when
accessing maps protected from modification via security_bpf_map.
The test includes a BPF program attached to security_bpf_map with two maps:
- A protected map that only allows read-only access
- An unprotected map that allows full access
The test script attaches the BPF program to security_bpf_map and
verifies that for the bpftool map command:
- Read access works on both maps
- Write access fails on the protected map
- Write access succeeds on the unprotected map
- These behaviors remain consistent when the maps are pinned
Signed-off-by: Slava Imameev <slava.imameev@crowdstrike.com>
Reviewed-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/r/20250620151812.13952-2-slava.imameev@crowdstrike.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
authored by
Slava Imameev
and committed by
Alexei Starovoitov
f8b19aec
d32179e8
+490
+1
tools/testing/selftests/bpf/Makefile
+1
tools/testing/selftests/bpf/Makefile
+22
tools/testing/selftests/bpf/progs/bpf_iter_map_elem.c
+22
tools/testing/selftests/bpf/progs/bpf_iter_map_elem.c
···
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// SPDX-License-Identifier: GPL-2.0-only
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#include "vmlinux.h"
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_helpers.h>
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char _license[] SEC("license") = "GPL";
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__u32 value_sum = 0;
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SEC("iter/bpf_map_elem")
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int dump_bpf_map_values(struct bpf_iter__bpf_map_elem *ctx)
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{
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__u32 value = 0;
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if (ctx->value == (void *)0)
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return 0;
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bpf_probe_read_kernel(&value, sizeof(value), ctx->value);
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value_sum += value;
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return 0;
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}
+69
tools/testing/selftests/bpf/progs/security_bpf_map.c
+69
tools/testing/selftests/bpf/progs/security_bpf_map.c
···
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// SPDX-License-Identifier: GPL-2.0-only
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#include "vmlinux.h"
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_helpers.h>
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char _license[] SEC("license") = "GPL";
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#define EPERM 1 /* Operation not permitted */
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/* From include/linux/mm.h. */
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#define FMODE_WRITE 0x2
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struct map;
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struct {
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__uint(type, BPF_MAP_TYPE_ARRAY);
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__type(key, __u32);
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__type(value, __u32);
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__uint(max_entries, 1);
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} prot_status_map SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__type(key, __u32);
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__type(value, __u32);
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__uint(max_entries, 3);
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} prot_map SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__type(key, __u32);
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__type(value, __u32);
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__uint(max_entries, 3);
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} not_prot_map SEC(".maps");
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SEC("fmod_ret/security_bpf_map")
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int BPF_PROG(fmod_bpf_map, struct bpf_map *map, int fmode)
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{
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__u32 key = 0;
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__u32 *status_ptr = bpf_map_lookup_elem(&prot_status_map, &key);
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if (!status_ptr || !*status_ptr)
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return 0;
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if (map == &prot_map) {
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/* Allow read-only access */
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if (fmode & FMODE_WRITE)
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return -EPERM;
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}
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return 0;
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}
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/*
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* This program keeps references to maps. This is needed to prevent
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* optimizing them out.
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*/
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SEC("fentry/bpf_fentry_test1")
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int BPF_PROG(fentry_dummy1, int a)
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{
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__u32 key = 0;
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__u32 val1 = a;
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__u32 val2 = a + 1;
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bpf_map_update_elem(&prot_map, &key, &val1, BPF_ANY);
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bpf_map_update_elem(¬_prot_map, &key, &val2, BPF_ANY);
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return 0;
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}
+398
tools/testing/selftests/bpf/test_bpftool_map.sh
+398
tools/testing/selftests/bpf/test_bpftool_map.sh
···
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#!/bin/sh
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# SPDX-License-Identifier: GPL-2.0
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# Kselftest framework requirement - SKIP code is 4.
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ksft_skip=4
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TESTNAME="bpftool_map"
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BPF_FILE="security_bpf_map.bpf.o"
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BPF_ITER_FILE="bpf_iter_map_elem.bpf.o"
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PROTECTED_MAP_NAME="prot_map"
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NOT_PROTECTED_MAP_NAME="not_prot_map"
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BPF_FS_TMP_PARENT="/tmp"
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BPF_FS_PARENT=$(awk '$3 == "bpf" {print $2; exit}' /proc/mounts)
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BPF_FS_PARENT=${BPF_FS_PARENT:-$BPF_FS_TMP_PARENT}
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# bpftool will mount bpf file system under BPF_DIR if it is not mounted
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# under BPF_FS_PARENT.
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BPF_DIR="$BPF_FS_PARENT/test_$TESTNAME"
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SCRIPT_DIR=$(dirname $(realpath "$0"))
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BPF_FILE_PATH="$SCRIPT_DIR/$BPF_FILE"
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BPF_ITER_FILE_PATH="$SCRIPT_DIR/$BPF_ITER_FILE"
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BPFTOOL_PATH="bpftool"
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# Assume the script is located under tools/testing/selftests/bpf/
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KDIR_ROOT_DIR=$(realpath "$SCRIPT_DIR"/../../../../)
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_cleanup()
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{
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set +eu
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# If BPF_DIR is a mount point this will not remove the mount point itself.
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[ -d "$BPF_DIR" ] && rm -rf "$BPF_DIR" 2> /dev/null
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# Unmount if BPF filesystem was temporarily created.
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if [ "$BPF_FS_PARENT" = "$BPF_FS_TMP_PARENT" ]; then
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# A loop and recursive unmount are required as bpftool might
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# create multiple mounts. For example, a bind mount of the directory
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# to itself. The bind mount is created to change mount propagation
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# flags on an actual mount point.
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max_attempts=3
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attempt=0
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while mountpoint -q "$BPF_DIR" && [ $attempt -lt $max_attempts ]; do
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umount -R "$BPF_DIR" 2>/dev/null
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attempt=$((attempt+1))
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done
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# The directory still exists. Remove it now.
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[ -d "$BPF_DIR" ] && rm -rf "$BPF_DIR" 2>/dev/null
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fi
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}
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cleanup_skip()
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{
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echo "selftests: $TESTNAME [SKIP]"
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_cleanup
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exit $ksft_skip
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}
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cleanup()
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{
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if [ "$?" = 0 ]; then
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echo "selftests: $TESTNAME [PASS]"
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else
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echo "selftests: $TESTNAME [FAILED]"
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fi
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_cleanup
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}
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check_root_privileges() {
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if [ $(id -u) -ne 0 ]; then
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echo "Need root privileges"
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exit $ksft_skip
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fi
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}
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# Function to verify bpftool path.
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# Parameters:
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# $1: bpftool path
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verify_bpftool_path() {
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local bpftool_path="$1"
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if ! "$bpftool_path" version > /dev/null 2>&1; then
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echo "Could not run test without bpftool"
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exit $ksft_skip
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fi
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}
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# Function to verify BTF support.
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# The test requires BTF support for fmod_ret programs.
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verify_btf_support() {
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if [ ! -f /sys/kernel/btf/vmlinux ]; then
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echo "Could not run test without BTF support"
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exit $ksft_skip
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fi
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}
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# Function to initialize map entries with keys [0..2] and values set to 0.
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# Parameters:
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# $1: Map name
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# $2: bpftool path
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initialize_map_entries() {
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local map_name="$1"
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local bpftool_path="$2"
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for key in 0 1 2; do
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"$bpftool_path" map update name "$map_name" key $key 0 0 0 value 0 0 0 $key
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done
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}
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# Test read access to the map.
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# Parameters:
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# $1: Name command (name/pinned)
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# $2: Map name
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# $3: bpftool path
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# $4: key
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access_for_read() {
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local name_cmd="$1"
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local map_name="$2"
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local bpftool_path="$3"
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local key="$4"
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# Test read access to the map.
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if ! "$bpftool_path" map lookup "$name_cmd" "$map_name" key $key 1>/dev/null; then
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echo " Read access to $key in $map_name failed"
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exit 1
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fi
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# Test read access to map's BTF data.
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if ! "$bpftool_path" btf dump map "$name_cmd" "$map_name" 1>/dev/null; then
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echo " Read access to $map_name for BTF data failed"
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exit 1
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fi
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}
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# Test write access to the map.
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# Parameters:
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# $1: Name command (name/pinned)
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# $2: Map name
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# $3: bpftool path
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# $4: key
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# $5: Whether write should succeed (true/false)
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access_for_write() {
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local name_cmd="$1"
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local map_name="$2"
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local bpftool_path="$3"
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local key="$4"
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local write_should_succeed="$5"
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local value="1 1 1 1"
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if "$bpftool_path" map update "$name_cmd" "$map_name" key $key value \
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$value 2>/dev/null; then
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if [ "$write_should_succeed" = "false" ]; then
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echo " Write access to $key in $map_name succeeded but should have failed"
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exit 1
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fi
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else
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if [ "$write_should_succeed" = "true" ]; then
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echo " Write access to $key in $map_name failed but should have succeeded"
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exit 1
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fi
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fi
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}
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# Test entry deletion for the map.
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# Parameters:
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# $1: Name command (name/pinned)
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# $2: Map name
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# $3: bpftool path
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# $4: key
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# $5: Whether write should succeed (true/false)
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access_for_deletion() {
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local name_cmd="$1"
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local map_name="$2"
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local bpftool_path="$3"
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local key="$4"
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local write_should_succeed="$5"
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local value="1 1 1 1"
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# Test deletion by key for the map.
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# Before deleting, check the key exists.
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if ! "$bpftool_path" map lookup "$name_cmd" "$map_name" key $key 1>/dev/null; then
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echo " Key $key does not exist in $map_name"
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exit 1
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fi
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# Delete by key.
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if "$bpftool_path" map delete "$name_cmd" "$map_name" key $key 2>/dev/null; then
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if [ "$write_should_succeed" = "false" ]; then
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echo " Deletion for $key in $map_name succeeded but should have failed"
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exit 1
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fi
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else
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if [ "$write_should_succeed" = "true" ]; then
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echo " Deletion for $key in $map_name failed but should have succeeded"
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exit 1
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fi
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fi
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# After deleting, check the entry existence according to the expected status.
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if "$bpftool_path" map lookup "$name_cmd" "$map_name" key $key 1>/dev/null; then
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if [ "$write_should_succeed" = "true" ]; then
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echo " Key $key for $map_name was not deleted but should have been deleted"
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exit 1
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fi
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else
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if [ "$write_should_succeed" = "false" ]; then
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echo "Key $key for $map_name was deleted but should have not been deleted"
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exit 1
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fi
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fi
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# Test creation of map's deleted entry, if deletion was successful.
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# Otherwise, the entry exists.
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if "$bpftool_path" map update "$name_cmd" "$map_name" key $key value \
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$value 2>/dev/null; then
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if [ "$write_should_succeed" = "false" ]; then
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echo " Write access to $key in $map_name succeeded after deletion attempt but should have failed"
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exit 1
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fi
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else
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if [ "$write_should_succeed" = "true" ]; then
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echo " Write access to $key in $map_name failed after deletion attempt but should have succeeded"
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exit 1
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fi
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fi
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}
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# Test map elements iterator.
227
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# Parameters:
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# $1: Name command (name/pinned)
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# $2: Map name
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# $3: bpftool path
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# $4: BPF_DIR
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# $5: bpf iterator object file path
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iterate_map_elem() {
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local name_cmd="$1"
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local map_name="$2"
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local bpftool_path="$3"
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local bpf_dir="$4"
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local bpf_file="$5"
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local pin_path="$bpf_dir/map_iterator"
240
+
241
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"$bpftool_path" iter pin "$bpf_file" "$pin_path" map "$name_cmd" "$map_name"
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if [ ! -f "$pin_path" ]; then
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echo " Failed to pin iterator to $pin_path"
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exit 1
245
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fi
246
+
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cat "$pin_path" 1>/dev/null
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rm "$pin_path" 2>/dev/null
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}
250
+
251
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# Function to test map access with configurable write expectations
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# Parameters:
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# $1: Name command (name/pinned)
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# $2: Map name
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# $3: bpftool path
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# $4: key for rw
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# $5: key to delete
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# $6: Whether write should succeed (true/false)
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# $7: BPF_DIR
260
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# $8: bpf iterator object file path
261
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access_map() {
262
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local name_cmd="$1"
263
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local map_name="$2"
264
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local bpftool_path="$3"
265
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local key_for_rw="$4"
266
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local key_to_del="$5"
267
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local write_should_succeed="$6"
268
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local bpf_dir="$7"
269
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local bpf_iter_file_path="$8"
270
+
271
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access_for_read "$name_cmd" "$map_name" "$bpftool_path" "$key_for_rw"
272
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access_for_write "$name_cmd" "$map_name" "$bpftool_path" "$key_for_rw" \
273
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"$write_should_succeed"
274
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access_for_deletion "$name_cmd" "$map_name" "$bpftool_path" "$key_to_del" \
275
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"$write_should_succeed"
276
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iterate_map_elem "$name_cmd" "$map_name" "$bpftool_path" "$bpf_dir" \
277
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"$bpf_iter_file_path"
278
+
}
279
+
280
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# Function to test map access with configurable write expectations
281
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# Parameters:
282
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# $1: Map name
283
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# $2: bpftool path
284
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# $3: BPF_DIR
285
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# $4: Whether write should succeed (true/false)
286
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# $5: bpf iterator object file path
287
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test_map_access() {
288
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local map_name="$1"
289
+
local bpftool_path="$2"
290
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local bpf_dir="$3"
291
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local pin_path="$bpf_dir/${map_name}_pinned"
292
+
local write_should_succeed="$4"
293
+
local bpf_iter_file_path="$5"
294
+
295
+
# Test access to the map by name.
296
+
access_map "name" "$map_name" "$bpftool_path" "0 0 0 0" "1 0 0 0" \
297
+
"$write_should_succeed" "$bpf_dir" "$bpf_iter_file_path"
298
+
299
+
# Pin the map to the BPF filesystem
300
+
"$bpftool_path" map pin name "$map_name" "$pin_path"
301
+
if [ ! -e "$pin_path" ]; then
302
+
echo " Failed to pin $map_name"
303
+
exit 1
304
+
fi
305
+
306
+
# Test access to the pinned map.
307
+
access_map "pinned" "$pin_path" "$bpftool_path" "0 0 0 0" "2 0 0 0" \
308
+
"$write_should_succeed" "$bpf_dir" "$bpf_iter_file_path"
309
+
}
310
+
311
+
# Function to test map creation and map-of-maps
312
+
# Parameters:
313
+
# $1: bpftool path
314
+
# $2: BPF_DIR
315
+
test_map_creation_and_map_of_maps() {
316
+
local bpftool_path="$1"
317
+
local bpf_dir="$2"
318
+
local outer_map_name="outer_map_tt"
319
+
local inner_map_name="inner_map_tt"
320
+
321
+
"$bpftool_path" map create "$bpf_dir/$inner_map_name" type array key 4 \
322
+
value 4 entries 4 name "$inner_map_name"
323
+
if [ ! -f "$bpf_dir/$inner_map_name" ]; then
324
+
echo " Failed to create inner map file at $bpf_dir/$outer_map_name"
325
+
return 1
326
+
fi
327
+
328
+
"$bpftool_path" map create "$bpf_dir/$outer_map_name" type hash_of_maps \
329
+
key 4 value 4 entries 2 name "$outer_map_name" inner_map name "$inner_map_name"
330
+
if [ ! -f "$bpf_dir/$outer_map_name" ]; then
331
+
echo " Failed to create outer map file at $bpf_dir/$outer_map_name"
332
+
return 1
333
+
fi
334
+
335
+
# Add entries to the outer map by name and by pinned path.
336
+
"$bpftool_path" map update pinned "$bpf_dir/$outer_map_name" key 0 0 0 0 \
337
+
value pinned "$bpf_dir/$inner_map_name"
338
+
"$bpftool_path" map update name "$outer_map_name" key 1 0 0 0 value \
339
+
name "$inner_map_name"
340
+
341
+
# The outer map should be full by now.
342
+
# The following map update command is expected to fail.
343
+
if "$bpftool_path" map update name "$outer_map_name" key 2 0 0 0 value name \
344
+
"$inner_map_name" 2>/dev/null; then
345
+
echo " Update for $outer_map_name succeeded but should have failed"
346
+
exit 1
347
+
fi
348
+
}
349
+
350
+
# Function to test map access with the btf list command
351
+
# Parameters:
352
+
# $1: bpftool path
353
+
test_map_access_with_btf_list() {
354
+
local bpftool_path="$1"
355
+
356
+
# The btf list command iterates over maps for
357
+
# loaded BPF programs.
358
+
if ! "$bpftool_path" btf list 1>/dev/null; then
359
+
echo " Failed to access btf data"
360
+
exit 1
361
+
fi
362
+
}
363
+
364
+
set -eu
365
+
366
+
trap cleanup_skip EXIT
367
+
368
+
check_root_privileges
369
+
370
+
verify_bpftool_path "$BPFTOOL_PATH"
371
+
372
+
verify_btf_support
373
+
374
+
trap cleanup EXIT
375
+
376
+
# Load and attach the BPF programs to control maps access.
377
+
"$BPFTOOL_PATH" prog loadall "$BPF_FILE_PATH" "$BPF_DIR" autoattach
378
+
379
+
initialize_map_entries "$PROTECTED_MAP_NAME" "$BPFTOOL_PATH"
380
+
initialize_map_entries "$NOT_PROTECTED_MAP_NAME" "$BPFTOOL_PATH"
381
+
382
+
# Activate the map protection mechanism. Protection status is controlled
383
+
# by a value stored in the prot_status_map at index 0.
384
+
"$BPFTOOL_PATH" map update name prot_status_map key 0 0 0 0 value 1 0 0 0
385
+
386
+
# Test protected map (write should fail).
387
+
test_map_access "$PROTECTED_MAP_NAME" "$BPFTOOL_PATH" "$BPF_DIR" "false" \
388
+
"$BPF_ITER_FILE_PATH"
389
+
390
+
# Test not protected map (write should succeed).
391
+
test_map_access "$NOT_PROTECTED_MAP_NAME" "$BPFTOOL_PATH" "$BPF_DIR" "true" \
392
+
"$BPF_ITER_FILE_PATH"
393
+
394
+
test_map_creation_and_map_of_maps "$BPFTOOL_PATH" "$BPF_DIR"
395
+
396
+
test_map_access_with_btf_list "$BPFTOOL_PATH"
397
+
398
+
exit 0