Commit 5897ca15 authored by Cheng-Yang Chou's avatar Cheng-Yang Chou Committed by Tejun Heo
Browse files

selftests/sched_ext: Add non_scx_kfunc_deny test 



Verify that the BPF verifier rejects a non-SCX struct_ops program
(tcp_congestion_ops) that attempts to call an SCX kfunc (scx_bpf_kick_cpu).
The test expects the load to fail with -EACCES from scx_kfunc_context_filter.

Signed-off-by: default avatarCheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 2d2b026c

tools/testing/selftests/sched_ext/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -175,6 +175,7 @@ auto-test-targets := \ 
	maximal				\

	maybe_null			\

	minimal				\

	non_scx_kfunc_deny		\

	numa				\

	allowed_cpus			\

	peek_dsq			\

tools/testing/selftests/sched_ext/non_scx_kfunc_deny.bpf.c

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/* SPDX-License-Identifier: GPL-2.0 */

/*

 * Verify that context-sensitive SCX kfuncs (even "unlocked" ones) are

 * restricted to only SCX struct_ops programs. Non-SCX struct_ops programs,

 * such as TCP congestion control programs, should be rejected by the BPF

 * verifier when attempting to call these kfuncs.

 *

 * Copyright (C) 2026 Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw>

 * Copyright (C) 2026 Cheng-Yang Chou <yphbchou0911@gmail.com>

 */



#include <vmlinux.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



/* SCX kfunc from scx_kfunc_ids_any set */

void scx_bpf_kick_cpu(s32 cpu, u64 flags) __ksym;



SEC("struct_ops/ssthresh")

__u32 BPF_PROG(tcp_ca_ssthresh, struct sock *sk)

{

	/*

	 * This call should be rejected by the verifier because this is a

	 * TCP congestion control program (non-SCX struct_ops).

	 */

	scx_bpf_kick_cpu(0, 0);

	return 2;

}



SEC("struct_ops/cong_avoid")

void BPF_PROG(tcp_ca_cong_avoid, struct sock *sk, __u32 ack, __u32 acked) {}



SEC("struct_ops/undo_cwnd")

__u32 BPF_PROG(tcp_ca_undo_cwnd, struct sock *sk) { return 2; }



SEC(".struct_ops")

struct tcp_congestion_ops tcp_non_scx_ca = {

	.ssthresh   = (void *)tcp_ca_ssthresh,

	.cong_avoid = (void *)tcp_ca_cong_avoid,

	.undo_cwnd  = (void *)tcp_ca_undo_cwnd,

	.name       = "tcp_kfunc_deny",

};



char _license[] SEC("license") = "GPL";

tools/testing/selftests/sched_ext/non_scx_kfunc_deny.c

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/* SPDX-License-Identifier: GPL-2.0 */

/*

 * Verify that context-sensitive SCX kfuncs (even "unlocked" ones) are

 * restricted to only SCX struct_ops programs. Non-SCX struct_ops programs,

 * such as TCP congestion control programs, should be rejected by the BPF

 * verifier when attempting to call these kfuncs.

 *

 * Copyright (C) 2026 Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw>

 * Copyright (C) 2026 Cheng-Yang Chou <yphbchou0911@gmail.com>

 */



#include <bpf/bpf.h>

#include <scx/common.h>

#include <unistd.h>

#include <errno.h>

#include <stdio.h>

#include "non_scx_kfunc_deny.bpf.skel.h"

#include "scx_test.h"



static enum scx_test_status run(void *ctx)

{

	struct non_scx_kfunc_deny *skel;

	int err;



	skel = non_scx_kfunc_deny__open();

	if (!skel) {

		SCX_ERR("Failed to open skel");

		return SCX_TEST_FAIL;

	}



	err = non_scx_kfunc_deny__load(skel);

	non_scx_kfunc_deny__destroy(skel);



	if (err == 0) {

		SCX_ERR("non-SCX BPF program loaded when it should have been rejected");

		return SCX_TEST_FAIL;

	}



	return SCX_TEST_PASS;

}



struct scx_test non_scx_kfunc_deny = {

	.name = "non_scx_kfunc_deny",

	.description = "Verify that non-SCX struct_ops programs cannot call SCX kfuncs",

	.run = run,

};

REGISTER_SCX_TEST(&non_scx_kfunc_deny)