Commit 62d2d0a3 authored by Song Liu's avatar Song Liu Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add tests for livepatch + bpf trampoline 



Both livepatch and BPF trampoline use ftrace. Special attention is needed
when livepatch and fexit program touch the same function at the same
time, because livepatch updates a kernel function and the BPF trampoline
need to call into the right version of the kernel function.

Use samples/livepatch/livepatch-sample.ko for the test.

The test covers two cases:
  1) When a fentry program is loaded first. This exercises the
     modify_ftrace_direct code path.
  2) When a fentry program is loaded first. This exercises the
     register_ftrace_direct code path.

Signed-off-by: default avatarSong Liu <song@kernel.org>
Reviewed-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20251027175023.1521602-4-song@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 3e9a18e1

tools/testing/selftests/bpf/config

+3 −0
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ CONFIG_IPV6_SIT=y 
CONFIG_IPV6_TUNNEL=y

CONFIG_KEYS=y

CONFIG_LIRC=y

CONFIG_LIVEPATCH=y

CONFIG_LWTUNNEL=y

CONFIG_MODULE_SIG=y

CONFIG_MODULE_SRCVERSION_ALL=y
@@ -111,6 +112,8 @@ CONFIG_IP6_NF_FILTER=y 
CONFIG_NF_NAT=y

CONFIG_PACKET=y

CONFIG_RC_CORE=y

CONFIG_SAMPLES=y

CONFIG_SAMPLE_LIVEPATCH=m

CONFIG_SECURITY=y

CONFIG_SECURITYFS=y

CONFIG_SYN_COOKIES=y

tools/testing/selftests/bpf/prog_tests/livepatch_trampoline.c

0 → 100644
+107 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */



#include <test_progs.h>

#include "testing_helpers.h"

#include "livepatch_trampoline.skel.h"



static int load_livepatch(void)

{

	char path[4096];



	/* CI will set KBUILD_OUTPUT */

	snprintf(path, sizeof(path), "%s/samples/livepatch/livepatch-sample.ko",

		 getenv("KBUILD_OUTPUT") ? : "../../../..");



	return load_module(path, env_verbosity > VERBOSE_NONE);

}



static void unload_livepatch(void)

{

	/* Disable the livepatch before unloading the module */

	system("echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled");



	unload_module("livepatch_sample", env_verbosity > VERBOSE_NONE);

}



static void read_proc_cmdline(void)

{

	char buf[4096];

	int fd, ret;



	fd = open("/proc/cmdline", O_RDONLY);

	if (!ASSERT_OK_FD(fd, "open /proc/cmdline"))

		return;



	ret = read(fd, buf, sizeof(buf));

	if (!ASSERT_GT(ret, 0, "read /proc/cmdline"))

		goto out;



	ASSERT_OK(strncmp(buf, "this has been live patched", 26), "strncmp");



out:

	close(fd);

}



static void __test_livepatch_trampoline(bool fexit_first)

{

	struct livepatch_trampoline *skel = NULL;

	int err;



	skel = livepatch_trampoline__open_and_load();

	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))

		goto out;



	skel->bss->my_pid = getpid();



	if (!fexit_first) {

		/* fentry program is loaded first by default */

		err = livepatch_trampoline__attach(skel);

		if (!ASSERT_OK(err, "skel_attach"))

			goto out;

	} else {

		/* Manually load fexit program first. */

		skel->links.fexit_cmdline = bpf_program__attach(skel->progs.fexit_cmdline);

		if (!ASSERT_OK_PTR(skel->links.fexit_cmdline, "attach_fexit"))

			goto out;



		skel->links.fentry_cmdline = bpf_program__attach(skel->progs.fentry_cmdline);

		if (!ASSERT_OK_PTR(skel->links.fentry_cmdline, "attach_fentry"))

			goto out;

	}



	read_proc_cmdline();



	ASSERT_EQ(skel->bss->fentry_hit, 1, "fentry_hit");

	ASSERT_EQ(skel->bss->fexit_hit, 1, "fexit_hit");

out:

	livepatch_trampoline__destroy(skel);

}



void test_livepatch_trampoline(void)

{

	int retry_cnt = 0;



retry:

	if (load_livepatch()) {

		if (retry_cnt) {

			ASSERT_OK(1, "load_livepatch");

			goto out;

		}

		/*

		 * Something else (previous run of the same test?) loaded

		 * the KLP module. Unload the KLP module and retry.

		 */

		unload_livepatch();

		retry_cnt++;

		goto retry;

	}



	if (test__start_subtest("fentry_first"))

		__test_livepatch_trampoline(false);



	if (test__start_subtest("fexit_first"))

		__test_livepatch_trampoline(true);

out:

	unload_livepatch();

}

tools/testing/selftests/bpf/progs/livepatch_trampoline.c

0 → 100644
+30 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */



#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



int fentry_hit;

int fexit_hit;

int my_pid;



SEC("fentry/cmdline_proc_show")

int BPF_PROG(fentry_cmdline)

{

	if (my_pid != (bpf_get_current_pid_tgid() >> 32))

		return 0;



	fentry_hit = 1;

	return 0;

}



SEC("fexit/cmdline_proc_show")

int BPF_PROG(fexit_cmdline)

{

	if (my_pid != (bpf_get_current_pid_tgid() >> 32))

		return 0;



	fexit_hit = 1;

	return 0;

}