selftest/bpf: Add test for allowed trampolines count

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

#define _GNU_SOURCE

#include <sched.h>

#include <sys/prctl.h>

#include <test_progs.h>

#define MAX_TRAMP_PROGS 40

struct inst {

	struct bpf_object *obj;

	struct bpf_link   *link_fentry;

	struct bpf_link   *link_fexit;

};

static int test_task_rename(void)

{

	int fd, duration = 0, err;

	char buf[] = "test_overhead";

	fd = open("/proc/self/comm", O_WRONLY|O_TRUNC);

	if (CHECK(fd < 0, "open /proc", "err %d", errno))

		return -1;

	err = write(fd, buf, sizeof(buf));

	if (err < 0) {

		CHECK(err < 0, "task rename", "err %d", errno);

		close(fd);

		return -1;

	}

	close(fd);

	return 0;

}

static struct bpf_link *load(struct bpf_object *obj, const char *name)

{

	struct bpf_program *prog;

	int duration = 0;

	prog = bpf_object__find_program_by_title(obj, name);

	if (CHECK(!prog, "find_probe", "prog '%s' not found\n", name))

		return ERR_PTR(-EINVAL);

	return bpf_program__attach_trace(prog);

}

void test_trampoline_count(void)

{

	const char *fentry_name = "fentry/__set_task_comm";

	const char *fexit_name = "fexit/__set_task_comm";

	const char *object = "test_trampoline_count.o";

	struct inst inst[MAX_TRAMP_PROGS] = { 0 };

	int err, i = 0, duration = 0;

	struct bpf_object *obj;

	struct bpf_link *link;

	char comm[16] = {};

	/* attach 'allowed' 40 trampoline programs */

	for (i = 0; i < MAX_TRAMP_PROGS; i++) {

		obj = bpf_object__open_file(object, NULL);

		if (CHECK(IS_ERR(obj), "obj_open_file", "err %ld\n", PTR_ERR(obj)))

			goto cleanup;

		err = bpf_object__load(obj);

		if (CHECK(err, "obj_load", "err %d\n", err))

			goto cleanup;

		inst[i].obj = obj;

		if (rand() % 2) {

			link = load(obj, fentry_name);

			if (CHECK(IS_ERR(link), "attach prog", "err %ld\n", PTR_ERR(link)))

				goto cleanup;

			inst[i].link_fentry = link;

		} else {

			link = load(obj, fexit_name);

			if (CHECK(IS_ERR(link), "attach prog", "err %ld\n", PTR_ERR(link)))

				goto cleanup;

			inst[i].link_fexit = link;

		}

	}

	/* and try 1 extra.. */

	obj = bpf_object__open_file(object, NULL);

	if (CHECK(IS_ERR(obj), "obj_open_file", "err %ld\n", PTR_ERR(obj)))

		goto cleanup;

	err = bpf_object__load(obj);

	if (CHECK(err, "obj_load", "err %d\n", err))

		goto cleanup_extra;

	/* ..that needs to fail */

	link = load(obj, fentry_name);

	if (CHECK(!IS_ERR(link), "cannot attach over the limit", "err %ld\n", PTR_ERR(link))) {

		bpf_link__destroy(link);

		goto cleanup_extra;

	}

	/* with E2BIG error */

	CHECK(PTR_ERR(link) != -E2BIG, "proper error check", "err %ld\n", PTR_ERR(link));

	/* and finaly execute the probe */

	if (CHECK_FAIL(prctl(PR_GET_NAME, comm, 0L, 0L, 0L)))

		goto cleanup_extra;

	CHECK_FAIL(test_task_rename());

	CHECK_FAIL(prctl(PR_SET_NAME, comm, 0L, 0L, 0L));

cleanup_extra:

	bpf_object__close(obj);

cleanup:

	while (--i) {

		bpf_link__destroy(inst[i].link_fentry);

		bpf_link__destroy(inst[i].link_fexit);

		bpf_object__close(inst[i].obj);

	}

}

// SPDX-License-Identifier: GPL-2.0

#include <stdbool.h>

#include <stddef.h>

#include <linux/bpf.h>

#include "bpf_trace_helpers.h"

struct task_struct;

SEC("fentry/__set_task_comm")

int BPF_PROG(prog1, struct task_struct *tsk, const char *buf, bool exec)

{

	return 0;

}

SEC("fexit/__set_task_comm")

int BPF_PROG(prog2, struct task_struct *tsk, const char *buf, bool exec)

{

	return 0;

}

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