selftests/bpf: Add __ksym extern selftest

// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2019 Facebook */

#include <test_progs.h>

#include "test_ksyms.skel.h"

#include <sys/stat.h>

static int duration;

static __u64 kallsyms_find(const char *sym)

{

	char type, name[500];

	__u64 addr, res = 0;

	FILE *f;

	f = fopen("/proc/kallsyms", "r");

	if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno))

		return 0;

	while (fscanf(f, "%llx %c %499s%*[^\n]\n", &addr, &type, name) > 0) {

		if (strcmp(name, sym) == 0) {

			res = addr;

			goto out;

		}

	}

	CHECK(false, "not_found", "symbol %s not found\n", sym);

out:

	fclose(f);

	return res;

}

void test_ksyms(void)

{

	__u64 link_fops_addr = kallsyms_find("bpf_link_fops");

	const char *btf_path = "/sys/kernel/btf/vmlinux";

	struct test_ksyms *skel;

	struct test_ksyms__data *data;

	struct stat st;

	__u64 btf_size;

	int err;

	if (CHECK(stat(btf_path, &st), "stat_btf", "err %d\n", errno))

		return;

	btf_size = st.st_size;

	skel = test_ksyms__open_and_load();

	if (CHECK(!skel, "skel_open", "failed to open and load skeleton\n"))

		return;

	err = test_ksyms__attach(skel);

	if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))

		goto cleanup;

	/* trigger tracepoint */

	usleep(1);

	data = skel->data;

	CHECK(data->out__bpf_link_fops != link_fops_addr, "bpf_link_fops",

	      "got 0x%llx, exp 0x%llx\n",

	      data->out__bpf_link_fops, link_fops_addr);

	CHECK(data->out__bpf_link_fops1 != 0, "bpf_link_fops1",

	      "got %llu, exp %llu\n", data->out__bpf_link_fops1, (__u64)0);

	CHECK(data->out__btf_size != btf_size, "btf_size",

	      "got %llu, exp %llu\n", data->out__btf_size, btf_size);

	CHECK(data->out__per_cpu_start != 0, "__per_cpu_start",

	      "got %llu, exp %llu\n", data->out__per_cpu_start, (__u64)0);

cleanup:

	test_ksyms__destroy(skel);

}

// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2019 Facebook */

#include <stdbool.h>

#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>

__u64 out__bpf_link_fops = -1;

__u64 out__bpf_link_fops1 = -1;

__u64 out__btf_size = -1;

__u64 out__per_cpu_start = -1;

extern const void bpf_link_fops __ksym;

extern const void __start_BTF __ksym;

extern const void __stop_BTF __ksym;

extern const void __per_cpu_start __ksym;

/* non-existing symbol, weak, default to zero */

extern const void bpf_link_fops1 __ksym __weak;

SEC("raw_tp/sys_enter")

int handler(const void *ctx)

{

	out__bpf_link_fops = (__u64)&bpf_link_fops;

	out__btf_size = (__u64)(&__stop_BTF - &__start_BTF);

	out__per_cpu_start = (__u64)&__per_cpu_start;

	out__bpf_link_fops1 = (__u64)&bpf_link_fops1;

	return 0;

}

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