selftests/bpf: Add selftests verifying bpf_trace_printk() behaviour

// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2020, Oracle and/or its affiliates. */

#include <test_progs.h>

#include "trace_printk.skel.h"

#define TRACEBUF	"/sys/kernel/debug/tracing/trace_pipe"

#define SEARCHMSG	"testing,testing"

void test_trace_printk(void)

{

	int err, iter = 0, duration = 0, found = 0;

	struct trace_printk__bss *bss;

	struct trace_printk *skel;

	char *buf = NULL;

	FILE *fp = NULL;

	size_t buflen;

	skel = trace_printk__open();

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

		return;

	err = trace_printk__load(skel);

	if (CHECK(err, "skel_load", "failed to load skeleton: %d\n", err))

		goto cleanup;

	bss = skel->bss;

	err = trace_printk__attach(skel);

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

		goto cleanup;

	fp = fopen(TRACEBUF, "r");

	if (CHECK(fp == NULL, "could not open trace buffer",

		  "error %d opening %s", errno, TRACEBUF))

		goto cleanup;

	/* We do not want to wait forever if this test fails... */

	fcntl(fileno(fp), F_SETFL, O_NONBLOCK);

	/* wait for tracepoint to trigger */

	usleep(1);

	trace_printk__detach(skel);

	if (CHECK(bss->trace_printk_ran == 0,

		  "bpf_trace_printk never ran",

		  "ran == %d", bss->trace_printk_ran))

		goto cleanup;

	if (CHECK(bss->trace_printk_ret <= 0,

		  "bpf_trace_printk returned <= 0 value",

		  "got %d", bss->trace_printk_ret))

		goto cleanup;

	/* verify our search string is in the trace buffer */

	while (getline(&buf, &buflen, fp) >= 0 || errno == EAGAIN) {

		if (strstr(buf, SEARCHMSG) != NULL)

			found++;

		if (found == bss->trace_printk_ran)

			break;

		if (++iter > 1000)

			break;

	}

	if (CHECK(!found, "message from bpf_trace_printk not found",

		  "no instance of %s in %s", SEARCHMSG, TRACEBUF))

		goto cleanup;

cleanup:

	trace_printk__destroy(skel);

	free(buf);

	if (fp)

		fclose(fp);

}

// SPDX-License-Identifier: GPL-2.0

// Copyright (c) 2020, Oracle and/or its affiliates.

#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>

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

int trace_printk_ret = 0;

int trace_printk_ran = 0;

SEC("tp/raw_syscalls/sys_enter")

int sys_enter(void *ctx)

{

	static const char fmt[] = "testing,testing %d\n";

	trace_printk_ret = bpf_trace_printk(fmt, sizeof(fmt),

					    ++trace_printk_ran);

	return 0;

}