From: Jiri Olsa <jolsa@kernel.org>
Date: Thu, 23 Jan 2020 17:15:08 +0100
Subject: selftest/bpf: Add test for allowed trampolines count
Patch-mainline: v5.6-rc1
Git-commit: d633d57902a510debd4ec5b7a374a009c8c2d620
References: bsc#1177028

There's limit of 40 programs tht can be attached
to trampoline for one function. Adding test that
tries to attach that many plus one extra that needs
to fail.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200123161508.915203-4-jolsa@kernel.org
Acked-by: Gary Lin <glin@suse.com>
---
 tools/testing/selftests/bpf/prog_tests/trampoline_count.c |  112 ++++++++++++++
 tools/testing/selftests/bpf/progs/test_trampoline_count.c |   21 ++
 2 files changed, 133 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/trampoline_count.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_trampoline_count.c

--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
@@ -0,0 +1,112 @@
+// 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);
+	}
+}
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_trampoline_count.c
@@ -0,0 +1,21 @@
+// 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";