selftests/bpf: Add stress test for maximum number of progs

Add stress test for maximum number of attached BPF programs per BPF trampoline.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-13-ast@kernel.org

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook */
+#include <test_progs.h>
+
+/* x86-64 fits 55 JITed and 43 interpreted progs into half page */
+#define CNT 40
+
+void test_fexit_stress(void)
+{
+	char test_skb[128] = {};
+	int fexit_fd[CNT] = {};
+	int link_fd[CNT] = {};
+	__u32 duration = 0;
+	char error[4096];
+	__u32 prog_ret;
+	int err, i, filter_fd;
+
+	const struct bpf_insn trace_program[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+
+	struct bpf_load_program_attr load_attr = {
+		.prog_type = BPF_PROG_TYPE_TRACING,
+		.license = "GPL",
+		.insns = trace_program,
+		.insns_cnt = sizeof(trace_program) / sizeof(struct bpf_insn),
+		.expected_attach_type = BPF_TRACE_FEXIT,
+	};
+
+	const struct bpf_insn skb_program[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+
+	struct bpf_load_program_attr skb_load_attr = {
+		.prog_type = BPF_PROG_TYPE_SOCKET_FILTER,
+		.license = "GPL",
+		.insns = skb_program,
+		.insns_cnt = sizeof(skb_program) / sizeof(struct bpf_insn),
+	};
+
+	err = libbpf_find_vmlinux_btf_id("bpf_fentry_test1",
+					 load_attr.expected_attach_type);
+	if (CHECK(err <= 0, "find_vmlinux_btf_id", "failed: %d\n", err))
+		goto out;
+	load_attr.attach_btf_id = err;
+
+	for (i = 0; i < CNT; i++) {
+		fexit_fd[i] = bpf_load_program_xattr(&load_attr, error, sizeof(error));
+		if (CHECK(fexit_fd[i] < 0, "fexit loaded",
+			  "failed: %d errno %d\n", fexit_fd[i], errno))
+			goto out;
+		link_fd[i] = bpf_raw_tracepoint_open(NULL, fexit_fd[i]);
+		if (CHECK(link_fd[i] < 0, "fexit attach failed",
+			  "prog %d failed: %d err %d\n", i, link_fd[i], errno))
+			goto out;
+	}
+
+	filter_fd = bpf_load_program_xattr(&skb_load_attr, error, sizeof(error));
+	if (CHECK(filter_fd < 0, "test_program_loaded", "failed: %d errno %d\n",
+		  filter_fd, errno))
+		goto out;
+
+	err = bpf_prog_test_run(filter_fd, 1, test_skb, sizeof(test_skb), 0,
+				0, &prog_ret, 0);
+	close(filter_fd);
+	CHECK_FAIL(err);
+out:
+	for (i = 0; i < CNT; i++) {
+		if (link_fd[i])
+			close(link_fd[i]);
+		if (fexit_fd[i])
+			close(fexit_fd[i]);
+	}
+}