selftests/bpf: Test for syscall program type

bpf_prog_type_syscall is a program that creates a bpf map,
updates it, and loads another bpf program using bpf_sys_bpf() helper.

Signed-off-by: Alexei Starovoitov <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

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

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <test_progs.h>
+#include "syscall.skel.h"
+
+struct args {
+	__u64 log_buf;
+	__u32 log_size;
+	int max_entries;
+	int map_fd;
+	int prog_fd;
+};
+
+void test_syscall(void)
+{
+	static char verifier_log[8192];
+	struct args ctx = {
+		.max_entries = 1024,
+		.log_buf = (uintptr_t) verifier_log,
+		.log_size = sizeof(verifier_log),
+	};
+	struct bpf_prog_test_run_attr tattr = {
+		.ctx_in = &ctx,
+		.ctx_size_in = sizeof(ctx),
+	};
+	struct syscall *skel = NULL;
+	__u64 key = 12, value = 0;
+	int err;
+
+	skel = syscall__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_load"))
+		goto cleanup;
+
+	tattr.prog_fd = bpf_program__fd(skel->progs.bpf_prog);
+	err = bpf_prog_test_run_xattr(&tattr);
+	ASSERT_EQ(err, 0, "err");
+	ASSERT_EQ(tattr.retval, 1, "retval");
+	ASSERT_GT(ctx.map_fd, 0, "ctx.map_fd");
+	ASSERT_GT(ctx.prog_fd, 0, "ctx.prog_fd");
+	ASSERT_OK(memcmp(verifier_log, "processed", sizeof("processed") - 1),
+		  "verifier_log");
+
+	err = bpf_map_lookup_elem(ctx.map_fd, &key, &value);
+	ASSERT_EQ(err, 0, "map_lookup");
+	ASSERT_EQ(value, 34, "map lookup value");
+cleanup:
+	syscall__destroy(skel);
+	if (ctx.prog_fd > 0)
+		close(ctx.prog_fd);
+	if (ctx.map_fd > 0)
+		close(ctx.map_fd);
+}

tools/testing/selftests/bpf/progs/syscall.c

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <../../../tools/include/linux/filter.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct args {
+	__u64 log_buf;
+	__u32 log_size;
+	int max_entries;
+	int map_fd;
+	int prog_fd;
+};
+
+SEC("syscall")
+int bpf_prog(struct args *ctx)
+{
+	static char license[] = "GPL";
+	static struct bpf_insn insns[] = {
+		BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+		BPF_LD_MAP_FD(BPF_REG_1, 0),
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	static union bpf_attr map_create_attr = {
+		.map_type = BPF_MAP_TYPE_HASH,
+		.key_size = 8,
+		.value_size = 8,
+	};
+	static union bpf_attr map_update_attr = { .map_fd = 1, };
+	static __u64 key = 12;
+	static __u64 value = 34;
+	static union bpf_attr prog_load_attr = {
+		.prog_type = BPF_PROG_TYPE_XDP,
+		.insn_cnt = sizeof(insns) / sizeof(insns[0]),
+	};
+	int ret;
+
+	map_create_attr.max_entries = ctx->max_entries;
+	prog_load_attr.license = (long) license;
+	prog_load_attr.insns = (long) insns;
+	prog_load_attr.log_buf = ctx->log_buf;
+	prog_load_attr.log_size = ctx->log_size;
+	prog_load_attr.log_level = 1;
+
+	ret = bpf_sys_bpf(BPF_MAP_CREATE, &map_create_attr, sizeof(map_create_attr));
+	if (ret <= 0)
+		return ret;
+	ctx->map_fd = ret;
+	insns[3].imm = ret;
+
+	map_update_attr.map_fd = ret;
+	map_update_attr.key = (long) &key;
+	map_update_attr.value = (long) &value;
+	ret = bpf_sys_bpf(BPF_MAP_UPDATE_ELEM, &map_update_attr, sizeof(map_update_attr));
+	if (ret < 0)
+		return ret;
+
+	ret = bpf_sys_bpf(BPF_PROG_LOAD, &prog_load_attr, sizeof(prog_load_attr));
+	if (ret <= 0)
+		return ret;
+	ctx->prog_fd = ret;
+	return 1;
+}