samples: bpf: Add bpf sched pick task sample

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5KUFB
CVE: NA

--------------------------------

The sample bpf program pick_next_task_kern.o sets the online task to be
the next task to run, When there are online tasks and offline tasks on rq.
Signed-off-by: NGuan Jing <guanjing6@huawei.com>

samples/bpf/Makefile

@@ -56,6 +56,7 @@ tprogs-y += ibumad
 tprogs-y += hbm
 tprogs-y += sched_preempt
 tprogs-y += sched_select_core
+tprogs-y += sched_pick_task
 
 # Libbpf dependencies
 LIBBPF = $(TOOLS_PATH)/lib/bpf/libbpf.a
@@ -115,6 +116,7 @@ ibumad-objs := bpf_load.o ibumad_user.o $(TRACE_HELPERS)
 hbm-objs := bpf_load.o hbm.o $(CGROUP_HELPERS)
 sched_preempt-objs := sched_preempt_user.o
 sched_select_core-objs := sched_select_core_user.o
+sched_pick_task-objs := sched_pick_task_user.o
 
 # Tell kbuild to always build the programs
 always-y := $(tprogs-y)
@@ -178,6 +180,7 @@ always-y += hbm_edt_kern.o
 always-y += xdpsock_kern.o
 always-y += sched_preempt_kern.o
 always-y += sched_select_core_kern.o
+always-y += sched_pick_task_kern.o
 
 ifeq ($(ARCH), arm)
 # Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux

samples/bpf/sched_pick_task_kern.c

+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2022. Huawei Technologies Co., Ltd. All rights reserved.
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+#include <linux/version.h>
+#include <linux/sched.h>
+#include <uapi/linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/libbpf_sched.h>
+
+#define PICK_CURR 1
+#define PICK_NOMAL 0
+#define ERROR -1
+
+enum task_type {
+	TASK_TYPE_OFFLINE = -1,
+	TASK_TYPE_ONLINE,
+	TASK_TYPE_MAX
+};
+
+/*
+ * Only implements the effect of the task selection strategy
+ * and needs to be used in conjunction with preempt and
+ * load balance. If quota is not configured, the priority
+ * inversion leads to system crash.
+ */
+SEC("sched/cfs_tag_pick_next_entity")
+int BPF_PROG(sched_cfs_tag_pick_next_entity, struct sched_entity *curr, struct sched_entity *next)
+{
+	int curr_type = 0;
+	int next_type = 0;
+
+	if (curr == NULL || next == NULL)
+		return PICK_NOMAL;
+
+	curr_type = libbpf_sched_se_tag_of(curr);
+	next_type = libbpf_sched_se_tag_of(next);
+
+	if (curr_type > next_type)
+		return PICK_CURR;
+
+	return PICK_NOMAL;
+}
+
+char _license[] SEC("license") = "GPL";
+

samples/bpf/sched_pick_task_user.c

+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2022. Huawei Technologies Co., Ltd. All rights reserved.
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/resource.h>
+#include <bpf/libbpf.h>
+
+#define TRACE_DIR	"/sys/kernel/debug/tracing/"
+#define BUF_SIZE	(4096)
+
+/* read trace logs from debug fs */
+void read_trace_pipe(void)
+{
+	int trace_fd;
+
+	trace_fd = open(TRACE_DIR "trace_pipe", O_RDONLY, 0);
+	if (trace_fd < 0)
+		return;
+
+	while (1) {
+		static char buf[BUF_SIZE];
+		ssize_t sz;
+
+		sz = read(trace_fd, buf, sizeof(buf) - 1);
+		if (sz > 0) {
+			buf[sz] = 0;
+			puts(buf);
+		}
+	}
+}
+
+int main(int argc, char **argv)
+{
+	char filename[256];
+	struct bpf_object *obj;
+	struct bpf_program *prog;
+	struct bpf_link *link;
+	int err;
+
+	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+	/* Open BPF application */
+	obj = bpf_object__open_file(filename, NULL);
+	if (libbpf_get_error(obj)) {
+		fprintf(stderr, "ERROR: opening BPF object file failed\n");
+		return 1;
+	}
+
+	/* Load and verify BPF program */
+	err = bpf_object__load(obj);
+	if (err) {
+		fprintf(stderr, "ERROR: loading BPF object file failed\n");
+		goto cleanup;
+	}
+
+	prog = bpf_object__find_program_by_name(obj, "sched_cfs_tag_pick_next_entity");
+	if (libbpf_get_error(prog)) {
+		fprintf(stderr, "ERROR: finding a prog in obj file failed\n");
+		goto cleanup;
+	}
+
+	link = bpf_program__attach(prog);
+	if (libbpf_get_error(link)) {
+		fprintf(stderr, "ERROR: loading BPF object file failed\n");
+		link = NULL;
+		goto cleanup;
+	}
+
+	printf("preempt BPF started, hit Ctrl+C to stop!\n");
+
+	read_trace_pipe();
+
+cleanup:
+	bpf_link__destroy(link);
+	bpf_object__close(obj);
+out:
+	return 0;
+}