bpf/tracing: add a bpf test for new ioctl query interface

Added a subtest in test_progs. The tracepoint is
sched/sched_switch. Multiple bpf programs are attached to
this tracepoint and the query interface is exercised.
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/include/uapi/linux/perf_event.h

@@ -418,6 +418,27 @@ struct perf_event_attr {
 	__u16	__reserved_2;	/* align to __u64 */
 };
 
+/*
+ * Structure used by below PERF_EVENT_IOC_QUERY_BPF command
+ * to query bpf programs attached to the same perf tracepoint
+ * as the given perf event.
+ */
+struct perf_event_query_bpf {
+	/*
+	 * The below ids array length
+	 */
+	__u32	ids_len;
+	/*
+	 * Set by the kernel to indicate the number of
+	 * available programs
+	 */
+	__u32	prog_cnt;
+	/*
+	 * User provided buffer to store program ids
+	 */
+	__u32	ids[0];
+};
+
 #define perf_flags(attr)	(*(&(attr)->read_format + 1))
 
 /*
@@ -433,6 +454,7 @@ struct perf_event_attr {
 #define PERF_EVENT_IOC_ID		_IOR('$', 7, __u64 *)
 #define PERF_EVENT_IOC_SET_BPF		_IOW('$', 8, __u32)
 #define PERF_EVENT_IOC_PAUSE_OUTPUT	_IOW('$', 9, __u32)
+#define PERF_EVENT_IOC_QUERY_BPF	_IOWR('$', 10, struct perf_event_query_bpf *)
 
 enum perf_event_ioc_flags {
 	PERF_IOC_FLAG_GROUP		= 1U << 0,

tools/testing/selftests/bpf/Makefile

@@ -17,7 +17,7 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
 
 TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test_obj_id.o \
 	test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \
-	sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o
+	sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o test_tracepoint.o
 
 TEST_PROGS := test_kmod.sh test_xdp_redirect.sh test_xdp_meta.sh \
 	test_offload.py

tools/testing/selftests/bpf/test_progs.c

@@ -21,8 +21,10 @@ typedef __u16 __sum16;
 #include <linux/ipv6.h>
 #include <linux/tcp.h>
 #include <linux/filter.h>
+#include <linux/perf_event.h>
 #include <linux/unistd.h>
 
+#include <sys/ioctl.h>
 #include <sys/wait.h>
 #include <sys/resource.h>
 #include <sys/types.h>
@@ -617,6 +619,136 @@ static void test_obj_name(void)
 	}
 }
 
+static void test_tp_attach_query(void)
+{
+	const int num_progs = 3;
+	int i, j, bytes, efd, err, prog_fd[num_progs], pmu_fd[num_progs];
+	__u32 duration = 0, info_len, saved_prog_ids[num_progs];
+	const char *file = "./test_tracepoint.o";
+	struct perf_event_query_bpf *query;
+	struct perf_event_attr attr = {};
+	struct bpf_object *obj[num_progs];
+	struct bpf_prog_info prog_info;
+	char buf[256];
+
+	snprintf(buf, sizeof(buf),
+		 "/sys/kernel/debug/tracing/events/sched/sched_switch/id");
+	efd = open(buf, O_RDONLY, 0);
+	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
+		return;
+	bytes = read(efd, buf, sizeof(buf));
+	close(efd);
+	if (CHECK(bytes <= 0 || bytes >= sizeof(buf),
+		  "read", "bytes %d errno %d\n", bytes, errno))
+		return;
+
+	attr.config = strtol(buf, NULL, 0);
+	attr.type = PERF_TYPE_TRACEPOINT;
+	attr.sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_CALLCHAIN;
+	attr.sample_period = 1;
+	attr.wakeup_events = 1;
+
+	query = malloc(sizeof(*query) + sizeof(__u32) * num_progs);
+	for (i = 0; i < num_progs; i++) {
+		err = bpf_prog_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj[i],
+				    &prog_fd[i]);
+		if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
+			goto cleanup1;
+
+		bzero(&prog_info, sizeof(prog_info));
+		prog_info.jited_prog_len = 0;
+		prog_info.xlated_prog_len = 0;
+		prog_info.nr_map_ids = 0;
+		info_len = sizeof(prog_info);
+		err = bpf_obj_get_info_by_fd(prog_fd[i], &prog_info, &info_len);
+		if (CHECK(err, "bpf_obj_get_info_by_fd", "err %d errno %d\n",
+			  err, errno))
+			goto cleanup1;
+		saved_prog_ids[i] = prog_info.id;
+
+		pmu_fd[i] = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
+				    0 /* cpu 0 */, -1 /* group id */,
+				    0 /* flags */);
+		if (CHECK(pmu_fd[i] < 0, "perf_event_open", "err %d errno %d\n",
+			  pmu_fd[i], errno))
+			goto cleanup2;
+		err = ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE, 0);
+		if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n",
+			  err, errno))
+			goto cleanup3;
+
+		if (i == 0) {
+			/* check NULL prog array query */
+			query->ids_len = num_progs;
+			err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF, query);
+			if (CHECK(err || query->prog_cnt != 0,
+				  "perf_event_ioc_query_bpf",
+				  "err %d errno %d query->prog_cnt %u\n",
+				  err, errno, query->prog_cnt))
+				goto cleanup3;
+		}
+
+		err = ioctl(pmu_fd[i], PERF_EVENT_IOC_SET_BPF, prog_fd[i]);
+		if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n",
+			  err, errno))
+			goto cleanup3;
+
+		if (i == 1) {
+			/* try to get # of programs only */
+			query->ids_len = 0;
+			err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF, query);
+			if (CHECK(err || query->prog_cnt != 2,
+				  "perf_event_ioc_query_bpf",
+				  "err %d errno %d query->prog_cnt %u\n",
+				  err, errno, query->prog_cnt))
+				goto cleanup3;
+
+			/* try a few negative tests */
+			/* invalid query pointer */
+			err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF,
+				    (struct perf_event_query_bpf *)0x1);
+			if (CHECK(!err || errno != EFAULT,
+				  "perf_event_ioc_query_bpf",
+				  "err %d errno %d\n", err, errno))
+				goto cleanup3;
+
+			/* no enough space */
+			query->ids_len = 1;
+			err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF, query);
+			if (CHECK(!err || errno != ENOSPC || query->prog_cnt != 2,
+				  "perf_event_ioc_query_bpf",
+				  "err %d errno %d query->prog_cnt %u\n",
+				  err, errno, query->prog_cnt))
+				goto cleanup3;
+		}
+
+		query->ids_len = num_progs;
+		err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF, query);
+		if (CHECK(err || query->prog_cnt != (i + 1),
+			  "perf_event_ioc_query_bpf",
+			  "err %d errno %d query->prog_cnt %u\n",
+			  err, errno, query->prog_cnt))
+			goto cleanup3;
+		for (j = 0; j < i + 1; j++)
+			if (CHECK(saved_prog_ids[j] != query->ids[j],
+				  "perf_event_ioc_query_bpf",
+				  "#%d saved_prog_id %x query prog_id %x\n",
+				  j, saved_prog_ids[j], query->ids[j]))
+				goto cleanup3;
+	}
+
+	i = num_progs - 1;
+	for (; i >= 0; i--) {
+ cleanup3:
+		ioctl(pmu_fd[i], PERF_EVENT_IOC_DISABLE);
+ cleanup2:
+		close(pmu_fd[i]);
+ cleanup1:
+		bpf_object__close(obj[i]);
+	}
+	free(query);
+}
+
 int main(void)
 {
 	struct rlimit rinf = { RLIM_INFINITY, RLIM_INFINITY };
@@ -630,6 +762,7 @@ int main(void)
 	test_bpf_obj_id();
 	test_pkt_md_access();
 	test_obj_name();
+	test_tp_attach_query();
 
 	printf("Summary: %d PASSED, %d FAILED\n", pass_cnt, error_cnt);
 	return error_cnt ? EXIT_FAILURE : EXIT_SUCCESS;

tools/testing/selftests/bpf/test_tracepoint.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017 Facebook
+
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
+struct sched_switch_args {
+	unsigned long long pad;
+	char prev_comm[16];
+	int prev_pid;
+	int prev_prio;
+	long long prev_state;
+	char next_comm[16];
+	int next_pid;
+	int next_prio;
+};
+
+SEC("tracepoint/sched/sched_switch")
+int oncpu(struct sched_switch_args *ctx)
+{
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+__u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */