samples/bpf: example of get selected PMU counter value

This is a simple example and shows how to use the new ability
to get the selected Hardware PMU counter value.

Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 100 insertions, 0 deletions

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4450fed91ab4..63e7d50e6a4f 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -12,6 +12,7 @@ hostprogs-y += tracex2
 hostprogs-y += tracex3
 hostprogs-y += tracex4
 hostprogs-y += tracex5
+hostprogs-y += tracex6
 hostprogs-y += lathist
 
 test_verifier-objs := test_verifier.o libbpf.o
@@ -25,6 +26,7 @@ tracex2-objs := bpf_load.o libbpf.o tracex2_user.o
 tracex3-objs := bpf_load.o libbpf.o tracex3_user.o
 tracex4-objs := bpf_load.o libbpf.o tracex4_user.o
 tracex5-objs := bpf_load.o libbpf.o tracex5_user.o
+tracex6-objs := bpf_load.o libbpf.o tracex6_user.o
 lathist-objs := bpf_load.o libbpf.o lathist_user.o
 
 # Tell kbuild to always build the programs
@@ -37,6 +39,7 @@ always += tracex2_kern.o
 always += tracex3_kern.o
 always += tracex4_kern.o
 always += tracex5_kern.o
+always += tracex6_kern.o
 always += tcbpf1_kern.o
 always += lathist_kern.o
 
@@ -51,6 +54,7 @@ HOSTLOADLIBES_tracex2 += -lelf
 HOSTLOADLIBES_tracex3 += -lelf
 HOSTLOADLIBES_tracex4 += -lelf -lrt
 HOSTLOADLIBES_tracex5 += -lelf
+HOSTLOADLIBES_tracex6 += -lelf
 HOSTLOADLIBES_lathist += -lelf
 
 # point this to your LLVM backend with bpf support
diff --git a/samples/bpf/bpf_helpers.h b/samples/bpf/bpf_helpers.h
index c77c872fe8ee..3a44d3a272af 100644
--- a/samples/bpf/bpf_helpers.h
+++ b/samples/bpf/bpf_helpers.h
@@ -31,6 +31,8 @@ static unsigned long long (*bpf_get_current_uid_gid)(void) =
         (void *) BPF_FUNC_get_current_uid_gid;
 static int (*bpf_get_current_comm)(void *buf, int buf_size) =
         (void *) BPF_FUNC_get_current_comm;
+static int (*bpf_perf_event_read)(void *map, int index) =
+        (void *) BPF_FUNC_perf_event_read;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions
diff --git a/samples/bpf/tracex6_kern.c b/samples/bpf/tracex6_kern.c
new file mode 100644
index 000000000000..23d1cffaf249
--- /dev/null
+++ b/samples/bpf/tracex6_kern.c
@@ -0,0 +1,26 @@
+#include <linux/version.h>
+#include <uapi/linux/bpf.h>
+#include "bpf_helpers.h"
+
+struct bpf_map_def SEC("maps") my_map = {
+        .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
+        .key_size = sizeof(int),
+        .value_size = sizeof(u32),
+        .max_entries = 32,
+};
+
+SEC("kprobe/sys_write")
+int bpf_prog1(struct pt_regs *ctx)
+{
+        u64 count;
+        u32 key = bpf_get_smp_processor_id();
+        char fmt[] = "CPU-%d   %llu\n";
+
+        count = bpf_perf_event_read(&my_map, key);
+        bpf_trace_printk(fmt, sizeof(fmt), key, count);
+
+        return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+u32 _version SEC("version") = LINUX_VERSION_CODE;
diff --git a/samples/bpf/tracex6_user.c b/samples/bpf/tracex6_user.c
new file mode 100644
index 000000000000..928f05eaa304
--- /dev/null
+++ b/samples/bpf/tracex6_user.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <sys/ioctl.h>
+#include <linux/perf_event.h>
+#include <linux/bpf.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+
+#define SAMPLE_PERIOD  0x7fffffffffffffffULL
+
+static void test_bpf_perf_event(void)
+{
+        int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
+        int *pmu_fd = malloc(nr_cpus * sizeof(int));
+        unsigned long value;
+        int i;
+
+        struct perf_event_attr attr_insn_pmu = {
+                .freq = 0,
+                .sample_period = SAMPLE_PERIOD,
+                .inherit = 0,
+                .type = PERF_TYPE_HARDWARE,
+                .read_format = 0,
+                .sample_type = 0,
+                .config = 0,/* PMU: cycles */
+        };
+
+        for (i = 0; i < nr_cpus; i++) {
+                pmu_fd[i] = perf_event_open(&attr_insn_pmu, -1/*pid*/, i/*cpu*/, -1/*group_fd*/, 0);
+                if (pmu_fd[i] < 0)
+                        printf("event syscall failed\n");
+
+                bpf_update_elem(map_fd[0], &i, &pmu_fd[i], BPF_ANY);
+                ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE, 0);
+        }
+
+        system("ls");
+        system("pwd");
+        system("sleep 2");
+
+        for (i = 0; i < nr_cpus; i++)
+                close(pmu_fd[i]);
+
+        close(map_fd);
+
+        free(pmu_fd);
+}
+
+int main(int argc, char **argv)
+{
+        char filename[256];
+
+        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+        if (load_bpf_file(filename)) {
+                printf("%s", bpf_log_buf);
+                return 1;
+        }
+
+        test_bpf_perf_event();
+
+        return 0;
+}