[PATCH v4 10/16] perf tools: Introduce bpf-output event

Wang Nan
2015-12-08T02:27:34Z

Commit a43eec304259a6c637f4014a6d4767159b6a3aa3 (bpf: introduce
bpf_perf_event_output() helper) add a helper to enable BPF program
output data to perf ring buffer through a new type of perf event
PERF_COUNT_SW_BPF_OUTPUT. This patch enable perf to create perf
event of that type. Now perf user can use following cmdline to
receive output data from BPF programs:

# ./perf record -a -e evt=bpf-output/no-inherit/ \
-e ./test_bpf_output.c/maps:channel.event=evt/ ls /
# ./perf script
perf 12927 [004] 355971.129276: 0 evt=bpf-output/no-inherit/: ffffffff811ed5f1 sys_write
perf 12927 [004] 355971.129279: 0 evt=bpf-output/no-inherit/: ffffffff811ed5f1 sys_write
...

Test result:
# cat ./test_bpf_output.c
/************************ BEGIN **************************/
typedef int u32;
typedef unsigned long long u64;

enum bpf_map_type {
BPF_MAP_TYPE_PERF_EVENT_ARRAY = 4,
};

struct bpf_map_def {
unsigned int type;
unsigned int key_size;
unsigned int value_size;
unsigned int max_entries;
};

#define SEC(NAME) __attribute__((section(NAME), used))
static u64 (*bpf_ktime_get_ns)(void) =
(void *)5;
static int (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) =
(void *)6;
static int (*bpf_get_smp_processor_id)(void) =
(void *)8;
static int (*bpf_perf_event_output)(void *, struct bpf_map_def *, int, void *, unsigned long) =
(void *)23;

struct bpf_map_def SEC("maps") channel = {
.type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
.key_size = sizeof(int),
.value_size = sizeof(u32),
.max_entries = __NR_CPUS__,
};

SEC("func_write=sys_write")
int func_write(void *ctx)
{
struct {
u64 ktime;
int cpuid;
} __attribute__((packed)) output_data;
char error_data[] = "Error: failed to output\n";

output_data.cpuid = bpf_get_smp_processor_id();
output_data.ktime = bpf_ktime_get_ns();
int err = bpf_perf_event_output(ctx, &channel, bpf_get_smp_processor_id(),
&output_data, sizeof(output_data));
if (err)
bpf_trace_printk(error_data, sizeof(error_data));
return 0;
}
char _license[] SEC("license") = "GPL";
int _version SEC("version") = LINUX_VERSION_CODE;
/************************ END ***************************/

# ./perf record -a -e evt=bpf-output/no-inherit/ \
-e ./test_bpf_output.c/maps:channel.event=evt/ ls /
# ./perf script | grep ls
ls 4085 [000] 2746114.230215: evt=bpf-output/no-inherit/: ffffffff811ed5f1 sys_write (/lib/modules/4.3.0-rc4+/build/vmlinux)
ls 4085 [000] 2746114.230244: evt=bpf-output/no-inherit/: ffffffff811ed5f1 sys_write (/lib/modules/4.3.0-rc4+/build/vmlinux)

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
tools/perf/util/evsel.c | 6 ++++++
tools/perf/util/parse-events.l | 1 +
2 files changed, 7 insertions(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 8e0e6f4..82ece81 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -224,6 +224,12 @@ struct perf_evsel *perf_evsel__new_idx(struct perf_event_attr *attr, int idx)
if (evsel != NULL)
perf_evsel__init(evsel, attr, idx);

+ if ((evsel->attr.type == PERF_TYPE_SOFTWARE) &&
+ (evsel->attr.config == PERF_COUNT_SW_BPF_OUTPUT)) {
+ evsel->attr.sample_type |= PERF_SAMPLE_RAW;
+ evsel->attr.sample_period = 1;
+ }
+
return evsel;
}

diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index 8bb3437..27d567f 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -249,6 +249,7 @@ cpu-migrations|migrations { return sym(yyscanner, PERF_TYPE_SOFTWARE, PERF_COU
alignment-faults { return sym(yyscanner, PERF_TYPE_SOFTWARE, PERF_COUNT_SW_ALIGNMENT_FAULTS); }
emulation-faults { return sym(yyscanner, PERF_TYPE_SOFTWARE, PERF_COUNT_SW_EMULATION_FAULTS); }
dummy { return sym(yyscanner, PERF_TYPE_SOFTWARE, PERF_COUNT_SW_DUMMY); }
+bpf-output { return sym(yyscanner, PERF_TYPE_SOFTWARE, PERF_COUNT_SW_BPF_OUTPUT); }

/*
* We have to handle the kernel PMU event cycles-ct/cycles-t/mem-loads/mem-stores separately.
--
1.8.3.4