• Wang Nan's avatar
    perf tools: Introduce bpf-output event · 03e0a7df
    Wang Nan authored
    Commit a43eec30 ("bpf: introduce bpf_perf_event_output() helper")
    adds a helper to enable a BPF program to output data to a perf ring
    buffer through a new type of perf event, PERF_COUNT_SW_BPF_OUTPUT. This
    patch enables perf to create events of that type. Now a perf user can
    use the following cmdline to receive output data from BPF programs:
    
      # perf record -a -e bpf-output/no-inherit,name=evt/ \
                        -e ./test_bpf_output.c/map:channel.event=evt/ ls /
      # perf script
         perf 1560 [004] 347747.086295:  evt: ffffffff811fd201 sys_write ...
         perf 1560 [004] 347747.086300:  evt: ffffffff811fd201 sys_write ...
         perf 1560 [004] 347747.086315:  evt: ffffffff811fd201 sys_write ...
                ...
    
    Test result:
    
      # cat test_bpf_output.c
      /************************ BEGIN **************************/
      #include <uapi/linux/bpf.h>
      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 (*ktime_get_ns)(void) =
     	(void *)BPF_FUNC_ktime_get_ns;
      static int (*trace_printk)(const char *fmt, int fmt_size, ...) =
     	(void *)BPF_FUNC_trace_printk;
      static int (*get_smp_processor_id)(void) =
     	(void *)BPF_FUNC_get_smp_processor_id;
      static int (*perf_event_output)(void *, struct bpf_map_def *, int, void *, unsigned long) =
     	(void *)BPF_FUNC_perf_event_output;
    
      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: %d\n";
    
     	output_data.cpuid = get_smp_processor_id();
     	output_data.ktime = ktime_get_ns();
     	int err = perf_event_output(ctx, &channel, get_smp_processor_id(),
     				    &output_data, sizeof(output_data));
     	if (err)
     		trace_printk(error_data, sizeof(error_data), err);
     	return 0;
      }
      char _license[] SEC("license") = "GPL";
      int _version SEC("version") = LINUX_VERSION_CODE;
      /************************ END ***************************/
    
      # perf record -a -e bpf-output/no-inherit,name=evt/ \
                        -e ./test_bpf_output.c/map:channel.event=evt/ ls /
      # perf script | grep ls
         ls  2242 [003] 347851.557563:   evt: ffffffff811fd201 sys_write ...
         ls  2242 [003] 347851.557571:   evt: ffffffff811fd201 sys_write ...
    Signed-off-by: default avatarWang Nan <wangnan0@huawei.com>
    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: Alexei Starovoitov <ast@kernel.org>
    Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
    Cc: Cody P Schafer <dev@codyps.com>
    Cc: He Kuang <hekuang@huawei.com>
    Cc: Jeremie Galarneau <jeremie.galarneau@efficios.com>
    Cc: Jiri Olsa <jolsa@kernel.org>
    Cc: Kirill Smelkov <kirr@nexedi.com>
    Cc: Li Zefan <lizefan@huawei.com>
    Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Zefan Li <lizefan@huawei.com>
    Cc: pi3orama@163.com
    Link: http://lkml.kernel.org/r/1456132275-98875-11-git-send-email-wangnan0@huawei.comSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    03e0a7df
parse-events.l 8.87 KB