• Wang Nan's avatar
    perf record: Apply config to BPF objects before recording · 8690a2a7
    Wang Nan authored
    bpf__apply_obj_config() is introduced as the core API to apply object
    config options to all BPF objects. This patch also does the real work
    for setting values for BPF_MAP_TYPE_PERF_ARRAY maps by inserting value
    stored in map's private field into the BPF map.
    
    This patch is required because we are not always able to set all BPF
    config during parsing. Further patch will set events created by perf to
    BPF_MAP_TYPE_PERF_EVENT_ARRAY maps, which is not exist until
    perf_evsel__open().
    
    bpf_map_foreach_key() is introduced to iterate over each key needs to be
    configured. This function would be extended to support more map types
    and different key settings.
    
    In perf record, before start recording, call bpf__apply_config() to turn
    on all BPF config options.
    
    Test result:
    
      # cat ./test_bpf_map_1.c
      /************************ BEGIN **************************/
      #include <uapi/linux/bpf.h>
      #define SEC(NAME) __attribute__((section(NAME), used))
      struct bpf_map_def {
          unsigned int type;
          unsigned int key_size;
          unsigned int value_size;
          unsigned int max_entries;
      };
      static void *(*map_lookup_elem)(struct bpf_map_def *, void *) =
          (void *)BPF_FUNC_map_lookup_elem;
      static int (*trace_printk)(const char *fmt, int fmt_size, ...) =
          (void *)BPF_FUNC_trace_printk;
      struct bpf_map_def SEC("maps") channel = {
          .type = BPF_MAP_TYPE_ARRAY,
          .key_size = sizeof(int),
          .value_size = sizeof(int),
          .max_entries = 1,
      };
      SEC("func=sys_nanosleep")
      int func(void *ctx)
      {
          int key = 0;
          char fmt[] = "%d\n";
          int *pval = map_lookup_elem(&channel, &key);
          if (!pval)
              return 0;
          trace_printk(fmt, sizeof(fmt), *pval);
          return 0;
      }
      char _license[] SEC("license") = "GPL";
      int _version SEC("version") = LINUX_VERSION_CODE;
      /************************* END ***************************/
    
      # echo "" > /sys/kernel/debug/tracing/trace
      # ./perf record -e './test_bpf_map_1.c/map:channel.value=11/' usleep 10
      [ perf record: Woken up 1 times to write data ]
      [ perf record: Captured and wrote 0.012 MB perf.data ]
      # cat /sys/kernel/debug/tracing/trace
      # tracer: nop
      #
      # entries-in-buffer/entries-written: 1/1   #P:8
      [SNIP]
      #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
      #              | |       |   ||||       |         |
                 usleep-18593 [007] d... 2394714.395539: : 11
      # ./perf record -e './test_bpf_map_1.c/map:channel.value=101/' usleep 10
      [ perf record: Woken up 1 times to write data ]
      [ perf record: Captured and wrote 0.012 MB perf.data ]
      # cat /sys/kernel/debug/tracing/trace
      # tracer: nop
      #
      # entries-in-buffer/entries-written: 1/1   #P:8
      [SNIP]
      #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
      #              | |       |   ||||       |         |
                 usleep-18593 [007] d... 2394714.395539: : 11
                 usleep-19000 [006] d... 2394831.057840: : 101
    Signed-off-by: default avatarWang Nan <wangnan0@huawei.com>
    Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.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/1456132275-98875-6-git-send-email-wangnan0@huawei.comSigned-off-by: default avatarHe Kuang <hekuang@huawei.com>
    Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    8690a2a7
bpf-loader.c 28.9 KB