Class: Bpfql::Runner

Inherits:
Object
  • Object
show all
Defined in:
lib/bpfql/runner.rb

Overview

TODO: REFACTOR ME!!

Instance Method Summary collapse

Constructor Details

#initialize(qobj) ⇒ Runner

Returns a new instance of Runner.



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# File 'lib/bpfql/runner.rb', line 6

def initialize(qobj)
  @query_builder = qobj
  @fmt = gen_fmt
  @start_ts = 0
end

Instance Method Details

#bpf_source ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 61

def bpf_source
  <<~SOURCE
    #include <linux/sched.h>
    #define BPFQL_ARY_MAX 64
    #define BPFQL_STR_MAX 64
    #{data_struct_source}

    BPF_PERF_OUTPUT(events);

    #{trace_func_source}
  SOURCE
end

#data_struct_source ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 74

def data_struct_source
  <<~STRUCT
    struct data_t {
      #{tracepoint_fields.map{|k| field_maps[k] + ";"}.join("\n  ")}
    };
  STRUCT
end

#field_maps ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 223

def field_maps
  {
    "pid"  => "u32 pid",
    "ts"   => "u64 ts",
    "comm" => "char comm[TASK_COMM_LEN]"
  }.merge(tracepoint_field_maps_from_format)
end

#fields_noncommon ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 195

def fields_noncommon
  tracepoint_fields - %w(pid ts comm)
end

#filter_clause ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 126

def filter_clause
  conds = []
  needle_section = ""
  qb.where.each do |filter|
    if filter[0] == "comm" # || field_maps[filter[0]] =~ /^const char \* #{filter[0]}$/
      ope = case filter[1].to_s
            when "is"; ""
            when "not"; "!"
            else
              raise "String comparation supports only == or !=; You put: #{filter}"
            end
      filter_string = %Q<"#{filter[2]}">
      needle_section = <<~NEEDLE
        bool matched   = true;
        char needle[] = #{filter_string};
        char haystack[sizeof(needle)] = {};
        bpf_probe_read(&haystack, sizeof(haystack), (void*)data.#{filter[0]});
        for (int i = 0; i < sizeof(needle) - 1; ++i) {
          if (needle[i] != haystack[i]) {
            matched = false;
          }
        }
      NEEDLE
      conds << %Q<#{ope}matched>
    else
      lhs = "data.#{filter[0]}"
      ope = case filter[1].to_s
            when "is"; "=="
            when "not"; "!="
            when "lt"; "<"
            when "gt"; ">"
            when "lteq"; "<="
            when "gteq"; ">="
            else
              raise "[BPFQL BUG] Cannot evaluate ope: #{filter}; This may be a bug"
            end
      rhs = filter[2]
    conds << [lhs, ope, rhs].join(" ")
    end
  end
  return <<~FILTER
    #{needle_section}
    if (#{conds.join("&&")}) {
  FILTER
end

#filter_end_clause ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 172

def filter_end_clause
  return "}"
end

#gen_extract_data(event) ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 46

def gen_extract_data(event)
  ret = []
  if tracepoint_fields.include?("ts")
    @start_ts = event.ts if @start_ts == 0
    time_s = ((event.ts - @start_ts).to_f) / 1000000000
    ret << time_s
  end

  tracepoint_fields_sorted.each do |f|
    next if f == 'ts'
    ret << event.send(f)
  end
  ret
end

#gen_fmt ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 31

def gen_fmt
  fmt = []
  fmt << '%-18.9f' if tracepoint_fields.include?("ts")
  fmt << '%-16s' if tracepoint_fields.include?("comm")
  fmt << '%-6d' if tracepoint_fields.include?("pid")
  fields_noncommon.each do |f|
    if field_maps[f] =~ /^char \w+\[\w+\]$/
      fmt << '%-16s'
    else
      fmt << '%-8d'
    end
  end
  fmt.join ' '
end

#run ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 12

def run
  $stderr.puts bpf_source if ENV['BPFQL_DEBUG']
  @module = RbBCC::BCC.new(text: bpf_source)
  puts(@fmt.gsub(/(\.\d+f|d)/, 's') % tracepoint_fields_sorted.map(&:upcase))

  @module["events"].open_perf_buffer do |cpu, data, size|
    event = @module["events"].event(data)
    puts(@fmt % gen_extract_data(event))
  end
  loop {
    begin
      @module.perf_buffer_poll()
    rescue Interrupt
      break
    end
  }
  puts "Exiting bpfql..."
end

#trace_func_source ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 82

def trace_func_source
  if qb.probe.tracepoint?
    src = <<~FUNCTION
      TRACEPOINT_PROBE(#{qb.probe.arg1}, #{qb.probe.arg2}) {
        struct data_t data = {};

        __ASSIGN_PID__
        __ASSIGN_TS__
        __ASSIGN_COMM__

        __ASSIGN_FIELDS__

        __FILTER__
          events.perf_submit(args, &data, sizeof(data));
        __FILTER_END__
        return 0;
      }
    FUNCTION
    src.sub!('__ASSIGN_PID__', tracepoint_fields.include?("pid") ? 'data.pid = bpf_get_current_pid_tgid();' : '')
    src.sub!('__ASSIGN_TS__', tracepoint_fields.include?("ts") ? 'data.ts = bpf_ktime_get_ns();' : '')
    src.sub!('__ASSIGN_COMM__', tracepoint_fields.include?("comm") ? 'bpf_get_current_comm(&data.comm, sizeof(data.comm));' : '')

    if fields_noncommon.empty?
      src.sub!('__ASSIGN_FIELDS__', '')
    else
      assigner = fields_noncommon.map { |field|
        "data.#{field} = args->#{field};"
      }.join("\n")
      src.sub!('__ASSIGN_FIELDS__', assigner)
    end

    if qb.where && !qb.where.empty?
      src.sub!('__FILTER__', filter_clause)
      src.sub!('__FILTER_END__', filter_end_clause)
    else
      src.sub!('__FILTER__', "")
      src.sub!('__FILTER_END__', "")
    end
    src
  else
    raise NotImplementedError, "unsupported probe: #{qb.probe.to_s}"
  end
end

#tracepoint_field_maps_from_format ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 199

def tracepoint_field_maps_from_format
  @_tfmap ||= begin
                fmt = File.read "/sys/kernel/debug/tracing/events/#{qb.probe.arg1}/#{qb.probe.arg2}/format"
                dst = {}
                fmt.each_line do |l|
                  next unless l.include?("field:")
                  next if l.include?("common_")
                  kv = l.split(";").map{|elm| elm.split(":").map(&:strip)}.reject{|e| e.size != 2 }
                  kv = Hash[kv]
                  field_name = kv['field'].split.last
                  field_type = if kv['field'] =~ /^const char \* #{field_name}$/
                                 "char #{field_name}[BPFQL_STR_MAX]"
                               elsif kv['field'] =~ /^const char \*const \* #{field_name}$/
                                 warn("not yet fully unsupported field type")
                                 "char #{field_name}[BPFQL_ARY_MAX][BPFQL_STR_MAX]"
                               else
                                 kv['field']
                               end
                  dst[field_name] = field_type
                end
                dst
              end
end

#tracepoint_fields ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 176

def tracepoint_fields
  @fields ||= begin
                if qb.select.members[0] == '*'
                  field_maps.keys
                else
                  qb.select.members
                end
              end
end

#tracepoint_fields_sorted ⇒ Object 



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# File 'lib/bpfql/runner.rb', line 186

def tracepoint_fields_sorted
  [].tap do |a|
    a << 'ts' if tracepoint_fields.include?("ts")
    a << 'comm' if tracepoint_fields.include?("comm")
    a << 'pid' if tracepoint_fields.include?("pid")
    a.concat fields_noncommon
  end
end