Fix tools still referencing ProcUtils (iovisor#625)

Recent USDT change removed `procstat.py`, which the `argdist` and `trace` tools are still referencing. This diff moves the only method (`which`) they are using into the `BPF` class.

Also, make `BPF.find_library` not to call `decode()` on `None`.

src/python/bcc/__init__.py

@@ -118,6 +118,35 @@ def _find_file(filename):
  raise Exception("Could not find file %s" % filename)
  return filename
 
+ @staticmethod
+ def _find_exe(cls, bin_path):
+ """
+ _find_exe(bin_path)
+
+ Traverses the PATH environment variable, looking for the first
+ directory that contains an executable file named bin_path, and
+ returns the full path to that file, or None if no such file
+ can be found. This is meant to replace invocations of the
+ "which" shell utility, which doesn't have portable semantics
+ for skipping aliases.
+ """
+ # Source: http:https://stackoverflow.com/a/377028
+ def is_exe(fpath):
+ return os.path.isfile(fpath) and \
+ os.access(fpath, os.X_OK)
+
+ fpath, fname = os.path.split(bin_path)
+ if fpath:
+ if is_exe(bin_path):
+ return bin_path
+ else:
+ for path in os.environ["PATH"].split(os.pathsep):
+ path = path.strip('"')
+ exe_file = os.path.join(path, bin_path)
+ if is_exe(exe_file):
+ return exe_file
+ return None
+
  def __init__(self, src_file="", hdr_file="", text=None, cb=None, debug=0,
  cflags=[], usdt=None):
  """Create a a new BPF module with the given source code.
@@ -487,7 +516,8 @@ def _check_path_symbol(cls, module, symname, addr):
 
  @staticmethod
  def find_library(libname):
- return lib.bcc_procutils_which_so(libname.encode("ascii")).decode()
+ res = lib.bcc_procutils_which_so(libname.encode("ascii"))
+ return res if res is None else res.decode()
 
  def attach_tracepoint(self, tp="", fn_name="", pid=-1, cpu=0, group_fd=-1):
  """attach_tracepoint(tp="", fn_name="", pid=-1, cpu=0, group_fd=-1)

tools/argdist.py

@@ -371,7 +371,7 @@ def generate_text(self):
  def _attach_u(self):
  libpath = BPF.find_library(self.library)
  if libpath is None:
- libpath = ProcUtils.which(self.library)
+ libpath = BPF._find_exe(self.library)
  if libpath is None or len(libpath) == 0:
  self._bail("unable to find library %s" % self.library)
 

tools/trace.py

@@ -9,7 +9,7 @@
 # Licensed under the Apache License, Version 2.0 (the "License")
 # Copyright (C) 2016 Sasha Goldshtein.
 
-from bcc import BPF, Tracepoint, Perf, ProcUtils, USDT
+from bcc import BPF, Tracepoint, Perf, USDT
 from time import sleep, strftime
 import argparse
 import re
@@ -416,7 +416,7 @@ def _attach_u(self, bpf):
  libpath = BPF.find_library(self.library)
  if libpath is None:
  # This might be an executable (e.g. 'bash')
- libpath = ProcUtils.which(self.library)
+ libpath = BPF._find_exe(self.library)
  if libpath is None or len(libpath) == 0:
  self._bail("unable to find library %s" % self.library)