Merge pull request iovisor#163 from iovisor/bblanco_dev

Add debug flag to enable prints from kernel verifier

src/cc/libbpf.c

@@ -122,23 +122,26 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
  const char *license, unsigned kern_version,
  char *log_buf, unsigned log_buf_size)
 {
- log_buf = log_buf ? log_buf : bpf_log_buf;
- log_buf_size = log_buf_size ? log_buf_size : LOG_BUF_SIZE;
  union bpf_attr attr = {
  .prog_type = prog_type,
  .insns = ptr_to_u64((void *) insns),
  .insn_cnt = prog_len / sizeof(struct bpf_insn),
  .license = ptr_to_u64((void *) license),
  .log_buf = ptr_to_u64(log_buf),
  .log_size = log_buf_size,
- .log_level = 1,
+ .log_level = log_buf ? 1 : 0,
  };
 
  attr.kern_version = kern_version;
- log_buf[0] = 0;
+ if (log_buf)
+ log_buf[0] = 0;
 
  int ret = syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
- if (ret < 0 && log_buf == bpf_log_buf) {
+ if (ret < 0 && !log_buf) {
+ // caller did not specify log_buf but failure should be printed,
+ // so call recursively and print the result to stderr
+ bpf_prog_load(prog_type, insns, prog_len, license, kern_version,
+ bpf_log_buf, LOG_BUF_SIZE);
  fprintf(stderr, "bpf: %s\n%s\n", strerror(errno), bpf_log_buf);
  }
  return ret;

src/python/bpf/__init__.py

@@ -259,6 +259,21 @@ def _find_file(filename):
  return filename
 
  def __init__(self, src_file="", hdr_file="", text=None, debug=0):
+ """Create a a new BPF module with the given source code.
+
+ Note:
+ All fields are marked as optional, but either `src_file` or `text`
+ must be supplied, and not both.
+
+ Args:
+ src_file (Optional[str]): Path to a source file for the module
+ hdr_file (Optional[str]): Path to a helper header file for the `src_file`
+ text (Optional[str]): Contents of a source file for the module
+ debug (Optional[int]): Flags used for debug prints, can be |'d together
+ 0x1: print LLVM IR to stderr
+ 0x2: print BPF bytecode to stderr
+ """
+
  self.debug = debug
  self.funcs = {}
  self.tables = {}
@@ -284,16 +299,19 @@ def load_func(self, func_name, prog_type):
  if lib.bpf_function_start(self.module, func_name.encode("ascii")) == None:
  raise Exception("Unknown program %s" % func_name)
 
+ log_buf = ct.create_string_buffer(65536) if self.debug else None
+
  fd = lib.bpf_prog_load(prog_type,
  lib.bpf_function_start(self.module, func_name.encode("ascii")),
  lib.bpf_function_size(self.module, func_name.encode("ascii")),
  lib.bpf_module_license(self.module),
  lib.bpf_module_kern_version(self.module),
- None, 0)
+ log_buf, ct.sizeof(log_buf) if log_buf else 0)
+
+ if self.debug & 0x2:
+ print(log_buf.value.decode(), file=sys.stderr)
 
  if fd < 0:
- print((ct.c_char * 65536).in_dll(lib, "bpf_log_buf").value)
- #print(ct.c_char_p.in_dll(lib, "bpf_log_buf").value)
  raise Exception("Failed to load BPF program %s" % func_name)
 
  fn = BPF.Function(self, func_name, fd)

tests/cc/test_trace4.py

@@ -4,7 +4,6 @@
 
 from bpf import BPF
 import os
-from socket import socket, AF_INET, SOCK_DGRAM
 import sys
 from unittest import main, TestCase
 
@@ -23,18 +22,13 @@ def setUp(self):
  return 0;
  }
  """)
- self.b.attach_kprobe(event_re="^SyS_send.*", fn_name="hello",
- pid=0, cpu=-1)
- self.b.attach_kretprobe(event_re="^SyS_send.*", fn_name="goodbye",
- pid=1, cpu=-1)
+ self.b.attach_kprobe(event_re="^SyS_bp.*", fn_name="hello")
+ self.b.attach_kretprobe(event_re="^SyS_bp.*", fn_name="goodbye")
 
  def test_send1(self):
- udp = socket(AF_INET, SOCK_DGRAM)
- udp.sendto(b"a" * 10, ("127.0.0.1", 5000))
- udp.close()
  k1 = self.b["stats"].Key(1)
  k2 = self.b["stats"].Key(2)
- self.assertEqual(self.b["stats"][k1].val, self.b["stats"][k2].val)
+ self.assertEqual(self.b["stats"][k1].val, self.b["stats"][k2].val + 1)
 
 if __name__ == "__main__":
  main()