bcc/utils: Avoid code duplication of __generate_streq_function

bcc tools like trace.py and argdist.py uses _generate_streq_function()
functions to convert char * read to bpf_probe_read/bpf_probe_read_user.
Refactor it and move the common functionality to utils.py.

Signed-off-by: Sumanth Korikkar <[email protected]>
Acked-by: Ilya Leoshkevich <[email protected]>

src/python/bcc/__init__.py

@@ -26,7 +26,7 @@
 from .libbcc import lib, bcc_symbol, bcc_symbol_option, bcc_stacktrace_build_id, _SYM_CB_TYPE
 from .table import Table, PerfEventArray
 from .perf import Perf
-from .utils import get_online_cpus, printb, _assert_is_bytes, ArgString
+from .utils import get_online_cpus, printb, _assert_is_bytes, ArgString, StrcmpRewrite
 from .version import __version__
 from .disassembler import disassemble_prog, decode_map
 

src/python/bcc/utils.py

@@ -15,6 +15,7 @@
 import sys
 import traceback
 import warnings
+import re
 
 from .libbcc import lib
 
@@ -97,3 +98,50 @@ def _assert_is_bytes(arg):
  return ArgString(arg).__bytes__()
  return arg
 
+class StrcmpRewrite(object):
+ @staticmethod
+ def _generate_streq_function(string, probe_read_func, streq_functions,
+ probeid):
+ fname = "streq_%d" % probeid
+ streq_functions += """
+static inline bool %s(char const *ignored, uintptr_t str) {
+ char needle[] = %s;
+ char haystack[sizeof(needle)];
+ %s(&haystack, sizeof(haystack), (void *)str);
+ for (int i = 0; i < sizeof(needle) - 1; ++i) {
+ if (needle[i] != haystack[i]) {
+ return false;
+ }
+ }
+ return true;
+}
+ """ % (fname, string, probe_read_func)
+ return fname, streq_functions
+
+ @staticmethod
+ def rewrite_expr(expr, bin_cmp, is_user, probe_user_list, streq_functions,
+ probeid):
+ if bin_cmp:
+ STRCMP_RE = 'STRCMP\\(\"([^"]+)\\",(.+?)\\)'
+ else:
+ STRCMP_RE = 'STRCMP\\(("[^"]+\\"),(.+?)\\)'
+ matches = re.finditer(STRCMP_RE, expr)
+ for match in matches:
+ string = match.group(1)
+ probe_read_func = "bpf_probe_read"
+ # if user probe or @user tag is specified, use
+ # bpf_probe_read_user for char* read
+ if is_user or \
+ match.group(2).strip() in probe_user_list:
+ probe_read_func = "bpf_probe_read_user"
+ fname, streq_functions = StrcmpRewrite._generate_streq_function(
+ string, probe_read_func,
+ streq_functions, probeid)
+ probeid += 1
+ expr = expr.replace("STRCMP", fname, 1)
+ rdict = {
+ "expr" : expr,
+ "streq_functions" : streq_functions,
+ "probeid" : probeid
+ }
+ return rdict