Fixing a flaky Linux exploitability unittest.

src/processor/exploitability_linux.cc

Index: src/processor/exploitability_linux.cc
diff --git a/src/processor/exploitability_linux.cc b/src/processor/exploitability_linux.cc
index a196da79ab78ea204714c11c9ea5efd30cc0fa20..c520059c10b2d386ffd48ac7a42432e82eba6da5 100644
--- a/src/processor/exploitability_linux.cc
+++ b/src/processor/exploitability_linux.cc
@@ -231,21 +231,10 @@ bool ExploitabilityLinux::EndedOnIllegalWrite(uint64_t instruction_ptr) {
                    MAX_OBJDUMP_BUFFER_LEN,
                    objdump_output_buffer);
 
-  // Put buffer data into stream to output line-by-line.
-  std::stringstream objdump_stream;
-  objdump_stream.str(string(objdump_output_buffer));
   string line;
-
-  // Pipe each output line into the string until the string contains
-  // the first instruction from objdump.
-  // Loop until the line shows the first instruction or there are no lines left.
-  do {
-    if (!getline(objdump_stream, line)) {
-      BPLOG(INFO) << "Objdump instructions not found";
-      return false;
-    }
-  } while (line.find("0:") == string::npos);
-  // This first instruction contains the above substring.
+  if (!GetObjdumpInstructionLine(objdump_output_buffer, &line)) {
+    return false;
+  }
 
   // Convert objdump instruction line into the operation and operands.
   string instruction = "";
@@ -399,6 +388,33 @@ bool ExploitabilityLinux::CalculateAddress(const string &address_expression,
   return true;
 }
 
+// static
+bool ExploitabilityLinux::GetObjdumpInstructionLine(
+    const char *objdump_output_buffer,
+    string *instruction_line) {
+  // Put buffer data into stream to output line-by-line.
+  std::stringstream objdump_stream;
+  objdump_stream.str(string(objdump_output_buffer));
+
+  // Pipe each output line into the string until the string contains the first
+  // instruction from objdump.  All lines before the "<.data>:" section are
+  // skipped.  Loop until the line shows the first instruction or there are no
+  // lines left.
+  bool data_section_seen = false;
+  do {
+    if (!getline(objdump_stream, *instruction_line)) {

[Mark Mentovai, 2016/02/17 02:24:18]

std::getline

[ivanpe, 2016/02/17 06:27:41]

I'll handle this in a new CL.

+      BPLOG(INFO) << "Objdump instructions not found";
+      return false;
+    }
+    if (instruction_line->find("<.data>:") != string::npos) {
+      data_section_seen = true;
+    }

[Mark Mentovai, 2016/02/17 02:24:18]

At some point after seeing <.data>:, if you enter another section without having
fallen out of this loop, shouldn’t data_section_seen be set back to false?

[ivanpe, 2016/02/17 06:27:41]

Here, we are parsing the output of objdump.  objdump is dissasembling a buffer. 
The buffer length guarantees that there will be at least one instruction.  So
the output should contain exactly one <.data>: section followed by an
instruction line that contains '0:'.  IMO, there is no need to complicate this
function any further.

+  } while (!data_section_seen || instruction_line->find("0:") == string::npos);
+  // This first instruction contains the above substring.
+
+  return true;
+}
+
 bool ExploitabilityLinux::TokenizeObjdumpInstruction(const string &line,
                                                      string *operation,
                                                      string *dest,