Detect corrupt symbol files during minidump processing. Recover from the errors and use the good data if possible.

More specifically:
 - Detect corrupt symbols during minidump processing and provide the list of modules with corrupt symbols in the ProcessState.  This will allow listing the corrupt symbol files in the final crash report.
 - Skip and recover from symbol data parse errors - don't give up until 100 parse errors are seen.
 - In order to recover from '\0' (null terminator) in the middle of a symbol file, a couple of methods have to be updated to require both buffer pointer and length.  Previously they required only a buffer pointer (char *) and the size of the buffer was evaluated using strlen which is not reliable when the data is corrupt.  Most of the changes are due to these signature updates.
 - Added and updated unittests.

Also, updated minidump_stackwalk to show a WARNING for corrupt symbols.  Output looks like this:
...
Loaded modules:
0x000da000 - 0x000dafff  Google Chrome Canary  ???  (main)
0x000e0000 - 0x0417dfff  Google Chrome Framework  0.1500.0.3  (WARNING: Corrupt symbols, Google Chrome Framework, 4682A6B4136436C4BFECEB62D498020E0)
0x044a8000 - 0x04571fff  IOBluetooth  0.1.0.0
...
Review URL: https://breakpad.appspot.com/613002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1200 4c0a9323-5329-0410-9bdc-e9ce6186880e

1 files changed, 68 insertions, 32 deletions

diff --git a/src/processor/basic_source_line_resolver.cc b/src/processor/basic_source_line_resolver.cc
index 55f8f9a1..6fb47b3b 100644
--- a/src/processor/basic_source_line_resolver.cc
+++ b/src/processor/basic_source_line_resolver.cc
@@ -60,25 +60,65 @@ namespace google_breakpad {
 #endif
 
 static const char *kWhitespace = " \r\n";
+static const int kMaxErrorsPrinted = 5;
+static const int kMaxErrorsBeforeBailing = 100;
 
 BasicSourceLineResolver::BasicSourceLineResolver() :
     SourceLineResolverBase(new BasicModuleFactory) { }
 
-bool BasicSourceLineResolver::Module::LoadMapFromMemory(char *memory_buffer) {
+// static
+void BasicSourceLineResolver::Module::LogParseError(
+   const string &message,
+   int line_number,
+   int *num_errors) {
+  if (++(*num_errors) <= kMaxErrorsPrinted) {
+    if (line_number > 0) {
+      BPLOG(ERROR) << "Line " << line_number << ": " << message;
+    } else {
+      BPLOG(ERROR) << message;
+    }
+  }
+}
+
+bool BasicSourceLineResolver::Module::LoadMapFromMemory(
+    char *memory_buffer,
+    size_t memory_buffer_size) {
   linked_ptr<Function> cur_func;
   int line_number = 0;
+  int num_errors = 0;
   char *save_ptr;
-  size_t map_buffer_length = strlen(memory_buffer);
 
   // If the length is 0, we can still pretend we have a symbol file. This is
   // for scenarios that want to test symbol lookup, but don't necessarily care
   // if certain modules do not have any information, like system libraries.
-  if (map_buffer_length == 0) {
+  if (memory_buffer_size == 0) {
     return true;
   }
 
-  if (memory_buffer[map_buffer_length - 1] == '\n') {
-    memory_buffer[map_buffer_length - 1] = '\0';
+  // Make sure the last character is null terminator.
+  size_t last_null_terminator = memory_buffer_size - 1;
+  if (memory_buffer[last_null_terminator] != '\0') {
+    memory_buffer[last_null_terminator] = '\0';
+  }
+
+  // Skip any null terminators at the end of the memory buffer, and make sure
+  // there are no other null terminators in the middle of the memory buffer.
+  bool has_null_terminator_in_the_middle = false;
+  while (last_null_terminator > 0 &&
+         memory_buffer[last_null_terminator - 1] == '\0') {
+    last_null_terminator--;
+  }
+  for (size_t i = 0; i < last_null_terminator; i++) {
+    if (memory_buffer[i] == '\0') {
+      memory_buffer[i] = '_';
+      has_null_terminator_in_the_middle = true;
+    }
+  }
+  if (has_null_terminator_in_the_middle) {
+    LogParseError(
+       "Null terminator is not expected in the middle of the symbol data",
+       line_number,
+       &num_errors);
   }
 
   char *buffer;
@@ -89,35 +129,28 @@ bool BasicSourceLineResolver::Module::LoadMapFromMemory(char *memory_buffer) {
 
     if (strncmp(buffer, "FILE ", 5) == 0) {
       if (!ParseFile(buffer)) {
-        BPLOG(ERROR) << "ParseFile on buffer failed at " <<
-            ":" << line_number;
-        return false;
+        LogParseError("ParseFile on buffer failed", line_number, &num_errors);
       }
     } else if (strncmp(buffer, "STACK ", 6) == 0) {
       if (!ParseStackInfo(buffer)) {
-        BPLOG(ERROR) << "ParseStackInfo failed at " <<
-            ":" << line_number;
-        return false;
+        LogParseError("ParseStackInfo failed", line_number, &num_errors);
       }
     } else if (strncmp(buffer, "FUNC ", 5) == 0) {
       cur_func.reset(ParseFunction(buffer));
       if (!cur_func.get()) {
-        BPLOG(ERROR) << "ParseFunction failed at " <<
-            ":" << line_number;
-        return false;
+        LogParseError("ParseFunction failed", line_number, &num_errors);
+      } else {
+        // StoreRange will fail if the function has an invalid address or size.
+        // We'll silently ignore this, the function and any corresponding lines
+        // will be destroyed when cur_func is released.
+        functions_.StoreRange(cur_func->address, cur_func->size, cur_func);
       }
-      // StoreRange will fail if the function has an invalid address or size.
-      // We'll silently ignore this, the function and any corresponding lines
-      // will be destroyed when cur_func is released.
-      functions_.StoreRange(cur_func->address, cur_func->size, cur_func);
     } else if (strncmp(buffer, "PUBLIC ", 7) == 0) {
       // Clear cur_func: public symbols don't contain line number information.
       cur_func.reset();
 
       if (!ParsePublicSymbol(buffer)) {
-        BPLOG(ERROR) << "ParsePublicSymbol failed at " <<
-            ":" << line_number;
-        return false;
+        LogParseError("ParsePublicSymbol failed", line_number, &num_errors);
       }
     } else if (strncmp(buffer, "MODULE ", 7) == 0) {
       // Ignore these.  They're not of any use to BasicSourceLineResolver,
@@ -132,21 +165,24 @@ bool BasicSourceLineResolver::Module::LoadMapFromMemory(char *memory_buffer) {
       // INFO CODE_ID <code id> <filename>
     } else {
       if (!cur_func.get()) {
-        BPLOG(ERROR) << "Found source line data without a function at " <<
-            ":" << line_number;
-        return false;
-      }
-      Line *line = ParseLine(buffer);
-      if (!line) {
-        BPLOG(ERROR) << "ParseLine failed at " << line_number << " for " <<
-            buffer;
-        return false;
+        LogParseError("Found source line data without a function",
+                       line_number, &num_errors);
+      } else {
+        Line *line = ParseLine(buffer);
+        if (!line) {
+          LogParseError("ParseLine failed", line_number, &num_errors);
+        } else {
+          cur_func->lines.StoreRange(line->address, line->size,
+                                     linked_ptr<Line>(line));
+        }
       }
-      cur_func->lines.StoreRange(line->address, line->size,
-                                 linked_ptr<Line>(line));
+    }
+    if (num_errors > kMaxErrorsBeforeBailing) {
+      break;
     }
     buffer = strtok_r(NULL, "\r\n", &save_ptr);
   }
+  is_corrupt_ = num_errors > 0;
   return true;
 }