Seccomp sandbox changes (performance and correctness fixes, primarily targetting x86-32)

sandbox/linux/seccomp/library.h

Index: sandbox/linux/seccomp/library.h
===================================================================
--- sandbox/linux/seccomp/library.h	(revision 39965)
+++ sandbox/linux/seccomp/library.h	(working copy)
@@ -1,3 +1,7 @@
+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
 #ifndef LIBRARY_H__
 #define LIBRARY_H__
 
@@ -30,6 +34,8 @@
 class Library {
   friend class Maps;
  public:
+  typedef Maps::string string;
+
   Library() :
       valid_(false),
       isVDSO_(false),
@@ -50,14 +56,24 @@
 
   void addMemoryRange(void* start, void* stop, Elf_Addr offset,
                       int prot, int isVDSO) {
+    isVDSO_ = isVDSO;
+    RangeMap::const_iterator iter = memory_ranges_.find(offset);
+    if (iter != memory_ranges_.end()) {
+      // It is possible to have overlapping mappings. This is particularly
+      // likely to happen with very small programs or libraries. If it does
+      // happen, we really only care about the text segment. Look for a
+      // mapping that is mapped executable.
+      if ((prot & PROT_EXEC) == 0) {
+        return;
+      }
+    }
     memory_ranges_.insert(std::make_pair(offset, Range(start, stop, prot)));
-    isVDSO_ = isVDSO;
   }
 
   char *get(Elf_Addr offset, char *buf, size_t len);
-  std::string get(Elf_Addr offset);
+  string get(Elf_Addr offset);
   char *getOriginal(Elf_Addr offset, char *buf, size_t len);
-  std::string getOriginal(Elf_Addr offset);
+  string getOriginal(Elf_Addr offset);
 
   template<class T>T* get(Elf_Addr offset, T* t) {
     if (!valid_) {
@@ -108,10 +124,8 @@
 
   bool parseElf();
   const Elf_Ehdr* getEhdr();
-  const Elf_Shdr* getSection(const std::string& section);
-  const int getSectionIndex(const std::string& section);
-  void **getRelocation(const std::string& symbol);
-  void *getSymbol(const std::string& symbol);
+  const Elf_Shdr* getSection(const string& section);
+  const int getSectionIndex(const string& section);
   void makeWritable(bool state) const;
   void patchSystemCalls();
   bool isVDSO() const { return isVDSO_; }
@@ -136,9 +150,9 @@
   };
 
   typedef std::map<Elf_Addr, Range, GreaterThan> RangeMap;
-  typedef std::map<std::string, std::pair<int, Elf_Shdr> > SectionTable;
-  typedef std::map<std::string, Elf_Sym> SymbolTable;
-  typedef std::map<std::string, Elf_Addr> PltTable;
+  typedef std::map<string, std::pair<int, Elf_Shdr> > SectionTable;
+  typedef std::map<string, Elf_Sym> SymbolTable;
+  typedef std::map<string, Elf_Addr> PltTable;
 
   char* getBytes(char* dst, const char* src, ssize_t len);
   static bool isSafeInsn(unsigned short insn);