Merge google-perftools r109 (the current contents of third_party/tcmalloc/vendor)

third_party/tcmalloc/chromium/src/base/vdso_support.h

 // Copyright 2008 Google Inc. All Rights Reserved.
 // Author: ppluzhnikov@google.com (Paul Pluzhnikov)
 //
 // Allow dynamic symbol lookup in the kernel VDSO page.
 //
 // VDSO stands for "Virtual Dynamic Shared Object" -- a page of
 // executable code, which looks like a shared library, but doesn't
 // necessarily exist anywhere on disk, and which gets mmap()ed into
 // every process by kernels which support VDSO, such as 2.6.x for 32-bit
 // executables, and 2.6.24 and above for 64-bit executables.
@@ skipping 12 matching lines @@
 //     fn = reinterpret_cast<FN>(info.address);
 //  }
 
 #ifndef BASE_VDSO_SUPPORT_H_
 #define BASE_VDSO_SUPPORT_H_
 
 #include <config.h>
 #ifdef HAVE_FEATURES_H
 #include <features.h>   // for __GLIBC__
 #endif
+#include "base/basictypes.h"
 
 // Maybe one day we can rewrite this file not to require the elf
 // symbol extensions in glibc, but for right now we need them.
 #if defined(__ELF__) && defined(__GLIBC__)
 
 #define HAVE_VDSO_SUPPORT 1
 
 #include <stdlib.h>     // for NULL
 #include <link.h>  // for ElfW
-#include "base/basictypes.h"
 
 namespace base {
 
 // NOTE: this class may be used from within tcmalloc, and can not
 // use any memory allocation routines.
 class VDSOSupport {
  public:
   // Sentinel: there could never be a VDSO at this address.
   static const void *const kInvalidBase;
 
   // Information about a single vdso symbol.
   // All pointers are into .dynsym, .dynstr, or .text of the VDSO.
   // Do not free() them or modify through them.
   struct SymbolInfo {
     const char      *name;      // E.g. "__vdso_getcpu"
     const char      *version;   // E.g. "LINUX_2.6", could be ""
                                 // for unversioned symbol.
     const void      *address;   // Relocated symbol address.
     const ElfW(Sym) *symbol;    // Symbol in the dynamic symbol table.
   };
 
   // Supports iteration over all dynamic symbols.
   class SymbolIterator {
    public:
-    friend struct VDSOSupport;
+    friend class VDSOSupport;
     const SymbolInfo *operator->() const;
     const SymbolInfo &operator*() const;
     SymbolIterator& operator++();
     bool operator!=(const SymbolIterator &rhs) const;
     bool operator==(const SymbolIterator &rhs) const;
    private:
     SymbolIterator(const void *const image, int index);
     void Update(int incr);
     SymbolInfo info_;
     int index_;
@@ skipping 62 matching lines @@
 
   // image_ represents VDSO ELF image in memory.
   // image_.ehdr_ == NULL implies there is no VDSO.
   ElfMemImage image_;
 
   // Cached value of auxv AT_SYSINFO_EHDR, computed once.
   // This is a tri-state:
   //   kInvalidBase   => value hasn't been determined yet.
   //              0   => there is no VDSO.
   //           else   => vma of VDSO Elf{32,64}_Ehdr.
+  //
+  // When testing with mock VDSO, low bit is set.
+  // The low bit is always available because vdso_base_ is
+  // page-aligned.
   static const void *vdso_base_;
 
   // NOLINT on 'long' because these routines mimic kernel api.
   // The 'cache' parameter may be used by some versions of the kernel,
   // and should be NULL or point to a static buffer containing at
   // least two 'long's.
   static long InitAndGetCPU(unsigned *cpu, void *cache,     // NOLINT 'long'.
                             void *unused);
   static long GetCPUViaSyscall(unsigned *cpu, void *cache,  // NOLINT 'long'.
                                void *unused);
@@ skipping 13 matching lines @@
 // Return current CPU, using (fast) __vdso_getcpu@LINUX_2.6 if present,
 // otherwise use syscall(SYS_getcpu,...).
 // May return -1 with errno == ENOSYS if the kernel doesn't
 // support SYS_getcpu.
 int GetCPU();
 }  // namespace base
 
 #endif  // __ELF__ and __GLIBC__
 
 #endif  // BASE_VDSO_SUPPORT_H_