Revert 126020 - Experiment for updating the tcmalloc chromium branch to r144 (gperftools 2.0).

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

-// Copyright (c) 2008, Google Inc.
-// All rights reserved.
+// Copyright 2008 Google Inc. All Rights Reserved.
+// Author: ppluzhnikov@google.com (Paul Pluzhnikov)
 //
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-// ---
-// Author: 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.
 //
 // More details could be found here:
 // http://www.trilithium.com/johan/2005/08/linux-gate/
 //
 // VDSOSupport -- a class representing kernel VDSO (if present).
 //
 // Example usage:
 //  VDSOSupport vdso;
 //  VDSOSupport::SymbolInfo info;
 //  typedef (*FN)(unsigned *, void *, void *);
 //  FN fn = NULL;
 //  if (vdso.LookupSymbol("__vdso_getcpu", "LINUX_2.6", STT_FUNC, &info)) {
 //     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"
-#include "base/elf_mem_image.h"
 
-#ifdef HAVE_ELF_MEM_IMAGE
+// 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
 
 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 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_;
+    const void *const image_;
+  };
+
   VDSOSupport();
 
-  typedef ElfMemImage::SymbolInfo SymbolInfo;
-  typedef ElfMemImage::SymbolIterator SymbolIterator;
-
   // Answers whether we have a vdso at all.
   bool IsPresent() const { return image_.IsPresent(); }
 
   // Allow to iterate over all VDSO symbols.
-  SymbolIterator begin() const { return image_.begin(); }
-  SymbolIterator end() const { return image_.end(); }
+  SymbolIterator begin() const;
+  SymbolIterator end() const;
 
   // Look up versioned dynamic symbol in the kernel VDSO.
   // Returns false if VDSO is not present, or doesn't contain given
   // symbol/version/type combination.
   // If info_out != NULL, additional details are filled in.
   bool LookupSymbol(const char *name, const char *version,
                     int symbol_type, SymbolInfo *info_out) const;
 
   // Find info about symbol (if any) which overlaps given address.
   // Returns true if symbol was found; false if VDSO isn't present
   // or doesn't have a symbol overlapping given address.
   // If info_out != NULL, additional details are filled in.
   bool LookupSymbolByAddress(const void *address, SymbolInfo *info_out) const;
 
   // Used only for testing. Replace real VDSO base with a mock.
   // Returns previous value of vdso_base_. After you are done testing,
   // you are expected to call SetBase() with previous value, in order to
   // reset state to the way it was.
   const void *SetBase(const void *s);
 
   // Computes vdso_base_ and returns it. Should be called as early as
   // possible; before any thread creation, chroot or setuid.
   static const void *Init();
 
  private:
+  // An in-memory ELF image (may not exist on disk).
+  class ElfMemImage {
+   public:
+    explicit ElfMemImage(const void *base);
+    void                 Init(const void *base);
+    bool                 IsPresent() const { return ehdr_ != NULL; }
+    const ElfW(Phdr)*    GetPhdr(int index) const;
+    const ElfW(Sym)*     GetDynsym(int index) const;
+    const ElfW(Versym)*  GetVersym(int index) const;
+    const ElfW(Verdef)*  GetVerdef(int index) const;
+    const ElfW(Verdaux)* GetVerdefAux(const ElfW(Verdef) *verdef) const;
+    const char*          GetDynstr(ElfW(Word) offset) const;
+    const void*          GetSymAddr(const ElfW(Sym) *sym) const;
+    const char*          GetVerstr(ElfW(Word) offset) const;
+    int                  GetNumSymbols() const;
+   private:
+    const ElfW(Ehdr) *ehdr_;
+    const ElfW(Sym) *dynsym_;
+    const ElfW(Versym) *versym_;
+    const ElfW(Verdef) *verdef_;
+    const ElfW(Word) *hash_;
+    const char *dynstr_;
+    size_t strsize_;
+    size_t verdefnum_;
+    ElfW(Addr) link_base_;     // Link-time base (p_vaddr of first PT_LOAD).
+  };
+
   // 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.
   //
@@ skipping 23 matching lines @@
 };
 
 // Same as sched_getcpu() on later glibc versions.
 // 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  // HAVE_ELF_MEM_IMAGE
+#endif  // __ELF__ and __GLIBC__
 
 #endif  // BASE_VDSO_SUPPORT_H_