Create builds configured for ARM and AARCH64.

tools/relocation_packer/src/elf_file.h

 // Copyright 2014 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.
 
 // ELF shared object file updates handler.
 //
-// Provides functions to remove R_ARM_RELATIVE relocations from the .rel.dyn
+// Provides functions to remove ARM relative relocations from the .rel.dyn
 // section and pack them in .android.rel.dyn, and unpack to return the file
 // to its pre-packed state.
 //
 // Files to be packed or unpacked must include an existing .android.rel.dyn
 // section.  A standard libchrome.<version>.so will not contain this section,
 // so the following can be used to add one:
 //
 //   echo -n 'NULL' >/tmp/small
 //   arm-linux-gnueabi-objcopy
 //       --add-section .android.rel.dyn=/tmp/small
 //       libchrome.<version>.so libchrome.<version>.so.packed
 //   rm /tmp/small
 //
 // To use, open the file and pass the file descriptor to the constructor,
 // then pack or unpack as desired.  Packing or unpacking will flush the file
 // descriptor on success.  Example:
 //
 //   int fd = open(..., O_RDWR);
 //   ElfFile elf_file(fd);
 //   bool status;
 //   if (is_packing)
 //     status = elf_file.PackRelocations();
 //   else
 //     status = elf_file.UnpackRelocations();
 //   close(fd);
 //
-// SetPadding() causes PackRelocations() to pad .rel.dyn with R_ARM_NONE
+// SetPadding() causes PackRelocations() to pad .rel.dyn with NONE-type
 // entries rather than cutting a hole out of the shared object file.  This
 // keeps all load addresses and offsets constant, and enables easier
 // debugging and testing.
 //
-// A packed shared object file has all of its R_ARM_RELATIVE relocations
+// A packed shared object file has all of its ARM relative relocations
 // removed from .rel.dyn, and replaced as packed data in .android.rel.dyn.
 // The resulting file is shorter than its non-packed original.
 //
 // Unpacking a packed file restores the file to its non-packed state, by
-// expanding the packed data in android.rel.dyn, combining the R_ARM_RELATIVE
+// expanding the packed data in android.rel.dyn, combining the ARM relative
 // relocations with the data already in .rel.dyn, and then writing back the
 // now expanded .rel.dyn section.
 
 #ifndef TOOLS_RELOCATION_PACKER_SRC_ELF_FILE_H_
 #define TOOLS_RELOCATION_PACKER_SRC_ELF_FILE_H_
 
 #include <string.h>
 
 #include "elf.h"
 #include "libelf.h"
 #include "packer.h"
 
 namespace relocation_packer {
 
-// An ElfFile reads shared objects, and shuttles R_ARM_RELATIVE relocations
+// An ElfFile reads shared objects, and shuttles ARM relative relocations

[rmcilroy, 2014/07/18 14:05:17]

Should we remove the "ARM" from here too if we are going to make this a
non-architecture specific header?

[simonb (inactive), 2014/07/21 12:15:49]

It's still only ARM, just arm32 and arm64.  I'd rather avoid giving the
impression it will all 'just work' for x86, x86_64 and so on, since it won't. 
At least not without considerable surgery.

 // between .rel.dyn and .android.rel.dyn sections.
 class ElfFile {
  public:
   explicit ElfFile(int fd) { memset(this, 0, sizeof(*this)); fd_ = fd; }
   ~ElfFile() {}
 
   // Set padding mode.  When padding, PackRelocations() will not shrink
-  // the .rel.dyn section, but instead replace R_ARM_RELATIVE with
-  // R_ARM_NONE entries.
+  // the .rel.dyn section, but instead replace ARM relative with
+  // NONE-type entries.
   // |flag| is true to pad .rel.dyn, false to shrink it.
   inline void SetPadding(bool flag) { is_padding_rel_dyn_ = flag; }
 
-  // Transfer R_ARM_RELATIVE relocations from .rel.dyn to a packed
+  // Transfer ARM relative relocations from .rel.dyn to a packed
   // representation in .android.rel.dyn.  Returns true on success.
   bool PackRelocations();
 
-  // Transfer R_ARM_RELATIVE relocations from a packed representation in
+  // Transfer ARM relative relocations from a packed representation in
   // .android.rel.dyn to .rel.dyn.  Returns true on success.
   bool UnpackRelocations();
 
  private:
   // Load a new ElfFile from a filedescriptor.  If flushing, the file must
   // be open for read/write.  Returns true on successful ELF file load.
   // |fd| is an open file descriptor for the shared object.
   bool Load();
 
   // Write ELF file changes.
@@ skipping 11 matching lines @@
 
   // Sections that we manipulate, assigned by Load().
   Elf_Scn* rel_dyn_section_;
   Elf_Scn* dynamic_section_;
   Elf_Scn* android_rel_dyn_section_;
 };
 
 }  // namespace relocation_packer
 
 #endif  // TOOLS_RELOCATION_PACKER_SRC_ELF_FILE_H_