Merge "Fix comment drift in assorted relocation packer modules."

tools/relocation_packer/src/elf_file.h

@@ -4,53 +4,16 @@
 
 // ELF shared object file updates handler.
 //
-// Provides functions to remove relative relocations from the .rel.dyn
+// Provides functions to pack relocations in the .rel.dyn or .rela.dyn
-// or .rela.dyn sections and pack into .android.rel.dyn or .android.rela.dyn,
+// sections, and unpack to return the file to its pre-packed state.
-// and unpack to return the file to its pre-packed state.
-//
-// Files to be packed or unpacked must include an existing .android.rel.dyn
-// or android.rela.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
-//   if file libchrome.<version>.so | grep -q 'ELF 32'; then
-//     arm-linux-androideabi-objcopy
-//         --add-section .android.rel.dyn=/tmp/small
-//         libchrome.<version>.so libchrome.<version>.so.packed
-//   else
-//     aarch64-linux-android-objcopy
-//         --add-section .android.rela.dyn=/tmp/small
-//         libchrome.<version>.so libchrome.<version>.so.packed
-//   fi
-//   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 or .rela.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 relative relocations
+// A packed shared object file is shorter than its non-packed original.
-// removed from .rel.dyn or .rela.dyn, and replaced as packed data in
+// Unpacking a packed file restores the file to its non-packed state.
-// .android.rel.dyn or .android.rela.dyn respectively.  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 or .android.rela.dyn,
-// combining the relative relocations with the data already in .rel.dyn
-// or .rela.dyn, and then writing back the now expanded section.
 
 #ifndef TOOLS_RELOCATION_PACKER_SRC_ELF_FILE_H_
 #define TOOLS_RELOCATION_PACKER_SRC_ELF_FILE_H_

tools/relocation_packer/src/leb128.h

@@ -4,9 +4,8 @@
 
 // LEB128 encoder and decoder for packed relative relocations.
 //
-// Run-length encoded relative relocations consist of a large number
+// Packed relocations consist of a large number of relatively small
-// of pairs of relatively small positive integer values.  Encoding these as
+// integer values.  Encoding these as LEB128 saves space.
-// LEB128 saves space.
 //
 // For more on LEB128 see http://en.wikipedia.org/wiki/LEB128.
 

tools/relocation_packer/src/main.cc

@@ -4,9 +4,6 @@
 
 // Tool to pack and unpack relative relocations in a shared library.
 //
-// Packing removes relative relocations from .rel.dyn and writes them
-// in a more compact form to .android.rel.dyn.  Unpacking does the reverse.
-//
 // Invoke with -v to trace actions taken when packing or unpacking.
 // Invoke with -p to pad removed relocations with R_*_NONE.  Suppresses
 // shrinking of .rel.dyn.

tools/relocation_packer/src/packer.h

@@ -3,43 +3,6 @@
 // found in the LICENSE file.
 
 // Pack relative relocations into a more compact form.
-//
-//
-// For relative relocations without addends (32 bit platforms)
-// -----------------------------------------------------------
-//
-// Applies two packing strategies.  The first is run-length encoding, which
-// turns a large set of relative relocations into a much smaller set
-// of delta-count pairs, prefixed with a two-word header comprising the
-// count of pairs and the initial relocation offset.  The second is LEB128
-// encoding, which compresses the result of run-length encoding.
-//
-// Once packed, data is prefixed by an identifier that allows for any later
-// versioning of packing strategies.
-//
-// A complete packed stream of relocations without addends might look
-// something like:
-//
-//   "APR1"   pairs  init_offset count1 delta1 count2 delta2 ...
-//   41505231 f2b003 b08ac716    e001   04     01     10     ...
-//
-//
-// For relative relocations with addends (64 bit platforms)
-// --------------------------------------------------------
-//
-// Applies two packing strategies.  The first is delta encoding, which
-// turns a large set of relative relocations into a smaller set
-// of offset and addend delta pairs, prefixed with a header indicating the
-// count of pairs.  The second is signed LEB128 encoding, which compacts
-// the result of delta encoding.
-//
-// Once packed, data is prefixed by an identifier that allows for any later
-// versioning of packing strategies.
-//
-// A complete packed stream might look something like:
-//
-//   "APA1"   pairs  offset_d1 addend_d1 offset_d2 addend_d2 ...
-//   41505232 f2b018 04        28        08        9f01      ...
 
 #ifndef TOOLS_RELOCATION_PACKER_SRC_PACKER_H_
 #define TOOLS_RELOCATION_PACKER_SRC_PACKER_H_

tools/relocation_packer/src/sleb128.h

@@ -4,9 +4,8 @@
 
 // SLEB128 encoder and decoder for packed relative relocations.
 //
-// Delta encoded relative relocations consist of a large number
+// Packed relocations consist of a large number of relatively small
-// of pairs signed integer values, many with small values.  Encoding these
+// integer values.  Encoding these as LEB128 saves space.
-// as signed LEB128 saves space.
 //
 // For more on LEB128 see http://en.wikipedia.org/wiki/LEB128.