[llvm] r316775 - ELF: Add support for emitting dynamic relocations in the Android relocation packing format.

[Peter Collingbourne via llvm-commits]

Author: pcc
Date: Fri Oct 27 10:49:40 2017
New Revision: 316775

URL: http://llvm.org/viewvc/llvm-project?rev=316775&view=rev
Log:
ELF: Add support for emitting dynamic relocations in the Android relocation packing format.

The Android relocation packing format is a more compact
format for dynamic relocations in executables and DSOs
that is based on delta encoding and SLEBs. An overview
of the format can be found in the Android source code:
https://android.googlesource.com/platform/bionic/+/refs/heads/master/tools/relocation_packer/src/delta_encoder.h

This patch implements relocation packing using that format.

This implementation uses a more intelligent algorithm for compressing
relative relocations than Android's own relocation packer. As a
result it can generally create smaller relocation sections than
that packer. If I link Chromium for Android targeting ARM32 I get a
.rel.dyn of size 174693 bytes, as compared to 371832 bytes with gold
and the Android packer.

Differential Revision: https://reviews.llvm.org/D39152

Modified:
    llvm/trunk/lib/Object/ELF.cpp
    llvm/trunk/tools/llvm-readobj/ELFDumper.cpp

Modified: llvm/trunk/lib/Object/ELF.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Object/ELF.cpp?rev=316775&r1=316774&r2=316775&view=diff
==============================================================================
--- llvm/trunk/lib/Object/ELF.cpp (original)
+++ llvm/trunk/lib/Object/ELF.cpp Fri Oct 27 10:49:40 2017
@@ -201,6 +201,8 @@ StringRef llvm::object::getELFSectionTyp
     STRINGIFY_ENUM_CASE(ELF, SHT_PREINIT_ARRAY);
     STRINGIFY_ENUM_CASE(ELF, SHT_GROUP);
     STRINGIFY_ENUM_CASE(ELF, SHT_SYMTAB_SHNDX);
+    STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_REL);
+    STRINGIFY_ENUM_CASE(ELF, SHT_ANDROID_RELA);
     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_ODRTAB);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH);

Modified: llvm/trunk/tools/llvm-readobj/ELFDumper.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-readobj/ELFDumper.cpp?rev=316775&r1=316774&r2=316775&view=diff
==============================================================================
--- llvm/trunk/tools/llvm-readobj/ELFDumper.cpp (original)
+++ llvm/trunk/tools/llvm-readobj/ELFDumper.cpp Fri Oct 27 10:49:40 2017
@@ -1513,6 +1513,10 @@ static const char *getTypeString(unsigne
     }
   }
   switch (Type) {
+  LLVM_READOBJ_TYPE_CASE(ANDROID_REL);
+  LLVM_READOBJ_TYPE_CASE(ANDROID_RELSZ);
+  LLVM_READOBJ_TYPE_CASE(ANDROID_RELA);
+  LLVM_READOBJ_TYPE_CASE(ANDROID_RELASZ);
   LLVM_READOBJ_TYPE_CASE(BIND_NOW);
   LLVM_READOBJ_TYPE_CASE(DEBUG);
   LLVM_READOBJ_TYPE_CASE(FINI);
@@ -1715,6 +1719,8 @@ void ELFDumper<ELFT>::printValue(uint64_
   case DT_INIT_ARRAYSZ:
   case DT_FINI_ARRAYSZ:
   case DT_PREINIT_ARRAYSZ:
+  case DT_ANDROID_RELSZ:
+  case DT_ANDROID_RELASZ:
     OS << Value << " (bytes)";
     break;
   case DT_NEEDED: