Add support for reading ARM ELF build attributes.

Build attribute sections can now be read if they exist via ELFObjectFile, and
the llvm-readobj tool has been extended with an option to dump this information
if requested. Regression tests are also included which exercise these features.

Also update the docs with a fixed ARM ABI link and a new link to the Addenda
which provides the build attributes specification.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181009 91177308-0d34-0410-b5e6-96231b3b80d8

11 files changed, 652 insertions, 140 deletions

diff --git a/docs/CompilerWriterInfo.rst b/docs/CompilerWriterInfo.rst
index e9a7bc876a..35a283ba86 100644
--- a/docs/CompilerWriterInfo.rst
+++ b/docs/CompilerWriterInfo.rst
@@ -18,7 +18,9 @@ ARM
 
 * `ARM documentation <http://www.arm.com/documentation/>`_ (`Processor Cores <http://www.arm.com/documentation/ARMProcessor_Cores/>`_ Cores)
 
-* `ABI <http://www.arm.com/products/DevTools/ABI.html>`_
+* `ELF ABI <http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044e/IHI0044E_aaelf.pdf>`_
+
+* `Addenda to the ARM ABI <http://infocenter.arm.com/help/topic/com.arm.doc.ihi0045d/IHI0045D_ABI_addenda.pdf>`_
 
 * `ARM C Language Extensions <http://infocenter.arm.com/help/topic/com.arm.doc.ihi0053a/IHI0053A_acle.pdf>`_
 
diff --git a/include/llvm/Object/ELF.h b/include/llvm/Object/ELF.h
index eb2390ab5d..908d8b1db1 100644
--- a/include/llvm/Object/ELF.h
+++ b/include/llvm/Object/ELF.h
@@ -19,11 +19,13 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Triple.h"
+#include "llvm/Object/ELF_ARM.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ELF.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/LEB128.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
@@ -601,6 +603,7 @@ private:
   const Elf_Shdr *dot_gnu_version_sec;   // .gnu.version
   const Elf_Shdr *dot_gnu_version_r_sec; // .gnu.version_r
   const Elf_Shdr *dot_gnu_version_d_sec; // .gnu.version_d
+  const Elf_Shdr *dot_arm_attributes_sec; // .ARM.attributes
 
   // Pointer to SONAME entry in dynamic string table
   // This is set the first time getLoadName is called.
@@ -643,6 +646,11 @@ private:
   const Elf_Shdr *getRelSection(DataRefImpl Rel) const {
     return getSection(Rel.w.b);
   }
+  // Helper to read a single ARM attribute at the given pointer and return the
+  // read pointer moved forward to the next attribute location.
+  uintptr_t readARMSingleAttribute(uintptr_t ReadPtr,
+                                  ARMBuildAttrs::ARMGenericBuildAttrInfo &Attrs,
+                                  SmallVector<unsigned, 16> &TagSet) const;
 
 public:
   bool            isRelocationHasAddend(DataRefImpl Rel) const;
@@ -838,6 +846,18 @@ public:
     return v->getType() == getELFType(ELFT::TargetEndianness == support::little,
                                       ELFT::Is64Bits);
   }
+
+  /// \brief Read the ARM build attributes of this object file.
+  /// \param Attrs The attributes container to put the attribute values.
+  /// \param TagsSet A list of attribute tags that were read.
+  error_code readARMBuildAttributes(
+                                  ARMBuildAttrs::ARMGenericBuildAttrInfo &Attrs,
+                                  SmallVector<unsigned, 16> &TagsSet) const;
+
+  /// \brief Checks if an ARM build attributes section exists.
+  bool hasARMBuildAttributes() const {
+    return dot_arm_attributes_sec ? true : false;
+  }
 };
 
 // Iterate through the version definitions, and place each Elf_Verdef
@@ -2330,6 +2350,7 @@ ELFObjectFile<ELFT>::ELFObjectFile(MemoryBuffer *Object, error_code &ec)
   , dot_gnu_version_sec(0)
   , dot_gnu_version_r_sec(0)
   , dot_gnu_version_d_sec(0)
+  , dot_arm_attributes_sec(0)
   , dt_soname(0)
  {
 
@@ -2421,6 +2442,13 @@ ELFObjectFile<ELFT>::ELFObjectFile(MemoryBuffer *Object, error_code &ec)
       dot_gnu_version_r_sec = sh;
       break;
     }
+    case ELF::SHT_ARM_ATTRIBUTES: {
+      if (dot_arm_attributes_sec != NULL)
+        // FIXME: Proper error handling.
+        report_fatal_error("More than one .arm.attributes section!");
+      dot_arm_attributes_sec = sh;
+      break;
+    }
     }
     ++sh;
   }
@@ -2970,6 +2998,164 @@ static inline error_code GetELFSymbolVersion(const ObjectFile *Obj,
   llvm_unreachable("Object passed to GetELFSymbolVersion() is not ELF");
 }
 
+template<class ELFT>
+error_code ELFObjectFile<ELFT>::readARMBuildAttributes(
+                                  ARMBuildAttrs::ARMGenericBuildAttrInfo &Attrs,
+                                  SmallVector<unsigned, 16> &TagsSet) const {
+  if (getArch() != Triple::arm)
+    return object_error::invalid_file_type;
+  if (!dot_arm_attributes_sec)
+    return object_error::parse_failed;
+
+  const char *SecStart = (const char*)base() +
+                          dot_arm_attributes_sec->sh_offset;
+  const char *SecEnd = SecStart + dot_arm_attributes_sec->sh_size;
+  char format_version = *SecStart;
+  if (format_version != ARMBuildAttrs::Format_Version)
+    return object_error::parse_failed;
+
+  uintptr_t SSectionPtr = (uintptr_t)SecStart + 1;
+  uintptr_t ReadPtr = SSectionPtr;
+  // Begin reading section after format-version byte
+  while (ReadPtr < (uintptr_t)SecEnd) {
+    // Read a subsection, starting with: <section-length> "vendor-name"
+    // For now, we only care about the "aeabi" pseudo-vendor subsection.
+    uint32_t SSectionLen = *(Elf_Word*)ReadPtr;
+    ReadPtr += sizeof(uint32_t);
+    StringRef Vendor((char*)(ReadPtr));
+    ReadPtr += Vendor.size() + 1; // Vendor string + NUL byte
+
+    if (Vendor != "aeabi") {
+      SSectionPtr += SSectionLen;
+      ReadPtr = SSectionPtr;
+      continue; //skip to the next sub-section
+    }
+
+    bool FoundFileTag = false;
+    uintptr_t SSSectionPtr = ReadPtr;
+    uint32_t SSSectionLen = *(Elf_Word*)ReadPtr;
+    // Found aeabi subsection, now find the File scope tag.
+    while (ReadPtr < SSectionPtr + SSectionLen) {
+      unsigned n = 0;
+      uint64_t Tag = decodeULEB128((uint8_t*)ReadPtr, &n);
+      ReadPtr += n;
+      SSSectionLen = *(Elf_Word*)ReadPtr;
+      if (Tag == ARMBuildAttrs::File) {
+        FoundFileTag = true;
+        break;
+      }
+      // We only handle File scope attributes, skip ahead to the next
+      // sub-subsection.
+      SSSectionPtr += SSSectionLen;
+      ReadPtr = SSSectionPtr;
+    }
+
+    if (!FoundFileTag)
+      return object_error::parse_failed;
+
+    ReadPtr += sizeof(uint32_t);
+    while (ReadPtr < SSSectionPtr + SSSectionLen) {
+      // Read any number of attributes.
+      // Attributes are pairs of <uleb128, uleb128> or <uleb128, NTBS>.
+      ReadPtr = readARMSingleAttribute(ReadPtr, Attrs, TagsSet);
+    }
+    Attrs.setValid(true);
+  }
+  return object_error::success;
+}
+
+#define SWITCH_ARM_ATTR_READ_ULEB(X) case ARMBuildAttrs::X: \
+  UlebValue = decodeULEB128((uint8_t*)ReadPtr, &n); \
+  ReadPtr += n; \
+  Attrs.Tag_##X = UlebValue; \
+  TagsSet.push_back(tag); \
+  break;
+
+template<class ELFT>
+uintptr_t ELFObjectFile<ELFT>::readARMSingleAttribute(uintptr_t ReadPtr,
+                                 ARMBuildAttrs::ARMGenericBuildAttrInfo &Attrs,
+                                 SmallVector<unsigned, 16> &TagsSet) const {
+  // The ABI says that tags in the range 0-63 must be handled by tools.
+  unsigned n = 0;
+  uint64_t tagInt = decodeULEB128((uint8_t*)ReadPtr, &n);
+  ARMBuildAttrs::AttrType tag = (ARMBuildAttrs::AttrType)tagInt;
+  ReadPtr += n;
+  uint64_t UlebValue = 0;
+  StringRef StrValue;
+  switch (tag) {
+  case ARMBuildAttrs::CPU_arch: // uleb128
+    UlebValue = decodeULEB128((uint8_t*)ReadPtr, &n);
+    ReadPtr += n;
+    Attrs.Tag_CPU_arch = (ARMBuildAttrs::CPUArch)UlebValue;
+    TagsSet.push_back(tag);
+    break;
+  case ARMBuildAttrs::CPU_raw_name: // NTBS
+    StrValue = (char*)ReadPtr;
+    Attrs.Tag_CPU_raw_name = StrValue;
+    TagsSet.push_back(ARMBuildAttrs::CPU_raw_name);
+    ReadPtr += StrValue.size() + 1;
+    break;
+  case ARMBuildAttrs::CPU_name: //NTBS
+    StrValue = (char*)ReadPtr;
+    Attrs.Tag_CPU_name = StrValue;
+    TagsSet.push_back(ARMBuildAttrs::CPU_name);
+    ReadPtr += StrValue.size() + 1;
+    break;
+  case ARMBuildAttrs::CPU_arch_profile: // uleb128
+    UlebValue = decodeULEB128((uint8_t*)ReadPtr, &n);
+    ReadPtr += n;
+    Attrs.Tag_CPU_arch_profile =
+      (ARMBuildAttrs::CPUArchProfile)UlebValue;
+    TagsSet.push_back(tag);
+    break;
+  SWITCH_ARM_ATTR_READ_ULEB(ARM_ISA_use)
+  SWITCH_ARM_ATTR_READ_ULEB(THUMB_ISA_use)
+  SWITCH_ARM_ATTR_READ_ULEB(FP_arch)
+  SWITCH_ARM_ATTR_READ_ULEB(WMMX_arch)
+  SWITCH_ARM_ATTR_READ_ULEB(Advanced_SIMD_arch)
+  SWITCH_ARM_ATTR_READ_ULEB(FP_HP_extension)
+  SWITCH_ARM_ATTR_READ_ULEB(CPU_unaligned_access)
+  SWITCH_ARM_ATTR_READ_ULEB(MPextension_use)
+  SWITCH_ARM_ATTR_READ_ULEB(DIV_use)
+  SWITCH_ARM_ATTR_READ_ULEB(T2EE_use)
+  SWITCH_ARM_ATTR_READ_ULEB(Virtualization_use)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_optimization_goals)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_FP_optimization_goals)
+  SWITCH_ARM_ATTR_READ_ULEB(PCS_config)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_PCS_R9_use)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_PCS_RW_data)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_PCS_RO_data)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_PCS_GOT_use)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_PCS_wchar_t)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_enum_size)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_align8_needed)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_align8_preserved)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_FP_rounding)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_FP_denormal)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_FP_number_model)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_FP_exceptions)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_FP_user_exceptions)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_HardFP_use)
+  SWITCH_ARM_ATTR_READ_ULEB(ABI_VFP_args)
+  default:
+    // Unhandled build attribute tag, according to the spec we should be able
+    // to infer the type of the value from (tag % 2) and skip over it.
+    if (tag & 0x1) {
+      // Value should be a null terminated byte string
+      StrValue = (char*)ReadPtr;
+      ReadPtr += StrValue.size() + 1;
+    } else {
+      // Value should be a uleb128
+      UlebValue = decodeULEB128((uint8_t*)ReadPtr, &n);
+      ReadPtr += n;
+    }
+    break;
+  }
+  return ReadPtr;
+}
+#undef SWITCH_ARM_ATTR_READ_ULEB
+
+
 /// This function returns the hash value for a symbol in the .dynsym section
 /// Name of the API remains consistent as specified in the libelf
 /// REF : http://www.sco.com/developers/gabi/latest/ch5.dynamic.html#hash
diff --git a/include/llvm/Object/ELF_ARM.h b/include/llvm/Object/ELF_ARM.h
new file mode 100644
index 0000000000..d1fab2aa20
--- /dev/null
+++ b/include/llvm/Object/ELF_ARM.h
@@ -0,0 +1,339 @@
+//===-- ELF_ARM.h - ARM ELF ABI ---------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains enumerations and support routines for ARM build attributes
+// as defined in ARM ABI addenda document (ABI release 2.08).
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_OBJECT_ELF_ARM_H
+#define LLVM_OBJECT_ELF_ARM_H
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/Endian.h"
+
+namespace llvm {
+
+namespace ARMBuildAttrs {
+enum SpecialAttr {
+  // This is for the .cpu asm attr. It translates into one or more
+  // AttrType (below) entries in the .ARM.attributes section in the ELF.
+  SEL_CPU
+};
+
+enum AttrType {
+  // Rest correspond to ELF/.ARM.attributes
+  File                      = 1,
+  Section                   = 2,
+  Symbol                    = 3,
+  CPU_raw_name              = 4,
+  CPU_name                  = 5,
+  CPU_arch                  = 6,
+  CPU_arch_profile          = 7,
+  ARM_ISA_use               = 8,
+  THUMB_ISA_use             = 9,
+  FP_arch                   = 10,
+  WMMX_arch                 = 11,
+  Advanced_SIMD_arch        = 12,
+  PCS_config                = 13,
+  ABI_PCS_R9_use            = 14,
+  ABI_PCS_RW_data           = 15,
+  ABI_PCS_RO_data           = 16,
+  ABI_PCS_GOT_use           = 17,
+  ABI_PCS_wchar_t           = 18,
+  ABI_FP_rounding           = 19,
+  ABI_FP_denormal           = 20,
+  ABI_FP_exceptions         = 21,
+  ABI_FP_user_exceptions    = 22,
+  ABI_FP_number_model       = 23,
+  ABI_align8_needed         = 24,
+  ABI_align8_preserved      = 25,
+  ABI_enum_size             = 26,
+  ABI_HardFP_use            = 27,
+  ABI_VFP_args              = 28,
+  ABI_WMMX_args             = 29,
+  ABI_optimization_goals    = 30,
+  ABI_FP_optimization_goals = 31,
+  compatibility             = 32,
+  CPU_unaligned_access      = 34,
+  FP_HP_extension           = 36,
+  ABI_FP_16bit_format       = 38,
+  MPextension_use           = 42, // was 70, 2.08 ABI
+  DIV_use                   = 44,
+  nodefaults                = 64,
+  also_compatible_with      = 65,
+  T2EE_use                  = 66,
+  conformance               = 67,
+  Virtualization_use        = 68,
+  MPextension_use_old       = 70
+};
+
+// Magic numbers for .ARM.attributes
+enum AttrMagic {
+  Format_Version  = 0x41
+};
+
+// Legal Values for CPU_arch, (=6), uleb128
+enum CPUArch {
+  Pre_v4       = 0,
+  v4       = 1,   // e.g. SA110
+  v4T      = 2,   // e.g. ARM7TDMI
+  v5T      = 3,   // e.g. ARM9TDMI
+  v5TE     = 4,   // e.g. ARM946E_S
+  v5TEJ    = 5,   // e.g. ARM926EJ_S
+  v6       = 6,   // e.g. ARM1136J_S
+  v6KZ     = 7,   // e.g. ARM1176JZ_S
+  v6T2     = 8,   // e.g. ARM1156T2F_S
+  v6K      = 9,   // e.g. ARM1136J_S
+  v7       = 10,  // e.g. Cortex A8, Cortex M3
+  v6_M     = 11,  // e.g. Cortex M1
+  v6S_M    = 12,  // v6_M with the System extensions
+  v7E_M    = 13,  // v7_M with DSP extensions
+  v8
+};
+
+enum CPUArchProfile { // (=7), uleb128
+  Not_Applicable = 0, // pre v7, or cross-profile code
+  ApplicationProfile = (0x41), // 'A' (e.g. for Cortex A8)
+  RealTimeProfile = (0x52), // 'R' (e.g. for Cortex R4)
+  MicroControllerProfile = (0x4D), // 'M' (e.g. for Cortex M3)
+  SystemProfile = (0x53) // 'S' Application or real-time profile
+};
+
+// The following have a lot of common use cases
+enum {
+  //ARMISAUse (=8), uleb128  and THUMBISAUse (=9), uleb128
+  Not_Allowed = 0,
+  Allowed = 1
+};
+
+enum {
+  // FP_arch (=10), uleb128 (formerly Tag_VFP_arch = 10)
+  AllowFPv2  = 2, // v2 FP ISA permitted (implies use of the v1 FP ISA)
+  AllowFPv3A = 3, // v3 FP ISA permitted (implies use of the v2 FP ISA)
+  AllowFPv3B = 4, // v3 FP ISA permitted, but only D0-D15, S0-S31
+  AllowFPv4A = 5, // v4 FP ISA permitted (implies use of v3 FP ISA)
+  AllowFPv4B = 6, // v4 FP ISA was permitted, but only D0-D15, S0-S31
+  AllowV8FP  = 7, // ARMv8-A FP ISA permitted
+  AllowV8FPB = 8  // ARMv8-A FP ISA permitted, but only D0-D15, S0-D31
+};
+
+enum {
+  // Tag_THUMB_ISA_use, (=9), uleb128
+  AllowThumb32 = 2 // 32-bit Thumb (implies 16-bit instructions)
+};
+
+enum {
+  // Tag_WMMX_arch, (=11), uleb128
+  AllowWMMXv1 = 1,  // The user permitted this entity to use WMMX v1
+  AllowWMMXv2 = 2   // The user permitted this entity to use WMMX v2
+};
+
+enum {
+  // Tag_ABI_FP_denormal, (=20), uleb128
+  MightFlushToZero = 0, // Denormal numbers might be flushed to (+) zero
+  IEEE754Denormal = 1 , // Depends on IEEE 754 denormal numbers
+  PreserveFPSign = 2    // Sign when flushed-to-zero is preserved
+};
+
+enum {
+  // Tag_ABI_FP_number_model, (=23), uleb128
+  AllowNormal = 1, // Use IEEE 754 format normal numbers only
+  AllowRTABI = 2,  // numbers, infinities, and one quiet NaN (see [RTABI])
+  AllowIEE754 = 3  // this code to use all the IEEE 754-defined FP encodings
+};
+
+enum {
+  // Tag_ABI_FP_rounding, (=19), uleb128
+  FPRoundingNearest = 0,  // Use the IEEE 754 round to nearest rounding mode
+  FPRoundingRuntime = 1   // Choose the IEEE 754 rounding mode at run time
+};
+
+enum {
+  // Tag_DIV_use, (=44), uleb128
+  AllowDIVThumb = 0,  // Allow SDIV, UDIV on Thumb ISA, e.g. Cortex R4 or M3
+  NotAllowedDIV = 1,  // Disallow SDIV and UDIV
+  AllowDIVv7a   = 2   // Allow SDIV, UDIV on v7-a with integer div extension
+};
+
+enum {
+  // Tag_Virtualization_use, (=42), uleb128
+  TrustZone = 1,  // Use of the TrustZone extension was permitted
+  VirtExts  = 2,  // Use of virtualization extensions (HVC, ERET) permitted
+  TrustZoneVirtExts = 3  // TrustZone and virtualization extensions permitted
+};
+
+enum {
+  // Tag_PCS_config, (=13), uleb128
+  PCS_none = 0,  // No standard configuration used, or no information recorded
+  PCS_bare = 1,        // Bare platform configuration
+  PCS_linux = 2,       // Linux application configuration
+  PCS_linux_dso = 3,   // Linux DSO configuration
+  PCS_palm_2004 = 4,   // Palm OS 2004 configuration
+  PCS_palm_future = 5, // Reserved to future Palm OS configuration
+  PCS_symbian_2004 = 6,   // Symbian OS 2004 configuration
+  PCS_symbian_future = 7  // Reserved to future Symbian OS configuration
+};
+
+enum {
+  // Tag_ABI_PCS_R9_use, (=14), uleb128
+  PCS_R9_normal = 0, // R9 used as V6 (just another callee-saved register,
+                     // implied by omitting the tag)
+  PCS_R9_SB = 1,     // R9 used as SB, a global Static Base register
+  PCS_R9_TLS = 2,    // R9 used as a Thread Local Storage (TLS) pointer
+  PCS_R9_none = 3    // R9 not used at all by code associated with
+                     // the attributed entity.
+};
+
+enum {
+  // Tag_ABI_PCS_RW_data, (=15), uleb128
+  PCS_RW_data_abs = 0, // RW static data permitted to be addressed absolutely
+  PCS_RW_data_pcrel = 1, // RW static data was only permitted to be
+                         // addressed PC-relative.
+  PCS_RW_data_sbrel = 2, // RW static data was only permitted to be addressed
+                         // SB-relative.
+  PCS_RW_data_none = 3   // No permission to use RW static data
+};
+
+enum {
+  // Tag_ABI_PCS_RO_data, (=16), uleb128
+  PCS_RO_data_abs = 0,  // RO static data permitted to be addressed absolutely
+  PCS_RO_data_pcrel = 1, // RO static data was only permitted to be
+                         // addressed PC-relative.
+  PCS_RO_data_none = 2   // No permission to use RO static data
+};
+
+enum {
+  // Tag_ABI_PCS_GOT_use, (=17), uleb128
+  PCS_GOT_none = 0,   // No permission to import static data
+  PCS_GOT_direct = 1, // Permission to address imported data directly
+  PCS_GOT_indirect = 2  // The user permitted this entity to address imported
+                        // data indirectly (e.g. via a GOT)
+};
+
+enum {
+  // Tag_ABI_PCS_wchar_t, (=18), uleb128
+  PCS_wchar_t_disallowed = 0, // The user prohibited the use of wchar_t
+  PCS_wchar_t_2 = 2,          // The user intended the size of wchar_t to be 2
+  PCS_wchar_t_4 = 4           // The user intended the size of wchar_t to be 4
+};
+
+enum {
+  // Tag_ABI_enum_size, (=26), uleb128
+  PCS_enum_size = 1,  // Enum values occupy the smallest container big enough
+                      // to hold all their values.
+  PCS_enum_size_32 = 2, // The user intended Enum containers to be 32-bit
+  PCS_enum_size_abi32 = 3  // The user intended that every enumeration visible
+    // across an ABI-complying interface contains a value needing 32 bits to
+    // encode it; other enums can be containerized.
+};
+
+enum {
+  // Tag_ABI_align_needed, (=24), uleb128
+  PCS_Align_needed_disallowed = 0, //  The user did not permit code to depend
+    // the alignment of 8-byte data or data with extended (>8-byte) alignment.
+  PCS_Align_needed_8 = 1, // Code was permitted to depend on the 8-byte
+                          // alignment of 8-byte data items.
+  PCS_Align_needed_4 = 2, // Code was permitted to depend on the 4-byte
+                          // alignment of 8-byte data items.
+  PCS_Align_needed_res = 3  // Reserved
+  // OR: n (in 4..12) Code was permitted to depend on the 8-byte alignment of
+  // 8-byte data items and the alignment of data items having up to 2^n byte
+  // extended alignment.
+};
+
+enum {
+  // Tag_ABI_align_preserved, (=25), uleb128
+  PCS_Align_preserved_none = 0, // The user did not require code to preserve
+                                // 8-byte alignment of 8-byte data objects.
+  PCS_Align_preserved_8 = 1, // Code was required to preserve 8-byte alignment
+                             // of 8-byte data objects.
+  PCS_Align_preserved_8sp = 2, // Code was required to preserve 8-byte
+    // alignment of 8-byte data objects and to ensure (SP MOD 8) = 0 at all
+    // instruction boundaries (not just at function calls).
+  PCS_Align_preserved_res = 3  // Reserved
+  // OR: n (in 4..12) Code was required to preserve the alignments of case 2
+  // and the alignment of data items having up to 2^n byte extended alignment
+};
+
+enum {
+  // Tag_ABI_HardFP_use, (=27), uleb128
+  HardFPImplied = 0,   // FP use should be implied by Tag_FP_arch
+  HardFP_SP_VFP = 1,   // Use only SP FP instructions
+  HardFP_Reserved = 2,      // Reserved
+  HardFP_ImpliedDup = 3  // Deprecated duplicate of the default HardFPImplied
+};
+
+enum {
+  // Tag_ABI_VFP_args, (=28), uleb128
+  VFPArgs_base = 0,  // FP parameter/result passing using AAPCS, base variant
+  VFPArgs_VFP = 1,   // FP parameter/result passing using AAPCS, VFP variant
+  VFPArgs_toolchain = 2, // FP parameter/result passing to conform to tool
+    // chain-specific conventions
+  VFPArgs_baseVFP = 3 // FP parameter/result passing using both base and VFP
+    //variants. Did not permit non-variadic functions to pass FP params/results.
+};
+
+/// Contains build ARM aeabi attribute values.
+class ARMGenericBuildAttrInfo {
+public:
+  ARMGenericBuildAttrInfo()
+    : Valid(false) {}
+
+  CPUArch Tag_CPU_arch;
+  CPUArchProfile Tag_CPU_arch_profile;
+  std::string Tag_CPU_raw_name;
+  std::string Tag_CPU_name;
+  unsigned Tag_ARM_ISA_use;
+  unsigned Tag_THUMB_ISA_use;
+  unsigned Tag_FP_arch;
+  unsigned Tag_WMMX_arch;
+  unsigned Tag_Advanced_SIMD_arch;
+  unsigned Tag_FP_HP_extension;
+  unsigned Tag_CPU_unaligned_access;
+  unsigned Tag_MPextension_use;
+  unsigned Tag_DIV_use;
+  unsigned Tag_T2EE_use;
+  unsigned Tag_Virtualization_use;
+  unsigned Tag_ABI_optimization_goals;
+  unsigned Tag_ABI_FP_optimization_goals;
+
+  //PCS/ABI attributes
+  unsigned Tag_PCS_config;
+  unsigned Tag_ABI_PCS_R9_use;
+  unsigned Tag_ABI_PCS_RW_data;
+  unsigned Tag_ABI_PCS_RO_data;
+  unsigned Tag_ABI_PCS_GOT_use;
+  unsigned Tag_ABI_PCS_wchar_t;
+  unsigned Tag_ABI_enum_size;
+  unsigned Tag_ABI_align8_needed;
+  unsigned Tag_ABI_align8_preserved;
+
+  //FP
+  unsigned Tag_ABI_FP_rounding;
+  unsigned Tag_ABI_FP_denormal;
+  unsigned Tag_ABI_FP_number_model;
+  unsigned Tag_ABI_FP_exceptions;
+  unsigned Tag_ABI_FP_user_exceptions;
+  unsigned Tag_ABI_HardFP_use;
+  unsigned Tag_ABI_VFP_args;
+
+private:
+  bool Valid;
+
+public:
+  /// Indicates whether this instance contains valid or default values.
+  bool isValid() { return Valid; }
+  void setValid(bool v) { Valid = v; }
+};
+
+}
+} // llvm
+
+#endif // LLVM_OBJECT_ELF_ARM_H
diff --git a/lib/Target/ARM/ARMAsmPrinter.cpp b/lib/Target/ARM/ARMAsmPrinter.cpp
index 13ec208793..2d5dca5c04 100644
--- a/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -15,7 +15,6 @@
 #define DEBUG_TYPE "asm-printer"
 #include "ARMAsmPrinter.h"
 #include "ARM.h"
-#include "ARMBuildAttrs.h"
 #include "ARMConstantPoolValue.h"
 #include "ARMMachineFunctionInfo.h"
 #include "ARMTargetMachine.h"
@@ -44,6 +43,7 @@
 #include "llvm/MC/MCSectionMachO.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
+#include "llvm/Object/ELF_ARM.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ELF.h"
@@ -90,7 +90,7 @@ namespace {
         break;
       /* GAS requires .fpu to be emitted regardless of EABI attribute */
       case ARMBuildAttrs::Advanced_SIMD_arch:
-      case ARMBuildAttrs::VFP_arch:
+      case ARMBuildAttrs::FP_arch:
         Streamer.EmitRawText(StringRef("\t.fpu ") + String.lower());
         break;
       }
@@ -798,24 +798,24 @@ void ARMAsmPrinter::emitAttributes() {
 
   /* VFPv4 + .fpu */
   if (Subtarget->hasVFP4()) {
-    AttrEmitter->EmitAttribute(ARMBuildAttrs::VFP_arch,
+    AttrEmitter->EmitAttribute(ARMBuildAttrs::FP_arch,
                                ARMBuildAttrs::AllowFPv4A);
     if (emitFPU)
-      AttrEmitter->EmitTextAttribute(ARMBuildAttrs::VFP_arch, "vfpv4");
+      AttrEmitter->EmitTextAttribute(ARMBuildAttrs::FP_arch, "vfpv4");
 
   /* VFPv3 + .fpu */
   } else if (Subtarget->hasVFP3()) {
-    AttrEmitter->EmitAttribute(ARMBuildAttrs::VFP_arch,
+    AttrEmitter->EmitAttribute(ARMBuildAttrs::FP_arch,
                                ARMBuildAttrs::AllowFPv3A);
     if (emitFPU)
-      AttrEmitter->EmitTextAttribute(ARMBuildAttrs::VFP_arch, "vfpv3");
+      AttrEmitter->EmitTextAttribute(ARMBuildAttrs::FP_arch, "vfpv3");
 
   /* VFPv2 + .fpu */
   } else if (Subtarget->hasVFP2()) {
-    AttrEmitter->EmitAttribute(ARMBuildAttrs::VFP_arch,
+    AttrEmitter->EmitAttribute(ARMBuildAttrs::FP_arch,
                                ARMBuildAttrs::AllowFPv2);
     if (emitFPU)
-      AttrEmitter->EmitTextAttribute(ARMBuildAttrs::VFP_arch, "vfpv2");
+      AttrEmitter->EmitTextAttribute(ARMBuildAttrs::FP_arch, "vfpv2");
   }
 
   /* TODO: ARMBuildAttrs::Allowed is not completely accurate,
diff --git a/lib/Target/ARM/ARMBuildAttrs.h b/lib/Target/ARM/ARMBuildAttrs.h
deleted file mode 100644
index 11bd6a4a8d..0000000000
--- a/lib/Target/ARM/ARMBuildAttrs.h
+++ /dev/null
@@ -1,131 +0,0 @@
-//===-- ARMBuildAttrs.h - ARM Build Attributes ------------------*- C++ -*-===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file contains enumerations and support routines for ARM build attributes
-// as defined in ARM ABI addenda document (ABI release 2.08).
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef __TARGET_ARMBUILDATTRS_H__
-#define __TARGET_ARMBUILDATTRS_H__
-
-namespace ARMBuildAttrs {
-  enum SpecialAttr {
-    // This is for the .cpu asm attr. It translates into one or more
-    // AttrType (below) entries in the .ARM.attributes section in the ELF.
-    SEL_CPU 
-  };
-
-  enum AttrType {
-    // Rest correspond to ELF/.ARM.attributes
-    File                      = 1,
-    Section                   = 2,
-    Symbol                    = 3,
-    CPU_raw_name              = 4,
-    CPU_name                  = 5,
-    CPU_arch                  = 6,
-    CPU_arch_profile          = 7,
-    ARM_ISA_use               = 8,
-    THUMB_ISA_use             = 9,
-    VFP_arch                  = 10,
-    WMMX_arch                 = 11,
-    Advanced_SIMD_arch        = 12,
-    PCS_config                = 13,
-    ABI_PCS_R9_use            = 14,
-    ABI_PCS_RW_data           = 15,
-    ABI_PCS_RO_data           = 16,
-    ABI_PCS_GOT_use           = 17,
-    ABI_PCS_wchar_t           = 18,
-    ABI_FP_rounding           = 19,
-    ABI_FP_denormal           = 20,
-    ABI_FP_exceptions         = 21,
-    ABI_FP_user_exceptions    = 22,
-    ABI_FP_number_model       = 23,
-    ABI_align8_needed         = 24,
-    ABI_align8_preserved      = 25,
-    ABI_enum_size             = 26,
-    ABI_HardFP_use            = 27,
-    ABI_VFP_args              = 28,
-    ABI_WMMX_args             = 29,
-    ABI_optimization_goals    = 30,
-    ABI_FP_optimization_goals = 31,
-    compatibility             = 32,
-    CPU_unaligned_access      = 34,
-    VFP_HP_extension          = 36,
-    ABI_FP_16bit_format       = 38,
-    MPextension_use           = 42, // was 70, 2.08 ABI
-    DIV_use                   = 44,
-    nodefaults                = 64,
-    also_compatible_with      = 65,
-    T2EE_use                  = 66,
-    conformance               = 67,
-    Virtualization_use        = 68,
-    MPextension_use_old       = 70
-  };
-
-  // Magic numbers for .ARM.attributes
-  enum AttrMagic {
-    Format_Version  = 0x41
-  };
-
-  // Legal Values for CPU_arch, (=6), uleb128
-  enum CPUArch {
-    Pre_v4       = 0,
-    v4       = 1,   // e.g. SA110
-    v4T      = 2,   // e.g. ARM7TDMI
-    v5T      = 3,   // e.g. ARM9TDMI
-    v5TE     = 4,   // e.g. ARM946E_S
-    v5TEJ    = 5,   // e.g. ARM926EJ_S
-    v6       = 6,   // e.g. ARM1136J_S
-    v6KZ     = 7,   // e.g. ARM1176JZ_S
-    v6T2     = 8,   // e.g. ARM1156T2F_S
-    v6K      = 9,   // e.g. ARM1136J_S
-    v7       = 10,  // e.g. Cortex A8, Cortex M3
-    v6_M     = 11,  // e.g. Cortex M1
-    v6S_M    = 12,  // v6_M with the System extensions
-    v7E_M    = 13   // v7_M with DSP extensions
-  };
-
-  enum CPUArchProfile { // (=7), uleb128 
-    Not_Applicable = 0, // pre v7, or cross-profile code
-    ApplicationProfile = (0x41), // 'A' (e.g. for Cortex A8)
-    RealTimeProfile = (0x52), // 'R' (e.g. for Cortex R4)
-    MicroControllerProfile = (0x4D), // 'M' (e.g. for Cortex M3)
-    SystemProfile = (0x53) // 'S' Application or real-time profile
-  };
-
-  // The following have a lot of common use cases
-  enum { 
-    //ARMISAUse (=8), uleb128  and THUMBISAUse (=9), uleb128
-    Not_Allowed = 0,
-    Allowed = 1,
-
-    // FP_arch (=10), uleb128 (formerly Tag_VFP_arch = 10)
-    AllowFPv2  = 2, // v2 FP ISA permitted (implies use of the v1 FP ISA)
-    AllowFPv3A = 3, // v3 FP ISA permitted (implies use of the v2 FP ISA)
-    AllowFPv3B = 4, // v3 FP ISA permitted, but only D0-D15, S0-S31 
-    AllowFPv4A = 5, // v4 FP ISA permitted (implies use of v3 FP ISA) 
-    AllowFPv4B = 6, // v4 FP ISA was permitted, but only D0-D15, S0-S31
-
-    // Tag_WMMX_arch, (=11), uleb128
-    AllowThumb32 = 2, // 32-bit Thumb (implies 16-bit instructions)
-    
-    // Tag_WMMX_arch, (=11), uleb128
-    AllowWMMXv1 = 2,  // The user permitted this entity to use WMMX v2
-
-    // Tag_ABI_FP_denormal, (=20), uleb128 
-    PreserveFPSign = 2, // sign when flushed-to-zero is preserved
-
-    // Tag_ABI_FP_number_model, (=23), uleb128
-    AllowRTABI = 2,  // numbers, infinities, and one quiet NaN (see [RTABI])
-    AllowIEE754 = 3 // this code to use all the IEEE 754-defined FP encodings
-  };
-}
-
-#endif // __TARGET_ARMBUILDATTRS_H__
diff --git a/test/Object/Inputs/arm-attributes.elf-arm b/test/Object/Inputs/arm-attributes.elf-arm
new file mode 100644
index 0000000000..69855d6ea0
--- /dev/null
+++ b/test/Object/Inputs/arm-attributes.elf-arm
diff --git a/test/Object/Inputs/trivial-object-test.elf-arm b/test/Object/Inputs/trivial-object-test.elf-arm
new file mode 100644
index 0000000000..adfe96ca6a
--- /dev/null
+++ b/test/Object/Inputs/trivial-object-test.elf-arm
diff --git a/test/Object/readobj-elf-arm-buildattrs.test b/test/Object/readobj-elf-arm-buildattrs.test
new file mode 100644
index 0000000000..e84570d72a
--- /dev/null
+++ b/test/Object/readobj-elf-arm-buildattrs.test
@@ -0,0 +1,46 @@
+RUN: llvm-readobj -arm-buildattrs %p/Inputs/trivial-object-test.elf-arm \
+RUN:         | FileCheck %s -check-prefix=SMALL
+RUN: llvm-readobj -arm-buildattrs %p/Inputs/arm-attributes.elf-arm \
+RUN:         | FileCheck %s -check-prefix=LARGE
+
+SMALL: ARMBuildAttributes {
+SMALL: Tag_CPU_name: Cortex-A8
+SMALL: Tag_CPU_arch: 10
+SMALL: Tag_ARM_ISA_use: 1
+SMALL: Tag_THUMB_ISA_use: 2
+SMALL: Tag_FP_arch: 3
+SMALL: Tag_Advanced_SIMD_arch: 1
+SMALL: Tag_ABI_FP_denormal: 1
+SMALL: Tag_ABI_FP_exceptions: 1
+SMALL: Tag_ABI_FP_number_model: 3
+SMALL: Tag_ABI_align8_needed: 1
+SMALL: Tag_ABI_align8_preserved: 1
+SMALL: Tag_ABI_HardFP_use: 3
+SMALL: Tag_ABI_VFP_args: 1
+SMALL: Tag_DIV_use: 1
+SMALL: Tag_Virtualization_use: 1
+
+LARGE: ARMBuildAttributes {
+LARGE: Tag_CPU_name: iwmmxt2
+LARGE: Tag_CPU_arch: 4
+LARGE: Tag_ARM_ISA_use: 1
+LARGE: Tag_THUMB_ISA_use: 1
+LARGE: Tag_WMMX_arch: 2
+LARGE: Tag_Advanced_SIMD_arch: 1
+LARGE: Tag_ABI_PCS_RW_data: 3
+LARGE: Tag_ABI_PCS_GOT_use: 2
+LARGE: Tag_ABI_PCS_wchar_t: 4
+LARGE: Tag_ABI_FP_rounding: 1
+LARGE: Tag_ABI_FP_denormal: 1
+LARGE: Tag_ABI_FP_exceptions: 1
+LARGE: Tag_ABI_FP_number_model: 3
+LARGE: Tag_ABI_align8_needed: 1
+LARGE: Tag_ABI_align8_preserved: 1
+LARGE: Tag_ABI_enum_size: 2
+LARGE: Tag_ABI_HardFP_use: 3
+LARGE: Tag_ABI_VFP_args: 1
+LARGE: Tag_ABI_optimization_goals: 1
+LARGE: Tag_CPU_unaligned_access: 1
+LARGE: Tag_FP_HP_extension: 1
+LARGE: Tag_DIV_use: 1
+LARGE: Tag_T2EE_use: 1
diff --git a/tools/llvm-readobj/ELFDumper.cpp b/tools/llvm-readobj/ELFDumper.cpp
index ea1b83f32f..6fa9026399 100644
--- a/tools/llvm-readobj/ELFDumper.cpp
+++ b/tools/llvm-readobj/ELFDumper.cpp
@@ -51,6 +51,7 @@ public:
   virtual void printDynamicTable() LLVM_OVERRIDE;
   virtual void printNeededLibraries() LLVM_OVERRIDE;
   virtual void printProgramHeaders() LLVM_OVERRIDE;
+  virtual void printARMBuildAttributes() LLVM_OVERRIDE;
 
 private:
   typedef ELFObjectFile<ELFT> ELFO;
@@ -858,3 +859,65 @@ void ELFDumper<ELFT>::printProgramHeaders() {
     W.printNumber("Alignment", PI->p_align);
   }
 }
+
+#define LLVM_READOBJ_ARMATTR_NUMCASE(X) case ARMBuildAttrs::X: \
+  W.printNumber("  Tag_" #X, BuildAttrs.Tag_##X); \
+  break; \
+
+#define LLVM_READOBJ_ARMATTR_STRCASE(X) case ARMBuildAttrs::X: \
+  W.printString("  Tag_" #X, BuildAttrs.Tag_##X); \
+  break; \
+
+template<class ELFT>
+void ELFDumper<ELFT>::printARMBuildAttributes() {
+  if (Obj->getArch() != Triple::arm || !Obj->hasARMBuildAttributes())
+    return;
+  ARMBuildAttrs::ARMGenericBuildAttrInfo BuildAttrs;
+  SmallVector<unsigned, 16> AttrsRead;
+  error_code EC = Obj->readARMBuildAttributes(BuildAttrs, AttrsRead);
+  if (error(EC))
+    return;
+
+  DictScope D(W, "ARMBuildAttributes");
+
+  for (SmallVector<unsigned, 16>::iterator I = AttrsRead.begin(),
+       E = AttrsRead.end(); I != E; ++I) {
+    switch (*I) {
+    LLVM_READOBJ_ARMATTR_STRCASE(CPU_name)
+    LLVM_READOBJ_ARMATTR_STRCASE(CPU_raw_name)
+    LLVM_READOBJ_ARMATTR_NUMCASE(CPU_arch)
+    LLVM_READOBJ_ARMATTR_NUMCASE(CPU_arch_profile)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ARM_ISA_use)
+    LLVM_READOBJ_ARMATTR_NUMCASE(THUMB_ISA_use)
+    LLVM_READOBJ_ARMATTR_NUMCASE(FP_arch)
+    LLVM_READOBJ_ARMATTR_NUMCASE(WMMX_arch)
+    LLVM_READOBJ_ARMATTR_NUMCASE(Advanced_SIMD_arch)
+    LLVM_READOBJ_ARMATTR_NUMCASE(PCS_config)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_PCS_R9_use)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_PCS_RW_data)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_PCS_RO_data)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_PCS_GOT_use)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_PCS_wchar_t)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_FP_rounding)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_FP_denormal)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_FP_exceptions)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_FP_user_exceptions)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_FP_number_model)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_align8_needed)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_align8_preserved)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_enum_size)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_HardFP_use)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_VFP_args)
+    LLVM_READOBJ_ARMATTR_NUMCASE(CPU_unaligned_access)
+    LLVM_READOBJ_ARMATTR_NUMCASE(FP_HP_extension)
+    LLVM_READOBJ_ARMATTR_NUMCASE(MPextension_use)
+    LLVM_READOBJ_ARMATTR_NUMCASE(DIV_use)
+    LLVM_READOBJ_ARMATTR_NUMCASE(T2EE_use)
+    LLVM_READOBJ_ARMATTR_NUMCASE(Virtualization_use)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_optimization_goals)
+    LLVM_READOBJ_ARMATTR_NUMCASE(ABI_FP_optimization_goals)
+    default:
+      break;
+    }
+  }
+}
diff --git a/tools/llvm-readobj/ObjDumper.h b/tools/llvm-readobj/ObjDumper.h
index 6918e28cb9..9a8f0c157a 100644
--- a/tools/llvm-readobj/ObjDumper.h
+++ b/tools/llvm-readobj/ObjDumper.h
@@ -39,6 +39,7 @@ public:
   virtual void printDynamicTable() { }
   virtual void printNeededLibraries() { }
   virtual void printProgramHeaders() { }
+  virtual void printARMBuildAttributes() { }
 
 protected:
   StreamWriter& W;
diff --git a/tools/llvm-readobj/llvm-readobj.cpp b/tools/llvm-readobj/llvm-readobj.cpp
index 2e95b6b551..d5eb85429c 100644
--- a/tools/llvm-readobj/llvm-readobj.cpp
+++ b/tools/llvm-readobj/llvm-readobj.cpp
@@ -128,6 +128,10 @@ namespace opts {
   // -expand-relocs
   cl::opt<bool> ExpandRelocs("expand-relocs",
     cl::desc("Expand each shown relocation to multiple lines"));
+
+  // -arm-buildattrs
+  cl::opt<bool> ArmBuildAttrs("arm-buildattrs",
+    cl::desc("Display ARM ELF build attributes"));
 } // namespace opts
 
 namespace llvm {
@@ -221,6 +225,8 @@ static void dumpObject(const ObjectFile *Obj) {
     Dumper->printNeededLibraries();
   if (opts::ProgramHeaders)
     Dumper->printProgramHeaders();
+  if (opts::ArmBuildAttrs)
+    Dumper->printARMBuildAttributes();
 }