Revert "Revert "[lld][Arm] Big Endian - Byte invariant support.""

This reverts commit d885138.

Reason: Applied the fix for the Asan buildbot failures.

lld/ELF/Arch/ARM.cpp

@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "InputFiles.h"
 #include "Symbols.h"
 #include "SyntheticSections.h"
 #include "Target.h"
@@ -44,8 +45,11 @@ class ARM final : public TargetInfo {
   void relocate(uint8_t *loc, const Relocation &rel,
                 uint64_t val) const override;
 };
+enum class CodeState { Data = 0, Thumb = 2, Arm = 4 };
 } // namespace
 
+static DenseMap<InputSection *, SmallVector<const Defined *, 0>> sectionMap{};
+
 ARM::ARM() {
   copyRel = R_ARM_COPY;
   relativeRel = R_ARM_RELATIVE;
@@ -68,16 +72,24 @@ uint32_t ARM::calcEFlags() const {
   // The ABIFloatType is used by loaders to detect the floating point calling
   // convention.
   uint32_t abiFloatType = 0;
+
+  // Set the EF_ARM_BE8 flag in the ELF header, if ELF file is big-endian
+  // with BE-8 code.
+  uint32_t armBE8 = 0;
+
   if (config->armVFPArgs == ARMVFPArgKind::Base ||
       config->armVFPArgs == ARMVFPArgKind::Default)
     abiFloatType = EF_ARM_ABI_FLOAT_SOFT;
   else if (config->armVFPArgs == ARMVFPArgKind::VFP)
     abiFloatType = EF_ARM_ABI_FLOAT_HARD;
 
+  if (!config->isLE && config->armBe8)
+    armBE8 = EF_ARM_BE8;
+
   // We don't currently use any features incompatible with EF_ARM_EABI_VER5,
   // but we don't have any firm guarantees of conformance. Linux AArch64
   // kernels (as of 2016) require an EABI version to be set.
-  return EF_ARM_EABI_VER5 | abiFloatType;
+  return EF_ARM_EABI_VER5 | abiFloatType | armBE8;
 }
 
 RelExpr ARM::getRelExpr(RelType type, const Symbol &s,
@@ -910,6 +922,117 @@ int64_t ARM::getImplicitAddend(const uint8_t *buf, RelType type) const {
   }
 }
 
+static bool isArmMapSymbol(const Symbol *b) {
+  return b->getName() == "$a" || b->getName().startswith("$a.");
+}
+
+static bool isThumbMapSymbol(const Symbol *s) {
+  return s->getName() == "$t" || s->getName().startswith("$t.");
+}
+
+static bool isDataMapSymbol(const Symbol *b) {
+  return b->getName() == "$d" || b->getName().startswith("$d.");
+}
+
+void elf::sortArmMappingSymbols() {
+  // For each input section make sure the mapping symbols are sorted in
+  // ascending order.
+  for (auto &kv : sectionMap) {
+    SmallVector<const Defined *, 0> &mapSyms = kv.second;
+    llvm::stable_sort(mapSyms, [](const Defined *a, const Defined *b) {
+      return a->value < b->value;
+    });
+  }
+}
+
+void elf::addArmInputSectionMappingSymbols() {
+  // Collect mapping symbols for every executable input sections.
+  // The linker generated mapping symbols for all the synthetic
+  // sections are adding into the sectionmap through the function
+  // addArmSyntheitcSectionMappingSymbol.
+  for (ELFFileBase *file : ctx.objectFiles) {
+    for (Symbol *sym : file->getLocalSymbols()) {
+      auto *def = dyn_cast<Defined>(sym);
+      if (!def)
+        continue;
+      if (!isArmMapSymbol(def) && !isDataMapSymbol(def) &&
+          !isThumbMapSymbol(def))
+        continue;
+      if (auto *sec = cast_if_present<InputSection>(def->section))
+        if (sec->flags & SHF_EXECINSTR)
+          sectionMap[sec].push_back(def);
+    }
+  }
+}
+
+// Synthetic sections are not backed by an ELF file where we can access the
+// symbol table, instead mapping symbols added to synthetic sections are stored
+// in the synthetic symbol table. Due to the presence of strip (--strip-all),
+// we can not rely on the synthetic symbol table retaining the mapping symbols.
+// Instead we record the mapping symbols locally.
+void elf::addArmSyntheticSectionMappingSymbol(Defined *sym) {
+  if (!isArmMapSymbol(sym) && !isDataMapSymbol(sym) && !isThumbMapSymbol(sym))
+    return;
+  if (auto *sec = cast_if_present<InputSection>(sym->section))
+    if (sec->flags & SHF_EXECINSTR)
+      sectionMap[sec].push_back(sym);
+}
+
+static void toLittleEndianInstructions(uint8_t *buf, uint64_t start,
+                                       uint64_t end, uint64_t width) {
+  CodeState curState = static_cast<CodeState>(width);
+  if (curState == CodeState::Arm)
+    for (uint64_t i = start; i < end; i += width)
+      write32le(buf + i, read32(buf + i));
+
+  if (curState == CodeState::Thumb)
+    for (uint64_t i = start; i < end; i += width)
+      write16le(buf + i, read16(buf + i));
+}
+
+// Arm BE8 big endian format requires instructions to be little endian, with
+// the initial contents big-endian. Convert the big-endian instructions to
+// little endian leaving literal data untouched. We use mapping symbols to
+// identify half open intervals of Arm code [$a, non $a) and Thumb code
+// [$t, non $t) and convert these to little endian a word or half word at a
+// time respectively.
+void elf::convertArmInstructionstoBE8(InputSection *sec, uint8_t *buf) {
+  if (!sectionMap.contains(sec))
+    return;
+
+  SmallVector<const Defined *, 0> &mapSyms = sectionMap[sec];
+
+  if (mapSyms.empty())
+    return;
+
+  CodeState curState = CodeState::Data;
+  uint64_t start = 0, width = 0, size = sec->getSize();
+  for (auto &msym : mapSyms) {
+    CodeState newState = CodeState::Data;
+    if (isThumbMapSymbol(msym))
+      newState = CodeState::Thumb;
+    else if (isArmMapSymbol(msym))
+      newState = CodeState::Arm;
+
+    if (newState == curState)
+      continue;
+
+    if (curState != CodeState::Data) {
+      width = static_cast<uint64_t>(curState);
+      toLittleEndianInstructions(buf, start, msym->value, width);
+    }
+    start = msym->value;
+    curState = newState;
+  }
+
+  // Passed last mapping symbol, may need to reverse
+  // up to end of section.
+  if (curState != CodeState::Data) {
+    width = static_cast<uint64_t>(curState);
+    toLittleEndianInstructions(buf, start, size, width);
+  }
+}
+
 TargetInfo *elf::getARMTargetInfo() {
   static ARM target;
   return &target;

lld/ELF/Config.h

@@ -201,6 +201,7 @@ struct Config {
   bool armHasMovtMovw = false;
   bool armJ1J2BranchEncoding = false;
   bool asNeeded = false;
+  bool armBe8 = false;
   BsymbolicKind bsymbolic = BsymbolicKind::None;
   bool callGraphProfileSort;
   bool checkSections;

lld/ELF/Driver.cpp

@@ -351,9 +351,12 @@ static void checkOptions() {
   if (config->fixCortexA8 && config->emachine != EM_ARM)
     error("--fix-cortex-a8 is only supported on ARM targets");
 
+  if (config->armBe8 && config->emachine != EM_ARM)
+    error("--be8 is only supported on ARM targets");
+
   if (config->fixCortexA8 && !config->isLE)
     error("--fix-cortex-a8 is not supported on big endian targets");
-  
+
   if (config->tocOptimize && config->emachine != EM_PPC64)
     error("--toc-optimize is only supported on PowerPC64 targets");
 
@@ -1115,6 +1118,7 @@ static void readConfigs(opt::InputArgList &args) {
                                             OPT_no_android_memtag_stack, false);
   config->androidMemtagMode = getMemtagMode(args);
   config->auxiliaryList = args::getStrings(args, OPT_auxiliary);
+  config->armBe8 = args.hasArg(OPT_be8);
   if (opt::Arg *arg =
           args.getLastArg(OPT_Bno_symbolic, OPT_Bsymbolic_non_weak_functions,
                           OPT_Bsymbolic_functions, OPT_Bsymbolic)) {

lld/ELF/Options.td

@@ -36,6 +36,8 @@ multiclass B<string name, string help1, string help2> {
 
 defm auxiliary: Eq<"auxiliary", "Set DT_AUXILIARY field to the specified name">;
 
+def be8: F<"be8">, HelpText<"write a Big Endian ELF file using BE8 format (AArch32 only)">;
+
 def Bno_symbolic: F<"Bno-symbolic">, HelpText<"Don't bind default visibility defined symbols locally for -shared (default)">;
 
 def Bsymbolic: F<"Bsymbolic">, HelpText<"Bind default visibility defined symbols locally for -shared">;

lld/ELF/OutputSections.cpp

@@ -496,6 +496,12 @@ void OutputSection::writeTo(uint8_t *buf, parallel::TaskGroup &tg) {
       else
         isec->writeTo<ELFT>(buf + isec->outSecOff);
 
+      // When in Arm BE8 mode, the linker has to convert the big-endian
+      // instructions to little-endian, leaving the data big-endian.
+      if (config->emachine == EM_ARM && !config->isLE && config->armBe8 &&
+          (flags & SHF_EXECINSTR))
+        convertArmInstructionstoBE8(isec, buf + isec->outSecOff);
+
       // Fill gaps between sections.
       if (nonZeroFiller) {
         uint8_t *start = buf + isec->outSecOff + isec->getSize();

lld/ELF/SyntheticSections.cpp

@@ -271,6 +271,13 @@ Defined *elf::addSyntheticLocal(StringRef name, uint8_t type, uint64_t value,
                            value, size, &section);
   if (in.symTab)
     in.symTab->addSymbol(s);
+
+  if (config->emachine == EM_ARM && !config->isLE && config->armBe8 &&
+      (section.flags & SHF_EXECINSTR))
+    // Adding Linker generated mapping symbols to the arm specific mapping
+    // symbols list.
+    addArmSyntheticSectionMappingSymbol(s);
+
   return s;
 }
 

lld/ELF/Target.h

@@ -223,6 +223,10 @@ uint64_t getPPC64TocBase();
 uint64_t getAArch64Page(uint64_t expr);
 void riscvFinalizeRelax(int passes);
 void mergeRISCVAttributesSections();
+void addArmInputSectionMappingSymbols();
+void addArmSyntheticSectionMappingSymbol(Defined *);
+void sortArmMappingSymbols();
+void convertArmInstructionstoBE8(InputSection *sec, uint8_t *buf);
 
 LLVM_LIBRARY_VISIBILITY extern const TargetInfo *target;
 TargetInfo *getTarget();

lld/ELF/Thunks.cpp

@@ -744,7 +744,8 @@ void ThumbV6MABSLongThunk::addSymbols(ThunkSection &isec) {
   addSymbol(saver().save("__Thumbv6MABSLongThunk_" + destination.getName()),
             STT_FUNC, 1, isec);
   addSymbol("$t", STT_NOTYPE, 0, isec);
-  addSymbol("$d", STT_NOTYPE, 8, isec);
+  if (!getMayUseShortThunk())
+    addSymbol("$d", STT_NOTYPE, 8, isec);
 }
 
 void ThumbV6MPILongThunk::writeLong(uint8_t *buf) {
@@ -767,7 +768,8 @@ void ThumbV6MPILongThunk::addSymbols(ThunkSection &isec) {
   addSymbol(saver().save("__Thumbv6MPILongThunk_" + destination.getName()),
             STT_FUNC, 1, isec);
   addSymbol("$t", STT_NOTYPE, 0, isec);
-  addSymbol("$d", STT_NOTYPE, 12, isec);
+  if (!getMayUseShortThunk())
+    addSymbol("$d", STT_NOTYPE, 12, isec);
 }
 
 void ARMV5LongLdrPcThunk::writeLong(uint8_t *buf) {
@@ -780,7 +782,8 @@ void ARMV5LongLdrPcThunk::addSymbols(ThunkSection &isec) {
   addSymbol(saver().save("__ARMv5LongLdrPcThunk_" + destination.getName()),
             STT_FUNC, 0, isec);
   addSymbol("$a", STT_NOTYPE, 0, isec);
-  addSymbol("$d", STT_NOTYPE, 4, isec);
+  if (!getMayUseShortThunk())
+    addSymbol("$d", STT_NOTYPE, 4, isec);
 }
 
 void ARMV4ABSLongBXThunk::writeLong(uint8_t *buf) {
@@ -794,7 +797,8 @@ void ARMV4ABSLongBXThunk::addSymbols(ThunkSection &isec) {
   addSymbol(saver().save("__ARMv4ABSLongBXThunk_" + destination.getName()),
             STT_FUNC, 0, isec);
   addSymbol("$a", STT_NOTYPE, 0, isec);
-  addSymbol("$d", STT_NOTYPE, 8, isec);
+  if (!getMayUseShortThunk())
+    addSymbol("$d", STT_NOTYPE, 8, isec);
 }
 
 void ThumbV4ABSLongBXThunk::writeLong(uint8_t *buf) {
@@ -810,7 +814,8 @@ void ThumbV4ABSLongBXThunk::addSymbols(ThunkSection &isec) {
             STT_FUNC, 1, isec);
   addSymbol("$t", STT_NOTYPE, 0, isec);
   addSymbol("$a", STT_NOTYPE, 4, isec);
-  addSymbol("$d", STT_NOTYPE, 8, isec);
+  if (!getMayUseShortThunk())
+    addSymbol("$d", STT_NOTYPE, 8, isec);
 }
 
 void ThumbV4ABSLongThunk::writeLong(uint8_t *buf) {
@@ -827,7 +832,8 @@ void ThumbV4ABSLongThunk::addSymbols(ThunkSection &isec) {
             STT_FUNC, 1, isec);
   addSymbol("$t", STT_NOTYPE, 0, isec);
   addSymbol("$a", STT_NOTYPE, 4, isec);
-  addSymbol("$d", STT_NOTYPE, 12, isec);
+  if (!getMayUseShortThunk())
+    addSymbol("$d", STT_NOTYPE, 12, isec);
 }
 
 void ARMV4PILongBXThunk::writeLong(uint8_t *buf) {
@@ -844,7 +850,8 @@ void ARMV4PILongBXThunk::addSymbols(ThunkSection &isec) {
   addSymbol(saver().save("__ARMv4PILongBXThunk_" + destination.getName()),
             STT_FUNC, 0, isec);
   addSymbol("$a", STT_NOTYPE, 0, isec);
-  addSymbol("$d", STT_NOTYPE, 12, isec);
+  if (!getMayUseShortThunk())
+    addSymbol("$d", STT_NOTYPE, 12, isec);
 }
 
 void ARMV4PILongThunk::writeLong(uint8_t *buf) {
@@ -860,7 +867,8 @@ void ARMV4PILongThunk::addSymbols(ThunkSection &isec) {
   addSymbol(saver().save("__ARMv4PILongThunk_" + destination.getName()),
             STT_FUNC, 0, isec);
   addSymbol("$a", STT_NOTYPE, 0, isec);
-  addSymbol("$d", STT_NOTYPE, 8, isec);
+  if (!getMayUseShortThunk())
+    addSymbol("$d", STT_NOTYPE, 8, isec);
 }
 
 void ThumbV4PILongBXThunk::writeLong(uint8_t *buf) {
@@ -879,7 +887,8 @@ void ThumbV4PILongBXThunk::addSymbols(ThunkSection &isec) {
             STT_FUNC, 1, isec);
   addSymbol("$t", STT_NOTYPE, 0, isec);
   addSymbol("$a", STT_NOTYPE, 4, isec);
-  addSymbol("$d", STT_NOTYPE, 12, isec);
+  if (!getMayUseShortThunk())
+    addSymbol("$d", STT_NOTYPE, 12, isec);
 }
 
 void ThumbV4PILongThunk::writeLong(uint8_t *buf) {
@@ -899,7 +908,8 @@ void ThumbV4PILongThunk::addSymbols(ThunkSection &isec) {
             STT_FUNC, 1, isec);
   addSymbol("$t", STT_NOTYPE, 0, isec);
   addSymbol("$a", STT_NOTYPE, 4, isec);
-  addSymbol("$d", STT_NOTYPE, 16, isec);
+  if (!getMayUseShortThunk())
+    addSymbol("$d", STT_NOTYPE, 16, isec);
 }
 
 // Use the long jump which covers a range up to 8MiB.

lld/ELF/Writer.cpp

@@ -2149,6 +2149,11 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
     sec->finalize();
 
   script->checkMemoryRegions();
+
+  if (config->emachine == EM_ARM && !config->isLE && config->armBe8) {
+    addArmInputSectionMappingSymbols();
+    sortArmMappingSymbols();
+  }
 }
 
 // Ensure data sections are not mixed with executable sections when

lld/docs/ld.lld.1

@@ -88,6 +88,8 @@ Bind default visibility defined function symbols locally for
 .It Fl Bsymbolic-non-weak-functions
 Bind default visibility defined STB_GLOBAL function symbols locally for
 .Fl shared.
+.It Fl --be8
+Write a Big Endian ELF File using BE8 format(AArch32 only)
 .It Fl -build-id Ns = Ns Ar value
 Generate a build ID note.
 .Ar value

lld/test/ELF/arm-bl-v6.s

@@ -13,6 +13,12 @@
 // RUN: llvm-objdump --no-print-imm-hex -d --triple=armv6eb-none-linux-gnueabi --start-address=0x22100c --stop-address=0x221014 %t2 | FileCheck --check-prefix=CHECK-ARM2-EB %s
 // RUN: llvm-objdump --no-print-imm-hex -d --triple=thumbv6eb-none-linux-gnueabi %t2 --start-address=0x622000 --stop-address=0x622002 | FileCheck --check-prefix=CHECK-THUMB2 %s
 
+// RUN: ld.lld --be8 %t -o %t2
+// RUN: llvm-objdump --no-print-imm-hex -d --triple=armv6eb-none-linux-gnueabi --start-address=0x21000 --stop-address=0x21008 %t2 | FileCheck --check-prefix=CHECK-ARM1 %s
+// RUN: llvm-objdump --no-print-imm-hex -d --triple=thumbv6eb-none-linux-gnueabi %t2 --start-address=0x21008 --stop-address=0x2100c | FileCheck --check-prefix=CHECK-THUMB1 %s
+// RUN: llvm-objdump --no-print-imm-hex -d --triple=armv6eb-none-linux-gnueabi --start-address=0x22100c --stop-address=0x221014 %t2 | FileCheck --check-prefix=CHECK-ARM2-EB %s
+// RUN: llvm-objdump --no-print-imm-hex -d --triple=thumbv6eb-none-linux-gnueabi %t2 --start-address=0x622000 --stop-address=0x622002 | FileCheck --check-prefix=CHECK-THUMB2 %s
+
 /// On Arm v6 the range of a Thumb BL instruction is only 4 megabytes as the
 /// extended range encoding is not supported. The following example has a Thumb
 /// BL that is out of range on ARM v6 and requires a range extension thunk.

lld/test/ELF/arm-data-relocs.s

@@ -9,6 +9,9 @@
 // RUN: ld.lld %t.be.o %t256.be.o -o %t.be
 // RUN: llvm-objdump -s %t.be | FileCheck %s --check-prefixes=CHECK,BE
 
+// RUN: ld.lld --be8 %t.be.o %t256.be.o -o %t.be8
+// RUN: llvm-objdump -s %t.be8 | FileCheck %s --check-prefixes=CHECK,BE
+
 .globl _start
 _start:
 .section .R_ARM_ABS, "ax","progbits"

lld/test/ELF/arm-exidx-emit-relocs.s

@@ -9,6 +9,10 @@
 // RUN: llvm-objdump -s --triple=armv7aeb-none-linux-gnueabi %t2 | FileCheck -check-prefix=CHECK-EB %s
 // RUN: llvm-readelf --relocs %t2 | FileCheck -check-prefix=CHECK-RELOCS %s
 
+// RUN: ld.lld --be8 --emit-relocs %t -o %t2
+// RUN: llvm-objdump -s --triple=armv7aeb-none-linux-gnueabi %t2 | FileCheck -check-prefix=CHECK-EB %s
+// RUN: llvm-readelf --relocs %t2 | FileCheck -check-prefix=CHECK-RELOCS %s
+
 /// LLD does not support --emit-relocs for .ARM.exidx sections as the relocations
 /// from synthetic table entries won't be represented. Given the known use cases
 /// of --emit-relocs, relocating kernels, and binary analysis, the former doesn't