[llvm-objdump] Teach -d about AArch64 mapping symbols

[davide]

Summary

AArch64 uses $d* and $x* to interleave between text and data.
llvm-objdump didn't know about this so it ended up printing garbage. This is the initial support to to teach llvm-objdump how to behave correctly in this situation.
I think llvm-objdump needs a lot of love. For now, this is a missing functionality that blocks my lld AArch64 testing, so I implemented it in the most straightforward way. Comments are welcome, and appreciated.

[Bigcheese]

I'd rather we not loop over all the mapping symbols each time. Or at least do a binary search. Other than that it looks fine.

[davide]

Reworked as per Rafael request.

[• rafael]

Much better, but I think it can still be improved.

auto DAI =
          std::lower_bound(Symbols.begin(), Symbols.end(), Index, SymCmp);

Index is >= Start, so you don't need to search past Symbols[si], no?

In fact, why do you need to search at all? When you are about to print a symbol from Start to End, you can check if the range for that symbol is data or not and you can do that by just maintaining a single "InCode" variable that is updated every time you pass a $x or $d.

[davide]

Updated. Thank you for your help, Rafael!
This also now matches better with GNU objdump does, not showing mapping symbols.

[davide]

git-clang-format.

[• rafael]

LGTM

[jmolloy]

tools/llvm-objdump/llvm-objdump.cpp

988

As this is a target-independent file, shouldn't we also make sure $a and $t (for AArch32) are covered here? Are you going to do this in another patch?

[davide]

tools/llvm-objdump/llvm-objdump.cpp

988

Hi James, I think I can take of this separately. Please file a PR and assign to me so I won't forget.

Thanks,

Davide

tools/llvm-objdump/llvm-objdump.cpp

 
     uint64_t SectionAddr = Section.getAddress();
     uint64_t SectSize = Section.getSize();
     if (!SectSize)
       continue;
 
     // Make a list of all the symbols in this section.
     std::vector<std::pair<uint64_t, StringRef>> Symbols;
-    std::vector<uint64_t> DataMappingSymsAddr;
-    std::vector<uint64_t> TextMappingSymsAddr;
     for (const SymbolRef &Symbol : Obj->symbols()) {
       if (Section.containsSymbol(Symbol)) {
         ErrorOr<uint64_t> AddressOrErr = Symbol.getAddress();
         error(AddressOrErr.getError());
         uint64_t Address = *AddressOrErr;
         Address -= SectionAddr;
         if (Address >= SectSize)
           continue;
 
         ErrorOr<StringRef> Name = Symbol.getName();
         error(Name.getError());
         Symbols.push_back(std::make_pair(Address, *Name));
-        if (Obj->isELF() && Obj->getArch() == Triple::aarch64) {
-          if (Name->startswith("$d"))
-            DataMappingSymsAddr.push_back(Address);
-          if (Name->startswith("$x"))
-            TextMappingSymsAddr.push_back(Address);
-        }
       }
     }
 
     // Sort the symbols by address, just in case they didn't come in that way.
     array_pod_sort(Symbols.begin(), Symbols.end());
-    std::sort(DataMappingSymsAddr.begin(), DataMappingSymsAddr.end());
-    std::sort(TextMappingSymsAddr.begin(), TextMappingSymsAddr.end());
 
     // Make a list of all the relocations for this section.
     std::vector<RelocationRef> Rels;
     if (InlineRelocs) {
       for (const SectionRef &RelocSec : SectionRelocMap[Section]) {
         for (const RelocationRef &Reloc : RelocSec.relocations()) {
           Rels.push_back(Reloc);
         }

     // Disassemble symbol by symbol.
     for (unsigned si = 0, se = Symbols.size(); si != se; ++si) {
 
       uint64_t Start = Symbols[si].first;
       // The end is either the section end or the beginning of the next symbol.
       uint64_t End = (si == se - 1) ? SectSize : Symbols[si + 1].first;
       // If this symbol has the same address as the next symbol, then skip it.
       if (Start == End)
         continue;
 
       outs() << '\n' << Symbols[si].second << ":\n";
 
 #ifndef NDEBUG
       raw_ostream &DebugOut = DebugFlag ? dbgs() : nulls();
 #else
       raw_ostream &DebugOut = nulls();
 #endif
 
       for (Index = Start; Index < End; Index += Size) {
         MCInst Inst;
 
         // AArch64 ELF binaries can interleave data and text in the
         // same section. We rely on the markers introduced to
         // understand what we need to dump.
-        if (Obj->isELF() && Obj->getArch() == Triple::aarch64) {
-          uint64_t Stride = 0;
-
-          auto DAI = std::lower_bound(DataMappingSymsAddr.begin(),
-                                      DataMappingSymsAddr.end(), Index);
-          if (DAI != DataMappingSymsAddr.end() && *DAI == Index) {
-            // Switch to data.
-            while (Index < End) {
-              outs() << format("%8" PRIx64 ":", SectionAddr + Index);
-              outs() << "\t";
-              if (Index + 4 <= End) {
-                Stride = 4;
-                dumpBytes(Bytes.slice(Index, 4), outs());
-                outs() << "\t.word";
-              } else if (Index + 2 <= End) {
-                Stride = 2;
-                dumpBytes(Bytes.slice(Index, 2), outs());
-                outs() << "\t.short";
-              } else {
-                Stride = 1;
-                dumpBytes(Bytes.slice(Index, 1), outs());
-                outs() << "\t.byte";
-              }
-              Index += Stride;
-              outs() << "\n";
-              auto TAI = std::lower_bound(TextMappingSymsAddr.begin(),
-                                          TextMappingSymsAddr.end(), Index);
-              if (TAI != TextMappingSymsAddr.end() && *TAI == Index)
-                break;
+        auto SymCmp = [](std::pair<uint64_t, StringRef> Sym, uint64_t Index)
+                          -> bool { return Sym.first < Index; };
+        uint64_t Stride = 0;
+
+        auto DAI =
+            std::lower_bound(Symbols.begin(), Symbols.end(), Index, SymCmp);
+        if (DAI != Symbols.end() && DAI->first == Index &&
+            DAI->second.startswith("$d")) {
+          while (Index < End) {
+            outs() << format("%8" PRIx64 ":", SectionAddr + Index);
+            outs() << "\t";
+            if (Index + 4 <= End) {
+              Stride = 4;
+              dumpBytes(Bytes.slice(Index, 4), outs());
+              outs() << "\t.word";
+            } else if (Index + 2 <= End) {
+              Stride = 2;
+              dumpBytes(Bytes.slice(Index, 2), outs());
+              outs() << "\t.short";
+            } else {
+              Stride = 1;
+              dumpBytes(Bytes.slice(Index, 1), outs());
+              outs() << "\t.byte";
             }
+            Index += Stride;
+            outs() << "\n";
+            auto TAI =
+                std::lower_bound(Symbols.begin(), Symbols.end(), Index, SymCmp);
+            if (TAI != Symbols.end() && TAI->first == Index &&
+                TAI->second.startswith("$x"))
+              break;
           }
         }
 
         if (Index >= End)
           break;
 
         if (DisAsm->getInstruction(Inst, Size, Bytes.slice(Index),
                                    SectionAddr + Index, DebugOut,