[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 ↗

(On Diff #36659)

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 ↗

(On Diff #36659)

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

llvm/trunk/test/tools/llvm-objdump/AArch64/elf-aarch64-mapping-symbols.test

+# RUN: llvm-mc -filetype=obj -triple=aarch64-unknown-freebsd %s -o %t
+# RUN: llvm-objdump -d %t | FileCheck %s
+
+.section .mysection,"ax",@progbits
+.globl _start
+_start:
+  adr x1,msg
+msg:  .asciz  "Hello, world\n"
+msgend:
+
+.section .myothersection,"ax",@progbits
+  adrp x1,mystr
+mystr:
+  .asciz "blah"
+  .size mystr, 4
+
+# CHECK: Disassembly of section .mysection:
+# CHECK: _start:
+# CHECK:        0:       21 00 00 10     adr     x1, #4
+# CHECK: msg:
+# CHECK:        4:       48 65 6c 6c     .word
+# CHECK:        8:       6f 2c 20 77     .word
+# CHECK:        c:       6f 72 6c 64     .word
+# CHECK:       10:       0a 00   .short
+# CHECK: Disassembly of section .myothersection:
+# CHECK: $x.2:
+# CHECK:        0:       01 00 00 90     adrp    x1, #0
+# CHECK: mystr:
+# CHECK:        4:       62 6c 61 68     .word
+# CHECK:        8:       00      .byte

llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp

for (const SectionRef &Section : ToolSectionFilter(*Obj)) {
 
     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);
         }
#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;
+            }
+          }
+        }
+
+        if (Index >= End)
+          break;
+
         if (DisAsm->getInstruction(Inst, Size, Bytes.slice(Index),
                                    SectionAddr + Index, DebugOut,
                                    CommentStream)) {
           PIP.printInst(*IP, &Inst,
                         Bytes.slice(Index, Size),
                         SectionAddr + Index, outs(), "", *STI);
           outs() << CommentStream.str();
           Comments.clear();