[PATCH] D48554: Handle absolute symbols as branch targets in disassembly.

[Sterling Augustine via Phabricator via llvm-commits]

saugustine created this revision.
Herald added a subscriber: llvm-commits.

Certain tests and embedded systems use sectionless symbols
as the target of branches or calls. Handle them in the disassembly.


Repository:
  rL LLVM

https://reviews.llvm.org/D48554

Files:
  test/tools/llvm-objdump/Inputs/call-absolute-symbol.elf-x86_64
  tools/llvm-objdump/llvm-objdump.cpp


Index: tools/llvm-objdump/llvm-objdump.cpp
===================================================================
--- tools/llvm-objdump/llvm-objdump.cpp
+++ tools/llvm-objdump/llvm-objdump.cpp
@@ -1323,6 +1323,7 @@
   // Create a mapping from virtual address to symbol name.  This is used to
   // pretty print the symbols while disassembling.
   std::map<SectionRef, SectionSymbolsTy> AllSymbols;
+  SectionSymbolsTy AbsoluteSymbols;
   for (const SymbolRef &Symbol : Obj->symbols()) {
     Expected<uint64_t> AddressOrErr = Symbol.getAddress();
     if (!AddressOrErr)
@@ -1338,15 +1339,17 @@
     Expected<section_iterator> SectionOrErr = Symbol.getSection();
     if (!SectionOrErr)
       report_error(Obj->getFileName(), SectionOrErr.takeError());
-    section_iterator SecI = *SectionOrErr;
-    if (SecI == Obj->section_end())
-      continue;
 
     uint8_t SymbolType = ELF::STT_NOTYPE;
     if (Obj->isELF())
       SymbolType = getElfSymbolType(Obj, Symbol);
 
-    AllSymbols[*SecI].emplace_back(Address, *Name, SymbolType);
+    section_iterator SecI = *SectionOrErr;
+    if (SecI != Obj->section_end())
+      AllSymbols[*SecI].emplace_back(Address, *Name, SymbolType);
+    else
+      AbsoluteSymbols.emplace_back(Address, *Name, SymbolType);
+
 
   }
   if (AllSymbols.empty() && Obj->isELF())
@@ -1382,13 +1385,16 @@
 
       if (Sec != SectionAddresses.end())
         AllSymbols[Sec->second].emplace_back(VA, Name, ELF::STT_NOTYPE);
+      else
+        AbsoluteSymbols.emplace_back(VA, Name, ELF::STT_NOTYPE);
     }
   }
 
   // Sort all the symbols, this allows us to use a simple binary search to find
   // a symbol near an address.
   for (std::pair<const SectionRef, SectionSymbolsTy> &SecSyms : AllSymbols)
     array_pod_sort(SecSyms.second.begin(), SecSyms.second.end());
+  array_pod_sort(AbsoluteSymbols.begin(), AbsoluteSymbols.end());
 
   for (const SectionRef &Section : ToolSectionFilter(*Obj)) {
     if (!DisassembleAll && (!Section.isText() || Section.isVirtual()))
@@ -1708,24 +1714,32 @@
             }
 
             // Find the first symbol in the section whose offset is less than
-            // or equal to the target.
-            if (TargetSectionSymbols) {
-              auto TargetSym = std::upper_bound(
-                  TargetSectionSymbols->begin(), TargetSectionSymbols->end(),
+            // or equal to the target. If there isn't a section that contains
+            // the target, find the nearest preceding absolute symbol.
+            auto TargetSym = std::upper_bound(
+                TargetSectionSymbols->begin(), TargetSectionSymbols->end(),
+                Target, [](uint64_t LHS,
+                           const std::tuple<uint64_t, StringRef, uint8_t> &RHS) {
+                  return LHS < std::get<0>(RHS);
+                });
+            if (TargetSym == TargetSectionSymbols->begin()) {
+              TargetSym = std::upper_bound(
+                  AbsoluteSymbols.begin(), AbsoluteSymbols.end(),
                   Target, [](uint64_t LHS,
                              const std::tuple<uint64_t, StringRef, uint8_t> &RHS) {
-                    return LHS < std::get<0>(RHS);
-                  });
-              if (TargetSym != TargetSectionSymbols->begin()) {
-                --TargetSym;
-                uint64_t TargetAddress = std::get<0>(*TargetSym);
-                StringRef TargetName = std::get<1>(*TargetSym);
-                outs() << " <" << TargetName;
-                uint64_t Disp = Target - TargetAddress;
-                if (Disp)
-                  outs() << "+0x" << Twine::utohexstr(Disp);
-                outs() << '>';
-              }
+                            return LHS < std::get<0>(RHS);
+                          });
+            }
+
+            if (TargetSym != TargetSectionSymbols->begin()) {
+              --TargetSym;
+              uint64_t TargetAddress = std::get<0>(*TargetSym);
+              StringRef TargetName = std::get<1>(*TargetSym);
+              outs() << " <" << TargetName;
+              uint64_t Disp = Target - TargetAddress;
+              if (Disp)
+                outs() << "+0x" << Twine::utohexstr(Disp);
+              outs() << '>';
             }
           }
         }


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