From 3605e121fbd4283246005545767fa4583f8f297a Mon Sep 17 00:00:00 2001
From: Sterling Augustine <saugustine@google.com>
Date: Thu, 28 Jun 2018 18:57:13 +0000
Subject: [PATCH] Handle absolute symbols as branch targets in disassembly.

https://reviews.llvm.org/D48554



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@335903 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../llvm-objdump/call-absolute-symbol-elf.test     |  4 ++
 tools/llvm-objdump/llvm-objdump.cpp                | 56 ++++++++++++++--------
 2 files changed, 39 insertions(+), 21 deletions(-)
 create mode 100644 test/tools/llvm-objdump/call-absolute-symbol-elf.test

diff --git a/test/tools/llvm-objdump/call-absolute-symbol-elf.test b/test/tools/llvm-objdump/call-absolute-symbol-elf.test
new file mode 100644
index 00000000000..aa3482b4b87
--- /dev/null
+++ b/test/tools/llvm-objdump/call-absolute-symbol-elf.test
@@ -0,0 +1,4 @@
+// RUN: echo -e ".text\ncallq foo\n" | llvm-mc -filetype=obj -triple=x86_64-pc-linux - -o %t1.o
+// RUN: ld.lld --defsym foo=0x100 %t1.o -o %t2
+// RUN: llvm-objdump --disassemble %t2 | FileCheck %s
+CHECK: 201000:	e8 fb f0 df ff 	callq	-2100997 <foo>
diff --git a/tools/llvm-objdump/llvm-objdump.cpp b/tools/llvm-objdump/llvm-objdump.cpp
index 2edd65be2ed..2598d930417 100644
--- a/tools/llvm-objdump/llvm-objdump.cpp
+++ b/tools/llvm-objdump/llvm-objdump.cpp
@@ -1282,6 +1282,7 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
   // 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)
@@ -1297,15 +1298,17 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
     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())
@@ -1341,6 +1344,8 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
 
       if (Sec != SectionAddresses.end())
         AllSymbols[Sec->second].emplace_back(VA, Name, ELF::STT_NOTYPE);
+      else
+        AbsoluteSymbols.emplace_back(VA, Name, ELF::STT_NOTYPE);
     }
   }
 
@@ -1348,6 +1353,7 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
   // 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()))
@@ -1662,29 +1668,37 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
                 --SectionAddress;
                 TargetSectionSymbols = &AllSymbols[SectionAddress->second];
               } else {
-                TargetSectionSymbols = nullptr;
+                TargetSectionSymbols = &AbsoluteSymbols;
               }
             }
 
             // 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()) {
+              TargetSectionSymbols = &AbsoluteSymbols;
+              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() << '>';
             }
           }
         }
-- 
2.11.0