From 01ea611601c7dc2e510d53b14848f4843a67bc22 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Fri, 26 Sep 2014 22:32:16 +0000
Subject: [PATCH] Object: BSS/virtual sections don't have contents

Users of getSectionContents shouldn't try to pass in BSS or virtual
sections.  In all instances, this is a bug in the code calling this
routine.

N.B. Some COFF implementations (like CL) will mark their BSS sections as
taking space on disk.  This would confuse COFFObjectFile into thinking
the section is larger than the file.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218549 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/DebugInfo/DWARFContext.cpp     |  9 +++++++++
 lib/Object/COFFObjectFile.cpp      |  4 ++++
 test/MC/PowerPC/lcomm.s            |  1 -
 tools/llvm-readobj/COFFDumper.cpp  |  3 ++-
 tools/llvm-readobj/ELFDumper.cpp   |  2 +-
 tools/llvm-readobj/MachODumper.cpp | 11 ++++++++---
 6 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/lib/DebugInfo/DWARFContext.cpp b/lib/DebugInfo/DWARFContext.cpp
index 1be0691a1d9..62e3b9ccf64 100644
--- a/lib/DebugInfo/DWARFContext.cpp
+++ b/lib/DebugInfo/DWARFContext.cpp
@@ -565,6 +565,15 @@ DWARFContextInMemory::DWARFContextInMemory(object::ObjectFile &Obj)
   for (const SectionRef &Section : Obj.sections()) {
     StringRef name;
     Section.getName(name);
+    // Skip BSS and Virtual sections, they aren't interesting.
+    bool IsBSS;
+    Section.isBSS(IsBSS);
+    if (IsBSS)
+      continue;
+    bool IsVirtual;
+    Section.isVirtual(IsVirtual);
+    if (IsVirtual)
+      continue;
     StringRef data;
     Section.getContents(data);
 
diff --git a/lib/Object/COFFObjectFile.cpp b/lib/Object/COFFObjectFile.cpp
index 7daef06f035..45de4341b3f 100644
--- a/lib/Object/COFFObjectFile.cpp
+++ b/lib/Object/COFFObjectFile.cpp
@@ -840,6 +840,10 @@ std::error_code COFFObjectFile::getSectionName(const coff_section *Sec,
 std::error_code
 COFFObjectFile::getSectionContents(const coff_section *Sec,
                                    ArrayRef<uint8_t> &Res) const {
+  // PointerToRawData and SizeOfRawData won't make sense for BSS sections, don't
+  // do anything interesting for them.
+  assert((Sec->Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0 &&
+         "BSS sections don't have contents!");
   // The only thing that we need to verify is that the contents is contained
   // within the file bounds. We don't need to make sure it doesn't cover other
   // data, as there's nothing that says that is not allowed.
diff --git a/test/MC/PowerPC/lcomm.s b/test/MC/PowerPC/lcomm.s
index b6beedea5fd..a84f138479b 100644
--- a/test/MC/PowerPC/lcomm.s
+++ b/test/MC/PowerPC/lcomm.s
@@ -19,4 +19,3 @@
 // CHECK-NEXT:     Info: 0
 // CHECK-NEXT:     AddressAlignment: 16
 // CHECK-NEXT:     EntrySize: 0
-// CHECK-NEXT:     SectionData (
diff --git a/tools/llvm-readobj/COFFDumper.cpp b/tools/llvm-readobj/COFFDumper.cpp
index 99a374d5a6a..3d71d832f99 100644
--- a/tools/llvm-readobj/COFFDumper.cpp
+++ b/tools/llvm-readobj/COFFDumper.cpp
@@ -635,7 +635,8 @@ void COFFDumper::printSections() {
     if (Name == ".debug$S" && opts::CodeViewLineTables)
       printCodeViewLineTables(Sec);
 
-    if (opts::SectionData) {
+    if (opts::SectionData &&
+        !(Section->Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA)) {
       StringRef Data;
       if (error(Sec.getContents(Data)))
         break;
diff --git a/tools/llvm-readobj/ELFDumper.cpp b/tools/llvm-readobj/ELFDumper.cpp
index 1791f5a3247..6da3318c931 100644
--- a/tools/llvm-readobj/ELFDumper.cpp
+++ b/tools/llvm-readobj/ELFDumper.cpp
@@ -604,7 +604,7 @@ void ELFDumper<ELFT>::printSections() {
       }
     }
 
-    if (opts::SectionData) {
+    if (opts::SectionData && Section->sh_type != ELF::SHT_NOBITS) {
       ArrayRef<uint8_t> Data = errorOrDefault(Obj->getSectionContents(Section));
       W.printBinaryBlock("SectionData",
                          StringRef((const char *)Data.data(), Data.size()));
diff --git a/tools/llvm-readobj/MachODumper.cpp b/tools/llvm-readobj/MachODumper.cpp
index 41a78e762fb..2d09282f11f 100644
--- a/tools/llvm-readobj/MachODumper.cpp
+++ b/tools/llvm-readobj/MachODumper.cpp
@@ -266,11 +266,16 @@ void MachODumper::printSections(const MachOObjectFile *Obj) {
     }
 
     if (opts::SectionData) {
-      StringRef Data;
-      if (error(Section.getContents(Data)))
+      bool IsBSS;
+      if (error(Section.isBSS(IsBSS)))
         break;
+      if (!IsBSS) {
+        StringRef Data;
+        if (error(Section.getContents(Data)))
+          break;
 
-      W.printBinaryBlock("SectionData", Data);
+        W.printBinaryBlock("SectionData", Data);
+      }
     }
   }
 }