From 1834682b97f498093684674f8f0d95113ef3cb66 Mon Sep 17 00:00:00 2001
From: Francis Visoiu Mistrih <francisvm@yahoo.com>
Date: Thu, 19 Apr 2018 17:02:57 +0000
Subject: [PATCH] [llvm-objdump] Print "..." instead of random data for virtual
 sections

When disassembling with -D, skip virtual sections by printing "..." for
each symbol.

This patch also implements `MachOObjectFile::isSectionVirtual`.

Test case comes from:

```
.zerofill __DATA,__common,_data64unsigned,472,3
```

Differential Revision: https://reviews.llvm.org/D45824

llvm-svn: 330342
---
 llvm/lib/Object/MachOObjectFile.cpp                       |   6 ++++--
 llvm/test/tools/llvm-objdump/AArch64/macho-zerofill.s     |   9 +++++++++
 .../tools/llvm-objdump/Inputs/zerofill.macho-x86_64.o     | Bin 0 -> 448 bytes
 llvm/tools/llvm-objdump/llvm-objdump.cpp                  |   7 +++++++
 4 files changed, 20 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/tools/llvm-objdump/AArch64/macho-zerofill.s
 create mode 100644 llvm/test/tools/llvm-objdump/Inputs/zerofill.macho-x86_64.o

diff --git a/llvm/lib/Object/MachOObjectFile.cpp b/llvm/lib/Object/MachOObjectFile.cpp
index adc54b4..ae5efc5 100644
--- a/llvm/lib/Object/MachOObjectFile.cpp
+++ b/llvm/lib/Object/MachOObjectFile.cpp
@@ -1968,8 +1968,10 @@ unsigned MachOObjectFile::getSectionID(SectionRef Sec) const {
 }
 
 bool MachOObjectFile::isSectionVirtual(DataRefImpl Sec) const {
-  // FIXME: Unimplemented.
-  return false;
+  uint32_t Flags = getSectionFlags(*this, Sec);
+  unsigned SectionType = Flags & MachO::SECTION_TYPE;
+  return SectionType == MachO::S_ZEROFILL ||
+         SectionType == MachO::S_GB_ZEROFILL;
 }
 
 bool MachOObjectFile::isSectionBitcode(DataRefImpl Sec) const {
diff --git a/llvm/test/tools/llvm-objdump/AArch64/macho-zerofill.s b/llvm/test/tools/llvm-objdump/AArch64/macho-zerofill.s
new file mode 100644
index 0000000..b790bb8
--- /dev/null
+++ b/llvm/test/tools/llvm-objdump/AArch64/macho-zerofill.s
@@ -0,0 +1,9 @@
+// RUN: llvm-mc < %s -triple aarch64-macho -filetype=obj | llvm-objdump -triple=aarch64-- -D - | FileCheck %s
+
+
+// Check that we don't print garbage when we dump zerofill sections.
+
+.zerofill __DATA,__common,_data64unsigned,472,3
+// CHECK: Disassembly of section __DATA,__common:
+// CHECK: ltmp1:
+// CHECK-NEXT: ...
diff --git a/llvm/test/tools/llvm-objdump/Inputs/zerofill.macho-x86_64.o b/llvm/test/tools/llvm-objdump/Inputs/zerofill.macho-x86_64.o
new file mode 100644
index 0000000000000000000000000000000000000000..272d7d5ccdffb26f5e9641b108370fc7a0e4ffbd
GIT binary patch
literal 448
zcmX^A>+L@t1_nk3AOI1}KpX((fkYS>B!Tz^n1!9V2vu8vqz9yu9g3Nt+T!C&QY%WJ
z93T}RAL1Gjg5aaG(9HwNHz2Etk5A6e&CSn)iN(jeIEFaFcnBKiK7<H_h2~rakUJ%S
z7-TOf3>E-s1t850!~sAI0w8e^1_2li;So=Y1C{b2SuP0T!vYD&21z0F8RAnCOA^gY
YO7n^{)ALeO7;;K-3k<=e0Z=Ie0A9TvdH?_b

literal 0
HcmV?d00001

diff --git a/llvm/tools/llvm-objdump/llvm-objdump.cpp b/llvm/tools/llvm-objdump/llvm-objdump.cpp
index 718d5749..5bea3a7 100644
--- a/llvm/tools/llvm-objdump/llvm-objdump.cpp
+++ b/llvm/tools/llvm-objdump/llvm-objdump.cpp
@@ -1494,6 +1494,13 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
 
       outs() << '\n' << std::get<1>(Symbols[si]) << ":\n";
 
+      // Don't print raw contents of a virtual section. A virtual section
+      // doesn't have any contents in the file.
+      if (Section.isVirtual()) {
+        outs() << "...\n";
+        continue;
+      }
+
 #ifndef NDEBUG
       raw_ostream &DebugOut = DebugFlag ? dbgs() : nulls();
 #else
-- 
2.7.4