Use zlib to uncompress debug sections in DWARF parser.

This makes llvm-dwarfdump and llvm-symbolizer understand
debug info sections compressed by ld.gold linker.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180088 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 41 insertions, 0 deletions

diff --git a/lib/DebugInfo/DWARFContext.cpp b/lib/DebugInfo/DWARFContext.cpp
index 74a8c36d7a..1e13731361 100644
--- a/lib/DebugInfo/DWARFContext.cpp
+++ b/lib/DebugInfo/DWARFContext.cpp
@@ -10,6 +10,8 @@
 #include "DWARFContext.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringSwitch.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Compression.h"
 #include "llvm/Support/Dwarf.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/Path.h"
@@ -483,6 +485,22 @@ DIInliningInfo DWARFContext::getInliningInfoForAddress(uint64_t Address,
   return InliningInfo;
 }
 
+static bool consumeCompressedDebugSectionHeader(StringRef &data,
+                                                uint64_t &OriginalSize) {
+  // Consume "ZLIB" prefix.
+  if (!data.startswith("ZLIB"))
+    return false;
+  data = data.substr(4);
+  // Consume uncompressed section size (big-endian 8 bytes).
+  DataExtractor extractor(data, false, 8);
+  uint32_t Offset = 0;
+  OriginalSize = extractor.getU64(&Offset);
+  if (Offset == 0)
+    return false;
+  data = data.substr(Offset);
+  return true;
+}
+
 DWARFContextInMemory::DWARFContextInMemory(object::ObjectFile *Obj) :
   IsLittleEndian(Obj->isLittleEndian()),
   AddressSize(Obj->getBytesInAddress()) {
@@ -497,6 +515,22 @@ DWARFContextInMemory::DWARFContextInMemory(object::ObjectFile *Obj) :
 
     name = name.substr(name.find_first_not_of("._")); // Skip . and _ prefixes.
 
+    // Check if debug info section is compressed with zlib.
+    if (name.startswith("zdebug_")) {
+      uint64_t OriginalSize;
+      if (!zlib::isAvailable() ||
+          !consumeCompressedDebugSectionHeader(data, OriginalSize))
+        continue;
+      OwningPtr<MemoryBuffer> UncompressedSection;
+      if (zlib::uncompress(data, UncompressedSection, OriginalSize) !=
+          zlib::StatusOK)
+        continue;
+      // Make data point to uncompressed section contents and save its contents.
+      name = name.substr(1);
+      data = UncompressedSection->getBuffer();
+      UncompressedSections.push_back(UncompressedSection.take());
+    }
+
     StringRef *Section = StringSwitch<StringRef*>(name)
         .Case("debug_info", &InfoSection)
         .Case("debug_abbrev", &AbbrevSection)
@@ -584,4 +618,8 @@ DWARFContextInMemory::DWARFContextInMemory(object::ObjectFile *Obj) :
   }
 }
 
+DWARFContextInMemory::~DWARFContextInMemory() {
+  DeleteContainerPointers(UncompressedSections);
+}
+
 void DWARFContextInMemory::anchor() { }
diff --git a/lib/DebugInfo/DWARFContext.h b/lib/DebugInfo/DWARFContext.h
index 37b272993f..78c18e6168 100644
--- a/lib/DebugInfo/DWARFContext.h
+++ b/lib/DebugInfo/DWARFContext.h
@@ -161,8 +161,11 @@ class DWARFContextInMemory : public DWARFContext {
   StringRef RangeDWOSection;
   StringRef AddrSection;
 
+  SmallVector<MemoryBuffer*, 4> UncompressedSections;
+
 public:
   DWARFContextInMemory(object::ObjectFile *);
+  ~DWARFContextInMemory();
   virtual bool isLittleEndian() const { return IsLittleEndian; }
   virtual uint8_t getAddressSize() const { return AddressSize; }
   virtual const RelocAddrMap &infoRelocMap() const { return InfoRelocMap; }