[llvm] 122c50d - Fix DWARFDataExtractor::getRelocatedValue near EOF

[Pavel Labath via llvm-commits]

Author: Pavel Labath
Date: 2020-04-15T12:47:57+02:00
New Revision: 122c50d5efc2d5bc8d6716a532ba0cc6b773ab3a

URL: https://github.com/llvm/llvm-project/commit/122c50d5efc2d5bc8d6716a532ba0cc6b773ab3a
DIFF: https://github.com/llvm/llvm-project/commit/122c50d5efc2d5bc8d6716a532ba0cc6b773ab3a.diff

LOG: Fix DWARFDataExtractor::getRelocatedValue near EOF

Summary:
If we have an (invalid) relocation which relocates bytes which partially
lie outside the range of the relocated section, the getRelocatedValue
would return confusing results. It would first read zero (because that's
what the underlying DataExtractor api does for out-of-bounds reads), and
then relocate that zero anyway.

A more appropriate behavior is to return zero straight away. This is
what this patch does.

Reviewers: dblaikie, jhenderson

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78113

Added: 
    

Modified: 
    llvm/lib/DebugInfo/DWARF/DWARFDataExtractor.cpp
    llvm/unittests/DebugInfo/DWARF/DWARFDataExtractorTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/DebugInfo/DWARF/DWARFDataExtractor.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDataExtractor.cpp
index 18b86b28ccab..886fe1dff976 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDataExtractor.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDataExtractor.cpp
@@ -50,9 +50,11 @@ uint64_t DWARFDataExtractor::getRelocatedValue(uint32_t Size, uint64_t *Off,
     *SecNdx = object::SectionedAddress::UndefSection;
   if (!Section)
     return getUnsigned(Off, Size, Err);
+
+  ErrorAsOutParameter ErrAsOut(Err);
   Optional<RelocAddrEntry> E = Obj->find(*Section, *Off);
   uint64_t A = getUnsigned(Off, Size, Err);
-  if (!E)
+  if (!E || (Err && *Err))
     return A;
   if (SecNdx)
     *SecNdx = E->SectionIndex;

diff  --git a/llvm/unittests/DebugInfo/DWARF/DWARFDataExtractorTest.cpp b/llvm/unittests/DebugInfo/DWARF/DWARFDataExtractorTest.cpp
index 6528cd074c86..46af26026147 100644
--- a/llvm/unittests/DebugInfo/DWARF/DWARFDataExtractorTest.cpp
+++ b/llvm/unittests/DebugInfo/DWARF/DWARFDataExtractorTest.cpp
@@ -7,6 +7,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/DWARF/DWARFDataExtractor.h"
+#include "llvm/DebugInfo/DWARF/DWARFContext.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/ObjectYAML/yaml2obj.h"
 #include "llvm/Testing/Support/Error.h"
 #include "gtest/gtest.h"
 
@@ -14,6 +17,54 @@ using namespace llvm;
 
 namespace {
 
+TEST(DWARFDataExtractorTest, getRelocatedValue) {
+  StringRef Yaml = R"(
+!ELF
+FileHeader:
+  Class:    ELFCLASS32
+  Data:     ELFDATA2LSB
+  Type:     ET_REL
+  Machine:  EM_386
+Sections:
+  - Name:     .text
+    Type:     SHT_PROGBITS
+    Size:     0x80
+  - Name:     .debug_line
+    Type:     SHT_PROGBITS
+    Content:  '000000000000'
+  - Name:     .rel.debug_line
+    Type:     SHT_REL
+    Info:     .debug_line
+    Relocations:
+      - Offset:   0
+        Symbol:   f
+        Type:     R_386_32
+      - Offset:   4
+        Symbol:   f
+        Type:     R_386_32
+Symbols:
+  - Name:     f
+    Type:     STT_SECTION
+    Section:  .text
+    Value:    0x42
+)";
+  SmallString<0> Storage;
+  std::unique_ptr<object::ObjectFile> Obj = yaml::yaml2ObjectFile(
+      Storage, Yaml, [](const Twine &Err) { errs() << Err; });
+  ASSERT_TRUE(Obj);
+  std::unique_ptr<DWARFContext> Ctx = DWARFContext::create(*Obj);
+  const DWARFObject &DObj = Ctx->getDWARFObj();
+  ASSERT_EQ(6u, DObj.getLineSection().Data.size());
+
+  DWARFDataExtractor Data(DObj, DObj.getLineSection(), Obj->isLittleEndian(),
+                          Obj->getBytesInAddress());
+  DataExtractor::Cursor C(0);
+  EXPECT_EQ(0x42u, Data.getRelocatedAddress(C));
+  EXPECT_EQ(0u, Data.getRelocatedAddress(C));
+  EXPECT_THAT_ERROR(C.takeError(),
+                    FailedWithMessage("unexpected end of data at offset 0x4"));
+}
+
 TEST(DWARFDataExtractorTest, getInitialLength) {
   auto GetWithError = [](ArrayRef<uint8_t> Bytes)
       -> Expected<std::tuple<uint64_t, dwarf::DwarfFormat, uint64_t>> {