[llvm-readobj][xcoff] implement parsing overflow section header.

[DiggerLin]

Summary

in the xcoff, if the number of relocation entries or line number entries is overflow(large than or equal 65535) , there will be overflow section for it. The interpret of overflow section is different with generic section header, the patch implement parsing the overflow section.

[hubert.reinterpretcast]

llvm/test/tools/llvm-readobj/xcoff-overflow-section.test

38

The same information, when conveyed not via an overflow header, is expressed in decimal format (and not hexadecimal).

39

Ditto.

42

According to the XCOFF documentation: The s_relptr and s_lnnoptr fields must have the same values as in the corresponding primary section header.

43

See above.

llvm/tools/llvm-readobj/XCOFFDumper.cpp

445–446

Since we removed the context of the code line from here, the comment is ambiguous. This should say that, for now, we dump only the section type (low order 16 bits).

446

Can we encode this into a function (getSectionType(const T &Section)) or constant (SectionFlagsTypeMask) with the comment:
The low order 16 bits of s_flags denotes the section type.

Also, the variable should be named SectionType or similar.

450

I think we should not be printing a "warning" to the same stream as the output.

451

"64-bit XCOFF object file".

457

s/TODO : /TODO /;
s/interpret/interpretation/;
s/, type check section header/, and type check section headers/;
s/from/from that of/;
s/generic section header/generic section headers/;
s/generic seciton header now/generic section headers for now/;

[DiggerLin]

llvm/test/tools/llvm-readobj/xcoff-overflow-section.test

38

changed as suggestion.

39

changed as suggestion.

42

changed raw data and test case

llvm/tools/llvm-readobj/XCOFFDumper.cpp

445–446

changed as suggestions.

450

changed

457

changed as suggestion.

[DiggerLin]

address some comments

[hubert.reinterpretcast]

llvm/tools/llvm-readobj/XCOFFDumper.cpp

58

Add a blank line here. Also, I am wondering if this should be part of llvm/BinaryFormat/XCOFF.h (perhaps in SectionHeader32, or in a base class thereof when 64-bit support lands).

455

The "TODO" still has a colon surrounded by spaces on both sides after it. I do not think that we have been using colons after "TODO".

Still missing "and" before "type check section headers".

Still missing "s" after "generic section header".

Typo "seciton" is still present.

463

Suggestion: "For now we just dump the section type portion of the flags."

[DiggerLin]

llvm/tools/llvm-readobj/XCOFFDumper.cpp

58

for consistent with SectionFlagsReservedMask, puting define SectionFlagsTypeMask here too, I think we maybe need to create a NFC patch to put SectionFlagsReservedMask and SectionFlagsTypeMask in the xcoff.h

455

changed as suggestion

463

changed as suggestion.

[hubert.reinterpretcast]

LGTM to land as-is. Not sure if other people have an opinion about the const.
@DiggerLin, I believe you have had a number of patches committed into the project. I think you can request commit access and land this yourself. Thanks.

llvm/tools/llvm-readobj/XCOFFDumper.cpp

46

I am not sure that I see a meaningful difference between the functions here that are const and the ones that are not. Given that there are already precedent cases of printing methods of ObjDumper subclasses that are const, I am okay with adding new ones that are const if we have reason to believe they will remain const.

58

Okay, I agree. Would you mind posting such an NFC patch after this patch lands?

455

For future reference, I believe we have been using "Oxford commas". That is, a comma before the "and" before (in this case) the third list item, would be appropriate.

[DiggerLin]

llvm/tools/llvm-readobj/XCOFFDumper.cpp

46

when I create a new function , I make as many functions const as possible so that accidental changes to objects are avoided.

58

OK, I will do it.

455

OK, got it , thanks

llvm/test/tools/llvm-readobj/xcoff-overflow-section.test

+# RUN: llvm-readobj --sections %p/Inputs/xcoff-reloc-overflow.o | \
+# RUN: FileCheck --check-prefix=SECOVERFLOW %s
+# SECOVERFLOW:      File: {{.*}}xcoff-reloc-overflow.o 
+# SECOVERFLOW-NEXT: Format: aixcoff-rs6000
+# SECOVERFLOW-NEXT: Arch: powerpc
+# SECOVERFLOW-NEXT: AddressSize: 32bit
+# SECOVERFLOW-NEXT: Sections [
+# SECOVERFLOW-NEXT:   Section {
+# SECOVERFLOW-NEXT:     Index: 1
+# SECOVERFLOW-NEXT:     Name: .text
+# SECOVERFLOW-NEXT:     PhysicalAddress: 0x0
+# SECOVERFLOW-NEXT:     VirtualAddress: 0x0
+# SECOVERFLOW-NEXT:     Size: 0x38
+# SECOVERFLOW-NEXT:     RawDataOffset: 0x8C
+# SECOVERFLOW-NEXT:     RelocationPointer: 0x0
+# SECOVERFLOW-NEXT:     LineNumberPointer: 0x0
+# SECOVERFLOW-NEXT:     NumberOfRelocations: 0
+# SECOVERFLOW-NEXT:     NumberOfLineNumbers: 0
+# SECOVERFLOW-NEXT:     Type: STYP_TEXT (0x20)
+# SECOVERFLOW-NEXT:   }
+# SECOVERFLOW-NEXT:   Section {
+# SECOVERFLOW-NEXT:     Index: 2
+# SECOVERFLOW-NEXT:     Name: .data
+# SECOVERFLOW-NEXT:     PhysicalAddress: 0x38
+# SECOVERFLOW-NEXT:     VirtualAddress: 0x38
+# SECOVERFLOW-NEXT:     Size: 0x1C
+# SECOVERFLOW-NEXT:     RawDataOffset: 0xC4
+# SECOVERFLOW-NEXT:     RelocationPointer: 0xE0
+# SECOVERFLOW-NEXT:     LineNumberPointer: 0x0
+# SECOVERFLOW-NEXT:     NumberOfRelocations: 65535
+# SECOVERFLOW-NEXT:     NumberOfLineNumbers: 65535
+# SECOVERFLOW-NEXT:     Type: STYP_DATA (0x40)
+# SECOVERFLOW-NEXT:   }
+# SECOVERFLOW-NEXT:   Section {
+# SECOVERFLOW-NEXT:     Index: 3
+# SECOVERFLOW-NEXT:     Name: .ovrflo
+# SECOVERFLOW-NEXT:     NumberOfRelocations: 3
+# SECOVERFLOW-NEXT:     NumberOfLineNumbers: 3
+# SECOVERFLOW-NEXT:     Size: 0x0
+# SECOVERFLOW-NEXT:     RawDataOffset: 0x0
+# SECOVERFLOW-NEXT:     RelocationPointer: 0xE0
+# SECOVERFLOW-NEXT:     LineNumberPointer: 0x0
+# SECOVERFLOW-NEXT:     IndexOfSectionOverflowed: 2
+# SECOVERFLOW-NEXT:     IndexOfSectionOverflowed: 2
+# SECOVERFLOW-NEXT:     Type: STYP_OVRFLO (0x8000)
+# SECOVERFLOW-NEXT:   }
+# SECOVERFLOW-NEXT: ]

llvm/tools/llvm-readobj/XCOFFDumper.cpp

public:
   void printSymbols() override;
   void printDynamicSymbols() override;
   void printUnwindInfo() override;
   void printStackMap() const override;
   void printNeededLibraries() override;
 
 private:
   template <typename T> void printSectionHeaders(ArrayRef<T> Sections);
+  template <typename T> void printGenericSectionHeader(T &Sec) const;
+  template <typename T> void printOverflowSectionHeader(T &Sec) const;
   void printFileAuxEnt(const XCOFFFileAuxEnt *AuxEntPtr);
   void printCsectAuxEnt32(const XCOFFCsectAuxEnt32 *AuxEntPtr);
   void printSectAuxEntForStat(const XCOFFSectAuxEntForStat *AuxEntPtr);
   void printSymbol(const SymbolRef &);
 
   // Least significant 3 bits are reserved.
   static constexpr unsigned SectionFlagsReservedMask = 0x7;
+
+  // The low order 16 bits of section flags denotes the section type.
+  static constexpr unsigned SectionFlagsTypeMask = 0xffffu;
   const XCOFFObjectFile &Obj;
 };
 } // anonymous namespace
 
 void XCOFFDumper::printFileHeaders() {
   DictScope DS(W, "FileHeader");
   W.printHex("Magic", Obj.getMagic());
   W.printNumber("NumberOfSections", Obj.getNumberOfSections());
 
#define ECase(X)                                                               \
     ECase(STYP_DATA),   ECase(STYP_BSS),   ECase(STYP_EXCEPT),
     ECase(STYP_INFO),   ECase(STYP_TDATA), ECase(STYP_TBSS),
     ECase(STYP_LOADER), ECase(STYP_DEBUG), ECase(STYP_TYPCHK),
     ECase(STYP_OVRFLO)
 #undef ECase
 };
 
 template <typename T>
-void XCOFFDumper::printSectionHeaders(ArrayRef<T> Sections) {
-  ListScope Group(W, "Sections");
-
-  uint16_t Index = 1;
-  for (const T &Sec : Sections) {
-    DictScope SecDS(W, "Section");
+void XCOFFDumper::printOverflowSectionHeader(T &Sec) const {
+  if (Obj.is64Bit()) {
+    reportWarning(make_error<StringError>("An 64-bit XCOFF object file may not "
+                                          "contain an overflow section header.",
+                                          object_error::parse_failed),
+                  Obj.getFileName());
+  }
 
-    W.printNumber("Index", Index++);
-    W.printString("Name", Sec.getName());
+  W.printNumber("NumberOfRelocations", Sec.PhysicalAddress);
+  W.printNumber("NumberOfLineNumbers", Sec.VirtualAddress);
+  W.printHex("Size", Sec.SectionSize);
+  W.printHex("RawDataOffset", Sec.FileOffsetToRawData);
+  W.printHex("RelocationPointer", Sec.FileOffsetToRelocationInfo);
+  W.printHex("LineNumberPointer", Sec.FileOffsetToLineNumberInfo);
+  W.printNumber("IndexOfSectionOverflowed", Sec.NumberOfRelocations);
+  W.printNumber("IndexOfSectionOverflowed", Sec.NumberOfLineNumbers);
+}
 
-    W.printHex("PhysicalAddress", Sec.PhysicalAddress);
-    W.printHex("VirtualAddress", Sec.VirtualAddress);
-    W.printHex("Size", Sec.SectionSize);
-    W.printHex("RawDataOffset", Sec.FileOffsetToRawData);
-    W.printHex("RelocationPointer", Sec.FileOffsetToRelocationInfo);
-    W.printHex("LineNumberPointer", Sec.FileOffsetToLineNumberInfo);
-
-    // TODO Need to add overflow handling when NumberOfX == _OVERFLOW_MARKER
-    // in 32-bit object files.
-    W.printNumber("NumberOfRelocations", Sec.NumberOfRelocations);
-    W.printNumber("NumberOfLineNumbers", Sec.NumberOfLineNumbers);
+template <typename T>
+void XCOFFDumper::printGenericSectionHeader(T &Sec) const {
+  W.printString("Name", Sec.getName());
+}
+
+template <typename T>
+void XCOFFDumper::printSectionHeaders(ArrayRef<T> Sections) {
+  ListScope Group(W, "Sections");
+
+  uint16_t Index = 1;
+  for (const T &Sec : Sections) {
+    DictScope SecDS(W, "Section");
+
+    W.printNumber("Index", Index++);
 
-    // The most significant 16-bits represent the DWARF section subtype. For
-    // now we just dump the section type flags.
-    uint16_t Flags = Sec.Flags & 0xffffu;
-    if (Flags & SectionFlagsReservedMask)
-      W.printHex("Flags", "Reserved", Flags);
+    uint16_t SectionType = Sec.Flags & SectionFlagsTypeMask;
+    switch (SectionType) {
+    case XCOFF::STYP_OVRFLO:
+      printOverflowSectionHeader(Sec);
+      break;
+    case XCOFF::STYP_LOADER:
+    case XCOFF::STYP_EXCEPT:
+    case XCOFF::STYP_TYPCHK:
+      // TODO : The interpretation of loader, exception, type check section
+      // headers are different from that of generic section header. We will
+      // implement them later. We interpret them as generic seciton headers for
+      // now.
+    default:
+      printGenericSectionHeader(Sec);
+      break;
+    }
+    // For now we just dump the section type flags.
+    if (SectionType & SectionFlagsReservedMask)
+      W.printHex("Flags", "Reserved", SectionType);
     else
-      W.printEnum("Type", Flags, makeArrayRef(SectionTypeFlagsNames));
+      W.printEnum("Type", SectionType, makeArrayRef(SectionTypeFlagsNames));
   }
 
   if (opts::SectionRelocations)
     report_fatal_error("Dumping section relocations is unimplemented");
 
   if (opts::SectionSymbols)
     report_fatal_error("Dumping symbols is unimplemented");