[llvm-readelf] - Report a warning instead of an error when dumping a broken section header.

[grimar]

Summary

There is no reason to report an error in printSectionHeaders(), we can report
a warning and continue dumping. This is what the patch does.

[MaskRay]

Thanks!

[jhenderson]

LGTM, with one suggestion. Thanks!

llvm/tools/llvm-readobj/ELFDumper.cpp

3829–3834

Consider using the following instead to limit the scope of SecStrTableOrErr:

if (Expected<StringRef> SecStrTableOrErr =
    Obj->getSectionStringTable(Sections, this->dumper()->WarningHandler);)
  SecStrTable = *SecStrTableOrErr;
else
  this->reportUniqueWarning(SecStrTableOrErr.takeError());

(I don't mind if you don't want to do that though)

[grimar]

llvm/tools/llvm-readobj/ELFDumper.cpp

3829–3834

Will do, I like the idea to limit scopes where possible. Thanks!

llvm/test/tools/llvm-readobj/ELF/invalid-shstrndx.test

 # RUN: yaml2obj %s -o %t
 # RUN: not llvm-readelf --headers -S 2>&1 %t | FileCheck %s -DFILE=%t --check-prefix=GNU
 # RUN: llvm-readobj --headers -S 2>&1 %t | FileCheck %s -DFILE=%t --check-prefix=LLVM
 
 # GNU:      ELF Header:
 # GNU:        Section header string table index: 255
 # GNU-NEXT:   There are 3 section headers, starting at offset 0x58:
 # GNU:      Section Headers:
-# GNU-NEXT:  [Nr] Name
-# GNU-NEXT:  error: '[[FILE]]': section header string table index 255 does not exist
+# GNU-NEXT:  [Nr] Name         Type   Address          Off    Size   ES Flg Lk Inf Al
+# GNU-NEXT: warning: '[[FILE]]': section header string table index 255 does not exist
+# GNU-NEXT:  [ 0] <no-strings> NULL   0000000000000000 000000 000000 00      0   0  0
+# GNU-NEXT:  [ 1] <no-strings> STRTAB 0000000000000000 000040 000001 00      0   0  1
+# GNU-NEXT:  [ 2] <no-strings> STRTAB 0000000000000000 000041 000013 00      0   0  1
+# GNU-NEXT: Key to Flags:
+# GNU:      Section to Segment mapping:
+# GNU-NEXT:   Segment Sections...
+# GNU-NEXT: error: '[[FILE]]': section header string table index 255 does not exist
 
 # LLVM:      ElfHeader {
 # LLVM:        StringTableSectionIndex: 255
 # LLVM-NEXT: }
 # LLVM-NEXT: Sections [
 # LLVM-NEXT: warning: '[[FILE]]': section header string table index 255 does not exist
 # LLVM-NEXT: Section {
 # LLVM-NEXT:   Index: 0

llvm/test/tools/llvm-readobj/ELF/many-sections.s

- Type: SHT_NULL
     Link: .shstrtab
     Size: 0x3
 
 ## Another case is when e_shoff field set to zero, but not e_shstrndx.
 ## We want to show that this corrupt case is handled correctly.
 
 # RUN: yaml2obj --docnum=2 %s -o %t2
 
-# RUN: not llvm-readelf --file-headers --sections %t2 2>&1 | \
+# RUN: llvm-readelf --file-headers --sections %t2 2>&1 | \
 # RUN:   FileCheck %s -DFILE=%t2 --check-prefix=GNU2
 # GNU2: Number of section headers:         0
 # GNU2: Section header string table index: 65535 (corrupt: out of range)
 
 # GNU2:       There are 0 section headers, starting at offset 0x0:
 # GNU2-EMPTY:
 # GNU2-NEXT:  Section Headers:
 # GNU2-NEXT:   [Nr] Name Type Address Off Size ES Flg Lk Inf Al
-# GNU2-NEXT:   error: '[[FILE]]': e_shstrndx == SHN_XINDEX, but the section header table is empty
+# GNU2-NEXT:  warning: '[[FILE]]': e_shstrndx == SHN_XINDEX, but the section header table is empty
+# GNU2-NEXT:  Key to Flags:
 
 # RUN: llvm-readobj --file-headers --sections %t2 | \
 # RUN:   FileCheck %s --check-prefix=LLVM2 --implicit-check-not="warning:"
 # LLVM2:       SectionHeaderCount: 0
 # LLVM2:       StringTableSectionIndex: 65535 (corrupt: out of range)
 # LLVM2-NEXT: }
 # LLVM2-NEXT: Sections [
 # LLVM2-NEXT: ]

llvm/tools/llvm-readobj/ELFDumper.cpp

Field Fields[11] = {
       {"[Nr]", 2},        {"Name", 7},        {"Type", 25},
       {"Address", 41},    {"Off", 58 - Bias}, {"Size", 65 - Bias},
       {"ES", 72 - Bias},  {"Flg", 75 - Bias}, {"Lk", 79 - Bias},
       {"Inf", 82 - Bias}, {"Al", 86 - Bias}};
   for (auto &F : Fields)
     printField(F);
   OS << "\n";
 
-  const ELFObjectFile<ELFT> *ElfObj = this->dumper()->getElfObject();
-  StringRef SecStrTable = unwrapOrError<StringRef>(
-      ElfObj->getFileName(),
-      Obj->getSectionStringTable(Sections, this->dumper()->WarningHandler));
+  StringRef SecStrTable;
+  Expected<StringRef> SecStrTableOrErr =
+      Obj->getSectionStringTable(Sections, this->dumper()->WarningHandler);
+  if (!SecStrTableOrErr)
+    this->reportUniqueWarning(SecStrTableOrErr.takeError());
+  else
+    SecStrTable = *SecStrTableOrErr;
+
   size_t SectionIndex = 0;
   for (const Elf_Shdr &Sec : Sections) {
     Fields[0].Str = to_string(SectionIndex);
     if (SecStrTable.empty())
       Fields[1].Str = "<no-strings>";
     else
       Fields[1].Str = std::string(unwrapOrError<StringRef>(
-          ElfObj->getFileName(), Obj->getSectionName(&Sec, SecStrTable)));
+          this->FileName, Obj->getSectionName(&Sec, SecStrTable)));
     Fields[2].Str =
         getSectionTypeString(Obj->getHeader()->e_machine, Sec.sh_type);
     Fields[3].Str =
         to_string(format_hex_no_prefix(Sec.sh_addr, ELFT::Is64Bits ? 16 : 8));
     Fields[4].Str = to_string(format_hex_no_prefix(Sec.sh_offset, 6));
     Fields[5].Str = to_string(format_hex_no_prefix(Sec.sh_size, 6));
     Fields[6].Str = to_string(format_hex_no_prefix(Sec.sh_entsize, 2));
     Fields[7].Str = getGNUFlags(Obj->getHeader()->e_machine, Sec.sh_flags);