[PATCH] D63074: [llvm-readobj/llvm-readelf] - Don't fail to dump the object if .dynsym has broken sh_link field.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
grimar added reviewers: jhenderson, rupprecht, jakehehrlich, MaskRay.
grimar planned changes to this revision.

This is https://bugs.llvm.org/show_bug.cgi?id=42215.

GNU readelf allows to dump the objects in that case,
but llvm-readobj/llvm-readelf reports an error and stops.

The patch fixes that.


https://reviews.llvm.org/D63074

Files:
  test/tools/llvm-readobj/Inputs/elf-broken-dynsym-link.elf-x86-64
  test/tools/llvm-readobj/elf-broken-dynsym-link.test
  tools/llvm-readobj/ELFDumper.cpp
  tools/llvm-readobj/llvm-readobj.h


Index: tools/llvm-readobj/llvm-readobj.h
===================================================================
--- tools/llvm-readobj/llvm-readobj.h
+++ tools/llvm-readobj/llvm-readobj.h
@@ -44,6 +44,16 @@
     OS.flush();
     reportError(Buf);
   }
+  template <class T> T unwrapOrWarn(Expected<T> EO) {
+    if (EO)
+      return *EO;
+    std::string Buf;
+    raw_string_ostream OS(Buf);
+    logAllUnhandledErrors(EO.takeError(), OS);
+    OS.flush();
+    reportWarning(Buf);
+    return {};
+  }
 } // namespace llvm
 
 namespace opts {
Index: tools/llvm-readobj/ELFDumper.cpp
===================================================================
--- tools/llvm-readobj/ELFDumper.cpp
+++ tools/llvm-readobj/ELFDumper.cpp
@@ -1423,7 +1423,7 @@
         // This is only used (if Elf_Shdr present)for naming section in GNU
         // style
         DynSymtabName = unwrapOrError(Obj->getSectionName(&Sec));
-        DynamicStringTable = unwrapOrError(Obj->getStringTableForSymtab(Sec));
+        DynamicStringTable = unwrapOrWarn(Obj->getStringTableForSymtab(Sec));
       }
       break;
     case ELF::SHT_SYMTAB_SHNDX:
Index: test/tools/llvm-readobj/elf-broken-dynsym-link.test
===================================================================
--- /dev/null
+++ test/tools/llvm-readobj/elf-broken-dynsym-link.test
@@ -0,0 +1,60 @@
+## Test that we are able to dump section headers even if the
+## .dynsym section's sh_link field is broken.
+
+## Case 1: sh_link is set to 0.
+# RUN: yaml2obj %s -o %t1
+# RUN: llvm-readobj -S %t1 2>&1 | FileCheck %s --check-prefixes=LLVM,ERR
+# RUN: llvm-readelf -S %t1 2>&1 | FileCheck %s --check-prefixes=GNU,ERR
+
+# ERR: warning: invalid sh_type for string table, expected SHT_STRTAB
+
+# LLVM:      Name: .dynsym
+# LLVM-NEXT:  Type: SHT_DYNSYM
+# LLVM-NEXT:  Flags [
+# LLVM-NEXT:    SHF_ALLOC
+# LLVM-NEXT:  ]
+# LLVM-NEXT:  Address: 0x0
+# LLVM-NEXT:  Offset: 0x180
+# LLVM-NEXT:  Size: 24
+# LLVM-NEXT:  Link: 0
+
+# GNU:      Section Headers:
+# GNU-NEXT:  [Nr] Name    Type   Address          Off    Size   ES Flg Lk
+# GNU-NEXT:  [ 0]         NULL   0000000000000000 000000 000000 00 0   0
+# GNU-NEXT:  [ 1] .dynsym DYNSYM 0000000000000000 000180 000018 18 A   0
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .dynsym
+    Type: SHT_DYNSYM
+
+## TODO: Remove precompiled input object after fixing yaml2obj.
+##       See https://bugs.llvm.org/show_bug.cgi?id=42216.
+
+## Case 2: sh_link is set to 255, which is larger than the number of the sections.
+# RUN: llvm-readobj -S %p/Inputs/elf-broken-dynsym-link.elf-x86-64 2>&1 \
+# RUN:   | FileCheck %s --check-prefixes=LLVM2,ERR2
+# RUN: llvm-readelf -S %p/Inputs/elf-broken-dynsym-link.elf-x86-64 2>&1 \
+# RUN:   | FileCheck %s --check-prefixes=GNU2,ERR2
+
+# ERR2: warning: invalid section index
+
+# LLVM2:      Name: .dynsym
+# LLVM2-NEXT:  Type: SHT_DYNSYM
+# LLVM2-NEXT:  Flags [
+# LLVM2-NEXT:    SHF_ALLOC
+# LLVM2-NEXT:  ]
+# LLVM2-NEXT:  Address: 0x0
+# LLVM2-NEXT:  Offset: 0x180
+# LLVM2-NEXT:  Size: 2
+# LLVM2-NEXT:  Link: 255
+
+# GNU2:      Section Headers:
+# GNU2-NEXT:  [Nr] Name    Type   Address          Off    Size   ES Flg Lk
+# GNU2-NEXT:  [ 0]         NULL   0000000000000000 000000 000000 00 0   0
+# GNU2-NEXT:  [ 1] .dynsym DYNSYM 0000000000000000 000180 000002 18 A   255


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