[obj2yaml] - Do not miss section index for special symbols.

This fixes https://bugs.llvm.org/show_bug.cgi?id=40786 
("obj2yaml symbol output missing section index for SHN_ABS and SHN_COMMON symbols")

Since SHN_ABS and SHN_COMMON symbols are special, we should preserve
the st_shndx for them. The patch does this for them and the other special symbols.

The test case is based on the test provided by James Henderson at the bug page!

Differential revision: https://reviews.llvm.org/D58498

llvm-svn: 354661

3 files changed, 53 insertions, 0 deletions

diff --git a/llvm/test/tools/obj2yaml/Inputs/shn_xindex.o b/llvm/test/tools/obj2yaml/Inputs/shn_xindex.o
new file mode 100644
index 00000000000..73e2b60ba1e
--- /dev/null
+++ b/llvm/test/tools/obj2yaml/Inputs/shn_xindex.o
diff --git a/llvm/test/tools/obj2yaml/special-symbol-indices.yaml b/llvm/test/tools/obj2yaml/special-symbol-indices.yaml
new file mode 100644
index 00000000000..127dc25a0df
--- /dev/null
+++ b/llvm/test/tools/obj2yaml/special-symbol-indices.yaml
@@ -0,0 +1,46 @@
+# RUN: yaml2obj %s > %t
+# RUN: obj2yaml %t | FileCheck %s
+
+## Test checks that we are able to handle symbols with special/reserved indices.
+
+# CHECK:      Symbols:
+# CHECK-NEXT:   Global:
+# CHECK-NEXT:     - Name:    absolute
+# CHECK-NEXT:       Index:   SHN_ABS
+# CHECK-NEXT:       Value:   0x0000000000001234
+# CHECK-NEXT:     - Name:    common
+# CHECK-NEXT:       Index:   SHN_COMMON
+# CHECK-NEXT:     - Name:    valid_index
+# CHECK-NEXT:       Section: .text
+# CHECK-NEXT:     - Name:    processor_specific_index
+# CHECK-NEXT:       Index:   SHN_HEXAGON_SCOMMON_1
+# CHECK-NEXT:     - Name:    unknown_index
+# CHECK-NEXT:       Index:   0x0000FFFE
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_HEXAGON
+Sections:
+  - Name: .text
+    Type: SHT_PROGBITS
+Symbols:
+  Global:
+    - Name:     absolute
+      Index:    SHN_ABS
+      Value:    0x1234
+    - Name:     common
+      Index:    SHN_COMMON
+    - Name:     valid_index
+      Index:    0x1
+    - Name:     processor_specific_index
+      Index:    SHN_HEXAGON_SCOMMON_1
+    - Name:     unknown_index
+      Index:    0xfffe
+
+## shn_xindex.o contains a symbol with st_shndx == SHN_XINDEX.
+## We do not support it at this moment.
+# RUN: not obj2yaml %S/Inputs/shn_xindex.o 2>&1 | FileCheck %s --check-prefix=ERR
+# ERR: Error reading file: {{.*}}shn_xindex.o: Feature not yet implemented.
diff --git a/llvm/tools/obj2yaml/elf2yaml.cpp b/llvm/tools/obj2yaml/elf2yaml.cpp
index b02c25ad153..7f5e9a28d72 100644
--- a/llvm/tools/obj2yaml/elf2yaml.cpp
+++ b/llvm/tools/obj2yaml/elf2yaml.cpp
@@ -284,6 +284,13 @@ ELFDumper<ELFT>::dumpSymbol(const Elf_Sym *Sym, const Elf_Shdr *SymTab,
     return errorToErrorCode(SymbolNameOrErr.takeError());
   S.Name = SymbolNameOrErr.get();
 
+  if (Sym->st_shndx >= ELF::SHN_LORESERVE) {
+    if (Sym->st_shndx == ELF::SHN_XINDEX)
+      return obj2yaml_error::not_implemented;
+    S.Index = (ELFYAML::ELF_SHN)Sym->st_shndx;
+    return obj2yaml_error::success;
+  }
+
   auto ShdrOrErr = Obj.getSection(Sym, SymTab, ShndxTable);
   if (!ShdrOrErr)
     return errorToErrorCode(ShdrOrErr.takeError());