Fix crash in llvm-objdump with proc-specific sections

[colinl]

Summary

getSection returns nullptr for some section types:

if (symb->st_shndx >= ELF::SHN_LORESERVE)
  return nullptr;

but getSymbolAddress was dereferencing this without checking.

[sidneym]

LGTM

[shankarke]

Can we use yaml2obj in the test ?

[colinl]

That seems like a possibility. I've never written one before so I'll have to figure out how. As long as they can generate process-specific elf sections it should be possible.

[• rafael]

Checking in binaries is fine.

include/llvm/Object/ELFObjectFile.h

318

Style: Don't use auto in here.

[colinl]

Changed auto to the full type.
Kept binary file as small as possible, 800 bytes.

include/llvm/Object/ELFObjectFile.h

       ESym->getType() == ELF::STT_FUNC)
     Result &= ~1;
 
-  if (Header->e_type == ELF::ET_REL)
-    Result += EF.getSection(ESym)->sh_addr;
+  if (Header->e_type == ELF::ET_REL) {
+    auto Section = EF.getSection(ESym);
+    if (Section != nullptr)
+      Result += Section->sh_addr;
+  }
 
   return object_error::success;
 }

test/tools/llvm-objdump/proc-specific-section-elf.test

+// RUN: llvm-objdump -t %p/Inputs/proc-specific-section-elf | FileCheck %s
+
+CHECK: 00000000         *UND*  00000000 print