[PATCH] D67547: [llvm-readobj/llvm-objdump] - Improve how tool locate the dynamic table and report warnings about that.

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added inline comments.


================
Comment at: tools/llvm-readobj/ELFDumper.cpp:1500
                   DynamicSec->sh_size, sizeof(Elf_Dyn), ObjF->getFileName()});
-    parseDynamicTable();
+    IsSecTableValid = !FromSec.getAsArrayRef<Elf_Dyn>().empty();
   }
----------------
The logic is:

```
findDynamic
  find PT_DYNAMIC
  find .dynamic
  if p_offset is out of bounds
    reportWarning
  if both PT_DYNAMIC and .dynamic exist
    check if the information matches

loadDynamicTable
  findDynamic()
  if PT_DYNAMIC exists
    IsPhdrTableValid = PT_DYNAMIC's DynRegionInfo is not empty
  if .dynamic exists
    IsSecTableValid = .dynamic's DynRegionInfo is not empty
  if either does not exist
    if (IsPhdrTableValid && IsSecTableValid)
      parseDynamicTable()
    else
      warn
    return

  validate information matches
  ...
```

Shall we check whether p_offset is out of bounds and whether DynRegionInfo of PT_DYNAMIC is empty together?

```
findDynamic
  find PT_DYNAMIC
  IsPhdrTableValid = whether PT_DYNAMIC exists
  if p_offset is out of bounds or DynRegionInfo not empty
    reportWarning
    IsPhdrTableValid = false

  find .dynamic
  validate .dynamic

  if either does not exist
    if ((DynamicPhdr && IsPhdrTableValid) || (DynamicSec && IsSecTableValid))
      parseDynamicTable()
    else
      warn
    return

  ...
  validate information matches
  parseDynamicTable()
```


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D67547/new/

https://reviews.llvm.org/D67547