[llvm-readobj] Downgrade 'PT_DYNAMIC segment offset + size exceeds the size of the file' from an error to a warning

[rupprecht]

Summary

This allows llvm-readobj to print other useful information for truncated files instead of giving up.

[grimar]

LGTM.

llvm/test/tools/llvm-readobj/elf-malformed-pt-dynamic.test

2

Should it be changed from error message -> message?

[jhenderson]

LGTM, aside from @grimar's comment.

llvm/test/Object/invalid.test

Sections:
   - Name:    .dynamic
     Type:    SHT_DYNAMIC
     Content: "00"
 
 ## PT_DYNAMIC's p_offset field is so large that p_offset + p_filesz is larger
 ## than the object size. Check llvm-readobj reports it.
 
 # RUN: yaml2obj %s --docnum=23 -o %t23
-# RUN: not llvm-readobj --dyn-relocations %t23 2>&1 | FileCheck --check-prefix=DYN-TABLE-PHDR %s
+# RUN: llvm-readobj --dyn-relocations %t23 2>&1 | FileCheck --check-prefix=DYN-TABLE-PHDR %s
 
-# DYN-TABLE-PHDR: error: PT_DYNAMIC segment offset + size exceeds the size of the file
+# DYN-TABLE-PHDR: warning: PT_DYNAMIC segment offset + size exceeds the size of the file
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_EXEC
   Machine: EM_X86_64
 Sections:
   - Name: .dynamic
     Type: SHT_DYNAMIC
     Entries:
       - Tag:   DT_NULL
         Value: 0
 ProgramHeaders:
   - Type:   PT_DYNAMIC
     Offset: 0xffff0000
     Sections:
       - Section: .dynamic
 
 ## PT_DYNAMIC's p_filesz field is so large that p_offset + p_filesz is larger
 ## than the object size. Check llvm-readobj reports it.
 
 # RUN: yaml2obj %s --docnum=24 -o %t24
-# RUN: not llvm-readobj --dyn-relocations %t24 2>&1 \
+# RUN: llvm-readobj --dyn-relocations %t24 2>&1 \
 # RUN:  | FileCheck --check-prefix=DYN-TABLE-PHDR %s
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_EXEC
   Machine: EM_X86_64

llvm/test/tools/llvm-readobj/elf-malformed-pt-dynamic.test

 # If the offset and/or size fields of the PT_DYNAMIC field become corrupted,
 # we should report a sensible error message.
 
 # Creating such a malformed file is hard. The easiest way to simulate it is to
 # truncate the file. Note that the section headers must first be stripped or
 # llvm-readobj will fail to parse the file due to the section header table
 # offset pointing outside the file.
 
 # RUN: yaml2obj %s -o %t.base
 # RUN: llvm-objcopy --strip-sections %t.base %t.stripped
 
 # Test case where the size is too large to fit in the file, but the start is
 # within the file.
 # RUN: cp %t.stripped %t.truncated1
 # RUN: %python -c "with open(r'%t.truncated1', 'r+') as f: f.truncate(0x1001)"
-# RUN: not llvm-readobj %t.truncated1 --dynamic-table 2>&1 | FileCheck %s
+# RUN: llvm-readobj %t.truncated1 --dynamic-table 2>&1 | FileCheck %s
 
 # Test case where the offset is too large to be in the file.
 # RUN: cp %t.stripped %t.truncated2
 # RUN: %python -c "with open(r'%t.truncated2', 'r+') as f: f.truncate(0xFFF)"
-# RUN: not llvm-readobj %t.truncated2 --dynamic-table 2>&1 | FileCheck %s
+# RUN: llvm-readobj %t.truncated2 --dynamic-table 2>&1 | FileCheck %s
 
-# CHECK: error: PT_DYNAMIC segment offset + size exceeds the size of the file
+# CHECK: warning: PT_DYNAMIC segment offset + size exceeds the size of the file
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_EXEC
   Machine: EM_X86_64
 Sections:

llvm/tools/llvm-readobj/ELFDumper.cpp

void ELFDumper<ELFT>::loadDynamicTable(const ELFFile<ELFT> *Obj) {
   }
 
   // If we have a PT_DYNAMIC header, we will either check the found dynamic
   // section or take the dynamic table data directly from the header.
   if (!DynamicPhdr)
     return;
 
   if (DynamicPhdr->p_offset + DynamicPhdr->p_filesz >
-      ObjF->getMemoryBufferRef().getBufferSize())
-    reportError(
+      ObjF->getMemoryBufferRef().getBufferSize()) {
+    reportWarning(
         "PT_DYNAMIC segment offset + size exceeds the size of the file");
+    return;
+  }
 
   if (!DynamicSec) {
     DynamicTable = createDRIFrom(DynamicPhdr, sizeof(Elf_Dyn));
     parseDynamicTable();
     return;
   }
 
   StringRef Name =