[Object/ELF] - Refine the error reported when section's offset + size overruns the file buffer.

[grimar]

Summary

This is a follow-up requested in comments for D70826.

It changes the message from
"section X has a sh_offset (Y) + sh_size (Z) that cannot be represented"
to
"section X has a sh_offset (Y) + sh_size (Z) that is greater than the file size S"

when section's sh_offset + sh_size overruns a file buffer.

[jhenderson]

Thanks for this. Just one comment.

llvm/include/llvm/Object/ELF.h

414

The file size should be in brackets and have the 0x prefix (i.e. file size (0x1234)).

[MaskRay]

LG

[grimar]

• Addressed review comment.

llvm/include/llvm/Object/ELF.h

414

Yeah, sorry, done.

[jhenderson]

LGTM.

llvm/include/llvm/Object/ELF.h

ELFFile<ELFT>::getSectionContentsAsArray(const Elf_Shdr *Sec) const {
   uintX_t Offset = Sec->sh_offset;
   uintX_t Size = Sec->sh_size;
 
   if (Size % sizeof(T))
     return createError("section " + getSecIndexForError(this, Sec) +
                        " has an invalid sh_size (" + Twine(Size) +
                        ") which is not a multiple of its sh_entsize (" +
                        Twine(Sec->sh_entsize) + ")");
-  if ((std::numeric_limits<uintX_t>::max() - Offset < Size) ||
-      Offset + Size > Buf.size())
+  if (std::numeric_limits<uintX_t>::max() - Offset < Size)
     return createError("section " + getSecIndexForError(this, Sec) +
                        " has a sh_offset (0x" + Twine::utohexstr(Offset) +
                        ") + sh_size (0x" + Twine::utohexstr(Size) +
                        ") that cannot be represented");
+  if (Offset + Size > Buf.size())
+    return createError("section " + getSecIndexForError(this, Sec) +
+                       " has a sh_offset (0x" + Twine::utohexstr(Offset) +
+                       ") + sh_size (0x" + Twine::utohexstr(Size) +
+                       ") that is greater than the file size (0x" +
+                       Twine::utohexstr(Buf.size()) + ")");
 
   if (Offset % alignof(T))
     // TODO: this error is untested.
     return createError("unaligned data");
 
   const T *Start = reinterpret_cast<const T *>(base() + Offset);
   return makeArrayRef(Start, Size / sizeof(T));
 }

llvm/test/Object/invalid.test

- Name: .shstrtab
     Size: 0
 
 ## Check that llvm-objdump reports an error when .shstrtab has an invalid
 ## size that goes past the end of the file.
 
 # RUN: not llvm-objdump -s %p/Inputs/invalid-strtab-size.elf 2>&1 \
 # RUN:   | FileCheck %s -DFILE=%p/Inputs/invalid-strtab-size.elf --check-prefix=INVALID-STRTAB-SIZE
 
-# INVALID-STRTAB-SIZE: error: '[[FILE]]': section [index 1] has a sh_offset (0x70) + sh_size (0xffffff) that cannot be represented
+# INVALID-STRTAB-SIZE: error: '[[FILE]]': section [index 1] has a sh_offset (0x70) + sh_size (0xffffff) that is greater than the file size (0x218)
 
 ## Check that llvm-dwarfdump reports an error during relocation resolution
 ## when instead of expected SHT_RELA section it locates a section of a different type.
 
 # RUN: yaml2obj %s --docnum=3 -o %t3
 # RUN: not llvm-dwarfdump -debug-line %t3 2>&1 | FileCheck --check-prefix=RELA %s
 
 # RELA: LLVM ERROR: Section is not SHT_RELA

 ## Check that llvm-readobj reports an error if a relocation section
 ## has a broken sh_offset (past the end of the file).
 
 # RUN: yaml2obj %s --docnum=12 -o %t12
 # RUN: yaml2obj %s --docnum=13 -o %t13
 # RUN: not llvm-readobj -r %t12 2>&1 | FileCheck -DFILE=%t12 --check-prefix=INVALID-RELOC-SH-OFFSET %s
 # RUN: not llvm-readobj -r %t13 2>&1 | FileCheck -DFILE=%t13 --check-prefix=INVALID-RELOC-SH-OFFSET %s
 
-# INVALID-RELOC-SH-OFFSET: error: '[[FILE]]': section [index 1] has a sh_offset (0x10000) + sh_size (0x0) that cannot be represented
+# INVALID-RELOC-SH-OFFSET: error: '[[FILE]]': section [index 1] has a sh_offset (0x10000) + sh_size (0x0) that is greater than the file size (0x160)
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_386
 Sections:

 
 # RUN: yaml2obj %s --docnum=14 -o %t14
 # RUN: not llvm-readobj --symbols %t14 2>&1 | FileCheck -DFILE=%t14 --check-prefix=INVALID-SECTION-SIZE2 %s
 
 # INVALID-SECTION-SIZE2: error: '[[FILE]]': section [index 1] has a sh_offset (0xffffffff) + sh_size (0x1b) that cannot be represented
 
 --- !ELF
 FileHeader:
-  Class:   ELFCLASS64
+  Class:   ELFCLASS32
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_386
 Sections:
   - Name:     .shstrtab
     Type:     SHT_STRTAB
     ShOffset: 0xFFFFFFFF
 Symbols: []

 
 ## Check that llvm-readobj reports an error if a section has a broken offset
 ## that goes past the end of the file.
 
 # RUN: yaml2obj %s --docnum=18 -o %t18
 # RUN: not llvm-readobj --sections --section-data %t18 2>&1 \
 # RUN:  | FileCheck -DFILE=%t18 --check-prefix=BROKEN-SECSHOFFSET %s
 
-# BROKEN-SECSHOFFSET: error: '[[FILE]]': section [index 1] has a sh_offset (0xffff0000) + sh_size (0x0) that cannot be represented
+# BROKEN-SECSHOFFSET: error: '[[FILE]]': section [index 1] has a sh_offset (0xffff0000) + sh_size (0x0) that is greater than the file size (0x160)
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_X86_64
 Sections:

llvm/test/tools/llvm-readobj/elf-verdef-invalid.test

- Name:    .gnu.version_d
     Entries: []
 
 ## Check that we report a warning when we can't read the content of the SHT_GNU_verdef section.
 
 # RUN: yaml2obj %s --docnum=3 -o %t3
 # RUN: llvm-readobj -V %t3 2>&1 | FileCheck %s --check-prefix=INVALID-DATA -DFILE=%t3
 # RUN: llvm-readelf -V %t3 2>&1 | FileCheck %s --check-prefix=INVALID-DATA -DFILE=%t3
 
-# INVALID-DATA: warning: '[[FILE]]': cannot read content of SHT_GNU_verdef section with index 1: section [index 1] has a sh_offset (0xffffffff) + sh_size (0x0) that cannot be represented
+# INVALID-DATA: warning: '[[FILE]]': cannot read content of SHT_GNU_verdef section with index 1: section [index 1] has a sh_offset (0xffffffff) + sh_size (0x0) that is greater than the file size (0x230)
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_DYN
   Machine: EM_X86_64
 Sections:

llvm/test/tools/llvm-readobj/elf-verneed-invalid.test

DynamicSymbols:
   - Name: foo
 
 ## Check that we report a warning when we can't read the content of the SHT_GNU_verneed section.
 
 # RUN: yaml2obj --docnum=7 %s -o %t7
 # RUN: llvm-readobj --sections -V %t7 2>&1 | FileCheck %s -DFILE=%t7 --check-prefix=INVALID-DATA
 # RUN: llvm-readelf --sections -V %t7 2>&1 | FileCheck %s -DFILE=%t7 --check-prefix=INVALID-DATA
 
-# INVALID-DATA: warning: '[[FILE]]': cannot read content of SHT_GNU_verneed section with index 1: section [index 1] has a sh_offset (0xffffffff) + sh_size (0x0) that cannot be represented
+# INVALID-DATA: warning: '[[FILE]]': cannot read content of SHT_GNU_verneed section with index 1: section [index 1] has a sh_offset (0xffffffff) + sh_size (0x0) that is greater than the file size (0x230)
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_EXEC
   Machine: EM_X86_64
 Sections: