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

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 (0xABC)"

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

Differential revision: https://reviews.llvm.org/D70893

Author: Georgii Rymar

llvm/include/llvm/Object/ELF.h

@@ -402,12 +402,17 @@ ELFFile<ELFT>::getSectionContentsAsArray(const Elf_Shdr *Sec) const {
                        " 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.

llvm/test/Object/invalid.test

@@ -41,7 +41,7 @@ Sections:
 # 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.
@@ -252,7 +252,7 @@ Symbols: []
 # 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:
@@ -286,7 +286,7 @@ Sections:
 
 --- !ELF
 FileHeader:
-  Class:   ELFCLASS64
+  Class:   ELFCLASS32
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_386
@@ -375,7 +375,7 @@ Sections:
 # 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:

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

@@ -52,7 +52,7 @@ Sections:
 # 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:

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

@@ -372,7 +372,7 @@ DynamicSymbols:
 # 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: