[libObject, llvm-readobj] - Reimplement ELFFile<ELFT>::getEntry.

Currently, `ELFFile<ELFT>::getEntry` does not check an index of
an entry. Because of that the code might read past the end of the symbol
table silently. I've added a test to `llvm-readobj\ELF\relocations.test`
to demonstrate the possible issue. Also, I've added a unit test for
this method.

After this change, `getEntry` stops reporting the section index and
reuses the `getSectionContentsAsArray` method, which already has
all the validation needed. Our related warnings now provide
more and better context sometimes.

Differential revision: https://reviews.llvm.org/D93209

Author: Georgii Rymar

lld/test/ELF/invalid/dynamic-section-broken.test

@@ -1,7 +1,7 @@
 ## .dynamic section has invalid sh_entsize, check we report it.
 # RUN: yaml2obj --docnum=1 %s -o %t.so
 # RUN: not ld.lld %t.so -o /dev/null 2>&1 | FileCheck %s --check-prefix=ERR1
-# ERR1: error: {{.*}}.so: section [index 1] has an invalid sh_entsize: 291
+# ERR1: error: {{.*}}.so: section [index 1] has invalid sh_entsize: expected 16, but got 291
 
 --- !ELF
 FileHeader:

llvm/include/llvm/Object/ELF.h

@@ -412,7 +412,8 @@ Expected<ArrayRef<T>>
 ELFFile<ELFT>::getSectionContentsAsArray(const Elf_Shdr &Sec) const {
   if (Sec.sh_entsize != sizeof(T) && sizeof(T) != 1)
     return createError("section " + getSecIndexForError(*this, Sec) +
-                       " has an invalid sh_entsize: " + Twine(Sec.sh_entsize));
+                       " has invalid sh_entsize: expected " + Twine(sizeof(T)) +
+                       ", but got " + Twine(Sec.sh_entsize));
 
   uintX_t Offset = Sec.sh_offset;
   uintX_t Size = Sec.sh_size;
@@ -618,17 +619,17 @@ template <class ELFT>
 template <typename T>
 Expected<const T *> ELFFile<ELFT>::getEntry(const Elf_Shdr &Section,
                                             uint32_t Entry) const {
-  if (sizeof(T) != Section.sh_entsize)
-    return createError("section " + getSecIndexForError(*this, Section) +
-                       " has invalid sh_entsize: expected " + Twine(sizeof(T)) +
-                       ", but got " + Twine(Section.sh_entsize));
-  uint64_t Pos = Section.sh_offset + (uint64_t)Entry * sizeof(T);
-  if (Pos + sizeof(T) > Buf.size())
-    return createError("unable to access section " +
-                       getSecIndexForError(*this, Section) + " data at 0x" +
-                       Twine::utohexstr(Pos) +
-                       ": offset goes past the end of file");
-  return reinterpret_cast<const T *>(base() + Pos);
+  Expected<ArrayRef<T>> EntriesOrErr = getSectionContentsAsArray<T>(Section);
+  if (!EntriesOrErr)
+    return EntriesOrErr.takeError();
+
+  ArrayRef<T> Arr = *EntriesOrErr;
+  if (Entry >= Arr.size())
+    return createError("can't read an entry at 0x" +
+                       Twine::utohexstr(Entry * sizeof(T)) +
+                       ": it goes past the end of the section (0x" +
+                       Twine::utohexstr(Section.sh_size) + ")");
+  return &Arr[Entry];
 }
 
 template <class ELFT>

llvm/test/Object/invalid.test

@@ -118,7 +118,7 @@ Symbols:
 # RUN: yaml2obj %s --docnum=6 -o %t6
 # RUN: llvm-readobj --symbols %t6 2>&1 | FileCheck -DFILE=%t6 --check-prefix=INVALID-SYM-SIZE %s
 
-# INVALID-SYM-SIZE: warning: '[[FILE]]': unable to read symbols from the SHT_SYMTAB section: section [index 1] has an invalid sh_entsize: 32
+# INVALID-SYM-SIZE: warning: '[[FILE]]': unable to read symbols from the SHT_SYMTAB section: section [index 1] has invalid sh_entsize: expected 24, but got 32
 
 --- !ELF
 FileHeader:
@@ -630,7 +630,7 @@ Symbols:
 # RUN: yaml2obj %s --docnum=29 -o %t29
 # RUN: llvm-readobj -V %t29 2>&1 | FileCheck -DFILE=%t29 --check-prefix=INVALID-VER-SHENTSIZE %s
 
-# INVALID-VER-SHENTSIZE: warning: '[[FILE]]': cannot read content of SHT_GNU_versym section with index 1: section [index 1] has an invalid sh_entsize: 3
+# INVALID-VER-SHENTSIZE: warning: '[[FILE]]': cannot read content of SHT_GNU_versym section with index 1: section [index 1] has invalid sh_entsize: expected 2, but got 3
 
 --- !ELF
 FileHeader:

llvm/test/tools/llvm-readobj/ELF/call-graph-profile.test

@@ -47,7 +47,7 @@ Symbols:
 # RUN: llvm-readelf %t2.o --cg-profile | FileCheck %s --check-prefix=GNU
 
 # LLVM-ERR:      CGProfile [
-# LLVM-ERR-NEXT: warning: '[[FILE]]': unable to dump the SHT_LLVM_CALL_GRAPH_PROFILE section: section [index 1] has an invalid sh_entsize: 15
+# LLVM-ERR-NEXT: warning: '[[FILE]]': unable to dump the SHT_LLVM_CALL_GRAPH_PROFILE section: section [index 1] has invalid sh_entsize: expected 16, but got 15
 # LLVM-ERR-NEXT: ]
 
 ## Check we report a warning when unable to dump a name of a symbol.

llvm/test/tools/llvm-readobj/ELF/reloc-symbol-with-versioning.test

@@ -1,6 +1,8 @@
 # RUN: yaml2obj %s -o %t.o
-# RUN: llvm-readobj --demangle -r %t.o | FileCheck %s --check-prefix LLVM
-# RUN: llvm-readelf --demangle -r %t.o | FileCheck %s --check-prefix GNU
+# RUN: llvm-readobj --demangle -r %t.o 2>&1 | \
+# RUN:   FileCheck %s --check-prefix=LLVM --implicit-check-not=warning:
+# RUN: llvm-readelf --demangle -r %t.o 2>&1 | \
+# RUN:   FileCheck %s --check-prefix=GNU --implicit-check-not=warning:
 
 # GNU:      Relocation section '.rela.plt' at offset {{.*}} contains 5 entries:
 # GNU-NEXT:     Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
@@ -30,7 +32,7 @@ Sections:
   - Name:    .gnu.version
     Type:    SHT_GNU_versym
     Flags:   [ SHF_ALLOC ]
-    Entries: [ 0, 2, 3, 4, 2 ]
+    Entries: [ 0, 2, 3, 4, 2, 1 ]
   - Name:         .gnu.version_r
     Type:         SHT_GNU_verneed
     Flags:        [ SHF_ALLOC ]

llvm/test/tools/llvm-readobj/ELF/relocation-errors.test

@@ -6,8 +6,8 @@
 
 # LLVM:      Relocations [
 # LLVM-NEXT:   Section (3) .rel.text {
-# LLVM-NEXT: warning: '[[FILE]]': unable to print relocation 1 in SHT_REL section with index 3: unable to access section [index 6] data at 0x17e7e7e8d0: offset goes past the end of file
-# LLVM-NEXT: warning: '[[FILE]]': unable to print relocation 2 in SHT_REL section with index 3: unable to access section [index 6] data at 0x17e7e7e8d0: offset goes past the end of file
+# LLVM-NEXT: warning: '[[FILE]]': unable to print relocation 1 in SHT_REL section with index 3: unable to read an entry with index 4278124286 from SHT_SYMTAB section with index 6: can't read an entry at 0x17e7e7e7d0: it goes past the end of the section (0x90)
+# LLVM-NEXT: warning: '[[FILE]]': unable to print relocation 2 in SHT_REL section with index 3: unable to read an entry with index 4278124286 from SHT_SYMTAB section with index 6: can't read an entry at 0x17e7e7e7d0: it goes past the end of the section (0x90)
 # LLVM-NEXT:     0x2 R_X86_64_NONE -{{$}}
 # LLVM-NEXT:     0x3 R_X86_64_NONE .sec.symbol1{{$}}
 # LLVM-NEXT: warning: '[[FILE]]': invalid section index: 255
@@ -23,8 +23,8 @@
 
 # GNU:       Relocation section '.rel.text' at offset 0x41 contains 7 entries:
 # GNU-NEXT:      Offset             Info             Type               Symbol's Value  Symbol's Name
-# GNU-NEXT:  warning: '[[FILE]]': unable to print relocation 1 in SHT_REL section with index 3: unable to access section [index 6] data at 0x17e7e7e8d0: offset goes past the end of file
-# GNU-NEXT:  warning: '[[FILE]]': unable to print relocation 2 in SHT_REL section with index 3: unable to access section [index 6] data at 0x17e7e7e8d0: offset goes past the end of file
+# GNU-NEXT:  warning: '[[FILE]]': unable to print relocation 1 in SHT_REL section with index 3: unable to read an entry with index 4278124286 from SHT_SYMTAB section with index 6: can't read an entry at 0x17e7e7e7d0: it goes past the end of the section (0x90)
+# GNU-NEXT:  warning: '[[FILE]]': unable to print relocation 2 in SHT_REL section with index 3: unable to read an entry with index 4278124286 from SHT_SYMTAB section with index 6: can't read an entry at 0x17e7e7e7d0: it goes past the end of the section (0x90)
 # GNU-NEXT:  0000000000000002  0000000000000000 R_X86_64_NONE
 # GNU-NEXT:  0000000000000003  0000000200000000 R_X86_64_NONE 0000000000000000 .sec.symbol1
 # GNU-NEXT:  warning: '[[FILE]]': invalid section index: 255

llvm/test/tools/llvm-readobj/ELF/relocations.test

@@ -207,7 +207,7 @@ Symbols:
 
 # BROKEN-REL-LLVM:      Relocations [
 # BROKEN-REL-LLVM-NEXT:   Section (2) .rel.text {
-# BROKEN-REL-LLVM-NEXT: warning: '[[FILE]]': unable to read relocations from SHT_REL section with index 2: section [index 2] has an invalid sh_entsize: 1
+# BROKEN-REL-LLVM-NEXT: warning: '[[FILE]]': unable to read relocations from SHT_REL section with index 2: section [index 2] has invalid sh_entsize: expected 16, but got 1
 # BROKEN-REL-LLVM-NEXT:   }
 # BROKEN-REL-LLVM-NEXT:   Section (3) .rela.text {
 # BROKEN-REL-LLVM-NEXT:     0x0 R_X86_64_NONE rela_0 0x0
@@ -220,7 +220,7 @@ Symbols:
 
 # BROKEN-REL-GNU:      Relocation section '.rel.text' at offset 0x51 contains 64 entries:
 # BROKEN-REL-GNU-NEXT:     Offset             Info             Type       Symbol's Value  Symbol's Name
-# BROKEN-REL-GNU-NEXT: warning: '[[FILE]]': unable to read relocations from SHT_REL section with index 2: section [index 2] has an invalid sh_entsize: 1
+# BROKEN-REL-GNU-NEXT: warning: '[[FILE]]': unable to read relocations from SHT_REL section with index 2: section [index 2] has invalid sh_entsize: expected 16, but got 1
 # BROKEN-REL-GNU:      Relocation section '.rela.text' at offset 0x91 contains 5 entries:
 # BROKEN-REL-GNU-NEXT:     Offset             Info             Type       Symbol's Value  Symbol's Name
 # BROKEN-REL-GNU-NEXT: 0000000000000000  0000000500000000 R_X86_64_NONE  0000000000000000 rela_0 + 0
@@ -245,7 +245,7 @@ Symbols:
 # BROKEN-RELA-LLVM-NEXT:     0x9 R_X86_64_64 rel_64{{$}}
 # BROKEN-RELA-LLVM-NEXT:   }
 # BROKEN-RELA-LLVM-NEXT:   Section (3) .rela.text {
-# BROKEN-RELA-LLVM-NEXT: warning: '[[FILE]]': unable to read relocations from SHT_RELA section with index 3: section [index 3] has an invalid sh_entsize: 1
+# BROKEN-RELA-LLVM-NEXT: warning: '[[FILE]]': unable to read relocations from SHT_RELA section with index 3: section [index 3] has invalid sh_entsize: expected 24, but got 1
 # BROKEN-RELA-LLVM-NEXT:   }
 # BROKEN-RELA-LLVM-NEXT: ]
 
@@ -258,7 +258,7 @@ Symbols:
 # BROKEN-RELA-GNU-EMPTY:
 # BROKEN-RELA-GNU-NEXT: Relocation section '.rela.text' at offset 0x91 contains 120 entries:
 # BROKEN-RELA-GNU-NEXT:     Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
-# BROKEN-RELA-GNU-NEXT: warning: '[[FILE]]': unable to read relocations from SHT_RELA section with index 3: section [index 3] has an invalid sh_entsize: 1
+# BROKEN-RELA-GNU-NEXT: warning: '[[FILE]]': unable to read relocations from SHT_RELA section with index 3: section [index 3] has invalid sh_entsize: expected 24, but got 1
 
 ## Case C: check the case when relocations can't be read from SHT_REL/SHT_RELA sections
 ##         because of broken sh_link fields.
@@ -498,3 +498,41 @@ Symbols:
 # GNU-SHNAME-NEXT: 0000000000000005  0000000700000004 R_X86_64_PLT32 0000000000000002 rela_pos + 2
 # GNU-SHNAME-NEXT: ffffffffffffffff  0000000800000001 R_X86_64_64    0000000000000003 rela_minneg - 8000000000000000
 # GNU-SHNAME-NEXT: 0000000000000009  000000090000000b R_X86_64_32S   ffffffffffffffff rela_maxpos + 7fffffffffffffff
+
+## Check that we report a warning when a relocation has a
+## symbol index past the end of the symbol table
+
+# RUN: yaml2obj %s --docnum=3 -o %t3
+# RUN: llvm-readobj --relocs %t3 2>&1 | \
+# RUN:   FileCheck %s --implicit-check-not=warning: -DFILE=%t3 --check-prefix=LLVM-SYMNDX
+# RUN: llvm-readelf --relocs %t3 2>&1 | \
+# RUN:   FileCheck %s --implicit-check-not=warning: -DFILE=%t3 --check-prefix=GNU-SYMNDX
+
+# LLVM-SYMNDX:      Relocations [
+# LLVM-SYMNDX-NEXT:   Section (1) .rela.text {
+# LLVM-SYMNDX-NEXT: warning: '[[FILE]]': unable to print relocation 1 in SHT_RELA section with index 1: unable to read an entry with index 2 from SHT_SYMTAB section with index 2: can't read an entry at 0x30: it goes past the end of the section (0x30)
+# LLVM-SYMNDX-NEXT: warning: '[[FILE]]': unable to print relocation 2 in SHT_RELA section with index 1: unable to read an entry with index 3 from SHT_SYMTAB section with index 2: can't read an entry at 0x48: it goes past the end of the section (0x30)
+# LLVM-SYMNDX-NEXT:   }
+# LLVM-SYMNDX-NEXT: ]
+
+# GNU-SYMNDX:      Relocation section '.rela.text' at offset 0x40 contains 2 entries:
+# GNU-SYMNDX-NEXT:     Offset             Info             Type     Symbol's Value  Symbol's Name + Addend
+# GNU-SYMNDX-NEXT: warning: '[[FILE]]': unable to print relocation 1 in SHT_RELA section with index 1: unable to read an entry with index 2 from SHT_SYMTAB section with index 2: can't read an entry at 0x30: it goes past the end of the section (0x30)
+# GNU-SYMNDX-NEXT: warning: '[[FILE]]': unable to print relocation 2 in SHT_RELA section with index 1: unable to read an entry with index 3 from SHT_SYMTAB section with index 2: can't read an entry at 0x48: it goes past the end of the section (0x30)
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .rela.text
+    Type: SHT_RELA
+    Relocations:
+      - Type:   R_X86_64_NONE
+        Symbol: 0x2
+      - Type:   R_X86_64_NONE
+        Symbol: 0x3
+Symbols:
+  - Name: foo

llvm/test/tools/llvm-readobj/ELF/relr-relocs.test

@@ -169,14 +169,14 @@ Sections:
 
 # BROKEN-LLVM:      Relocations [
 # BROKEN-LLVM-NEXT:   Section (1) .relr.dyn {
-# BROKEN-LLVM-NEXT: warning: '[[FILE]]': unable to read relocations from [[SECNAME]] section with index 1: section [index 1] has an invalid sh_entsize: 1
+# BROKEN-LLVM-NEXT: warning: '[[FILE]]': unable to read relocations from [[SECNAME]] section with index 1: section [index 1] has invalid sh_entsize: expected 4, but got 1
 # BROKEN-LLVM-NEXT:   }
 # BROKEN-LLVM-NEXT: ]
 
-# BROKEN-GNU:      warning: '[[FILE]]': unable to get the number of relocations in [[SECNAME]] section with index 1: section [index 1] has an invalid sh_entsize: 1
+# BROKEN-GNU:      warning: '[[FILE]]': unable to get the number of relocations in [[SECNAME]] section with index 1: section [index 1] has invalid sh_entsize: expected 4, but got 1
 # BROKEN-GNU:      Relocation section '.relr.dyn' at offset 0x34 contains <?> entries:
 # BROKEN-GNU-NEXT:  Offset     Info    Type                Sym. Value  Symbol's Name
-# BROKEN-GNU-NEXT: warning: '[[FILE]]': unable to read relocations from [[SECNAME]] section with index 1: section [index 1] has an invalid sh_entsize: 1
+# BROKEN-GNU-NEXT: warning: '[[FILE]]': unable to read relocations from [[SECNAME]] section with index 1: section [index 1] has invalid sh_entsize: expected 4, but got 1
 
 ## Case B: check the case when relocations can't be read from an SHT_ANDROID_RELR section.
 ##         SHT_ANDROID_RELR = 0x6fffff00.