[llvm-objdump] Rework .gnu.version_d dumping

and fix crash when vd_aux is invalid (llvm#86611).

vd_version, vd_flags, vd_ndx, and vd_cnt in Elf{32,64}_Verdef are
16-bit. Change VerDef to use uint16_t instead.

vda_name specifies a NUL-terminated string. Update getVersionDefinitions
to remove some `.c_str()`.

Pull Request: llvm#128434

Author: MaskRay

llvm/include/llvm/Object/ELF.h

@@ -41,10 +41,10 @@ struct VerdAux {
 
 struct VerDef {
   unsigned Offset;
-  unsigned Version;
-  unsigned Flags;
-  unsigned Ndx;
-  unsigned Cnt;
+  uint16_t Version;
+  uint16_t Flags;
+  uint16_t Ndx;
+  uint16_t Cnt;
   unsigned Hash;
   std::string Name;
   std::vector<VerdAux> AuxV;
@@ -1057,8 +1057,8 @@ ELFFile<ELFT>::getVersionDefinitions(const Elf_Shdr &Sec) const {
 
     VerdAux Aux;
     Aux.Offset = VerdauxBuf - Start;
-    if (Verdaux->vda_name <= StrTabOrErr->size())
-      Aux.Name = std::string(StrTabOrErr->drop_front(Verdaux->vda_name));
+    if (Verdaux->vda_name < StrTabOrErr->size())
+      Aux.Name = std::string(StrTabOrErr->drop_front(Verdaux->vda_name).data());
     else
       Aux.Name = ("<invalid vda_name: " + Twine(Verdaux->vda_name) + ">").str();
     return Aux;

llvm/test/tools/llvm-objdump/ELF/private-headers.test

@@ -38,6 +38,7 @@ Sections:
        Value: 0x0
   - Name:            .gnu.version_d
     Type:            SHT_GNU_verdef
+    AddressAlign:    4
     Entries:
       - Version:         1
         Flags:           1

llvm/test/tools/llvm-objdump/ELF/verdef-invalid.test

@@ -0,0 +1,77 @@
+## Adapted from test/llvm-readobj/ELF/verdef-invalid.test
+## Check that we report a warning when a SHT_GNU_verdef section contains a version definition
+## that refers to an auxiliary entry that goes past the end of the section.
+
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-objdump -p %t 2>&1 | FileCheck %s --check-prefix=AUX-PAST-END -DFILE=%t
+
+# AUX-PAST-END: warning: '[[FILE]]': invalid SHT_GNU_verdef section with index 1: version definition 1 refers to an auxiliary entry that goes past the end of the section
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_DYN
+Sections:
+  - Name: .gnu.version_d
+    Type: SHT_GNU_verdef
+    Entries:
+      - Names:
+          - FOO
+    ## The correct sh_size is 28.
+    ShSize: 27
+DynamicSymbols:
+  - Name: foo
+
+## Check we report a warning when a version definition is not correctly aligned in memory.
+
+# RUN: yaml2obj %s --docnum=2 -o %t2
+# RUN: llvm-objdump -p %t2 2>&1 | FileCheck %s --check-prefix=MISALIGNED-DEF -DFILE=%t2
+
+# MISALIGNED-DEF: warning: '[[FILE]]': invalid SHT_GNU_verdef section with index 1: found a misaligned version definition entry at offset 0x0
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_DYN
+Sections:
+  - Type: Fill
+    Size: 0x1
+  - Name: .gnu.version_d
+    Type: SHT_GNU_verdef
+    Link: .dynstr
+    Info: 0x1
+    Entries:
+      - Names:
+          - FOO
+DynamicSymbols:
+  - Name: foo
+
+## Check we report "invalid vda_name" when vda_name = size(.dynstr)
+
+# RUN: yaml2obj %s --docnum=3 -o %t3
+# RUN: llvm-objdump -p %t3 2>&1 | FileCheck %s --check-prefix=VDANAME-PAST-END --implicit-check-not=warning:
+
+# VDANAME-PAST-END:      Version definitions:
+# VDANAME-PAST-END-NEXT: 0 0x00 0x00000000 V0
+# VDANAME-PAST-END-NEXT:         <invalid vda_name: 7>
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_DYN
+Sections:
+  - Name:  .gnu.version_d
+    Type:  SHT_GNU_verdef
+    Flags: [ SHF_ALLOC ]
+    Link:  .dynstr
+    Info:  0x1
+## The byte offset to the auxiliary entry is 0x13, i.e. it is not correctly aligned in memory.
+    Content: "010000000000020000000000140000000000000004000000080000000700000000000000"
+DynamicSymbols:
+  - Name:    V1
+    Binding: STB_GLOBAL
+  - Name:    V0
+    Binding: STB_GLOBAL

llvm/test/tools/llvm-objdump/ELF/verdef.test

@@ -1,12 +1,14 @@
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-objdump -p %t | FileCheck --strict-whitespace %s
+# RUN: llvm-objdump -p %t | FileCheck --match-full-lines --strict-whitespace %s
 
-# CHECK:      Dynamic Section:
-# CHECK-EMPTY:
-# CHECK-NEXT: Version definitions:
-# CHECK-NEXT: 1 0x01 0x075bcd15 foo
-# CHECK-NEXT: 2 0x02 0x3ade68b1 VERSION_1
-# CHECK-NEXT: 	                VERSION_2 
+#      CHECK:Dynamic Section:
+#CHECK-EMPTY:
+# CHECK-NEXT:Version definitions:
+# CHECK-NEXT:2 0x01 0x075bcd15 foo
+# CHECK-NEXT:3 0x02 0x3ade68b1 VERSION_1
+# CHECK-NEXT:	VERSION_2
+# CHECK-NEXT:4 0x00 0x0000007b VERSION_3
+# CHECK-NEXT:	VERSION_4 VERSION_5
 
 --- !ELF
 FileHeader:
@@ -24,17 +26,25 @@ Sections:
     Entries:
       - Version:         1
         Flags:           1
-        VersionNdx:      1
+        VersionNdx:      2
         Hash:            123456789
         Names:
           - foo
       - Version:         1
         Flags:           2
-        VersionNdx:      2
+        VersionNdx:      3
         Hash:            987654321
         Names:
           - VERSION_1
           - VERSION_2
+      - Version:         1
+        Flags:           0
+        VersionNdx:      4
+        Hash:            123
+        Names:
+          - VERSION_3
+          - VERSION_4
+          - VERSION_5
 DynamicSymbols:
   - Name:    bar
     Binding: STB_GLOBAL

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

@@ -128,7 +128,8 @@ Sections:
     Entries:
       - Names:
           - FOO
-    ShSize: 21
+    ## The correct sh_size is 28.
+    ShSize: 27
 DynamicSymbols:
   - Name: foo
 
@@ -290,3 +291,36 @@ Sections:
 DynamicSymbols:
   - Name:    foo
     Binding: STB_GLOBAL
+
+## Check we report "invalid vda_name" when vda_name = size(.dynstr)
+
+# RUN: yaml2obj %s --docnum=10 -o %t11
+# RUN: llvm-readobj -V %t11 2>&1 | FileCheck %s --check-prefix=VDANAME-PAST-END-LLVM -DFILE=%t11 --implicit-check-not=warning:
+# RUN: llvm-readelf -V %t11 2>&1 | FileCheck %s --check-prefix=VDANAME-PAST-END-GNU -DFILE=%t11 --implicit-check-not=warning:
+
+# VDANAME-PAST-END-LLVM:      Name: V0
+# VDANAME-PAST-END-LLVM-NEXT: Predecessors: [<invalid vda_name: 7>]
+
+# VDANAME-PAST-END-GNU:      Version definition section '.gnu.version_d' contains 1 entries:
+# VDANAME-PAST-END-GNU-NEXT:  Addr: 0000000000000000  Offset: 0x000040  Link: 3 (.dynstr)
+# VDANAME-PAST-END-GNU-NEXT:   0x0000: Rev: 1  Flags: none  Index: 0  Cnt: 2  Name: V0
+# VDANAME-PAST-END-GNU-NEXT:   0x001c: Parent 1: <invalid vda_name: 7>
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_DYN
+Sections:
+  - Name:  .gnu.version_d
+    Type:  SHT_GNU_verdef
+    Flags: [ SHF_ALLOC ]
+    Link:  .dynstr
+    Info:  0x1
+## The byte offset to the auxiliary entry is 0x13, i.e. it is not correctly aligned in memory.
+    Content: "010000000000020000000000140000000000000004000000080000000700000000000000"
+DynamicSymbols:
+  - Name:    V1
+    Binding: STB_GLOBAL
+  - Name:    V0
+    Binding: STB_GLOBAL

llvm/tools/llvm-objdump/ELFDump.cpp

@@ -378,38 +378,6 @@ void ELFDumper<ELFT>::printSymbolVersionDependency(
   }
 }
 
-template <class ELFT>
-static void printSymbolVersionDefinition(const typename ELFT::Shdr &Shdr,
-                                         ArrayRef<uint8_t> Contents,
-                                         StringRef StrTab) {
-  outs() << "\nVersion definitions:\n";
-
-  const uint8_t *Buf = Contents.data();
-  uint32_t VerdefIndex = 1;
-  // sh_info contains the number of entries in the SHT_GNU_verdef section. To
-  // make the index column have consistent width, we should insert blank spaces
-  // according to sh_info.
-  uint16_t VerdefIndexWidth = std::to_string(Shdr.sh_info).size();
-  while (Buf) {
-    auto *Verdef = reinterpret_cast<const typename ELFT::Verdef *>(Buf);
-    outs() << format_decimal(VerdefIndex++, VerdefIndexWidth) << " "
-           << format("0x%02" PRIx16 " ", (uint16_t)Verdef->vd_flags)
-           << format("0x%08" PRIx32 " ", (uint32_t)Verdef->vd_hash);
-
-    const uint8_t *BufAux = Buf + Verdef->vd_aux;
-    uint16_t VerdauxIndex = 0;
-    while (BufAux) {
-      auto *Verdaux = reinterpret_cast<const typename ELFT::Verdaux *>(BufAux);
-      if (VerdauxIndex)
-        outs() << std::string(VerdefIndexWidth + 17, ' ');
-      outs() << StringRef(StrTab.drop_front(Verdaux->vda_name).data()) << '\n';
-      BufAux = Verdaux->vda_next ? BufAux + Verdaux->vda_next : nullptr;
-      ++VerdauxIndex;
-    }
-    Buf = Verdef->vd_next ? Buf + Verdef->vd_next : nullptr;
-  }
-}
-
 template <class ELFT> void ELFDumper<ELFT>::printSymbolVersion() {
   const ELFFile<ELFT> &Elf = getELFFile();
   StringRef FileName = Obj.getFileName();
@@ -426,10 +394,26 @@ template <class ELFT> void ELFDumper<ELFT>::printSymbolVersion() {
         unwrapOrError(Elf.getSection(Shdr.sh_link), FileName);
     StringRef StrTab = unwrapOrError(Elf.getStringTable(*StrTabSec), FileName);
 
-    if (Shdr.sh_type == ELF::SHT_GNU_verneed)
+    if (Shdr.sh_type == ELF::SHT_GNU_verneed) {
       printSymbolVersionDependency(Shdr);
-    else
-      printSymbolVersionDefinition<ELFT>(Shdr, Contents, StrTab);
+    } else {
+      OS << "\nVersion definitions:\n";
+      Expected<std::vector<VerDef>> V =
+          getELFFile().getVersionDefinitions(Shdr);
+      if (!V) {
+        this->reportUniqueWarning(V.takeError());
+        continue;
+      }
+      for (const VerDef &Def : *V) {
+        OS << Def.Ndx << ' ' << format_hex(Def.Flags, 4) << ' '
+           << format_hex(Def.Hash, 10) << ' ' << Def.Name << '\n';
+        if (!Def.AuxV.empty()) {
+          for (auto [I, Aux] : enumerate(Def.AuxV))
+            OS << (I ? ' ' : '\t') << Aux.Name;
+          OS << '\n';
+        }
+      }
+    }
   }
 }
 

llvm/tools/llvm-objdump/llvm-objdump.cpp

@@ -360,7 +360,7 @@ static StringRef ToolName;
 
 std::unique_ptr<BuildIDFetcher> BIDFetcher;
 
-Dumper::Dumper(const object::ObjectFile &O) : O(O) {
+Dumper::Dumper(const object::ObjectFile &O) : O(O), OS(outs()) {
   WarningHandler = [this](const Twine &Msg) {
     if (Warnings.insert(Msg.str()).second)
       reportWarning(Msg, this->O.getFileName());

llvm/tools/llvm-objdump/llvm-objdump.h

@@ -77,6 +77,7 @@ class Dumper {
   StringSet<> Warnings;
 
 protected:
+  llvm::raw_ostream &OS;
   std::function<Error(const Twine &Msg)> WarningHandler;
 
 public:

llvm/tools/llvm-readobj/ELFDumper.cpp

@@ -7668,7 +7668,7 @@ void LLVMELFDumper<ELFT>::printVersionDefinitionSection(const Elf_Shdr *Sec) {
     W.printFlags("Flags", D.Flags, ArrayRef(SymVersionFlags));
     W.printNumber("Index", D.Ndx);
     W.printNumber("Hash", D.Hash);
-    W.printString("Name", D.Name.c_str());
+    W.printString("Name", D.Name);
     W.printList(
         "Predecessors", D.AuxV,
         [](raw_ostream &OS, const VerdAux &Aux) { OS << Aux.Name.c_str(); });