llvm-objdump/ELF: fix crash when reading dyn str table (#87519)

When reading the dynamic string table, llvm-objdump used to crash if the
ELF was malformed, due to an erroneous consumption of error status.
Instead, propogate the error status to the caller, fixing the crash, and
printing a warning.

Author: artagnon

llvm/test/tools/llvm-objdump/ELF/dynamic-malformed.test

@@ -12,7 +12,6 @@ FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_EXEC
-  Machine: EM_X86_64
 Sections:
   - Name: .dynamic
     Type: SHT_DYNAMIC
@@ -29,10 +28,35 @@ FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_EXEC
-  Machine: EM_X86_64
 Sections:
   - Name: .dynamic
     Type: SHT_DYNAMIC
     Entries:
       - Tag:   DT_SONAME
         Value: 1
+
+# RUN: yaml2obj %s --docnum=3 -o %t.invalidaddr
+# RUN: llvm-objdump -p %t.invalidaddr 2>&1 | \
+# RUN:   FileCheck %s -DFILE=%t.invalidaddr --implicit-check-not=warning: --check-prefix=ADDR
+
+# ADDR:       Dynamic Section:
+# ADDR-NEXT:  warning: '[[FILE]]': virtual address is not in any segment: 0x474
+# ADDR-NEXT:    NEEDED       0xffffffffbe5a0b5f
+# ADDR-NEXT:    STRTAB       0x0000000000000474
+
+---
+!ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data: ELFDATA2LSB
+  Type: ET_DYN
+Sections:
+  - Name: .dynamic
+    Type: SHT_DYNAMIC
+    Entries:
+      - Tag: DT_NEEDED
+        Value: 0xFFFFFFFFBE5A0B5F
+      - Tag: DT_STRTAB
+        Value: 0x474
+      - Tag: DT_NULL
+        Value: 0x0

llvm/tools/llvm-objdump/ELFDump.cpp

@@ -68,7 +68,7 @@ static Expected<StringRef> getDynamicStrTab(const ELFFile<ELFT> &Elf) {
     if (Dyn.d_tag == ELF::DT_STRTAB) {
       auto MappedAddrOrError = Elf.toMappedAddr(Dyn.getPtr());
       if (!MappedAddrOrError)
-        consumeError(MappedAddrOrError.takeError());
+        return MappedAddrOrError.takeError();
       return StringRef(reinterpret_cast<const char *>(*MappedAddrOrError));
     }
   }
@@ -223,7 +223,6 @@ template <class ELFT> void ELFDumper<ELFT>::printDynamicSection() {
       continue;
 
     std::string Str = Elf.getDynamicTagAsString(Dyn.d_tag);
-    outs() << format(TagFmt.c_str(), Str.c_str());
 
     const char *Fmt =
         ELFT::Is64Bits ? "0x%016" PRIx64 "\n" : "0x%08" PRIx64 "\n";
@@ -232,14 +231,16 @@ template <class ELFT> void ELFDumper<ELFT>::printDynamicSection() {
         Dyn.d_tag == ELF::DT_AUXILIARY || Dyn.d_tag == ELF::DT_FILTER) {
       Expected<StringRef> StrTabOrErr = getDynamicStrTab(Elf);
       if (StrTabOrErr) {
-        const char *Data = StrTabOrErr.get().data();
-        outs() << (Data + Dyn.d_un.d_val) << "\n";
+        const char *Data = StrTabOrErr->data();
+        outs() << format(TagFmt.c_str(), Str.c_str()) << Data + Dyn.getVal()
+               << "\n";
         continue;
       }
       reportWarning(toString(StrTabOrErr.takeError()), Obj.getFileName());
       consumeError(StrTabOrErr.takeError());
     }
-    outs() << format(Fmt, (uint64_t)Dyn.d_un.d_val);
+    outs() << format(TagFmt.c_str(), Str.c_str())
+           << format(Fmt, (uint64_t)Dyn.getVal());
   }
 }