[ELF] - Fixed padding for CIE/FDE entries of .eh_frame section

[grimar]

Summary

Both gold and ld do align entries to the size of platform pointer.
https://sourceware.org/bugzilla/show_bug.cgi?id=2657#c3
https://sourceware.org/ml/binutils/2006-05/msg00242.html

That seems to be consistent with spec that says both CIE/FDE has
"Padding
Extra bytes to align the CIE structure to an addressing unit size boundary."
https://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-PDA/LSB-PDA/ehframechpt.html

[ruiu]

LGTM

ELF/OutputSections.cpp

1047

AlignedLen -> Len

(Since padding is included in length field.)

ELF/OutputSections.cpp

if (ID == 0) {
         SymbolBody &Body = *S->getFile()->getSymbolBody(SymIndex)->repl();
         Personality = Body.getName();
       }
 
       std::pair<StringRef, StringRef> CieInfo(Entry, Personality);
       auto P = CieMap.insert(std::make_pair(CieInfo, Cies.size()));
       if (P.second) {
         Cies.push_back(C);
-        this->Header.sh_size += Length;
+        this->Header.sh_size += RoundUpToAlignment(Length, sizeof(uintX_t));
       }
       OffsetToIndex[Offset] = P.first->second;
     } else {
       if (!HasReloc)
         error("FDE doesn't reference another section");
       InputSectionBase<ELFT> *Target = S->getRelocTarget(*RelI);
       if (Target != &InputSection<ELFT>::Discarded && Target->isLive()) {
         uint32_t CieOffset = Offset + 4 - ID;
         auto I = OffsetToIndex.find(CieOffset);
         if (I == OffsetToIndex.end())
           error("Invalid CIE reference");
         Cies[I->second].Fdes.push_back(EHRegion<ELFT>(S, Index));
-        this->Header.sh_size += Length;
+        this->Header.sh_size += RoundUpToAlignment(Length, sizeof(uintX_t));
       }
     }
 
     Offset = NextOffset;
     D = D.slice(Length);
   }
 }
 
template <class ELFT> void EHOutputSection<ELFT>::writeTo(uint8_t *Buf) {
   const endianness E = ELFT::TargetEndianness;
   size_t Offset = 0;
   for (const Cie<ELFT> &C : Cies) {
     size_t CieOffset = Offset;
 
     StringRef CieData = C.data();
     memcpy(Buf + Offset, CieData.data(), CieData.size());
     C.S->Offsets[C.Index].second = Offset;
-    Offset += CieData.size();
+    Offset += RoundUpToAlignment(CieData.size(), sizeof(uintX_t));
 
     for (const EHRegion<ELFT> &F : C.Fdes) {
       StringRef FdeData = F.data();
-      memcpy(Buf + Offset, FdeData.data(), 4);              // Length
+      uintX_t AlignedLen = RoundUpToAlignment(FdeData.size(), sizeof(uintX_t));
+      write32<E>(Buf + Offset, AlignedLen - 4); // Length
       write32<E>(Buf + Offset + 4, Offset + 4 - CieOffset); // Pointer
       memcpy(Buf + Offset + 8, FdeData.data() + 8, FdeData.size() - 8);
       F.S->Offsets[F.Index].second = Offset;
-      Offset += FdeData.size();
+      Offset += AlignedLen;
     }
   }
 
   for (EHInputSection<ELFT> *S : Sections) {
     const Elf_Shdr *RelSec = S->RelocSection;
     if (!RelSec)
       continue;
     ELFFile<ELFT> &EObj = S->getFile()->getObj();

test/ELF/eh-frame-merge.s

 
 // CHECK:      Name: .eh_frame
 // CHECK-NEXT: Type: SHT_X86_64_UNWIND
 // CHECK-NEXT: Flags [
 // CHECK-NEXT:   SHF_ALLOC
 // CHECK-NEXT: ]
 // CHECK-NEXT: Address:
 // CHECK-NEXT: Offset:
-// CHECK-NEXT: Size:
+// CHECK-NEXT: Size: 96
 // CHECK-NEXT: Link: 0
 // CHECK-NEXT: Info: 0
 // CHECK-NEXT: AddressAlignment: 8
 // CHECK-NEXT: EntrySize: 0
 // CHECK-NEXT: SectionData (
-// CHECK-NEXT:   0000: 14000000 00000000 017A5200 01781001  |
-// CHECK-NEXT:   0010: 1B0C0708 90010000 10000000 1C000000  |
-// CHECK-NEXT:   0020: 180E0000 01000000 00000000 10000000  |
-// CHECK-NEXT:   0030: 30000000 060E0000 02000000 00000000  |
-// CHECK-NEXT:   0040: 10000000 44000000 F10D0000 01000000  |
-// CHECK-NEXT:   0050: 00000000                             |
+// CHECK-NEXT: 0000: 14000000 00000000 017A5200 01781001  |
+// CHECK-NEXT: 0010: 1B0C0708 90010000 14000000 1C000000  |
+// CHECK-NEXT: 0020: 180E0000 01000000 00000000 00000000  |
+// CHECK-NEXT: 0030: 14000000 34000000 020E0000 02000000  |
+// CHECK-NEXT: 0040: 00000000 00000000 14000000 4C000000  |
+// CHECK-NEXT: 0050: E90D0000 01000000 00000000 00000000  |
 // CHECK-NEXT: )
 
 // CHECK:      Name: foo
 // CHECK-NEXT: Type: SHT_PROGBITS
 // CHECK-NEXT: Flags [
 // CHECK-NEXT:   SHF_ALLOC
 // CHECK-NEXT:   SHF_EXECINSTR
 // CHECK-NEXT: ]