llvm-readobj: fix printing number of relocations in Android packed format.

[rahulchaudhry]

Summary

With '-elf-output-style=GNU -relocations', a header containing the number
of entries is printed before all the relocation entries in the section.
For Android packed format, we need to perform the unpacking first before
we can get the actual number of relocations in the section.

[pcc]

LGTM

tools/llvm-readobj/ELFDumper.cpp

2644 ↗

(On Diff #150044)

Rename AndroidRelas to match the surrounding code.

[rahulchaudhry]

Renamed android_relas -> AndroidRelas

[rahulchaudhry]

Thanks for the review.
Can you land this one as well. I am new to llvm and don't have commit access.

llvm/trunk/test/tools/llvm-readobj/elf-packed-relocs.test

 # The binary blobs in this file were created like this:
 # llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu Inputs/elf-packed-relocs1.s -o - | obj2yaml | grep Content:
 
 # RUN: yaml2obj -docnum 1 %s | llvm-readobj -elf-output-style=LLVM -relocations - | FileCheck --check-prefix=LLVM1 %s
 # LLVM1:      Section (1) .rela.dyn {
 # LLVM1-NEXT:   0x1100 R_X86_64_RELATIVE - 0x0
 # LLVM1-NEXT:   0x1180 R_X86_64_RELATIVE - 0x0
 # LLVM1-NEXT:   0x1188 R_X86_64_64 sym1 0x0
 # LLVM1-NEXT:   0x1190 R_X86_64_64 sym2 0x0
 # LLVM1-NEXT:   0x1191 R_X86_64_64 sym1 0x8
 # LLVM1-NEXT:   0x1193 R_X86_64_64 sym2 0xC
 # LLVM1-NEXT:   0x1197 R_X86_64_64 sym1 0xA
 # LLVM1-NEXT:   0x119F R_X86_64_64 sym2 0xA
 # LLVM1-NEXT: }
 
 # RUN: yaml2obj -docnum 1 %s | llvm-readobj -elf-output-style=GNU -relocations - | FileCheck --check-prefix=GNU1 %s
+# GNU1:      Relocation section '.rela.dyn' at offset 0x180 contains 8 entries:
 # GNU1:      0000000000001100  0000000000000008 R_X86_64_RELATIVE                 0
 # GNU1-NEXT: 0000000000001180  0000000000000008 R_X86_64_RELATIVE                 0
 # GNU1-NEXT: 0000000000001188  0000000100000001 R_X86_64_64            0000000000000000 sym1 + 0
 # GNU1-NEXT: 0000000000001190  0000000200000001 R_X86_64_64            0000000000000000 sym2 + 0
 # GNU1-NEXT: 0000000000001191  0000000100000001 R_X86_64_64            0000000000000000 sym1 + 8
 # GNU1-NEXT: 0000000000001193  0000000200000001 R_X86_64_64            0000000000000000 sym2 + c
 # GNU1-NEXT: 0000000000001197  0000000100000001 R_X86_64_64            0000000000000000 sym1 + a
 # GNU1-NEXT: 000000000000119f  0000000200000001 R_X86_64_64            0000000000000000 sym2 + a

 # LLVM2-NEXT:   0x1000 R_386_RELATIVE - 0x0
 # LLVM2-NEXT:   0xFFC R_386_RELATIVE - 0x0
 # LLVM2-NEXT:   0xFF8 R_386_RELATIVE - 0x0
 # LLVM2-NEXT:   0xFF4 R_386_RELATIVE - 0x0
 # LLVM2-NEXT:   0xFF0 R_386_RELATIVE - 0x0
 # LLVM2-NEXT: }
 
 # RUN: yaml2obj -docnum 2 %s | llvm-readobj -elf-output-style=GNU -relocations - | FileCheck --check-prefix=GNU2 %s
+# GNU2:      Relocation section '.rel.dyn' at offset 0xfc contains 10 entries:
 # GNU2:      00001008  00000101 R_386_32               00000000   sym1
 # GNU2-NEXT: 00001010  00000203 R_386_GOT32            00000000   sym2
 # GNU2-NEXT: 0000100c  00000008 R_386_RELATIVE
 # GNU2-NEXT: 00001008  00000008 R_386_RELATIVE
 # GNU2-NEXT: 00001004  00000008 R_386_RELATIVE
 # GNU2-NEXT: 00001000  00000008 R_386_RELATIVE
 # GNU2-NEXT: 00000ffc  00000008 R_386_RELATIVE
 # GNU2-NEXT: 00000ff8  00000008 R_386_RELATIVE

llvm/trunk/tools/llvm-readobj/ELFDumper.cpp

template <class ELFT> void GNUStyle<ELFT>::printRelocations(const ELFO *Obj) {
   for (const Elf_Shdr &Sec : unwrapOrError(Obj->sections())) {
     if (Sec.sh_type != ELF::SHT_REL && Sec.sh_type != ELF::SHT_RELA &&
         Sec.sh_type != ELF::SHT_ANDROID_REL &&
         Sec.sh_type != ELF::SHT_ANDROID_RELA)
       continue;
     HasRelocSections = true;
     StringRef Name = unwrapOrError(Obj->getSectionName(&Sec));
     unsigned Entries = Sec.getEntityCount();
+    std::vector<Elf_Rela> AndroidRelas;
+    if (Sec.sh_type == ELF::SHT_ANDROID_REL ||
+        Sec.sh_type == ELF::SHT_ANDROID_RELA) {
+      // Android's packed relocation section needs to be unpacked first
+      // to get the actual number of entries.
+      AndroidRelas = unwrapOrError(Obj->android_relas(&Sec));
+      Entries = AndroidRelas.size();
+    }
     uintX_t Offset = Sec.sh_offset;
     OS << "\nRelocation section '" << Name << "' at offset 0x"
        << to_hexString(Offset, false) << " contains " << Entries
        << " entries:\n";
     printRelocHeader(OS, ELFT::Is64Bits,
                      Sec.sh_type == ELF::SHT_RELA ||
                          Sec.sh_type == ELF::SHT_ANDROID_RELA);
     const Elf_Shdr *SymTab = unwrapOrError(Obj->getSection(Sec.sh_link));
     switch (Sec.sh_type) {
     case ELF::SHT_REL:
       for (const auto &R : unwrapOrError(Obj->rels(&Sec))) {
         Elf_Rela Rela;
         Rela.r_offset = R.r_offset;
         Rela.r_info = R.r_info;
         Rela.r_addend = 0;
         printRelocation(Obj, SymTab, Rela, false);
       }
       break;
     case ELF::SHT_RELA:
       for (const auto &R : unwrapOrError(Obj->relas(&Sec)))
         printRelocation(Obj, SymTab, R, true);
       break;
     case ELF::SHT_ANDROID_REL:
     case ELF::SHT_ANDROID_RELA:
-      for (const auto &R : unwrapOrError(Obj->android_relas(&Sec)))
+      for (const auto &R : AndroidRelas)
         printRelocation(Obj, SymTab, R, Sec.sh_type == ELF::SHT_ANDROID_RELA);
       break;
     }
   }
   if (!HasRelocSections)
     OS << "\nThere are no relocations in this file.\n";
 }