llvm-readobj: Fix addend in relocations for android packed format

[yo]

Summary

If a relocation group doesn't have the RELOCATION_GROUP_HAS_ADDEND_FLAG set, then this implies the group's addend equals zero.
In this case android packed format won't encode an explicit addend delta, instead we need to set Addend, the "previous addend" variable, to zero by ourself.
Fixes: rL316543

[pcc]

lib/Object/ELF.cpp

403–404

This can be simplified to

if (GroupHasAddend && !GroupedByAddend)
  Addend += ReadSLEB();
R.r_addend = Addend;

[pcc]

LGTM

Do you have commit access?

[yo]

Nope. Please commit it for me. Thanks!

[yo]

Ping! Please submit this on my behalf.

lib/Object/ELF.cpp

while (NumRelocs) {
 
     uint64_t GroupRInfo;
     if (GroupedByInfo)
       GroupRInfo = ReadSLEB();
 
     if (GroupedByAddend && GroupHasAddend)
       Addend += ReadSLEB();
 
+    if (!GroupHasAddend)
+      Addend = 0;
+
     for (uint64_t I = 0; I != NumRelocsInGroup; ++I) {
       Elf_Rela R;
       Offset += GroupedByOffsetDelta ? GroupOffsetDelta : ReadSLEB();
       R.r_offset = Offset;
       R.r_info = GroupedByInfo ? GroupRInfo : ReadSLEB();
-
-      if (GroupHasAddend) {
-        if (!GroupedByAddend)
-          Addend += ReadSLEB();
-        R.r_addend = Addend;
-      } else {
-        R.r_addend = 0;
-      }
-
+      if (GroupHasAddend && !GroupedByAddend)
       Relocs.push_back(R);
 
       if (ErrStr)
         return createError(ErrStr);
     }
 
     if (ErrStr)
       return createError(ErrStr);

test/tools/llvm-readobj/Inputs/elf-packed-relocs3.s

+.ascii "APS2"
+.sleb128 6    // Number of relocations
+.sleb128 4096 // Initial offset
+
+.sleb128 2 // Number of relocations in group
+.sleb128 8 // RELOCATION_GROUP_HAS_ADDEND_FLAG
+
+.sleb128 256 // Reloc 1: r_offset delta
+.sleb128 8   // Reloc 1: r_info R_X86_RELATIVE
+.sleb128 0   // Reloc 1: r_addend delta
+.sleb128 128 // Reloc 2: r_offset delta
+.sleb128 8   // Reloc 2: r_info R_X86_RELATIVE
+.sleb128 8   // Reloc 2: r_addend delta
+
+.sleb128 2 // Number of relocations in group
+.sleb128 0 // No RELOCATION_GROUP_HAS_ADDEND_FLAG
+
+.sleb128 128           // reloc 1: r_offset delta
+.sleb128 (1 << 32) | 1 // r_x86_64_64 (sym index 1)
+.sleb128 8             // reloc 2: r_offset delta
+.sleb128 (2 << 32) | 1 // r_x86_64_64 (sym index 2)
+
+.sleb128 2 // Number of relocations in group
+.sleb128 8 // RELOCATION_GROUP_HAS_ADDEND_FLAG
+
+.sleb128 8             // reloc 1: r_offset delta
+.sleb128 (1 << 32) | 1 // r_x86_64_64 (sym index 1)
+.sleb128 0             // reloc 1: r_addend delta
+.sleb128 8             // reloc 2: r_offset delta
+.sleb128 (2 << 32) | 1 // r_x86_64_64 (sym index 2)
+.sleb128 8             // reloc 2: r_addend delta

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

- Name:            .rel.dyn
     Link:            .symtab
     AddressAlign:    0x0000000000000001
     Content:         415053320A80200202088102830408037C08
 Symbols:
   Global:
     - Name:            sym1
     - Name:            sym2
 ...
+
+# RUN: yaml2obj -docnum 3 %s | llvm-readobj -elf-output-style=LLVM -relocations - | FileCheck --check-prefix=LLVM3 %s
+#
+# LLVM3:      Section (1) .rela.dyn {
+# LLVM3-NEXT:   0x1100 R_X86_64_RELATIVE - 0x0
+# LLVM3-NEXT:   0x1180 R_X86_64_RELATIVE - 0x8
+# LLVM3-NEXT:   0x1200 R_X86_64_64 sym1 0x0
+# LLVM3-NEXT:   0x1208 R_X86_64_64 sym2 0x0
+# LLVM3-NEXT:   0x1210 R_X86_64_64 sym1 0x0
+# LLVM3-NEXT:   0x1218 R_X86_64_64 sym2 0x8
+# LLVM3-NEXT: }
+
+# RUN: yaml2obj -docnum 3 %s | llvm-readobj -elf-output-style=GNU -relocations - | FileCheck --check-prefix=GNU3 %s
+# GNU3:      Relocation section '.rela.dyn' at offset 0x180 contains 6 entries:
+# GNU3: 0000000000001100  0000000000000008 R_X86_64_RELATIVE                 0
+# GNU3-NEXT: 0000000000001180  0000000000000008 R_X86_64_RELATIVE                 8
+# GNU3-NEXT: 0000000000001200  0000000100000001 R_X86_64_64            0000000000000000 sym1 + 0
+# GNU3-NEXT: 0000000000001208  0000000200000001 R_X86_64_64            0000000000000000 sym2 + 0
+# GNU3-NEXT: 0000000000001210  0000000100000001 R_X86_64_64            0000000000000000 sym1 + 0
+# GNU3-NEXT: 0000000000001218  0000000200000001 R_X86_64_64            0000000000000000 sym2 + 8
+
+# elf-packed-relocs3.s
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_DYN
+  Machine:         EM_X86_64
+  Entry:           0x0000000000001000
+Sections:
+  - Name:            .rela.dyn
+    Type:            SHT_ANDROID_RELA
+    Flags:           [ SHF_ALLOC ]
+    Address:         0x00000000000001C8
+    Link:            .symtab
+    AddressAlign:    0x0000000000000001
+    Content:         415053320680200208800208008001080802008001818080801008818080802002080881808080100008818080802008
+Symbols:
+  Global:
+    - Name:            sym1
+    - Name:            sym2
+...