[ELF2][mips] Support both big and little endian MIPS 32-bit targets

[atanasyan]

Summary

• Make the MipsTargetInfo template class with ELFType argument. Use the argument to select an appropriate relocation type and read/write routines.
• Add template function add32 to add-and-write relocation value in both big and little endian cases. Keep the add32le to reduce code changes.

[ruiu]

LGTM with nits.

ELF/Target.cpp

93 ↗

(On Diff #37343)

template <bool IsLE> would be better for consistency.

93–101 ↗

(On Diff #37343)

I'd define add32be and use add32le and add32be from add32<>.

template <> void add32<true>(uint8_t *L, int32_t V) { add32le(L, V); }
template <> void add32<false>(uint8_t *L, int32_t V) { add32be(L, V); }

585–586 ↗

(On Diff #37343)

Unrelated style change.

[atanasyan]

Thanks for your review.

ELF/Target.cpp

585–586 ↗

(On Diff #37343)

Due the <ELFT> it is now impossible to keep both BaseAddr and SymVA arguments on the same line without 80-column restriction violation.

lld/trunk/ELF/Target.h

void writePltEntry(uint8_t *Buf, uint64_t GotEntryAddr,
                      uint64_t PltEntryAddr) const override;
   bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const override;
   bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const override;
   void relocateOne(uint8_t *Buf, uint8_t *BufEnd, const void *RelP,
                    uint32_t Type, uint64_t BaseAddr,
                    uint64_t SymVA) const override;
 };
 
-class MipsTargetInfo final : public TargetInfo {
+template <class ELFT> class MipsTargetInfo final : public TargetInfo {
 public:
   MipsTargetInfo();
   void writePltEntry(uint8_t *Buf, uint64_t GotEntryAddr,
                      uint64_t PltEntryAddr) const override;
   bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const override;
   bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const override;
   void relocateOne(uint8_t *Buf, uint8_t *BufEnd, const void *RelP,
                    uint32_t Type, uint64_t BaseAddr,

lld/trunk/ELF/Target.cpp

 
 TargetInfo *createTarget() {
   switch (Config->EMachine) {
   case EM_386:
     return new X86TargetInfo();
   case EM_AARCH64:
     return new AArch64TargetInfo();
   case EM_MIPS:
-    return new MipsTargetInfo();
+    switch (Config->EKind) {
+    case ELF32LEKind:
+      return new MipsTargetInfo<ELF32LE>();
+    case ELF32BEKind:
+      return new MipsTargetInfo<ELF32BE>();
+    default:
+      error("Unsupported MIPS target");
+    }
   case EM_PPC:
     return new PPCTargetInfo();
   case EM_PPC64:
     return new PPC64TargetInfo();
   case EM_X86_64:
     return new X86_64TargetInfo();
   }
   error("Unknown target machine");
bool X86TargetInfo::relocPointsToGot(uint32_t Type) const {
   return Type == R_386_GOTPC;
 }
 
 bool X86TargetInfo::relocNeedsPlt(uint32_t Type, const SymbolBody &S) const {
   return Type == R_386_PLT32 || (Type == R_386_PC32 && S.isShared());
 }
 
 static void add32le(uint8_t *L, int32_t V) { write32le(L, read32le(L) + V); }
+static void add32be(uint8_t *L, int32_t V) { write32be(L, read32be(L) + V); }
 static void or32le(uint8_t *L, int32_t V) { write32le(L, read32le(L) | V); }
 
+template <bool IsLE> static void add32(uint8_t *L, int32_t V);
+template <> void add32<true>(uint8_t *L, int32_t V) { add32le(L, V); }
+template <> void add32<false>(uint8_t *L, int32_t V) { add32be(L, V); }
+
 void X86TargetInfo::relocateOne(uint8_t *Buf, uint8_t *BufEnd, const void *RelP,
                                 uint32_t Type, uint64_t BaseAddr,
                                 uint64_t SymVA) const {
   typedef ELFFile<ELF32LE>::Elf_Rel Elf_Rel;
   auto &Rel = *reinterpret_cast<const Elf_Rel *>(RelP);
 
   uint32_t Offset = Rel.r_offset;
   uint8_t *Loc = Buf + Offset;
case R_AARCH64_ADR_PREL_PG_HI21: {
     updateAArch64Adr(L, (X >> 12) & 0x1FFFFF); // X[32:12]
     break;
   }
   default:
     error("unrecognized reloc " + Twine(Type));
   }
 }
 
-MipsTargetInfo::MipsTargetInfo() {
+template <class ELFT> MipsTargetInfo<ELFT>::MipsTargetInfo() {
   // PCRelReloc = FIXME
   // GotReloc = FIXME
   PageSize = 65536;
 }
 
-void MipsTargetInfo::writePltEntry(uint8_t *Buf, uint64_t GotEntryAddr,
+template <class ELFT>
+void MipsTargetInfo<ELFT>::writePltEntry(uint8_t *Buf, uint64_t GotEntryAddr,
                                          uint64_t PltEntryAddr) const {}
 
-bool MipsTargetInfo::relocNeedsGot(uint32_t Type, const SymbolBody &S) const {
+template <class ELFT>
+bool MipsTargetInfo<ELFT>::relocNeedsGot(uint32_t Type,
+                                         const SymbolBody &S) const {
   return false;
 }
 
-bool MipsTargetInfo::relocNeedsPlt(uint32_t Type, const SymbolBody &S) const {
+template <class ELFT>
+bool MipsTargetInfo<ELFT>::relocNeedsPlt(uint32_t Type,
+                                         const SymbolBody &S) const {
   return false;
 }
 
-void MipsTargetInfo::relocateOne(uint8_t *Buf, uint8_t *BufEnd,
+template <class ELFT>
+void MipsTargetInfo<ELFT>::relocateOne(uint8_t *Buf, uint8_t *BufEnd,
                                        const void *RelP, uint32_t Type,
-                                 uint64_t BaseAddr, uint64_t SymVA) const {
-  typedef ELFFile<ELF32LE>::Elf_Rel Elf_Rel;
+                                       uint64_t BaseAddr,
+                                       uint64_t SymVA) const {
+  const bool IsLE = ELFT::TargetEndianness == support::little;
+  typedef typename ELFFile<ELFT>::Elf_Rel Elf_Rel;
   auto &Rel = *reinterpret_cast<const Elf_Rel *>(RelP);
 
   switch (Type) {
   case R_MIPS_32:
-    add32le(Buf + Rel.r_offset, SymVA);
+    add32<IsLE>(Buf + Rel.r_offset, SymVA);
     break;
   default:
     error("unrecognized reloc " + Twine(Type));
   }
 }
 }
 }

lld/trunk/test/elf2/mips-relocs.s

 # Check R_MIPS_32 relocation calculation.
-# RUN: llvm-mc -filetype=obj -triple=mipsel-unknown-linux %s -o %t.o
-# RUN: ld.lld2 %t.o -o %t.exe
-# RUN: llvm-objdump -s -t %t.exe | FileCheck %s
+
+# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux %s -o %t-be.o
+# RUN: ld.lld2 %t-be.o -o %t-be.exe
+# RUN: llvm-objdump -t %t-be.exe | FileCheck %s
+# RUN: llvm-objdump -s %t-be.exe | FileCheck -check-prefix=BE %s
+
+# RUN: llvm-mc -filetype=obj -triple=mipsel-unknown-linux %s -o %t-el.o
+# RUN: ld.lld2 %t-el.o -o %t-el.exe
+# RUN: llvm-objdump -t %t-el.exe | FileCheck %s
+# RUN: llvm-objdump -s %t-el.exe | FileCheck -check-prefix=EL %s
 
 # REQUIRES: mips
 
   .globl  __start
 __start:
   nop
 
   .data
   .type  v1,@object
   .size  v1,4
 v1:
   .word 0
 
   .globl v2
   .type  v2,@object
   .size  v2,8
 v2:
   .word v2+4 # R_MIPS_32 target v2 addend 4
   .word v1   # R_MIPS_32 target v1 addend 0
 
-# CHECK: Contents of section .data:
-# CHECK-NEXT: 30000 00000000 08000300 00000300
-#                            ^-- v2+4 ^-- v1
-
 # CHECK: SYMBOL TABLE:
 # CHECK: 00030000 l       .data           00000004 v1
 # CHECK: 00030004 g       .data           00000008 v2
+
+# BE: Contents of section .data:
+# BE-NEXT: 30000 00000000 00030008 00030000
+#                         ^-- v2+4 ^-- v1
+
+# EL: Contents of section .data:
+# EL-NEXT: 30000 00000000 08000300 00000300
+#                         ^-- v2+4 ^-- v1