[ELF] Add a new e_machine value EM_CSKY and add some CSKY relocation types

[zixuan-wu]

Summary

This is the split part of D86269, which add a new ELF machine flag called EM_CSKY and related relocations.
Some target-specific flags and tests for csky can be added in follow-up patches later.

[arsenm]

llvm/include/llvm/BinaryFormat/ELF.h

315

This doesn't look registered? https://www.sco.com/developers/gabi/latest/ch4.eheader.html

[MaskRay]

This looks good to me, but I guess the target may need an official approval (from LLVM Foundation Board of Directors?) first.
From very few reports on c-sky I can find on the Internet, the v1 and v2 of the chip csky uses the "c-sky" architecture. v3 uses RISC-V. I am a bit worrisome whether this organization backing the target will commit to maintain for a sufficiently long time in LLVM. (If you look at existing lib/Target/* targets, many have been there for 10 years. For the younger ones, I think there are commitments from the companies).

llvm/include/llvm/BinaryFormat/ELF.h

315

See the thread "Machine Request - 65816/65c816" in the generic-abi google group.
binutils has the definition
https://sourceware.org/legacy-ml/binutils/2018-05/msg00242.html
and the value is known by several folks on generic-abi.

Unfortunately the website has been unmaintained for a few years now.

llvm/test/Object/CSKY/elf-flags.yaml

1 ↗

(On Diff #287915)

llvm/unittests/Object/ELFObjectFileTest.cpp may be more suitable. We don't need to teach llvm-readobj about every EM_* value.

[zixuan-wu]

I think http://lists.llvm.org/pipermail/llvm-dev/2020-August/144587.html may answer your concern. @MaskRay

llvm/include/llvm/BinaryFormat/ELF.h

315

I find the page https://www.sco.com/developers/gabi/latest/ch4.eheader.html is out-of-date and have been unmaintained. You can check https://groups.google.com/g/generic-abi/c/qaPzp2lRzDA?pli=1.

And the binutils have contained this EM_CSKY.

llvm/test/Object/CSKY/elf-flags.yaml

1 ↗

(On Diff #287915)

Good, thank you. I will add a unittest at ELFObjectFileTest. And I think I can keep elf-flags.yaml for target flags check later.

[arsenm]

In D86610#2239950, @MaskRay wrote:

This looks good to me, but I guess the target may need an official approval (from LLVM Foundation Board of Directors?) first.

I don't think it's necessary to hold up this patch on anything like that. It would be reasonable to define the reserved enum values independently of the target

[zixuan-wu]

In D86610#2241879, @arsenm wrote:

In D86610#2239950, @MaskRay wrote:

This looks good to me, but I guess the target may need an official approval (from LLVM Foundation Board of Directors?) first.

I don't think it's necessary to hold up this patch on anything like that. It would be reasonable to define the reserved enum values independently of the target

The test ELFObjectFileTest.cpp depends on the Triple::csky so it would be follow-up of triple patch if that patch is representing the target acceptance.

[MaskRay]

llvm/include/llvm/BinaryFormat/ELFRelocs/CSKY.def

7

For relocation type changes, we have tests in test/tools/llvm-readobj/ELF/reloc-types-elf-*.test. I don't know replicating every value is useful (you'll probably just copy and paste the value anyway), but having a few should not hurt.

[MaskRay]

[ELF] Add new EM called EM_CSKY

Add a new e_machine value EM_CSKY and add some CSKY relocation types

[grimar]

llvm/include/llvm/BinaryFormat/ELFRelocs/CSKY.def

10

Please be consistent. All other *.def files have a different style.
E.g:

ELF_RELOC(R_390_NONE,          0)
ELF_RELOC(R_390_8,             1)
ELF_RELOC(R_390_12,            2)
ELF_RELOC(R_390_16,            3)
ELF_RELOC(R_390_32,            4)
...

llvm/include/llvm/Object/ELFObjectFile.h

1116

This value should be tested in
llvm\unittests\Object\ELFObjectFileTest.cpp

llvm/lib/Object/ELF.cpp

205

I think we do not have unit tests for getRelativeRelocationType,
but you probably can add the first one (for EM_CSKY) to ELFObjectFileTest.cpp to test this value.

[zixuan-wu]

Address comments.

[zixuan-wu]

llvm/include/llvm/BinaryFormat/ELFRelocs/CSKY.def

7

Sorry to know what your meaning less. Should I add test under test/tools/llvm-readobj/ELF/reloc-types-elf-*.test?

[grimar]

llvm/include/llvm/BinaryFormat/ELFRelocs/CSKY.def

75

No newline at end of file

This should be fixed (the same below).

llvm/test/Object/CSKY/elf-flags.yaml

1 ↗

(On Diff #287915)

I think you can remove this test case, it doesn't do any useful job right now.

aside:

1. it calls obj2yaml, but test/Object/CSKY/ is not the right place for obj2yaml testing.
2. EM_AMDGPU flags printed by llvm-readobj are tested in llvm-readobj\ELF\amdgpu-elf-headers.test, though perhaps we should test flags in ELFObjectFileTest.cpp instead.

llvm/unittests/Object/ELFObjectFileTest.cpp

296

No full stop at the end of comment.

297

I'd make it generic. I.e. remove "ForCSKY". Then we can add other EM_* types here.

[zixuan-wu]

Address comments.

[grimar]

I have no more comment, thanks! Lets see what others think.

[MaskRay]

In D86610#2254135, @grimar wrote:

I have no more comment, thanks! Lets see what others think.

Even if this had high chance to be accepted, I think it needs an official approval (even for this binary format patch). For an unknown arch, supporting EM_* is fine, but not R_*_RELATIVE and its list of relocation types.

There is no need to revert, though.

llvm/include/llvm/BinaryFormat/ELF.h

enum {
   EM_COOL = 217,          // iCelero CoolEngine
   EM_NORC = 218,          // Nanoradio Optimized RISC
   EM_CSR_KALIMBA = 219,   // CSR Kalimba architecture family
   EM_AMDGPU = 224,        // AMD GPU architecture
   EM_RISCV = 243,         // RISC-V
   EM_LANAI = 244,         // Lanai 32-bit processor
   EM_BPF = 247,           // Linux kernel bpf virtual machine
   EM_VE = 251,            // NEC SX-Aurora VE
+  EM_CSKY = 252,          // C-SKY 32-bit processor
 };
 
 // Object file classes.
 enum {
   ELFCLASSNONE = 0,
   ELFCLASS32 = 1, // 32-bit object file
   ELFCLASS64 = 2  // 64-bit object file
 };

 #include "ELFRelocs/MSP430.def"
 };
 
 // ELF Relocation type for VE.
 enum {
 #include "ELFRelocs/VE.def"
 };
 
+
+// ELF Relocation types for CSKY
+enum {
+#include "ELFRelocs/CSKY.def"
+};
+
 #undef ELF_RELOC
 
 // Section header.
 struct Elf32_Shdr {
   Elf32_Word sh_name;      // Section name (index into string table)
   Elf32_Word sh_type;      // Section type (SHT_*)
   Elf32_Word sh_flags;     // Section flags (SHF_*)
   Elf32_Addr sh_addr;      // Address where section is to be loaded

llvm/include/llvm/BinaryFormat/ELFRelocs/CSKY.def

+
+#ifndef ELF_RELOC
+#error "ELF_RELOC must be defined"
+#endif
+
+ELF_RELOC(R_CKCORE_NONE,                        0)
+ELF_RELOC(R_CKCORE_ADDR32,                      1)
+ELF_RELOC(R_CKCORE_PCREL_IMM8_4,                2)
+ELF_RELOC(R_CKCORE_PCREL_IMM11_2,               3)
+ELF_RELOC(R_CKCORE_PCREL_IMM4_2,                4)
+ELF_RELOC(R_CKCORE_PCREL32,                     5)
+ELF_RELOC(R_CKCORE_PCREL_JSR_IMM11_2,           6)
+ELF_RELOC(R_CKCORE_GNU_VTINHERIT,               7)
+ELF_RELOC(R_CKCORE_GNU_VTENTRY,                 8)
+ELF_RELOC(R_CKCORE_RELATIVE,                    9)
+ELF_RELOC(R_CKCORE_COPY,                       10)
+ELF_RELOC(R_CKCORE_GLOB_DAT,                   11)
+ELF_RELOC(R_CKCORE_JUMP_SLOT,                  12)
+ELF_RELOC(R_CKCORE_GOTOFF,                     13)
+ELF_RELOC(R_CKCORE_GOTPC,                      14)
+ELF_RELOC(R_CKCORE_GOT32,                      15)
+ELF_RELOC(R_CKCORE_PLT32,                      16)
+ELF_RELOC(R_CKCORE_ADDRGOT,                    17)
+ELF_RELOC(R_CKCORE_ADDRPLT,                    18)
+ELF_RELOC(R_CKCORE_PCREL_IMM26_2,              19)
+ELF_RELOC(R_CKCORE_PCREL_IMM16_2,              20)
+ELF_RELOC(R_CKCORE_PCREL_IMM16_4,              21)
+ELF_RELOC(R_CKCORE_PCREL_IMM10_2,              22)
+ELF_RELOC(R_CKCORE_PCREL_IMM10_4,              23)
+ELF_RELOC(R_CKCORE_ADDR_HI16,                  24)
+ELF_RELOC(R_CKCORE_ADDR_LO16,                  25)
+ELF_RELOC(R_CKCORE_GOTPC_HI16,                 26)
+ELF_RELOC(R_CKCORE_GOTPC_LO16,                 27)
+ELF_RELOC(R_CKCORE_GOTOFF_HI16,                28)
+ELF_RELOC(R_CKCORE_GOTOFF_LO16,                29)
+ELF_RELOC(R_CKCORE_GOT12,                      30)
+ELF_RELOC(R_CKCORE_GOT_HI16,                   31)
+ELF_RELOC(R_CKCORE_GOT_LO16,                   32)
+ELF_RELOC(R_CKCORE_PLT12,                      33)
+ELF_RELOC(R_CKCORE_PLT_HI16,                   34)
+ELF_RELOC(R_CKCORE_PLT_LO16,                   35)
+ELF_RELOC(R_CKCORE_ADDRGOT_HI16,               36)
+ELF_RELOC(R_CKCORE_ADDRGOT_LO16,               37)
+ELF_RELOC(R_CKCORE_ADDRPLT_HI16,               38)
+ELF_RELOC(R_CKCORE_ADDRPLT_LO16,               39)
+ELF_RELOC(R_CKCORE_PCREL_JSR_IMM26_2,          40)
+ELF_RELOC(R_CKCORE_TOFFSET_LO16,               41)
+ELF_RELOC(R_CKCORE_DOFFSET_LO16,               42)
+ELF_RELOC(R_CKCORE_PCREL_IMM18_2,              43)
+ELF_RELOC(R_CKCORE_DOFFSET_IMM18,              44)
+ELF_RELOC(R_CKCORE_DOFFSET_IMM18_2,            45)
+ELF_RELOC(R_CKCORE_DOFFSET_IMM18_4,            46)
+ELF_RELOC(R_CKCORE_GOTOFF_IMM18,               47)
+ELF_RELOC(R_CKCORE_GOT_IMM18_4,                48)
+ELF_RELOC(R_CKCORE_PLT_IMM18_4,                49)
+ELF_RELOC(R_CKCORE_PCREL_IMM7_4,               50)
+ELF_RELOC(R_CKCORE_TLS_LE32,                   51)
+ELF_RELOC(R_CKCORE_TLS_IE32,                   52)
+ELF_RELOC(R_CKCORE_TLS_GD32,                   53)
+ELF_RELOC(R_CKCORE_TLS_LDM32,                  54)
+ELF_RELOC(R_CKCORE_TLS_LDO32,                  55)
+ELF_RELOC(R_CKCORE_TLS_DTPMOD32,               56)
+ELF_RELOC(R_CKCORE_TLS_DTPOFF32,               57)
+ELF_RELOC(R_CKCORE_TLS_TPOFF32,                58)
+ELF_RELOC(R_CKCORE_PCREL_FLRW_IMM8_4,          59)
+ELF_RELOC(R_CKCORE_NOJSRI,                     60)
+ELF_RELOC(R_CKCORE_CALLGRAPH,                  61)
+ELF_RELOC(R_CKCORE_IRELATIVE,                  62)
+ELF_RELOC(R_CKCORE_PCREL_BLOOP_IMM4_4,         63)
+ELF_RELOC(R_CKCORE_PCREL_BLOOP_IMM12_4,        64)
+ELF_RELOC(R_CKCORE_PCREL_VLRW_IMM12_1,         65)
+ELF_RELOC(R_CKCORE_PCREL_VLRW_IMM12_2,         66)
+ELF_RELOC(R_CKCORE_PCREL_VLRW_IMM12_4,         67)
+ELF_RELOC(R_CKCORE_PCREL_VLRW_IMM12_8,         68)

llvm/include/llvm/Object/ELFObjectFile.h

case ELF::ELFCLASS32:
     case ELF::EM_MIPS:
       return "elf32-mips";
     case ELF::EM_MSP430:
       return "elf32-msp430";
     case ELF::EM_PPC:
       return "elf32-powerpc";
     case ELF::EM_RISCV:
       return "elf32-littleriscv";
+    case ELF::EM_CSKY:
+      return "elf32-csky";
     case ELF::EM_SPARC:
     case ELF::EM_SPARC32PLUS:
       return "elf32-sparc";
     case ELF::EM_AMDGPU:
       return "elf32-amdgpu";
     default:
       return "elf32-unknown";
     }
case ELF::EM_AMDGPU: {
     return Triple::UnknownArch;
   }
 
   case ELF::EM_BPF:
     return IsLittleEndian ? Triple::bpfel : Triple::bpfeb;
 
   case ELF::EM_VE:
     return Triple::ve;
+  case ELF::EM_CSKY:
+    return Triple::csky;
   default:
     return Triple::UnknownArch;
   }
 }
 
 template <class ELFT>
 Expected<uint64_t> ELFObjectFile<ELFT>::getStartAddress() const {
   return EF.getHeader()->e_entry;

llvm/lib/Object/ELF.cpp

#include "llvm/BinaryFormat/ELFRelocs/MSP430.def"
     break;
   case ELF::EM_VE:
     switch (Type) {
 #include "llvm/BinaryFormat/ELFRelocs/VE.def"
     default:
       break;
     }
     break;
+  case ELF::EM_CSKY:
+    switch (Type) {
+#include "llvm/BinaryFormat/ELFRelocs/CSKY.def"
+    default:
+      break;
+    }
+    break;
   default:
     break;
   }
   return "Unknown";
 }
 
 #undef ELF_RELOC
 
uint32_t llvm::object::getELFRelativeRelocationType(uint32_t Machine) {
   case ELF::EM_RISCV:
     return ELF::R_RISCV_RELATIVE;
   case ELF::EM_S390:
     return ELF::R_390_RELATIVE;
   case ELF::EM_SPARC:
   case ELF::EM_SPARC32PLUS:
   case ELF::EM_SPARCV9:
     return ELF::R_SPARC_RELATIVE;
+  case ELF::EM_CSKY:
+    return ELF::R_CKCORE_RELATIVE;
   case ELF::EM_AMDGPU:
     break;
   case ELF::EM_BPF:
     break;
   default:
     break;
   }
   return 0;

llvm/lib/ObjectYAML/ELFYAML.cpp

#define ECase(X) IO.enumCase(Value, #X, ELF::X)
   ECase(EM_VIDEOCORE5);
   ECase(EM_78KOR);
   ECase(EM_56800EX);
   ECase(EM_AMDGPU);
   ECase(EM_RISCV);
   ECase(EM_LANAI);
   ECase(EM_BPF);
   ECase(EM_VE);
+  ECase(EM_CSKY);
 #undef ECase
   IO.enumFallback<Hex16>(Value);
 }
 
 void ScalarEnumerationTraits<ELFYAML::ELF_ELFCLASS>::enumeration(
     IO &IO, ELFYAML::ELF_ELFCLASS &Value) {
 #define ECase(X) IO.enumCase(Value, #X, ELF::X)
   // Since the semantics of ELFCLASSNONE is "invalid", just don't accept it

 #include "llvm/BinaryFormat/ELFRelocs/AMDGPU.def"
     break;
   case ELF::EM_BPF:
 #include "llvm/BinaryFormat/ELFRelocs/BPF.def"
     break;
   case ELF::EM_VE:
 #include "llvm/BinaryFormat/ELFRelocs/VE.def"
     break;
+  case ELF::EM_CSKY:
+#include "llvm/BinaryFormat/ELFRelocs/CSKY.def"
+    break;
   case ELF::EM_PPC64:
 #include "llvm/BinaryFormat/ELFRelocs/PowerPC64.def"
     break;
   default:
     // Nothing to do.
     break;
   }
 #undef ELF_RELOC

llvm/unittests/Object/ELFObjectFileTest.cpp

 
 TEST(ELFObjectFileTest, MachineTestForMSP430) {
   std::array<StringRef, 4> Formats = {"elf32-msp430", "elf32-msp430",
                                       "elf64-unknown", "elf64-unknown"};
   size_t I = 0;
   for (const DataForTest &D : generateData(ELF::EM_MSP430))
     checkFormatAndArch(D, Formats[I++], Triple::msp430);
 }
+
+TEST(ELFObjectFileTest, MachineTestForCSKY) {
+  std::array<StringRef, 4> Formats = {"elf32-csky", "elf32-csky",
+                                      "elf64-unknown", "elf64-unknown"};
+  size_t I = 0;
+  for (const DataForTest &D : generateData(ELF::EM_CSKY))
+    checkFormatAndArch(D, Formats[I++], Triple::csky);
+}
+
+
+
+// ELF relative relocation type test.
+TEST(ELFObjectFileTest, RelativeRelocationTypeTest) {
+  EXPECT_EQ(ELF::R_CKCORE_RELATIVE, getELFRelativeRelocationType(ELF::EM_CSKY));
+}