[ELF] Stub support for PPC

[davide]

Summary

It's the first time I touch this ABI. Please forgive omissions.

[ruiu]

ELF/Target.cpp

966

Can you fill this function to handle some basic relocations, so that it can handle some basic programs (such as a hello world written in assembly)? You can create another patch which depends on this if you want to separate them. The point is that I don't want to leave this stub empty for a long period of time.

[davide]

SS

ELF/Target.cpp

966

Sure thing. As already mentioned I'm not really PPC savvy so it might take a little bit (a day) before I study the assembler and come up with a non-trivial example. @hfinkel, do you have any recommendations?

[davide]

The code now handles basic relocations correctly (enough to link an ASM hello world, as proposed by Rui).

[davide]

Addressed Rui's comment(s).

[ruiu]

LGTM with a few nits.

ELF/Target.cpp

964

Add a blank line before this line.

test/ELF/basicppc.s

2

Rename basicppc.s -> basic-ppc.s

test/ELF/ppc-relocs.s

4 ↗

(On Diff #44355)

Above file has "REQUIRES: ppc" and here we have "REQUIRES: powerpc". Which is correct? Even if both are correct, please choose one of them and use it consistently.

ELF/Target.cpp

                          uint64_t SA) const;
 };
 
+class PPCTargetInfo final : public TargetInfo {
+public:
+  PPCTargetInfo();
+  void writeGotPltEntry(uint8_t *Buf, uint64_t Plt) const override;
+  void writePltZeroEntry(uint8_t *Buf, uint64_t GotEntryAddr,
+                         uint64_t PltEntryAddr) const override;
+  void writePltEntry(uint8_t *Buf, uint64_t GotAddr, uint64_t GotEntryAddr,
+                     uint64_t PltEntryAddr, int32_t Index,
+                     unsigned RelOff) 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 *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
+                   uint64_t SA, uint64_t ZA = 0,
+                   uint8_t *PairedLoc = nullptr) const override;
+  bool isRelRelative(uint32_t Type) const override;
+};
+
 class PPC64TargetInfo final : public TargetInfo {
 public:
   PPC64TargetInfo();

     default:
       error("Unsupported MIPS target");
     }
+  case EM_PPC:
+    return new PPCTargetInfo();
   case EM_PPC64:
     return new PPC64TargetInfo();
   case EM_X86_64:

 static uint16_t applyPPCHighest(uint64_t V) { return V >> 48; }
 static uint16_t applyPPCHighesta(uint64_t V) { return (V + 0x8000) >> 48; }
 
+PPCTargetInfo::PPCTargetInfo() {}
+void PPCTargetInfo::writeGotPltEntry(uint8_t *Buf, uint64_t Plt) const {}
+void PPCTargetInfo::writePltZeroEntry(uint8_t *Buf, uint64_t GotEntryAddr,
+                                        uint64_t PltEntryAddr) const {}
+void PPCTargetInfo::writePltEntry(uint8_t *Buf, uint64_t GotAddr,
+                                  uint64_t GotEntryAddr,
+                                  uint64_t PltEntryAddr, int32_t Index,
+                                  unsigned RelOff) const {}
+bool PPCTargetInfo::relocNeedsGot(uint32_t Type, const SymbolBody &S) const {
+  return false;
+}
+bool PPCTargetInfo::relocNeedsPlt(uint32_t Type, const SymbolBody &S) const {
+  return false;
+}
+bool PPCTargetInfo::isRelRelative(uint32_t Type) const { return false; }
+void PPCTargetInfo::relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
+                                uint64_t P, uint64_t SA, uint64_t ZA,
+                                uint8_t *PairedLoc) const {}
+
 PPC64TargetInfo::PPC64TargetInfo() {
   PCRelReloc = R_PPC64_REL24;
   GotReloc = R_PPC64_GLOB_DAT;

test/ELF/basicppc.s

+# RUN: llvm-mc -filetype=obj -triple=powerpc-unknown-freebsd %s -o %t
+# RUN: ld.lld -discard-all -shared %t -o %t2
+# RUN: llvm-readobj -file-headers -sections -section-data -program-headers %t2 | FileCheck %s
+# REQUIRES: ppc
+
+# exits with return code 42 on FreeBSD
+.text
+  li      0,1
+  li      3,1
+  sc
+
+// CHECK: Format: ELF32-ppc
+// CHECK-NEXT: Arch: powerpc
+// CHECK-NEXT: AddressSize: 32bit
+// CHECK-NEXT: LoadName:
+// CHECK-NEXT: ElfHeader {
+// CHECK-NEXT:   Ident {
+// CHECK-NEXT:     Magic: (7F 45 4C 46)
+// CHECK-NEXT:     Class: 32-bit (0x1)
+// CHECK-NEXT:     DataEncoding: BigEndian (0x2)
+// CHECK-NEXT:     FileVersion: 1
+// CHECK-NEXT:     OS/ABI: FreeBSD (0x9)
+// CHECK-NEXT:     ABIVersion: 0
+// CHECK-NEXT:     Unused: (00 00 00 00 00 00 00)
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Type: SharedObject (0x3)
+// CHECK-NEXT:   Machine: EM_PPC (0x14)
+// CHECK-NEXT:   Version: 1
+// CHECK-NEXT:   Entry: 0x0
+// CHECK-NEXT:   ProgramHeaderOffset: 0x34
+// CHECK-NEXT:   SectionHeaderOffset: 0x2084
+// CHECK-NEXT:   Flags [ (0x0)
+// CHECK-NEXT:   ]
+// CHECK-NEXT:   HeaderSize: 52
+// CHECK-NEXT:   ProgramHeaderEntrySize: 32
+// CHECK-NEXT:   ProgramHeaderCount: 7
+// CHECK-NEXT:   SectionHeaderEntrySize: 40
+// CHECK-NEXT:   SectionHeaderCount: 9
+// CHECK-NEXT:   StringTableSectionIndex: 7
+// CHECK-NEXT: }
+// CHECK-NEXT: Sections [
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index: 0
+// CHECK-NEXT:     Name:  (0)
+// CHECK-NEXT:     Type: SHT_NULL (0x0)
+// CHECK-NEXT:     Flags [ (0x0)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address: 0x0
+// CHECK-NEXT:     Offset: 0x0
+// CHECK-NEXT:     Size: 0
+// CHECK-NEXT:     Link: 0
+// CHECK-NEXT:     Info: 0
+// CHECK-NEXT:     AddressAlignment: 0
+// CHECK-NEXT:     EntrySize: 0
+// CHECK-NEXT:     SectionData (
+// CHECK-NEXT:     )
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index: 1
+// CHECK-NEXT:     Name: .dynsym (1)
+// CHECK-NEXT:     Type: SHT_DYNSYM (0xB)
+// CHECK-NEXT:     Flags [ (0x2)
+// CHECK-NEXT:       SHF_ALLOC (0x2)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address: 0x114
+// CHECK-NEXT:     Offset: 0x114
+// CHECK-NEXT:     Size: 16
+// CHECK-NEXT:     Link: 3
+// CHECK-NEXT:     Info: 1
+// CHECK-NEXT:     AddressAlignment: 4
+// CHECK-NEXT:     EntrySize: 16
+// CHECK-NEXT:     SectionData (
+// CHECK-NEXT:       0000: 00000000 00000000 00000000 00000000  |................|
+// CHECK-NEXT:     )
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index: 2
+// CHECK-NEXT:     Name: .hash (9)
+// CHECK-NEXT:     Type: SHT_HASH (0x5)
+// CHECK-NEXT:     Flags [ (0x2)
+// CHECK-NEXT:       SHF_ALLOC (0x2)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address: 0x124
+// CHECK-NEXT:     Offset: 0x124
+// CHECK-NEXT:     Size: 16
+// CHECK-NEXT:     Link: 1
+// CHECK-NEXT:     Info: 0
+// CHECK-NEXT:     AddressAlignment: 4
+// CHECK-NEXT:     EntrySize: 4
+// CHECK-NEXT:     SectionData (
+// CHECK-NEXT:       0000: 00000001 00000001 00000000 00000000  |................|
+// CHECK-NEXT:     )
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index: 3
+// CHECK-NEXT:     Name: .dynstr (15)
+// CHECK-NEXT:     Type: SHT_STRTAB (0x3)
+// CHECK-NEXT:     Flags [ (0x2)
+// CHECK-NEXT:       SHF_ALLOC (0x2)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address: 0x134
+// CHECK-NEXT:     Offset: 0x134
+// CHECK-NEXT:     Size: 1
+// CHECK-NEXT:     Link: 0
+// CHECK-NEXT:     Info: 0
+// CHECK-NEXT:     AddressAlignment: 1
+// CHECK-NEXT:     EntrySize: 0
+// CHECK-NEXT:     SectionData (
+// CHECK-NEXT:       0000: 00                                   |.|
+// CHECK-NEXT:     )
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index: 4
+// CHECK-NEXT:     Name: .text (23)
+// CHECK-NEXT:     Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:     Flags [ (0x6)
+// CHECK-NEXT:       SHF_ALLOC (0x2)
+// CHECK-NEXT:       SHF_EXECINSTR (0x4)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address: 0x1000
+// CHECK-NEXT:     Offset: 0x1000
+// CHECK-NEXT:     Size: 12
+// CHECK-NEXT:     Link: 0
+// CHECK-NEXT:     Info: 0
+// CHECK-NEXT:     AddressAlignment: 4
+// CHECK-NEXT:     EntrySize: 0
+// CHECK-NEXT:     SectionData (
+// CHECK-NEXT:       0000: 38000001 38600001 44000002           |8...8`..D...|
+// CHECK-NEXT:     )
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index: 5
+// CHECK-NEXT:     Name: .dynamic (29)
+// CHECK-NEXT:     Type: SHT_DYNAMIC (0x6)
+// CHECK-NEXT:     Flags [ (0x3)
+// CHECK-NEXT:       SHF_ALLOC (0x2)
+// CHECK-NEXT:       SHF_WRITE (0x1)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address: 0x2000
+// CHECK-NEXT:     Offset: 0x2000
+// CHECK-NEXT:     Size: 48
+// CHECK-NEXT:     Link: 3
+// CHECK-NEXT:     Info: 0
+// CHECK-NEXT:     AddressAlignment: 4
+// CHECK-NEXT:     EntrySize: 8
+// CHECK-NEXT:     SectionData (
+// CHECK-NEXT:       0000: 00000006 00000114 0000000B 00000010  |................|
+// CHECK-NEXT:       0010: 00000005 00000134 0000000A 00000001  |.......4........|
+// CHECK-NEXT:       0020: 00000004 00000124 00000000 00000000  |.......$........|
+// CHECK-NEXT:     )
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index: 6
+// CHECK-NEXT:     Name: .symtab (38)
+// CHECK-NEXT:     Type: SHT_SYMTAB (0x2)
+// CHECK-NEXT:     Flags [ (0x0)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address: 0x0
+// CHECK-NEXT:     Offset: 0x2030
+// CHECK-NEXT:     Size: 16
+// CHECK-NEXT:     Link: 8
+// CHECK-NEXT:     Info: 1
+// CHECK-NEXT:     AddressAlignment: 4
+// CHECK-NEXT:     EntrySize: 16
+// CHECK-NEXT:     SectionData (
+// CHECK-NEXT:       0000: 00000000 00000000 00000000 00000000  |................|
+// CHECK-NEXT:     )
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index: 7
+// CHECK-NEXT:     Name: .shstrtab (46)
+// CHECK-NEXT:     Type: SHT_STRTAB (0x3)
+// CHECK-NEXT:     Flags [ (0x0)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address: 0x0
+// CHECK-NEXT:     Offset: 0x2040
+// CHECK-NEXT:     Size: 64
+// CHECK-NEXT:     Link: 0
+// CHECK-NEXT:     Info: 0
+// CHECK-NEXT:     AddressAlignment: 1
+// CHECK-NEXT:     EntrySize: 0
+// CHECK-NEXT:     SectionData (
+// CHECK-NEXT:       0000: 002E6479 6E73796D 002E6861 7368002E  |..dynsym..hash..|
+// CHECK-NEXT:       0010: 64796E73 7472002E 74657874 002E6479  |dynstr..text..dy|
+// CHECK-NEXT:       0020: 6E616D69 63002E73 796D7461 62002E73  |namic..symtab..s|
+// CHECK-NEXT:       0030: 68737472 74616200 2E737472 74616200  |hstrtab..strtab.|
+// CHECK-NEXT:     )
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index: 8
+// CHECK-NEXT:     Name: .strtab (56)
+// CHECK-NEXT:     Type: SHT_STRTAB (0x3)
+// CHECK-NEXT:     Flags [ (0x0)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address: 0x0
+// CHECK-NEXT:     Offset: 0x2080
+// CHECK-NEXT:     Size: 1
+// CHECK-NEXT:     Link: 0
+// CHECK-NEXT:     Info: 0
+// CHECK-NEXT:     AddressAlignment: 1
+// CHECK-NEXT:     EntrySize: 0
+// CHECK-NEXT:     SectionData (
+// CHECK-NEXT:       0000: 00                                   |.|
+// CHECK-NEXT:     )
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]
+// CHECK-NEXT: ProgramHeaders [
+// CHECK-NEXT:   ProgramHeader {
+// CHECK-NEXT:     Type: PT_PHDR (0x6)
+// CHECK-NEXT:     Offset: 0x34
+// CHECK-NEXT:     VirtualAddress: 0x34
+// CHECK-NEXT:     PhysicalAddress: 0x34
+// CHECK-NEXT:     FileSize: 224
+// CHECK-NEXT:     MemSize: 224
+// CHECK-NEXT:     Flags [ (0x4)
+// CHECK-NEXT:       PF_R (0x4)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Alignment: 8
+// CHECK-NEXT:   }
+// CHECK-NEXT:   ProgramHeader {
+// CHECK-NEXT:     Type: PT_LOAD (0x1)
+// CHECK-NEXT:     Offset: 0x0
+// CHECK-NEXT:     VirtualAddress: 0x0
+// CHECK-NEXT:     PhysicalAddress: 0x0
+// CHECK-NEXT:     FileSize: 309
+// CHECK-NEXT:     MemSize: 309
+// CHECK-NEXT:     Flags [ (0x4)
+// CHECK-NEXT:       PF_R (0x4)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Alignment: 4096
+// CHECK-NEXT:   }
+// CHECK-NEXT:   ProgramHeader {
+// CHECK-NEXT:     Type: PT_LOAD (0x1)
+// CHECK-NEXT:     Offset: 0x1000
+// CHECK-NEXT:     VirtualAddress: 0x1000
+// CHECK-NEXT:     PhysicalAddress: 0x1000
+// CHECK-NEXT:     FileSize: 12
+// CHECK-NEXT:     MemSize: 12
+// CHECK-NEXT:     Flags [ (0x5)
+// CHECK-NEXT:       PF_R (0x4)
+// CHECK-NEXT:       PF_X (0x1)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Alignment: 4096
+// CHECK-NEXT:   }
+// CHECK-NEXT:   ProgramHeader {
+// CHECK-NEXT:     Type: PT_LOAD (0x1)
+// CHECK-NEXT:     Offset: 0x2000
+// CHECK-NEXT:     VirtualAddress: 0x2000
+// CHECK-NEXT:     PhysicalAddress: 0x2000
+// CHECK-NEXT:     FileSize: 48
+// CHECK-NEXT:     MemSize: 48
+// CHECK-NEXT:     Flags [ (0x6)
+// CHECK-NEXT:       PF_R (0x4)
+// CHECK-NEXT:       PF_W (0x2)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Alignment: 4096
+// CHECK-NEXT:   }
+// CHECK-NEXT:   ProgramHeader {
+// CHECK-NEXT:     Type: PT_DYNAMIC (0x2)
+// CHECK-NEXT:     Offset: 0x2000
+// CHECK-NEXT:     VirtualAddress: 0x2000
+// CHECK-NEXT:     PhysicalAddress: 0x2000
+// CHECK-NEXT:     FileSize: 48
+// CHECK-NEXT:     MemSize: 48
+// CHECK-NEXT:     Flags [ (0x6)
+// CHECK-NEXT:       PF_R (0x4)
+// CHECK-NEXT:       PF_W (0x2)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Alignment: 4
+// CHECK-NEXT:   }
+// CHECK-NEXT:   ProgramHeader {
+// CHECK-NEXT:     Type: PT_GNU_RELRO (0x6474E552)
+// CHECK-NEXT:     Offset: 0x2000
+// CHECK-NEXT:     VirtualAddress: 0x2000
+// CHECK-NEXT:     PhysicalAddress: 0x2000
+// CHECK-NEXT:     FileSize: 48
+// CHECK-NEXT:     MemSize: 48
+// CHECK-NEXT:     Flags [ (0x4)
+// CHECK-NEXT:       PF_R (0x4)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Alignment: 1
+// CHECK-NEXT:   }
+// CHECK-NEXT:   ProgramHeader {
+// CHECK-NEXT:     Type: PT_GNU_STACK (0x6474E551)
+// CHECK-NEXT:     Offset: 0x0
+// CHECK-NEXT:     VirtualAddress: 0x0
+// CHECK-NEXT:     PhysicalAddress: 0x0
+// CHECK-NEXT:     FileSize: 0
+// CHECK-NEXT:     MemSize: 0
+// CHECK-NEXT:     Flags [ (0x6)
+// CHECK-NEXT:       PF_R (0x4)
+// CHECK-NEXT:       PF_W (0x2)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Alignment: 0
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]