[lld] Add target support for SystemZ (s390x) (#75643)

This patch adds full support for linking SystemZ (ELF s390x) object
files. Support should be generally complete:
- All relocation types are supported.
- Full shared library support (DYNAMIC, GOT, PLT, ifunc).
- Relaxation of TLS and GOT relocations where appropriate.
- Platform-specific test cases.

In addition to new platform code and the obvious changes, there were a
few additional changes to common code:

- Add three new RelExpr members (R_GOTPLT_OFF, R_GOTPLT_PC, and
R_PLT_GOTREL) needed to support certain s390x relocations. I chose not
to use a platform-specific name since nothing in the definition of these
relocs is actually platform-specific; it is well possible that other
platforms will need the same.

- A couple of tweaks to TLS relocation handling, as the particular
semantics of the s390x versions differ slightly. See comments in the
code.

This was tested by building and testing >1500 Fedora packages, with only
a handful of failures; as these also have issues when building with LLD
on other architectures, they seem unrelated.

Co-authored-by: Tulio Magno Quites Machado Filho <tuliom@redhat.com>

lld/ELF/CMakeLists.txt

@@ -33,6 +33,7 @@ add_lld_library(lldELF
   Arch/PPC64.cpp
   Arch/RISCV.cpp
   Arch/SPARCV9.cpp
+  Arch/SystemZ.cpp
   Arch/X86.cpp
   Arch/X86_64.cpp
   ARMErrataFix.cpp

lld/ELF/Driver.cpp

@@ -200,6 +200,7 @@ static std::tuple<ELFKind, uint16_t, uint8_t> parseEmulation(StringRef emul) {
           .Case("msp430elf", {ELF32LEKind, EM_MSP430})
           .Case("elf64_amdgpu", {ELF64LEKind, EM_AMDGPU})
           .Case("elf64loongarch", {ELF64LEKind, EM_LOONGARCH})
+          .Case("elf64_s390", {ELF64BEKind, EM_S390})
           .Default({ELFNoneKind, EM_NONE});
 
   if (ret.first == ELFNoneKind)
@@ -1137,7 +1138,7 @@ static SmallVector<StringRef, 0> getSymbolOrderingFile(MemoryBufferRef mb) {
 static bool getIsRela(opt::InputArgList &args) {
   // The psABI specifies the default relocation entry format.
   bool rela = is_contained({EM_AARCH64, EM_AMDGPU, EM_HEXAGON, EM_LOONGARCH,
-                            EM_PPC, EM_PPC64, EM_RISCV, EM_X86_64},
+                            EM_PPC, EM_PPC64, EM_RISCV, EM_S390, EM_X86_64},
                            config->emachine);
   // If -z rel or -z rela is specified, use the last option.
   for (auto *arg : args.filtered(OPT_z)) {

lld/ELF/InputFiles.cpp

@@ -1614,6 +1614,8 @@ static uint16_t getBitcodeMachineKind(StringRef path, const Triple &t) {
     return EM_RISCV;
   case Triple::sparcv9:
     return EM_SPARCV9;
+  case Triple::systemz:
+    return EM_S390;
   case Triple::x86:
     return t.isOSIAMCU() ? EM_IAMCU : EM_386;
   case Triple::x86_64:

lld/ELF/InputSection.cpp

@@ -655,6 +655,7 @@ static int64_t getTlsTpOffset(const Symbol &s) {
 
     // Variant 2.
   case EM_HEXAGON:
+  case EM_S390:
   case EM_SPARCV9:
   case EM_386:
   case EM_X86_64:
@@ -717,6 +718,10 @@ uint64_t InputSectionBase::getRelocTargetVA(const InputFile *file, RelType type,
   case R_GOT_PC:
   case R_RELAX_TLS_GD_TO_IE:
     return sym.getGotVA() + a - p;
+  case R_GOTPLT_GOTREL:
+    return sym.getGotPltVA() + a - in.got->getVA();
+  case R_GOTPLT_PC:
+    return sym.getGotPltVA() + a - p;
   case R_LOONGARCH_GOT_PAGE_PC:
     if (sym.hasFlag(NEEDS_TLSGD))
       return getLoongArchPageDelta(in.got->getGlobalDynAddr(sym) + a, p, type);
@@ -808,6 +813,8 @@ uint64_t InputSectionBase::getRelocTargetVA(const InputFile *file, RelType type,
     return getLoongArchPageDelta(sym.getPltVA() + a, p, type);
   case R_PLT_GOTPLT:
     return sym.getPltVA() + a - in.gotPlt->getVA();
+  case R_PLT_GOTREL:
+    return sym.getPltVA() + a - in.got->getVA();
   case R_PPC32_PLTREL:
     // R_PPC_PLTREL24 uses the addend (usually 0 or 0x8000) to indicate r30
     // stores _GLOBAL_OFFSET_TABLE_ or .got2+0x8000. The addend is ignored for

lld/ELF/Relocations.cpp

@@ -203,8 +203,9 @@ static bool isAbsoluteValue(const Symbol &sym) {
 
 // Returns true if Expr refers a PLT entry.
 static bool needsPlt(RelExpr expr) {
-  return oneof<R_PLT, R_PLT_PC, R_PLT_GOTPLT, R_LOONGARCH_PLT_PAGE_PC,
-               R_PPC32_PLTREL, R_PPC64_CALL_PLT>(expr);
+  return oneof<R_PLT, R_PLT_PC, R_PLT_GOTREL, R_PLT_GOTPLT, R_GOTPLT_GOTREL,
+               R_GOTPLT_PC, R_LOONGARCH_PLT_PAGE_PC, R_PPC32_PLTREL,
+               R_PPC64_CALL_PLT>(expr);
 }
 
 bool lld::elf::needsGot(RelExpr expr) {
@@ -233,6 +234,8 @@ static RelExpr toPlt(RelExpr expr) {
     return R_PLT_PC;
   case R_ABS:
     return R_PLT;
+  case R_GOTREL:
+    return R_PLT_GOTREL;
   default:
     return expr;
   }
@@ -253,6 +256,8 @@ static RelExpr fromPlt(RelExpr expr) {
     return R_ABS;
   case R_PLT_GOTPLT:
     return R_GOTPLTREL;
+  case R_PLT_GOTREL:
+    return R_GOTREL;
   default:
     return expr;
   }
@@ -979,10 +984,10 @@ bool RelocationScanner::isStaticLinkTimeConstant(RelExpr e, RelType type,
   if (oneof<R_GOTPLT, R_GOT_OFF, R_RELAX_HINT, R_MIPS_GOT_LOCAL_PAGE,
             R_MIPS_GOTREL, R_MIPS_GOT_OFF, R_MIPS_GOT_OFF32, R_MIPS_GOT_GP_PC,
             R_AARCH64_GOT_PAGE_PC, R_GOT_PC, R_GOTONLY_PC, R_GOTPLTONLY_PC,
-            R_PLT_PC, R_PLT_GOTPLT, R_PPC32_PLTREL, R_PPC64_CALL_PLT,
-            R_PPC64_RELAX_TOC, R_RISCV_ADD, R_AARCH64_GOT_PAGE,
-            R_LOONGARCH_PLT_PAGE_PC, R_LOONGARCH_GOT, R_LOONGARCH_GOT_PAGE_PC>(
-          e))
+            R_PLT_PC, R_PLT_GOTREL, R_PLT_GOTPLT, R_GOTPLT_GOTREL, R_GOTPLT_PC,
+            R_PPC32_PLTREL, R_PPC64_CALL_PLT, R_PPC64_RELAX_TOC, R_RISCV_ADD,
+            R_AARCH64_GOT_PAGE, R_LOONGARCH_PLT_PAGE_PC, R_LOONGARCH_GOT,
+            R_LOONGARCH_GOT_PAGE_PC>(e))
     return true;
 
   // These never do, except if the entire file is position dependent or if
@@ -1374,8 +1379,8 @@ static unsigned handleTlsRelocation(RelType type, Symbol &sym,
             R_LOONGARCH_GOT_PAGE_PC, R_GOT_OFF, R_TLSIE_HINT>(expr)) {
     ctx.hasTlsIe.store(true, std::memory_order_relaxed);
     // Initial-Exec relocs can be optimized to Local-Exec if the symbol is
-    // locally defined.
-    if (execOptimize && isLocalInExecutable) {
+    // locally defined.  This is not supported on SystemZ.
+    if (execOptimize && isLocalInExecutable && config->emachine != EM_S390) {
       c.addReloc({R_RELAX_TLS_IE_TO_LE, type, offset, addend, &sym});
     } else if (expr != R_TLSIE_HINT) {
       sym.setFlags(NEEDS_TLSIE);
@@ -1534,8 +1539,10 @@ void RelocationScanner::scan(ArrayRef<RelTy> rels) {
   // For EhInputSection, OffsetGetter expects the relocations to be sorted by
   // r_offset. In rare cases (.eh_frame pieces are reordered by a linker
   // script), the relocations may be unordered.
+  // On SystemZ, all sections need to be sorted by r_offset, to allow TLS
+  // relaxation to be handled correctly - see SystemZ::getTlsGdRelaxSkip.
   SmallVector<RelTy, 0> storage;
-  if (isa<EhInputSection>(sec))
+  if (isa<EhInputSection>(sec) || config->emachine == EM_S390)
     rels = sortRels(rels, storage);
 
   end = static_cast<const void *>(rels.end());

lld/ELF/Relocations.h

@@ -40,11 +40,14 @@ enum RelExpr {
   R_GOTPLT,
   R_GOTPLTREL,
   R_GOTREL,
+  R_GOTPLT_GOTREL,
+  R_GOTPLT_PC,
   R_NONE,
   R_PC,
   R_PLT,
   R_PLT_PC,
   R_PLT_GOTPLT,
+  R_PLT_GOTREL,
   R_RELAX_HINT,
   R_RELAX_GOT_PC,
   R_RELAX_GOT_PC_NOPIC,

lld/ELF/ScriptParser.cpp

@@ -445,6 +445,7 @@ static std::pair<ELFKind, uint16_t> parseBfdName(StringRef s) {
       .Case("elf32-msp430", {ELF32LEKind, EM_MSP430})
       .Case("elf32-loongarch", {ELF32LEKind, EM_LOONGARCH})
       .Case("elf64-loongarch", {ELF64LEKind, EM_LOONGARCH})
+      .Case("elf64-s390", {ELF64BEKind, EM_S390})
       .Default({ELFNoneKind, EM_NONE});
 }
 

lld/ELF/SyntheticSections.cpp

@@ -1419,6 +1419,9 @@ DynamicSection<ELFT>::computeContents() {
     case EM_MIPS:
       addInSec(DT_MIPS_PLTGOT, *in.gotPlt);
       break;
+    case EM_S390:
+      addInSec(DT_PLTGOT, *in.got);
+      break;
     case EM_SPARCV9:
       addInSec(DT_PLTGOT, *in.plt);
       break;

lld/ELF/Target.cpp

@@ -87,6 +87,8 @@ TargetInfo *elf::getTarget() {
     return getRISCVTargetInfo();
   case EM_SPARCV9:
     return getSPARCV9TargetInfo();
+  case EM_S390:
+    return getSystemZTargetInfo();
   case EM_X86_64:
     return getX86_64TargetInfo();
   default:

lld/ELF/Target.h

@@ -188,6 +188,7 @@ TargetInfo *getPPC64TargetInfo();
 TargetInfo *getPPCTargetInfo();
 TargetInfo *getRISCVTargetInfo();
 TargetInfo *getSPARCV9TargetInfo();
+TargetInfo *getSystemZTargetInfo();
 TargetInfo *getX86TargetInfo();
 TargetInfo *getX86_64TargetInfo();
 template <class ELFT> TargetInfo *getMipsTargetInfo();

lld/test/ELF/Inputs/systemz-init.s

@@ -0,0 +1,5 @@
+// glibc < 2.39 used to align .init and .fini code at a 4-byte boundary.
+// This file aims to recreate that behavior.
+	.section        .init,"ax",@progbits
+	.align	4
+	lg %r4, 272(%r15)

lld/test/ELF/basic-systemz.s

@@ -0,0 +1,63 @@
+# REQUIRES: systemz
+# RUN: llvm-mc -filetype=obj -triple=s390x-unknown-linux %s -o %t.o
+# RUN: ld.lld --hash-style=sysv -discard-all -shared %t.o -o %t.so
+# RUN: llvm-readelf --file-header --program-headers --section-headers --dynamic-table %t.so | FileCheck %s
+
+# Exits with return code 55 on linux.
+.text
+  lghi 2,55
+  svc 1
+
+# CHECK:       ELF Header:
+# CHECK-NEXT:  Magic:   7f 45 4c 46 02 02 01 00 00 00 00 00 00 00 00 00
+# CHECK-NEXT:  Class:                             ELF64
+# CHECK-NEXT:  Data:                              2's complement, big endian
+# CHECK-NEXT:  Version:                           1 (current)
+# CHECK-NEXT:  OS/ABI:                            UNIX - System V
+# CHECK-NEXT:  ABI Version:                       0
+# CHECK-NEXT:  Type:                              DYN (Shared object file)
+# CHECK-NEXT:  Machine:                           IBM S/390
+# CHECK-NEXT:  Version:                           0x1
+# CHECK-NEXT:  Entry point address:               0x0
+# CHECK-NEXT:  Start of program headers:          64 (bytes into file)
+# CHECK-NEXT:  Start of section headers:          768 (bytes into file)
+# CHECK-NEXT:  Flags:                             0x0
+# CHECK-NEXT:  Size of this header:               64 (bytes)
+# CHECK-NEXT:  Size of program headers:           56 (bytes)
+# CHECK-NEXT:  Number of program headers:         7
+# CHECK-NEXT:  Size of section headers:           64 (bytes)
+# CHECK-NEXT:  Number of section headers:         11
+# CHECK-NEXT:  Section header string table index: 9
+
+# CHECK:       Section Headers:
+# CHECK-NEXT:  [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
+# CHECK-NEXT:  [ 0]                   NULL            0000000000000000 000000 000000 00      0   0  0
+# CHECK-NEXT:  [ 1] .dynsym           DYNSYM          00000000000001c8 0001c8 000018 18   A  3   1  8
+# CHECK-NEXT:  [ 2] .hash             HASH            00000000000001e0 0001e0 000010 04   A  1   0  4
+# CHECK-NEXT:  [ 3] .dynstr           STRTAB          00000000000001f0 0001f0 000001 00   A  0   0  1
+# CHECK-NEXT:  [ 4] .text             PROGBITS        00000000000011f4 0001f4 000006 00  AX  0   0  4
+# CHECK-NEXT:  [ 5] .dynamic          DYNAMIC         0000000000002200 000200 000060 10  WA  3   0  8
+# CHECK-NEXT:  [ 6] .relro_padding    NOBITS          0000000000002260 000260 000da0 00  WA  0   0  1
+# CHECK-NEXT:  [ 7] .comment          PROGBITS        0000000000000000 000260 000008 01  MS  0   0  1
+# CHECK-NEXT:  [ 8] .symtab           SYMTAB          0000000000000000 000268 000030 18     10   2  8
+# CHECK-NEXT:  [ 9] .shstrtab         STRTAB          0000000000000000 000298 000058 00      0   0  1
+# CHECK-NEXT:  [10] .strtab           STRTAB          0000000000000000 0002f0 00000a 00      0   0  1
+
+# CHECK:       Program Headers:
+# CHECK-NEXT:  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg Align
+# CHECK-NEXT:  PHDR           0x000040 0x0000000000000040 0x0000000000000040 0x000188 0x000188 R   0x8
+# CHECK-NEXT:  LOAD           0x000000 0x0000000000000000 0x0000000000000000 0x0001f1 0x0001f1 R   0x1000
+# CHECK-NEXT:  LOAD           0x0001f4 0x00000000000011f4 0x00000000000011f4 0x000006 0x000006 R E 0x1000
+# CHECK-NEXT:  LOAD           0x000200 0x0000000000002200 0x0000000000002200 0x000060 0x000e00 RW  0x1000
+# CHECK-NEXT:  DYNAMIC        0x000200 0x0000000000002200 0x0000000000002200 0x000060 0x000060 RW  0x8
+# CHECK-NEXT:  GNU_RELRO      0x000200 0x0000000000002200 0x0000000000002200 0x000060 0x000e00 R   0x1
+# CHECK-NEXT:  GNU_STACK      0x000000 0x0000000000000000 0x0000000000000000 0x000000 0x000000 RW  0x0
+
+# CHECK:       Dynamic section at offset 0x200 contains 6 entries:
+# CHECK-NEXT:  Tag                Type     Name/Value
+# CHECK-NEXT:  0x0000000000000006 (SYMTAB) 0x1c8
+# CHECK-NEXT:  0x000000000000000b (SYMENT) 24 (bytes)
+# CHECK-NEXT:  0x0000000000000005 (STRTAB) 0x1f0
+# CHECK-NEXT:  0x000000000000000a (STRSZ)  1 (bytes)
+# CHECK-NEXT:  0x0000000000000004 (HASH)   0x1e0
+# CHECK-NEXT:  0x0000000000000000 (NULL)   0x0

lld/test/ELF/emulation-systemz.s

@@ -0,0 +1,29 @@
+# REQUIRES: systemz
+# RUN: llvm-mc -filetype=obj -triple=s390x-unknown-linux %s -o %t.o
+# RUN: ld.lld -m elf64_s390 %t.o -o %t1
+# RUN: llvm-readelf --file-header %t1 | FileCheck %s
+# RUN: ld.lld %t.o -o %t2
+# RUN: llvm-readelf --file-header %t2 | FileCheck %s
+# RUN: echo 'OUTPUT_FORMAT(elf64-s390)' > %t.script
+# RUN: ld.lld %t.script %t.o -o %t3
+# RUN: llvm-readelf --file-header %t3 | FileCheck %s
+
+# CHECK:       ELF Header:
+# CHECK-NEXT:  Magic:   7f 45 4c 46 02 02 01 00 00 00 00 00 00 00 00 00
+# CHECK-NEXT:  Class:                             ELF64
+# CHECK-NEXT:  Data:                              2's complement, big endian
+# CHECK-NEXT:  Version:                           1 (current)
+# CHECK-NEXT:  OS/ABI:                            UNIX - System V
+# CHECK-NEXT:  ABI Version:                       0
+# CHECK-NEXT:  Type:                              EXEC (Executable file)
+# CHECK-NEXT:  Machine:                           IBM S/390
+# CHECK-NEXT:  Version:                           0x1
+# CHECK-NEXT:  Entry point address:
+# CHECK-NEXT:  Start of program headers:          64 (bytes into file)
+# CHECK-NEXT:  Start of section headers:
+# CHECK-NEXT:  Flags:                             0x0
+# CHECK-NEXT:  Size of this header:               64 (bytes)
+# CHECK-NEXT:  Size of program headers:           56 (bytes)
+
+.globl _start
+_start:

lld/test/ELF/lto/systemz.ll

@@ -0,0 +1,18 @@
+; REQUIRES: systemz
+;; Test we can infer the e_machine value EM_S390 from a bitcode file.
+
+; RUN: llvm-as %s -o %t.o
+; RUN: ld.lld %t.o -o %t
+; RUN: llvm-readobj -h %t | FileCheck %s
+
+; CHECK: Class: 64-bit
+; CHECK: DataEncoding: BigEndian
+; CHECK: Machine: EM_S390
+
+target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64"
+target triple = "s390x-unknown-linux-gnu"
+
+define void @_start() {
+entry:
+  ret void
+}

lld/test/ELF/systemz-got.s

@@ -0,0 +1,16 @@
+# REQUIRES: systemz
+# RUN: llvm-mc -filetype=obj -triple=s390x-unknown-linux %s -o %t.o
+# RUN: llvm-mc -filetype=obj -triple=s390x-unknown-linux %p/Inputs/shared.s -o %t2.o
+# RUN: ld.lld -shared %t2.o -soname=%t2.so -o %t2.so
+
+# RUN: ld.lld -dynamic-linker /lib/ld64.so.1 %t.o %t2.so -o %t
+# RUN: llvm-readelf -S -r  %t | FileCheck %s
+
+# CHECK: .got              PROGBITS        {{.*}} {{.*}} 000020 00  WA  0   0  8
+
+# CHECK: Relocation section '.rela.dyn' at offset {{.*}} contains 1 entries:
+# CHECK: {{.*}}  000000010000000a R_390_GLOB_DAT         0000000000000000 bar + 0
+
+.global _start
+_start:
+	lgrl  %r1,bar@GOT

lld/test/ELF/systemz-gotent-relax-align.s

@@ -0,0 +1,48 @@
+# REQUIRES: systemz
+## Verify that R_390_GOTENT optimization is not performed on misaligned symbols.
+
+# RUN: llvm-mc -filetype=obj -relax-relocations -triple=s390x-unknown-linux %s -o %t.o
+# RUN: ld.lld %t.o -o %t1
+# RUN: llvm-readelf -S -r -x .got -x .got.plt %t1 | FileCheck --check-prefixes=CHECK %s
+# RUN: llvm-objdump --no-print-imm-hex -d %t1 | FileCheck --check-prefix=DISASM %s
+
+## We retain one .got entry for the unaligned symbol.
+# CHECK:      Name              Type            Address          Off    Size   ES Flg Lk Inf Al
+# CHECK:      .got              PROGBITS        00000000010021e0 0001e0 000020 00  WA  0   0  8
+# CHECK-NEXT: .relro_padding    NOBITS          0000000001002200 000200 000e00 00  WA  0   0  1
+# CHECK-NEXT: .data             PROGBITS        0000000001003200 000200 000006 00  WA  0   0  2
+
+# CHECK-LABEL: Hex dump of section '.got':
+# CHECK-NEXT:    0x010021e0 00000000 00000000 00000000 00000000
+# CHECK-NEXT:    0x010021f0 00000000 00000000 00000000 01003205
+
+# DISASM:      Disassembly of section .text:
+# DISASM:      <_start>:
+# DISASM-NEXT:   larl    %r1, 0x1003200
+# DISASM-NEXT:   larl    %r1, 0x1003200
+# DISASM-NEXT:   lgrl    %r1, 0x10021f8
+# DISASM-NEXT:   lgrl    %r1, 0x10021f8
+
+.data
+.globl var_align
+.hidden var_align
+ .align 2
+var_align:
+ .long 0
+
+.data
+.globl var_unalign
+.hidden var_unalign
+ .align 2
+ .byte 0
+var_unalign:
+ .byte 0
+
+.text
+.globl _start
+.type _start, @function
+_start:
+ lgrl %r1, var_align@GOT
+ lgrl %r1, var_align@GOT
+ lgrl %r1, var_unalign@GOT
+ lgrl %r1, var_unalign@GOT