Use GOT for CHERI-RISC-V and align modifiers and relocations with RISC-V

lld/ELF/Arch/Cheri.h

@@ -15,12 +15,10 @@ namespace elf {
 
 struct SymbolAndOffset {
 public:
-  SymbolAndOffset(Symbol *s, int64_t o) : symOrSec(s), offset(o) {
+  SymbolAndOffset(llvm::PointerUnion<Symbol *, InputSectionBase *> s, int64_t o)
+      : symOrSec(s), offset(o) {
     assert(s && "Should not be null");
   }
-  SymbolAndOffset(InputSectionBase *isec, int64_t o) : symOrSec(isec), offset(o) {
-    assert(isec && "Should not be null");
-  }
   SymbolAndOffset(const SymbolAndOffset &) = default;
   SymbolAndOffset &operator=(const SymbolAndOffset &) = default;
 
@@ -186,9 +184,9 @@ class CheriCapRelocsSection : public SyntheticSection {
 // +---------------------------------------+
 // TODO: TLS caps also need to be per file/function
 
-class CheriCapTableSection : public SyntheticSection {
+class MipsCheriCapTableSection : public SyntheticSection {
 public:
-  CheriCapTableSection();
+  MipsCheriCapTableSection();
   // InputFile and Offset is needed in order to implement per-file/per-function
   // tables
   void addEntry(Symbol &sym, RelExpr expr, InputSectionBase *isec,
@@ -266,7 +264,7 @@ class CheriCapTableSection : public SyntheticSection {
   CaptableMap dynTlsEntries;
   CaptableMap tlsEntries;
   bool valuesAssigned = false;
-  friend class CheriCapTableMappingSection;
+  friend class MipsCheriCapTableMappingSection;
 };
 
 // TODO: could shrink these to reduce size overhead but this is experimental
@@ -280,13 +278,13 @@ struct CaptableMappingEntry {
 
 // Map from symbol vaddr -> captable subset so that RTLD can setup the correct
 // trampolines to initialize $cgp to the correct subset
-class CheriCapTableMappingSection : public SyntheticSection {
+class MipsCheriCapTableMappingSection : public SyntheticSection {
 public:
-  CheriCapTableMappingSection();
+  MipsCheriCapTableMappingSection();
   bool isNeeded() const override {
     if (config->capTableScope == CapTableScopePolicy::All)
       return false;
-    return in.cheriCapTable && in.cheriCapTable->isNeeded();
+    return in.mipsCheriCapTable && in.mipsCheriCapTable->isNeeded();
   }
   void writeTo(uint8_t *buf) override;
   size_t getSize() const override;
@@ -320,11 +318,11 @@ inline void readOnlyCapRelocsError(Symbol &sym, const Twine &sourceMsg) {
 }
 
 template <typename ELFT>
-void addCapabilityRelocation(Symbol *sym, RelType type, InputSectionBase *sec,
-                             uint64_t offset, RelExpr expr, int64_t addend,
-                             bool isCallExpr,
-                             llvm::function_ref<std::string()> referencedBy,
-                             RelocationBaseSection *dynRelSec = nullptr);
+void addCapabilityRelocation(
+    llvm::PointerUnion<Symbol *, InputSectionBase *> target, RelType type,
+    InputSectionBase *sec, uint64_t offset, RelExpr expr, int64_t addend,
+    bool isCallExpr, llvm::function_ref<std::string()> referencedBy,
+    RelocationBaseSection *dynRelSec = nullptr);
 } // namespace elf
 } // namespace lld
 

lld/ELF/Arch/Mips.cpp

@@ -123,7 +123,7 @@ RelExpr MIPS<ELFT>::getRelExpr(RelType type, const Symbol &s,
   case R_MICROMIPS_GPREL7_S2:
     return R_MIPS_GOTREL;
   case R_MIPS_CHERI_CAPTABLEREL16:
-    return R_CHERI_CAPABILITY_TABLE_REL;
+    return R_MIPS_CHERI_CAPTAB_REL;
   case R_MIPS_26:
   case R_MICROMIPS_26_S1:
     return R_PLT;
@@ -212,16 +212,16 @@ RelExpr MIPS<ELFT>::getRelExpr(RelType type, const Symbol &s,
     return R_CHERI_CAPABILITY;
   case R_MIPS_CHERI_CAPTAB_LO16:
   case R_MIPS_CHERI_CAPTAB_HI16:
-    return R_CHERI_CAPABILITY_TABLE_INDEX;
+    return R_MIPS_CHERI_CAPTAB_INDEX;
   case R_MIPS_CHERI_CAPCALL_LO16:
   case R_MIPS_CHERI_CAPCALL_HI16:
-    return R_CHERI_CAPABILITY_TABLE_INDEX_CALL;
+    return R_MIPS_CHERI_CAPTAB_INDEX_CALL;
   case R_MIPS_CHERI_CAPTAB_CLC11:
   case R_MIPS_CHERI_CAPTAB20:
-    return R_CHERI_CAPABILITY_TABLE_INDEX_SMALL_IMMEDIATE;
+    return R_MIPS_CHERI_CAPTAB_INDEX_SMALL_IMMEDIATE;
   case R_MIPS_CHERI_CAPCALL_CLC11:
   case R_MIPS_CHERI_CAPCALL20:
-    return R_CHERI_CAPABILITY_TABLE_INDEX_CALL_SMALL_IMMEDIATE;
+    return R_MIPS_CHERI_CAPTAB_INDEX_CALL_SMALL_IMMEDIATE;
   case R_MIPS_CHERI_CAPTAB_TLS_GD_LO16:
   case R_MIPS_CHERI_CAPTAB_TLS_GD_HI16:
     return R_MIPS_CHERI_CAPTAB_TLSGD;

lld/ELF/Arch/RISCV.cpp

@@ -68,7 +68,6 @@ enum Op {
   CIncOffsetImm = 0x105b,
   CLC_64 = 0x3003,
   CLC_128 = 0x200f,
-  CSub = 0x2800005b,
 };
 
 enum Reg {
@@ -112,10 +111,7 @@ RISCV::RISCV() {
   pltRel = R_RISCV_JUMP_SLOT;
   relativeRel = R_RISCV_RELATIVE;
   iRelativeRel = R_RISCV_IRELATIVE;
-  sizeRel = R_RISCV_CHERI_SIZE;
   cheriCapRel = R_RISCV_CHERI_CAPABILITY;
-  // TODO: R_RISCV_CHERI_JUMP_SLOT in a separate .got.plt / .captable.plt
-  cheriCapCallRel = R_RISCV_CHERI_CAPABILITY;
   if (config->is64) {
     symbolicRel = R_RISCV_64;
     tlsModuleIndexRel = R_RISCV_TLS_DTPMOD64;
@@ -127,7 +123,10 @@ RISCV::RISCV() {
     tlsOffsetRel = R_RISCV_TLS_DTPREL32;
     tlsGotRel = R_RISCV_TLS_TPREL32;
   }
-  gotRel = symbolicRel;
+  if (config->isCheriAbi)
+    gotRel = *cheriCapRel;
+  else
+    gotRel = symbolicRel;
   absPointerRel = symbolicRel;
 
   // .got[0] = _DYNAMIC
@@ -222,6 +221,10 @@ void RISCV::writeGotHeader(uint8_t *buf) const {
 }
 
 void RISCV::writeGotPlt(uint8_t *buf, const Symbol &s) const {
+  // Initialised by __cap_relocs for CHERI
+  if (config->isCheriAbi)
+    return;
+
   if (config->is64)
     write64le(buf, in.plt->getVA());
   else
@@ -238,14 +241,7 @@ void RISCV::writeIgotPlt(uint8_t *buf, const Symbol &s) const {
 }
 
 void RISCV::writePltHeader(uint8_t *buf) const {
-  // TODO: Remove once we have a CHERI .got.plt and R_RISCV_CHERI_JUMP_SLOT.
-  // Without those there can be no lazy binding support (though the former
-  // requirement can be relaxed provided .captable[0] is _dl_runtime_resolve,
-  // at least when the PLT is non-empty), so for now we emit a header full of
-  // trapping instructions to ensure we don't accidentally end up trying to use
-  // it. Ideally we would have a header size of 0, but isCheriAbi isn't known
-  // in the constructor.
-  if (config->isCheriAbi) {
+  if (config->isCheriAbi && !config->zCheriRiscvJumpSlot) {
     memset(buf, 0, pltHeaderSize);
     return;
   }
@@ -259,7 +255,6 @@ void RISCV::writePltHeader(uint8_t *buf) const {
   // (c)jr (c)t3
   // (if shift == 0): nop
   uint32_t offset = in.gotPlt->getVA() - in.plt->getVA();
-  uint32_t ptrsub = config->isCheriAbi ? CSub : SUB;
   uint32_t ptrload = config->isCheriAbi ? config->is64 ? CLC_128 : CLC_64
                                         : config->is64 ? LD : LW;
   uint32_t ptraddi = config->isCheriAbi ? CIncOffsetImm : ADDI;
@@ -268,7 +263,7 @@ void RISCV::writePltHeader(uint8_t *buf) const {
   uint32_t ptrsize = config->isCheriAbi ? config->capabilitySize
                                         : config->wordsize;
   write32le(buf + 0, utype(AUIPC, X_T2, hi20(offset)));
-  write32le(buf + 4, rtype(ptrsub, X_T1, X_T1, X_T3));
+  write32le(buf + 4, rtype(SUB, X_T1, X_T1, X_T3));
   write32le(buf + 8, itype(ptrload, X_T3, X_T2, lo12(offset)));
   write32le(buf + 12, itype(ADDI, X_T1, X_T1, -target->pltHeaderSize - 12));
   write32le(buf + 16, itype(ptraddi, X_T0, X_T2, lo12(offset)));
@@ -288,8 +283,9 @@ void RISCV::writePlt(uint8_t *buf, const Symbol &sym,
   // nop
   uint32_t ptrload = config->isCheriAbi ? config->is64 ? CLC_128 : CLC_64
                                         : config->is64 ? LD : LW;
-  uint32_t entryva = config->isCheriAbi ? sym.getCapTableVA(in.plt.get(), 0)
-                                        : sym.getGotPltVA();
+  uint32_t entryva = config->isCheriAbi && !config->zCheriRiscvJumpSlot
+                         ? sym.getGotVA()
+                         : sym.getGotPltVA();
   uint32_t offset = entryva - pltEntryAddr;
   write32le(buf + 0, utype(AUIPC, X_T3, hi20(offset)));
   write32le(buf + 4, itype(ptrload, X_T3, X_T3, lo12(offset)));
@@ -363,12 +359,13 @@ RelExpr RISCV::getRelExpr(const RelType type, const Symbol &s,
     return config->relax ? R_RELAX_HINT : R_NONE;
   case R_RISCV_CHERI_CAPABILITY:
     return R_CHERI_CAPABILITY;
+  // TODO: Deprecate and eventually remove these
   case R_RISCV_CHERI_CAPTAB_PCREL_HI20:
-    return R_CHERI_CAPABILITY_TABLE_ENTRY_PC;
+    return R_GOT_PC;
   case R_RISCV_CHERI_TLS_IE_CAPTAB_PCREL_HI20:
-    return R_CHERI_CAPABILITY_TABLE_TLSIE_ENTRY_PC;
+    return R_GOT_PC;
   case R_RISCV_CHERI_TLS_GD_CAPTAB_PCREL_HI20:
-    return R_CHERI_CAPABILITY_TABLE_TLSGD_ENTRY_PC;
+    return R_TLSGD_PC;
   default:
     error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) +
           ") against symbol " + toString(s));

lld/ELF/Config.h

@@ -308,6 +308,7 @@ struct Config {
   // -z captabledebug: add additional symbols $captable_load_<symbols> before
   // each captable clc instruction that indicates which symbol should be loaded
   bool zCapTableDebug;
+  bool zCheriRiscvJumpSlot;
   bool zCombreloc;
   bool zCopyreloc;
   bool zForceBti;

lld/ELF/Driver.cpp

@@ -535,6 +535,7 @@ static uint8_t getZStartStopVisibility(opt::InputArgList &args) {
 
 constexpr const char *knownZFlags[] = {
     "captabledebug",
+    "cheri-riscv-jump-slot",
     "combreloc",
     "copyreloc",
     "defs",
@@ -1433,6 +1434,7 @@ static void readConfigs(opt::InputArgList &args) {
       args.hasFlag(OPT_warn_symbol_ordering, OPT_no_warn_symbol_ordering, true);
   config->whyExtract = args.getLastArgValue(OPT_why_extract);
   config->zCapTableDebug = getZFlag(args, "captabledebug", "nocaptabledebug", false);
+  config->zCheriRiscvJumpSlot = hasZOption(args, "cheri-riscv-jump-slot");
   config->zCombreloc = getZFlag(args, "combreloc", "nocombreloc", true);
   config->zCopyreloc = getZFlag(args, "copyreloc", "nocopyreloc", true);
   config->zForceBti = hasZOption(args, "force-bti");

lld/ELF/InputSection.cpp

@@ -863,44 +863,28 @@ uint64_t InputSectionBase::getRelocTargetVA(const InputFile *file, RelType type,
     return in.got->getTlsIndexVA() + a - p;
   case R_CHERI_CAPABILITY:
     llvm_unreachable("R_CHERI_CAPABILITY should not be handled here!");
-  case R_CHERI_CAPABILITY_TABLE_INDEX:
-  case R_CHERI_CAPABILITY_TABLE_INDEX_SMALL_IMMEDIATE:
-  case R_CHERI_CAPABILITY_TABLE_INDEX_CALL:
-  case R_CHERI_CAPABILITY_TABLE_INDEX_CALL_SMALL_IMMEDIATE:
+  case R_MIPS_CHERI_CAPTAB_INDEX:
+  case R_MIPS_CHERI_CAPTAB_INDEX_SMALL_IMMEDIATE:
+  case R_MIPS_CHERI_CAPTAB_INDEX_CALL:
+  case R_MIPS_CHERI_CAPTAB_INDEX_CALL_SMALL_IMMEDIATE:
     assert(a == 0 && "capability table index relocs should not have addends");
-    return sym.getCapTableOffset(isec, offset);
-  case R_CHERI_CAPABILITY_TABLE_ENTRY_PC: {
-    assert(a == 0 && "capability table entry relocs should not have addends");
-    return sym.getCapTableVA(isec, offset) - p;
-  }
-  case R_CHERI_CAPABILITY_TABLE_TLSGD_ENTRY_PC: {
-    assert(a == 0 && "capability table index relocs should not have addends");
-    uint64_t capTableOffset =
-        in.cheriCapTable->getDynTlsOffset(sym);
-    return ElfSym::cheriCapabilityTable->getVA() + capTableOffset - p;
-  }
-  case R_CHERI_CAPABILITY_TABLE_TLSIE_ENTRY_PC: {
-    assert(a == 0 && "capability table index relocs should not have addends");
-    uint64_t capTableOffset =
-        in.cheriCapTable->getTlsOffset(sym);
-    return ElfSym::cheriCapabilityTable->getVA() + capTableOffset - p;
-  }
-  case R_CHERI_CAPABILITY_TABLE_REL:
-    if (!ElfSym::cheriCapabilityTable) {
+    return sym.getMipsCheriCapTableOffset(isec, offset);
+  case R_MIPS_CHERI_CAPTAB_REL:
+    if (!ElfSym::mipsCheriCapabilityTable) {
       error("cannot compute difference between non-existent "
             "CheriCapabilityTable and symbol " + toString(sym));
       return sym.getVA(a);
     }
-    return sym.getVA(a) - ElfSym::cheriCapabilityTable->getVA();
+    return sym.getVA(a) - ElfSym::mipsCheriCapabilityTable->getVA();
   case R_MIPS_CHERI_CAPTAB_TLSGD:
     assert(a == 0 && "capability table index relocs should not have addends");
-    return in.cheriCapTable->getDynTlsOffset(sym);
+    return in.mipsCheriCapTable->getDynTlsOffset(sym);
   case R_MIPS_CHERI_CAPTAB_TLSLD:
     assert(a == 0 && "capability table index relocs should not have addends");
-    return in.cheriCapTable->getTlsIndexOffset();
+    return in.mipsCheriCapTable->getTlsIndexOffset();
   case R_MIPS_CHERI_CAPTAB_TPREL:
     assert(a == 0 && "capability table index relocs should not have addends");
-    return in.cheriCapTable->getTlsOffset(sym);
+    return in.mipsCheriCapTable->getTlsOffset(sym);
   default:
     llvm_unreachable("invalid expression");
   }