Subzero: Add sandboxing for x86-32.

src/IceInstX8632.cpp

 //===- subzero/src/IceInstX8632.cpp - X86-32 instruction implementation ---===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the InstX8632 and OperandX8632 classes,
@@ skipping 182 matching lines @@
   if (TargetFalse == OldNode) {
     TargetFalse = NewNode;
     return true;
   } else if (TargetTrue == OldNode) {
     TargetTrue = NewNode;
     return true;
   }
   return false;
 }
 
+InstX8632Jmp::InstX8632Jmp(Cfg *Func, Operand *Target)
+    : InstX8632(Func, InstX8632::Jmp, 1, nullptr) {
+  addSource(Target);
+}
+
 InstX8632Call::InstX8632Call(Cfg *Func, Variable *Dest, Operand *CallTarget)
     : InstX8632(Func, InstX8632::Call, 1, Dest) {
   HasSideEffects = true;
   addSource(CallTarget);
 }
 
 InstX8632Cmov::InstX8632Cmov(Cfg *Func, Variable *Dest, Operand *Source,
                              CondX86::BrCond Condition)
     : InstX8632(Func, InstX8632::Cmov, 2, Dest), Condition(Condition) {
   // The final result is either the original Dest, or Source, so mark
@@ skipping 230 matching lines @@
   if (Label) {
     Str << ", label %" << Label->getName(Func);
   } else {
     Str << ", label %" << getTargetTrue()->getName();
     if (getTargetFalse()) {
       Str << ", label %" << getTargetFalse()->getName();
     }
   }
 }
 
+void InstX8632Jmp::emit(const Cfg *Func) const {
+  if (!ALLOW_DUMP)
+    return;
+  Ostream &Str = Func->getContext()->getStrEmit();
+  assert(getSrcSize() == 1);
+  Str << "\tjmp\t*";
+  getSrc(0)->emit(Func);
+}
+
+void InstX8632Jmp::emitIAS(const Cfg *Func) const {
+  // Note: Adapted (mostly copied) from InstX8632Call::emitIAS().
+  x86::AssemblerX86 *Asm = Func->getAssembler<x86::AssemblerX86>();
+  Operand *Target = getSrc(0);
+  if (const auto Var = llvm::dyn_cast<Variable>(Target)) {
+    if (Var->hasReg()) {
+      Asm->jmp(RegX8632::getEncodedGPR(Var->getRegNum()));
+    } else {
+      // The jmp instruction with a memory operand should be possible
+      // to encode, but it isn't a valid sandboxed instruction, and
+      // there shouldn't be a register allocation issue to jump
+      // through a scratch register, so we don't really need to bother
+      // implementing it.
+      llvm::report_fatal_error("Assembler can't jmp to memory operand");
+    }
+  } else if (const auto Mem = llvm::dyn_cast<OperandX8632Mem>(Target)) {
+    assert(Mem->getSegmentRegister() == OperandX8632Mem::DefaultSegment);
+    llvm::report_fatal_error("Assembler can't jmp to memory operand");
+  } else if (const auto CR = llvm::dyn_cast<ConstantRelocatable>(Target)) {
+    assert(CR->getOffset() == 0 && "We only support jumping to a function");
+    Asm->jmp(CR);
+  } else if (const auto Imm = llvm::dyn_cast<ConstantInteger32>(Target)) {
+    // NaCl trampoline calls refer to an address within the sandbox directly.
+    // This is usually only needed for non-IRT builds and otherwise not
+    // very portable or stable. For this, we would use the 0xE8 opcode
+    // (relative version of call) and there should be a PC32 reloc too.
+    // The PC32 reloc will have symbol index 0, and the absolute address
+    // would be encoded as an offset relative to the next instruction.
+    // TODO(jvoung): Do we need to support this?
+    (void)Imm;
+    llvm::report_fatal_error("Unexpected jmp to absolute address");
+  } else {
+    llvm::report_fatal_error("Unexpected operand type");
+  }
+}
+
+void InstX8632Jmp::dump(const Cfg *Func) const {
+  if (!ALLOW_DUMP)
+    return;
+  Ostream &Str = Func->getContext()->getStrDump();
+  Str << "jmp ";
+  getSrc(0)->dump(Func);
+}
+
 void InstX8632Call::emit(const Cfg *Func) const {
   if (!ALLOW_DUMP)
     return;
   Ostream &Str = Func->getContext()->getStrEmit();
   assert(getSrcSize() == 1);
   Str << "\tcall\t";
   if (const auto CallTarget =
           llvm::dyn_cast<ConstantRelocatable>(getCallTarget())) {
     // TODO(stichnot): All constant targets should suppress the '$',
     // not just relocatables.
@@ skipping 2424 matching lines @@
   }
   Str << "(";
   if (Func)
     Var->dump(Func);
   else
     Var->dump(Str);
   Str << ")";
 }
 
 } // end of namespace Ice