Rebased PNaCl localmods in LLVM to 223109

lib/Target/ARM/MCTargetDesc/ARMMCNaCl.cpp

+//=== ARMMCNaCl.cpp -  Expansion of NaCl pseudo-instructions     --*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "arm-mc-nacl"
+
+#include "MCTargetDesc/ARMBaseInfo.h"
+#include "MCTargetDesc/ARMMCExpr.h"
+#include "MCTargetDesc/ARMMCNaCl.h"
+#include "MCTargetDesc/ARMMCTargetDesc.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+
+using namespace llvm;
+
+/// Two helper functions for emitting the actual guard instructions
+
+static void EmitBICMask(const MCSubtargetInfo &STI, MCStreamer &Out,
+                        unsigned Addr, int64_t Pred, unsigned Mask) {
+  // bic\Pred \Addr, \Addr, #Mask
+  MCInst BICInst;
+  BICInst.setOpcode(ARM::BICri);
+  BICInst.addOperand(MCOperand::CreateReg(Addr)); // rD
+  BICInst.addOperand(MCOperand::CreateReg(Addr)); // rS
+  BICInst.addOperand(MCOperand::CreateImm(Mask)); // imm
+  BICInst.addOperand(MCOperand::CreateImm(Pred));  // predicate
+  BICInst.addOperand(MCOperand::CreateReg(ARM::CPSR)); // CPSR
+  BICInst.addOperand(MCOperand::CreateReg(0)); // flag out
+  Out.EmitInstruction(BICInst, STI);
+}
+
+static void EmitTST(const MCSubtargetInfo &STI, MCStreamer &Out, unsigned Reg) {
+  // tst \reg, #\MASK typically 0xc0000000
+  const unsigned Mask = 0xC0000000;
+  MCInst TSTInst;
+  TSTInst.setOpcode(ARM::TSTri);
+  TSTInst.addOperand(MCOperand::CreateReg(Reg));  // rS
+  TSTInst.addOperand(MCOperand::CreateImm(Mask)); // imm
+  TSTInst.addOperand(MCOperand::CreateImm((int64_t)ARMCC::AL)); // Always
+  TSTInst.addOperand(MCOperand::CreateImm(0)); // flag out
+  Out.EmitInstruction(TSTInst, STI);
+}
+
+
+// This is ONLY used for sandboxing stack changes.
+// The reason why SFI_NOP_IF_AT_BUNDLE_END gets handled here is that
+// it must ensure that the two instructions are in the same bundle.
+// It just so happens that the SFI_NOP_IF_AT_BUNDLE_END is always
+// emitted in conjunction with a SFI_DATA_MASK
+//
+static void EmitDataMask(const MCSubtargetInfo &STI, int I, MCInst Saved[],
+                         MCStreamer &Out) {
+  assert(I == 3 && (ARM::SFI_NOP_IF_AT_BUNDLE_END == Saved[0].getOpcode()) &&
+         (ARM::SFI_DATA_MASK == Saved[2].getOpcode()) &&
+         "Unexpected SFI Pseudo while lowering");
+
+  unsigned Addr = Saved[2].getOperand(0).getReg();
+  int64_t  Pred = Saved[2].getOperand(2).getImm();
+  assert((ARM::SP == Addr) && "Unexpected register at stack guard");
+
+  Out.EmitBundleLock(false);
+  Out.EmitInstruction(Saved[1], STI);
+  EmitBICMask(STI, Out, Addr, Pred, 0xC0000000);
+  Out.EmitBundleUnlock();
+}
+
+static void EmitDirectGuardCall(const MCSubtargetInfo &STI, int I,
+                                MCInst Saved[], MCStreamer &Out) {
+  // sfi_call_preamble cond=
+  //   sfi_nops_to_force_slot3
+  assert(I == 2 && (ARM::SFI_GUARD_CALL == Saved[0].getOpcode()) &&
+         "Unexpected SFI Pseudo while lowering SFI_GUARD_CALL");
+  Out.EmitBundleLock(true);
+  Out.EmitInstruction(Saved[1], STI);
+  Out.EmitBundleUnlock();
+}
+
+static void EmitIndirectGuardCall(const MCSubtargetInfo &STI, int I,
+                                  MCInst Saved[], MCStreamer &Out) {
+  // sfi_indirect_call_preamble link cond=
+  //   sfi_nops_to_force_slot2
+  //   sfi_code_mask \link \cond
+  assert(I == 2 && (ARM::SFI_GUARD_INDIRECT_CALL == Saved[0].getOpcode()) &&
+         "Unexpected SFI Pseudo while lowering SFI_GUARD_CALL");
+  unsigned Reg = Saved[0].getOperand(0).getReg();
+  int64_t Pred = Saved[0].getOperand(2).getImm();
+  Out.EmitBundleLock(true);
+  EmitBICMask(STI, Out, Reg, Pred, 0xC000000F);
+  Out.EmitInstruction(Saved[1], STI);
+  Out.EmitBundleUnlock();
+}
+
+static void EmitIndirectGuardJmp(const MCSubtargetInfo &STI, int I,
+                                 MCInst Saved[], MCStreamer &Out) {
+  //  sfi_indirect_jump_preamble link cond=
+  //   sfi_nop_if_at_bundle_end
+  //   sfi_code_mask \link \cond
+  assert(I == 2 && (ARM::SFI_GUARD_INDIRECT_JMP == Saved[0].getOpcode()) &&
+         "Unexpected SFI Pseudo while lowering SFI_GUARD_CALL");
+  unsigned Reg = Saved[0].getOperand(0).getReg();
+  int64_t Pred = Saved[0].getOperand(2).getImm();
+
+  Out.EmitBundleLock(false);
+  EmitBICMask(STI, Out, Reg, Pred, 0xC000000F);
+  Out.EmitInstruction(Saved[1], STI);
+  Out.EmitBundleUnlock();
+}
+
+static void EmitGuardReturn(const MCSubtargetInfo &STI, int I, MCInst Saved[],
+                            MCStreamer &Out) {
+  // sfi_return_preamble reg cond=
+  //    sfi_nop_if_at_bundle_end
+  //    sfi_code_mask \reg \cond
+  assert(I == 2 && (ARM::SFI_GUARD_RETURN == Saved[0].getOpcode()) &&
+         "Unexpected SFI Pseudo while lowering SFI_GUARD_RETURN");
+  int64_t Pred = Saved[0].getOperand(0).getImm();
+
+  Out.EmitBundleLock(false);
+  EmitBICMask(STI, Out, ARM::LR, Pred, 0xC000000F);
+  Out.EmitInstruction(Saved[1], STI);
+  Out.EmitBundleUnlock();
+}
+
+static void EmitGuardLoadOrStore(const MCSubtargetInfo &STI, int I,
+                                 MCInst Saved[], MCStreamer &Out) {
+  // sfi_store_preamble reg cond ---->
+  //    sfi_nop_if_at_bundle_end
+  //    sfi_data_mask \reg, \cond
+  assert(I == 2 && (ARM::SFI_GUARD_LOADSTORE == Saved[0].getOpcode()) &&
+         "Unexpected SFI Pseudo while lowering SFI_GUARD_RETURN");
+  unsigned Reg = Saved[0].getOperand(0).getReg();
+  int64_t Pred = Saved[0].getOperand(2).getImm();
+
+  Out.EmitBundleLock(false);
+  EmitBICMask(STI, Out, Reg, Pred, 0xC0000000);
+  Out.EmitInstruction(Saved[1], STI);
+  Out.EmitBundleUnlock();
+}
+
+static void EmitGuardLoadOrStoreTst(const MCSubtargetInfo &STI, int I,
+                                    MCInst Saved[], MCStreamer &Out) {
+  // sfi_cstore_preamble reg -->
+  //   sfi_nop_if_at_bundle_end
+  //   sfi_data_tst \reg
+  assert(I == 2 && (ARM::SFI_GUARD_LOADSTORE_TST == Saved[0].getOpcode()) &&
+         "Unexpected SFI Pseudo while lowering");
+  unsigned Reg = Saved[0].getOperand(0).getReg();
+
+  Out.EmitBundleLock(false);
+  EmitTST(STI, Out, Reg);
+  Out.EmitInstruction(Saved[1], STI);
+  Out.EmitBundleUnlock();
+}
+
+// This is ONLY used for loads into the stack pointer.
+static void EmitGuardSpLoad(const MCSubtargetInfo &STI, int I, MCInst Saved[],
+                            MCStreamer &Out) {
+  assert(I == 4 &&
+         (ARM::SFI_GUARD_SP_LOAD == Saved[0].getOpcode()) &&
+         (ARM::SFI_NOP_IF_AT_BUNDLE_END == Saved[1].getOpcode()) &&
+         (ARM::SFI_DATA_MASK == Saved[3].getOpcode()) &&
+         "Unexpected SFI Pseudo while lowering");
+
+  unsigned AddrReg = Saved[0].getOperand(0).getReg();
+  unsigned SpReg = Saved[3].getOperand(0).getReg();
+  int64_t  Pred = Saved[3].getOperand(2).getImm();
+  assert((ARM::SP == SpReg) && "Unexpected register at stack guard");
+
+  Out.EmitBundleLock(false);
+  EmitBICMask(STI, Out, AddrReg, Pred, 0xC0000000);
+  Out.EmitInstruction(Saved[2], STI);
+  EmitBICMask(STI, Out, SpReg, Pred, 0xC0000000);
+  Out.EmitBundleUnlock();
+}
+
+namespace llvm {
+
+const int ARMMCNaClSFIState::MaxSaved;
+
+// CustomExpandInstNaClARM -
+//   If Inst is a NaCl pseudo instruction, emits the substitute
+//   expansion to the MCStreamer and returns true.
+//   Otherwise, returns false.
+//
+//   NOTE: Each time this function calls Out.EmitInstruction(), it will be
+//   called again recursively to rewrite the new instruction being emitted.
+//   Care must be taken to ensure that this does not result in an infinite
+//   loop. Also, global state must be managed carefully so that it is
+//   consistent during recursive calls.
+bool CustomExpandInstNaClARM(const MCSubtargetInfo &STI, const MCInst &Inst,
+                             MCStreamer &Out, ARMMCNaClSFIState &State) {
+  // Logic:
+  // This is somewhat convoluted, but in the current model, the SFI
+  // guard pseudo instructions occur PRIOR to the actual instruction.
+  // So, the bundling/alignment operation has to refer to the FOLLOWING
+  // instructions.
+  //
+  // When a SFI pseudo is detected, it is saved. Then, the saved SFI
+  // pseudo and the very next instructions (their amount depending on the kind
+  // of the SFI pseudo) are used as arguments to the Emit*() functions in
+  // this file.
+  //
+  // Some state data is used to preserve state accross calls:
+  //
+  // Saved:      the saved instructions (starting with the SFI_ pseudo).
+  // SavedCount: the amount of saved instructions required for the SFI pseudo
+  //             that's being expanded.
+  // I:          the index of the currently saved instruction - used to track
+  //             where in Saved to insert the instruction and how many more
+  //             remain.
+  //
+
+  // If we are emitting to .s, just emit all pseudo-instructions directly.
+  if (Out.hasRawTextSupport()) {
+    return false;
+  }
+
+  // Protect against recursive execution. If State.RecurseiveCall == true, it
+  // means we're already in the process of expanding a custom instruction, and
+  // we don't need to run recursively on anything generated by such an
+  // expansion.
+  if (State.RecursiveCall)
+    return false;
+
+  DEBUG(dbgs() << "CustomExpandInstNaClARM("; Inst.dump(); dbgs() << ")\n");
+
+  if ((State.I == 0) && (State.SaveCount == 0)) {
+    // Base state: no SFI guard identified yet and no saving started.
+    switch (Inst.getOpcode()) {
+      default:
+        // We don't handle non-SFI guards here
+        return false;
+      case ARM::SFI_NOP_IF_AT_BUNDLE_END:
+        // Note: SFI_NOP_IF_AT_BUNDLE_END is only emitted directly as part of
+        // a stack guard in conjunction with a SFI_DATA_MASK.
+        State.SaveCount = 3;
+        break;
+      case ARM::SFI_DATA_MASK:
+        llvm_unreachable(
+            "SFI_DATA_MASK found without preceding SFI_NOP_IF_AT_BUNDLE_END");
+        return false;
+      case ARM::SFI_GUARD_CALL:
+      case ARM::SFI_GUARD_INDIRECT_CALL:
+      case ARM::SFI_GUARD_INDIRECT_JMP:
+      case ARM::SFI_GUARD_RETURN:
+      case ARM::SFI_GUARD_LOADSTORE:
+      case ARM::SFI_GUARD_LOADSTORE_TST:
+        State.SaveCount = 2;
+        break;
+      case ARM::SFI_GUARD_SP_LOAD:
+        State.SaveCount = 4;
+        break;
+    }
+  }
+
+  // We're in "saving instructions" state
+  if (State.I < State.SaveCount) {
+    // This instruction has to be saved
+    assert(State.I < State.MaxSaved && "Trying to save too many instructions");
+    State.Saved[State.I++] = Inst;
+    if (State.I < State.SaveCount)
+      return true;
+  }
+
+  // We're in "saved enough instructions, time to emit" state
+  assert(State.I == State.SaveCount && State.SaveCount > 0 && "Bookeeping Error");
+
+  // When calling Emit* functions, do that with RecurseGuard set (the comment
+  // at the beginning of this function explains why)
+  State.RecursiveCall = true;
+  switch (State.Saved[0].getOpcode()) {
+    default:
+      break;
+    case ARM::SFI_NOP_IF_AT_BUNDLE_END:
+      EmitDataMask(STI, State.I, State.Saved, Out);
+      break;
+    case ARM::SFI_DATA_MASK:
+      llvm_unreachable("SFI_DATA_MASK can't start a SFI sequence");
+      break;
+    case ARM::SFI_GUARD_CALL:
+      EmitDirectGuardCall(STI, State.I, State.Saved, Out);
+      break;
+    case ARM::SFI_GUARD_INDIRECT_CALL:
+      EmitIndirectGuardCall(STI, State.I, State.Saved, Out);
+      break;
+    case ARM::SFI_GUARD_INDIRECT_JMP:
+      EmitIndirectGuardJmp(STI, State.I, State.Saved, Out);
+      break;
+    case ARM::SFI_GUARD_RETURN:
+      EmitGuardReturn(STI, State.I, State.Saved, Out);
+      break;
+    case ARM::SFI_GUARD_LOADSTORE:
+      EmitGuardLoadOrStore(STI, State.I, State.Saved, Out);
+      break;
+    case ARM::SFI_GUARD_LOADSTORE_TST:
+      EmitGuardLoadOrStoreTst(STI, State.I, State.Saved, Out);
+      break;
+    case ARM::SFI_GUARD_SP_LOAD:
+      EmitGuardSpLoad(STI, State.I, State.Saved, Out);
+      break;
+  }
+  assert(State.RecursiveCall && "Illegal Depth");
+  State.RecursiveCall = false;
+
+  // We're done expanding a SFI guard. Reset state vars.
+  State.SaveCount = 0;
+  State.I = 0;
+  return true;
+}
+
+} // namespace llvm