src/hotspot/cpu/arm/gc/shared/barrierSetNMethod_arm.cpp

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 *
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#include "code/nativeInst.hpp"
#include "gc/shared/barrierSetAssembler.hpp"
#include "gc/shared/barrierSetNMethod.hpp"
#include "logging/log.hpp"
#include "memory/resourceArea.hpp"
#include "runtime/frame.inline.hpp"
#include "runtime/javaThread.hpp"
#include "runtime/registerMap.hpp"
#include "runtime/sharedRuntime.hpp"
#include "utilities/align.hpp"
#include "utilities/debug.hpp"

// The constant below reflects the size of the barrier
// in barrierSetAssembler_arm.cpp
static const int entry_barrier_bytes = 9 * NativeInstruction::size();

class NativeNMethodBarrier: public NativeInstruction {
  address instruction_address() const { return addr_at(0); }

  int *guard_addr() const {
    // Last instruction in a barrier
    return reinterpret_cast<int*>(instruction_address() + entry_barrier_bytes - wordSize);
  }

public:
  int get_value() {
    return Atomic::load_acquire(guard_addr());
  }

  void set_value(int value) {
    Atomic::release_store(guard_addr(), value);
  }

  void verify() const;
};

// Check the first instruction of the nmethod entry barrier
// to make sure that the offsets are not skewed.
void NativeNMethodBarrier::verify() const {
  NativeInstruction *ni = (NativeInstruction *) instruction_address();
  if (!ni->is_ldr()) {
    uint32_t *addr = (uint32_t *) ni;
    tty->print_cr("Addr: " INTPTR_FORMAT " Code: 0x%x", (intptr_t) addr, (uint32_t) *addr);
    fatal("not an ldr instruction.");
  }
}

static NativeNMethodBarrier* native_nmethod_barrier(nmethod* nm) {
  address barrier_address = nm->code_begin() + nm->frame_complete_offset() - entry_barrier_bytes;
  NativeNMethodBarrier* barrier = reinterpret_cast<NativeNMethodBarrier*>(barrier_address);
  DEBUG_ONLY(barrier->verify());
  return barrier;
}

/* We're called from an nmethod when we need to deoptimize it. We do
   this by throwing away the nmethod's frame and jumping to the
   ic_miss stub. This looks like there has been an IC miss at the
   entry of the nmethod, so we resolve the call, which will fall back
   to the interpreter if the nmethod has been unloaded. */
void BarrierSetNMethod::deoptimize(nmethod* nm, address* return_address_ptr) {

  typedef struct {
    intptr_t *sp; intptr_t *fp; address lr; address pc;
  } frame_pointers_t;

  frame_pointers_t *new_frame = (frame_pointers_t *)(return_address_ptr - 5);

  JavaThread *thread = JavaThread::current();
  RegisterMap reg_map(thread,
                      RegisterMap::UpdateMap::skip,
                      RegisterMap::ProcessFrames::include,
                      RegisterMap::WalkContinuation::skip);
  frame frame = thread->last_frame();

  assert(frame.is_compiled_frame() || frame.is_native_frame(), "must be");
  assert(frame.cb() == nm, "must be");
  frame = frame.sender(&reg_map);

  LogTarget(Trace, nmethod, barrier) out;
  if (out.is_enabled()) {
    ResourceMark mark;
    log_trace(nmethod, barrier)("deoptimize(nmethod: %s(%p), return_addr: %p, osr: %d, thread: %p(%s), making rsp: %p) -> %p",
                                nm->method()->name_and_sig_as_C_string(),
                                nm, *(address *) return_address_ptr, nm->is_osr_method(), thread,
                                thread->name(), frame.sp(), nm->verified_entry_point());
  }

  new_frame->sp = frame.sp();
  new_frame->fp = frame.fp();
  new_frame->lr = frame.pc();
  new_frame->pc = SharedRuntime::get_handle_wrong_method_stub();
}

void BarrierSetNMethod::set_guard_value(nmethod* nm, int value) {
  if (!supports_entry_barrier(nm)) {
    return;
  }

  // Disarms the nmethod guard emitted by BarrierSetAssembler::nmethod_entry_barrier.
  // Symmetric "LDR; DMB ISHLD" is in the nmethod barrier.
  NativeNMethodBarrier* barrier = native_nmethod_barrier(nm);
  barrier->set_value(value);
}

int BarrierSetNMethod::guard_value(nmethod* nm) {
  if (!supports_entry_barrier(nm)) {
    return disarmed_guard_value();
  }

  NativeNMethodBarrier* barrier = native_nmethod_barrier(nm);
  return barrier->get_value();
}