jdk/src/hotspot/os_cpu/linux_s390/os_linux_s390.cpp

/*
 * Copyright (c) 2016, 2026, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2016, 2024 SAP SE. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * 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.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

// This file is organized as os_linux_x86.cpp.

#include "asm/assembler.inline.hpp"
#include "classfile/vmSymbols.hpp"
#include "code/nativeInst.hpp"
#include "code/vtableStubs.hpp"
#include "compiler/disassembler.hpp"
#include "cppstdlib/cstdlib.hpp"
#include "interpreter/interpreter.hpp"
#include "jvm.h"
#include "memory/allocation.inline.hpp"
#include "nativeInst_s390.hpp"
#include "os_linux.hpp"
#include "os_posix.hpp"
#include "prims/jniFastGetField.hpp"
#include "prims/jvm_misc.hpp"
#include "runtime/arguments.hpp"
#include "runtime/frame.inline.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "runtime/java.hpp"
#include "runtime/javaCalls.hpp"
#include "runtime/javaThread.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/osThread.hpp"
#include "runtime/safepointMechanism.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/stubRoutines.hpp"
#include "runtime/timer.hpp"
#include "signals_posix.hpp"
#include "utilities/events.hpp"
#include "utilities/debug.hpp"
#include "utilities/vmError.hpp"

// put OS-includes here
# include <sys/types.h>
# include <sys/mman.h>
# include <pthread.h>
# include <signal.h>
# include <errno.h>
# include <dlfcn.h>
# include <stdio.h>
# include <unistd.h>
# include <sys/resource.h>
# include <pthread.h>
# include <sys/stat.h>
# include <sys/time.h>
# include <sys/utsname.h>
# include <sys/socket.h>
# include <sys/wait.h>
# include <pwd.h>
# include <poll.h>
# include <ucontext.h>

address os::current_stack_pointer() {
  intptr_t* csp;

  // Inline assembly for `z_lgr regno(csp), Z_SP' (Z_SP = Z_R15):
  __asm__ __volatile__ ("lgr %0, 15":"=r"(csp):);

  assert(((uint64_t)csp & (frame::alignment_in_bytes-1)) == 0, "SP must be aligned");
  return (address) csp;
}

char* os::non_memory_address_word() {
  // Must never look like an address returned by reserve_memory,
  // even in its subfields (as defined by the CPU immediate fields,
  // if the CPU splits constants across multiple instructions).
  return (char*) -1;
}

// Frame information (pc, sp, fp) retrieved via ucontext
// always looks like a C-frame according to the frame
// conventions in frame_s390.hpp.
address os::Posix::ucontext_get_pc(const ucontext_t * uc) {
  return (address)uc->uc_mcontext.psw.addr;
}

void os::Posix::ucontext_set_pc(ucontext_t * uc, address pc) {
  uc->uc_mcontext.psw.addr = (unsigned long)pc;
}

static address ucontext_get_lr(const ucontext_t * uc) {
  return (address)uc->uc_mcontext.gregs[14/*LINK*/];
}

intptr_t* os::Linux::ucontext_get_sp(const ucontext_t * uc) {
  return (intptr_t*)uc->uc_mcontext.gregs[15/*REG_SP*/];
}

intptr_t* os::Linux::ucontext_get_fp(const ucontext_t * uc) {
  return nullptr;
}

address os::fetch_frame_from_context(const void* ucVoid,
                    intptr_t** ret_sp, intptr_t** ret_fp) {

  address epc;
  const ucontext_t* uc = (const ucontext_t*)ucVoid;

  if (uc != nullptr) {
    epc = os::Posix::ucontext_get_pc(uc);
    if (ret_sp) { *ret_sp = os::Linux::ucontext_get_sp(uc); }
    if (ret_fp) { *ret_fp = os::Linux::ucontext_get_fp(uc); }
  } else {
    epc = nullptr;
    if (ret_sp) { *ret_sp = (intptr_t *)nullptr; }
    if (ret_fp) { *ret_fp = (intptr_t *)nullptr; }
  }

  return epc;
}

frame os::fetch_frame_from_context(const void* ucVoid) {
  intptr_t* sp;
  intptr_t* fp;
  address epc = fetch_frame_from_context(ucVoid, &sp, &fp);
  if (!is_readable_pointer(epc)) {
    // Try to recover from calling into bad memory
    // Assume new frame has not been set up, the same as
    // compiled frame stack bang
    return fetch_compiled_frame_from_context(ucVoid);
  }
  return frame(sp, epc);
}

frame os::fetch_compiled_frame_from_context(const void* ucVoid) {
  const ucontext_t* uc = (const ucontext_t*)ucVoid;
  intptr_t* sp = os::Linux::ucontext_get_sp(uc);
  address lr = ucontext_get_lr(uc);
  return frame(sp, lr);
}

intptr_t* os::fetch_bcp_from_context(const void* ucVoid) {
  Unimplemented();
  return nullptr;
}

frame os::get_sender_for_C_frame(frame* fr) {
  if (*fr->sp() == 0) {
    // fr is the last C frame.
    return frame();
  }

  // If its not one of our frames, the return pc is saved at gpr14
  // stack slot. The call_stub stores the return_pc to the stack slot
  // of gpr10.
  if ((Interpreter::code() != nullptr && Interpreter::contains(fr->pc())) ||
      (CodeCache::contains(fr->pc()) && !StubRoutines::contains(fr->pc()))) {
    return frame(fr->sender_sp(), fr->sender_pc());
  } else {
    if (StubRoutines::contains(fr->pc())) {
      StubCodeDesc* desc = StubCodeDesc::desc_for(fr->pc());
      if (desc && !strcmp(desc->name(),"call_stub")) {
        return frame(fr->sender_sp(), fr->callstub_sender_pc());
      } else {
        return frame(fr->sender_sp(), fr->sender_pc());
      }
    } else {
      intptr_t* sender_sp = fr->sender_sp();
      address   sender_fp = (address)*sender_sp;
      ptrdiff_t entry_len = sender_fp - (address)sender_sp;
      if (entry_len < frame::z_abi_160_size) {
        return frame(sender_sp, fr->sender_pc());
      } else {
        return frame(sender_sp, fr->native_sender_pc());
      }
    }
  }
}

frame os::current_frame() {
  // Expected to return the stack pointer of this method.
  // But if inlined, returns the stack pointer of our caller!
  intptr_t* csp = (intptr_t*) *((intptr_t*) os::current_stack_pointer());
  assert (csp != nullptr, "sp should not be null");
  // Pass a dummy pc. This way we don't have to load it from the
  // stack, since we don't know in which slot we can find it.
  frame topframe(csp, (address)0x8);
  if (os::is_first_C_frame(&topframe)) {
    // Stack is not walkable.
    return frame();
  } else {
    frame senderFrame = os::get_sender_for_C_frame(&topframe);
    assert(senderFrame.pc() != nullptr, "Sender pc should not be null");
    // Return sender of sender of current topframe which hopefully
    // both have pc != nullptr.
#ifdef _NMT_NOINLINE_   // Is set in slowdebug builds.
    // Current_stack_pointer is not inlined, we must pop one more frame.
    frame tmp = os::get_sender_for_C_frame(&topframe);
    return os::get_sender_for_C_frame(&tmp);
#else
    return os::get_sender_for_C_frame(&topframe);
#endif
  }
}

bool PosixSignals::pd_hotspot_signal_handler(int sig, siginfo_t* info,
                                             ucontext_t* uc, JavaThread* thread) {

  // Decide if this trap can be handled by a stub.
  address stub    = nullptr;
  address pc      = nullptr;  // Pc as retrieved from PSW. Usually points past failing instruction.
  address trap_pc = nullptr;  // Pc of the instruction causing the trap.

  //%note os_trap_1
  if (info != nullptr && uc != nullptr && thread != nullptr) {
    pc = os::Posix::ucontext_get_pc(uc);
    if (TraceTraps) {
      tty->print_cr("     pc at " INTPTR_FORMAT, p2i(pc));
    }
    if ((unsigned long)(pc - (address)info->si_addr) <= (unsigned long)Assembler::instr_maxlen() ) {
      trap_pc = (address)info->si_addr;
      if (TraceTraps) {
        tty->print_cr("trap_pc at " INTPTR_FORMAT, p2i(trap_pc));
      }
    }

    // Handle ALL stack overflow variations here
    if (sig == SIGSEGV) {
      address addr = (address)info->si_addr; // Address causing SIGSEGV, usually mem ref target.

      // Check if fault address is within thread stack.
      if (thread->is_in_full_stack(addr)) {
        // stack overflow
        if (os::Posix::handle_stack_overflow(thread, addr, pc, uc, &stub)) {
          return true; // continue
        }
      }
    }

    if (thread->thread_state() == _thread_in_Java) {
      // Java thread running in Java code => find exception handler if any
      // a fault inside compiled code, the interpreter, or a stub

      if (sig == SIGSEGV &&
               SafepointMechanism::is_poll_address((address)info->si_addr)) {
        if (TraceTraps) {
          tty->print_cr("trap: safepoint_poll at " INTPTR_FORMAT " (SIGSEGV)", p2i(pc));
        }
        stub = SharedRuntime::get_poll_stub(pc);

        // Info->si_addr only points to the page base address, so we
        // must extract the real si_addr from the instruction and the
        // ucontext.
        assert(((NativeInstruction*)pc)->is_safepoint_poll(), "must be safepoint poll");
        const address real_si_addr = ((NativeInstruction*)pc)->get_poll_address(uc);
      }

      // SIGTRAP-based implicit null check in compiled code.
      else if ((sig == SIGFPE) &&
               TrapBasedNullChecks &&
               (trap_pc != nullptr) &&
               Assembler::is_sigtrap_zero_check(trap_pc)) {
        if (TraceTraps) {
          tty->print_cr("trap: NULL_CHECK at " INTPTR_FORMAT " (SIGFPE)", p2i(trap_pc));
        }
        stub = SharedRuntime::continuation_for_implicit_exception(thread, trap_pc, SharedRuntime::IMPLICIT_NULL);
      }

      else if (sig == SIGSEGV && ImplicitNullChecks &&
               CodeCache::contains((void*) pc) &&
               MacroAssembler::uses_implicit_null_check(info->si_addr)) {
        if (TraceTraps) {
          tty->print_cr("trap: null_check at " INTPTR_FORMAT " (SIGSEGV)", p2i(pc));
        }
        stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
      }

#ifdef COMPILER2
      // SIGTRAP-based implicit range check in compiled code.
      else if (sig == SIGFPE && TrapBasedRangeChecks &&
               (trap_pc != nullptr) &&
               Assembler::is_sigtrap_range_check(trap_pc)) {
        if (TraceTraps) {
          tty->print_cr("trap: RANGE_CHECK at " INTPTR_FORMAT " (SIGFPE)", p2i(trap_pc));
        }
        stub = SharedRuntime::continuation_for_implicit_exception(thread, trap_pc, SharedRuntime::IMPLICIT_NULL);
      }
#endif

      else if (sig == SIGFPE && info->si_code == FPE_INTDIV) {
        stub = SharedRuntime::continuation_for_implicit_exception(thread, trap_pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
      }

      else if (sig == SIGBUS) {
        // BugId 4454115: A read from a MappedByteBuffer can fault here if the
        // underlying file has been truncated. Do not crash the VM in such a case.
        CodeBlob* cb = CodeCache::find_blob(pc);
        nmethod* nm = (cb != nullptr) ? cb->as_nmethod_or_null() : nullptr;
        if (nm != nullptr && nm->has_unsafe_access()) {
          // We don't really need a stub here! Just set the pending exception and
          // continue at the next instruction after the faulting read. Returning
          // garbage from this read is ok.
          thread->set_pending_unsafe_access_error();
          uc->uc_mcontext.psw.addr = ((unsigned long)pc) + Assembler::instr_len(pc);
          return true;
        }
      }
    }

    else { // thread->thread_state() != _thread_in_Java
      if ((sig == SIGILL) && VM_Version::is_determine_features_test_running()) {
        // SIGILL must be caused by VM_Version::determine_features()
        // when attempting to execute a non-existing instruction.
        //*(int *) (pc-6)=0; // Patch instruction to 0 to indicate that it causes a SIGILL.
                             // Flushing of icache is not necessary.
        stub = pc; // Continue with next instruction.
      } else if ((sig == SIGFPE) && VM_Version::is_determine_features_test_running()) {
        // SIGFPE is known to be caused by trying to execute a vector instruction
        // when the vector facility is installed, but operating system support is missing.
        VM_Version::reset_has_VectorFacility();
        stub = pc; // Continue with next instruction.
      } else if ((thread->thread_state() == _thread_in_vm ||
                  thread->thread_state() == _thread_in_native) &&
                 sig == SIGBUS && thread->doing_unsafe_access()) {
        // We don't really need a stub here! Just set the pending exception and
        // continue at the next instruction after the faulting read. Returning
        // garbage from this read is ok.
        thread->set_pending_unsafe_access_error();
        os::Posix::ucontext_set_pc(uc, pc + Assembler::instr_len(pc));
        return true;
      }
    }

    // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
    // and the heap gets shrunk before the field access.
    if ((sig == SIGSEGV) || (sig == SIGBUS)) {
      address addr = JNI_FastGetField::find_slowcase_pc(pc);
      if (addr != (address)-1) {
        stub = addr;
      }
    }
  }

  if (stub != nullptr) {
    // Save all thread context in case we need to restore it.
    if (thread != nullptr) thread->set_saved_exception_pc(pc);
    os::Posix::ucontext_set_pc(uc, stub);
    return true;
  }

  return false;
}

void os::Linux::init_thread_fpu_state(void) {
  // Nothing to do on z/Architecture.
}

int os::Linux::get_fpu_control_word(void) {
  // Nothing to do on z/Architecture.
  return 0;
}

void os::Linux::set_fpu_control_word(int fpu_control) {
  // Nothing to do on z/Architecture.
}

////////////////////////////////////////////////////////////////////////////////
// thread stack

// Minimum usable stack sizes required to get to user code. Space for
// HotSpot guard pages is added later.
size_t os::_compiler_thread_min_stack_allowed = (52 DEBUG_ONLY(+ 32)) * K;
size_t os::_java_thread_min_stack_allowed = (32 DEBUG_ONLY(+ 8)) * K;
size_t os::_vm_internal_thread_min_stack_allowed = 32 * K;

// Return default stack size for thr_type.
size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
  // Default stack size (compiler thread needs larger stack).
  size_t s = (thr_type == os::compiler_thread ? 4 * M : 1024 * K);
  return s;
}

/////////////////////////////////////////////////////////////////////////////
// helper functions for fatal error handler

void os::print_context(outputStream *st, const void *context) {
  if (context == nullptr) return;

  const ucontext_t* uc = (const ucontext_t*)context;

  st->print_cr("Processor state:");
  st->print_cr("----------------");
  st->print_cr("        ip = " INTPTR_FORMAT " ", uc->uc_mcontext.psw.addr);
  st->print_cr(" proc mask = " INTPTR_FORMAT " ", uc->uc_mcontext.psw.mask);
  st->print_cr("   fpc reg = 0x%8.8x "          , uc->uc_mcontext.fpregs.fpc);
  st->cr();

  st->print_cr("General Purpose Registers:");
  st->print_cr("--------------------------");
  for( int i = 0; i < 16; i+=2 ) {
    st->print("  r%-2d = " INTPTR_FORMAT "  " ,  i,   uc->uc_mcontext.gregs[i]);
    st->print("  r%-2d = " INTPTR_FORMAT "  |",  i+1, uc->uc_mcontext.gregs[i+1]);
    st->print("  r%-2d = %23.1ld  "           ,  i,   uc->uc_mcontext.gregs[i]);
    st->print("  r%-2d = %23.1ld  "           ,  i+1, uc->uc_mcontext.gregs[i+1]);
    st->cr();
  }
  st->cr();

  st->print_cr("Access Registers:");
  st->print_cr("-----------------");
  for( int i = 0; i < 16; i+=2 ) {
    st->print("  ar%-2d = 0x%8.8x  ", i,   uc->uc_mcontext.aregs[i]);
    st->print("  ar%-2d = 0x%8.8x  ", i+1, uc->uc_mcontext.aregs[i+1]);
    st->cr();
  }
  st->cr();

  st->print_cr("Float Registers:");
  st->print_cr("----------------");
  for (int i = 0; i < 16; i += 2) {
    st->print("  fr%-2d = " INTPTR_FORMAT "  " , i,   (int64_t)(uc->uc_mcontext.fpregs.fprs[i].d));
    st->print("  fr%-2d = " INTPTR_FORMAT "  |", i+1, (int64_t)(uc->uc_mcontext.fpregs.fprs[i+1].d));
    st->print("  fr%-2d = %23.15e  "           , i,   (uc->uc_mcontext.fpregs.fprs[i].d));
    st->print("  fr%-2d = %23.15e  "           , i+1, (uc->uc_mcontext.fpregs.fprs[i+1].d));
    st->cr();
  }
  st->cr();
  st->cr();
}

void os::print_register_info(outputStream *st, const void *context, int& continuation) {
  const int register_count = 16 /* r0-r15 */ + 1 /* pc */;
  int n = continuation;
  assert(n >= 0 && n <= register_count, "Invalid continuation value");
  if (context == nullptr || n == register_count) {
    return;
  }

  const ucontext_t *uc = (const ucontext_t*)context;
  while (n < register_count) {
    // Update continuation with next index before printing location
    continuation = n + 1;
    if (n == register_count - 1) {
      st->print("pc ="); print_location(st, (intptr_t)uc->uc_mcontext.psw.addr);
    } else {
      st->print("r%-2d=", n);
      print_location(st, uc->uc_mcontext.gregs[n]);
    }
    ++n;
  }
}

#ifndef PRODUCT
void os::verify_stack_alignment() {
}
#endif

int os::extra_bang_size_in_bytes() {
  // z/Architecture does not require the additional stack bang.
  return 0;
}

void os::setup_fpu() {}