/*

   +----------------------------------------------------------------------+

   | Zend Engine                                                          |

   +----------------------------------------------------------------------+

   | Copyright © Zend Technologies Ltd., a subsidiary company of          |

   |     Perforce Software, Inc., and Contributors.                       |

   +----------------------------------------------------------------------+

   | This source file is subject to the Modified BSD License that is      |

   | bundled with this package in the file LICENSE, and is available      |

   | through the World Wide Web at <https://www.php.net/license/>.        |

   |                                                                      |

   | SPDX-License-Identifier: BSD-3-Clause                                |

   +----------------------------------------------------------------------+

   | Authors: Aaron Piotrowski <aaron@trowski.com>                        |

   |          Martin Schröder <m.schroeder2007@gmail.com>                 |

   +----------------------------------------------------------------------+

*/

#include "zend.h"

#include "zend_API.h"

#include "zend_gc.h"

#include "zend_ini.h"

#include "zend_variables.h"

#include "zend_vm.h"

#include "zend_exceptions.h"

#include "zend_builtin_functions.h"

#include "zend_observer.h"

#include "zend_mmap.h"

#include "zend_compile.h"

#include "zend_closures.h"

#include "zend_generators.h"

#include "zend_fibers.h"

#include "zend_fibers_arginfo.h"

#ifdef HAVE_VALGRIND

# include <valgrind/valgrind.h>

#endif

#ifdef ZEND_FIBER_UCONTEXT

# include <ucontext.h>

#endif

#ifndef ZEND_WIN32

# include <unistd.h>

# include <sys/mman.h>

# include <limits.h>

# if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)

#  define MAP_ANONYMOUS MAP_ANON

# endif

/* FreeBSD require a first (i.e. addr) argument of mmap(2) is not NULL

 * if MAP_STACK is passed.

 * http://www.FreeBSD.org/cgi/query-pr.cgi?pr=158755 */

# if !defined(MAP_STACK) || defined(__FreeBSD__) || defined(__FreeBSD_kernel__)

#  undef MAP_STACK

#  define MAP_STACK 0

# endif

# ifndef MAP_FAILED

#  define MAP_FAILED ((void * ) -1)

# endif

#endif

#ifdef __SANITIZE_ADDRESS__

# include <sanitizer/asan_interface.h>

# include <sanitizer/common_interface_defs.h>

#endif

# if defined __CET__

#  include <cet.h>

#  define SHSTK_ENABLED (__CET__ & 0x2)

#  define BOOST_CONTEXT_SHADOW_STACK (SHSTK_ENABLED && SHADOW_STACK_SYSCALL)

#  define __NR_map_shadow_stack 451

# ifndef SHADOW_STACK_SET_TOKEN

#  define SHADOW_STACK_SET_TOKEN 0x1

#endif

#endif

/* Encapsulates the fiber C stack with extension for debugging tools. */

struct _zend_fiber_stack {

  void *pointer;

  size_t size;

#ifdef HAVE_VALGRIND

  unsigned int valgrind_stack_id;

#endif

#ifdef __SANITIZE_ADDRESS__

  const void *asan_pointer;

  size_t asan_size;

#endif

#ifdef ZEND_FIBER_UCONTEXT

  /* Embedded ucontext to avoid unnecessary memory allocations. */

  ucontext_t ucontext;

#elif BOOST_CONTEXT_SHADOW_STACK

  /* Shadow stack: base, size */

  void *ss_base;

  size_t ss_size;

#endif

};

/* Zend VM state that needs to be captured / restored during fiber context switch. */

typedef struct _zend_fiber_vm_state {

  zend_vm_stack vm_stack;

  zval *vm_stack_top;

  zval *vm_stack_end;

  size_t vm_stack_page_size;

  zend_execute_data *current_execute_data;

  int error_reporting;

  uint32_t jit_trace_num;

  JMP_BUF *bailout;

  zend_fiber *active_fiber;

#ifdef ZEND_CHECK_STACK_LIMIT

  void *stack_base;

  void *stack_limit;

#endif

} zend_fiber_vm_state;

static zend_always_inline void zend_fiber_capture_vm_state(zend_fiber_vm_state *state)

{

  state->vm_stack = EG(vm_stack);

  state->vm_stack_top = EG(vm_stack_top);

  state->vm_stack_end = EG(vm_stack_end);

  state->vm_stack_page_size = EG(vm_stack_page_size);

  state->current_execute_data = EG(current_execute_data);

  state->error_reporting = EG(error_reporting);

  state->jit_trace_num = EG(jit_trace_num);

  state->bailout = EG(bailout);

  state->active_fiber = EG(active_fiber);

#ifdef ZEND_CHECK_STACK_LIMIT

  state->stack_base = EG(stack_base);

  state->stack_limit = EG(stack_limit);

#endif

}

static zend_always_inline void zend_fiber_restore_vm_state(zend_fiber_vm_state *state)

{

  EG(vm_stack) = state->vm_stack;

  EG(vm_stack_top) = state->vm_stack_top;

  EG(vm_stack_end) = state->vm_stack_end;

  EG(vm_stack_page_size) = state->vm_stack_page_size;

  EG(current_execute_data) = state->current_execute_data;

  EG(error_reporting) = state->error_reporting;

  EG(jit_trace_num) = state->jit_trace_num;

  EG(bailout) = state->bailout;

  EG(active_fiber) = state->active_fiber;

#ifdef ZEND_CHECK_STACK_LIMIT

  EG(stack_base) = state->stack_base;

  EG(stack_limit) = state->stack_limit;

#endif

}

#ifdef ZEND_FIBER_UCONTEXT

ZEND_TLS zend_fiber_transfer *transfer_data;

#else

/* boost_context_data is our customized definition of struct transfer_t as

 * provided by boost.context in fcontext.hpp:

 *

 * typedef void* fcontext_t;

 *

 * struct transfer_t {

 *     fcontext_t fctx;

 *     void *data;

 * }; */

typedef struct {

  void *handle;

  zend_fiber_transfer *transfer;

} boost_context_data;

/* These functions are defined in assembler files provided by boost.context (located in "Zend/asm"). */

extern void *make_fcontext(void *sp, size_t size, void (*fn)(boost_context_data));

extern ZEND_INDIRECT_RETURN boost_context_data jump_fcontext(void *to, zend_fiber_transfer *transfer);

#endif

ZEND_API zend_class_entry *zend_ce_fiber;

static zend_class_entry *zend_ce_fiber_error;

static zend_object_handlers zend_fiber_handlers;

static zend_function zend_fiber_function = { ZEND_INTERNAL_FUNCTION };

ZEND_TLS uint32_t zend_fiber_switch_blocking = 0;

#define ZEND_FIBER_DEFAULT_PAGE_SIZE 4096

static size_t zend_fiber_get_page_size(void)

{

  static size_t page_size = 0;

  if (!page_size) {

    page_size = zend_get_page_size();

    if (!page_size || (page_size & (page_size - 1))) {

      /* anyway, we have to return a valid result */

      page_size = ZEND_FIBER_DEFAULT_PAGE_SIZE;

    }

  }

  return page_size;

}

static zend_fiber_stack *zend_fiber_stack_allocate(size_t size)

{

  void *pointer;

  const size_t page_size = zend_fiber_get_page_size();

  const size_t minimum_stack_size = page_size + ZEND_FIBER_GUARD_PAGES * page_size

#ifdef __SANITIZE_ADDRESS__

  // necessary correction due to ASAN redzones

  * 6

#endif

  ;

  if (size < minimum_stack_size) {

    zend_throw_exception_ex(NULL, 0, "Fiber stack size is too small, it needs to be at least %zu bytes", minimum_stack_size);

    return NULL;

  }

  const size_t stack_size = (size + page_size - 1) / page_size * page_size;

  const size_t alloc_size = stack_size + ZEND_FIBER_GUARD_PAGES * page_size;

#ifdef ZEND_WIN32

  pointer = VirtualAlloc(0, alloc_size, MEM_COMMIT, PAGE_READWRITE);

  if (!pointer) {

    DWORD err = GetLastError();

    char *errmsg = php_win32_error_to_msg(err);

    zend_throw_exception_ex(NULL, 0, "Fiber stack allocate failed: VirtualAlloc failed: [0x%08lx] %s", err, errmsg[0] ? errmsg : "Unknown");

    php_win32_error_msg_free(errmsg);

    return NULL;

  }

# if ZEND_FIBER_GUARD_PAGES

  DWORD protect;

  if (!VirtualProtect(pointer, ZEND_FIBER_GUARD_PAGES * page_size, PAGE_READWRITE | PAGE_GUARD, &protect)) {

    DWORD err = GetLastError();

    char *errmsg = php_win32_error_to_msg(err);

    zend_throw_exception_ex(NULL, 0, "Fiber stack protect failed: VirtualProtect failed: [0x%08lx] %s", err, errmsg[0] ? errmsg : "Unknown");

    php_win32_error_msg_free(errmsg);

    VirtualFree(pointer, 0, MEM_RELEASE);

    return NULL;

  }

# endif

#else

  pointer = mmap(NULL, alloc_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);

  if (pointer == MAP_FAILED) {

    zend_throw_exception_ex(NULL, 0, "Fiber stack allocate failed: mmap failed: %s (%d)", strerror(errno), errno);

    return NULL;

  }

#if defined(MADV_NOHUGEPAGE)

  /* Multiple reasons to fail, ignore all errors only needed

   * for linux < 6.8 */

  (void) madvise(pointer, alloc_size, MADV_NOHUGEPAGE);

#endif

  zend_mmap_set_name(pointer, alloc_size, "zend_fiber_stack");

# if ZEND_FIBER_GUARD_PAGES

  if (mprotect(pointer, ZEND_FIBER_GUARD_PAGES * page_size, PROT_NONE) < 0) {

    zend_throw_exception_ex(NULL, 0, "Fiber stack protect failed: mprotect failed: %s (%d)", strerror(errno), errno);

    munmap(pointer, alloc_size);

    return NULL;

  }

# endif

#endif

  zend_fiber_stack *stack = emalloc(sizeof(zend_fiber_stack));

  stack->pointer = (void *) ((uintptr_t) pointer + ZEND_FIBER_GUARD_PAGES * page_size);

  stack->size = stack_size;

#if !defined(ZEND_FIBER_UCONTEXT) && BOOST_CONTEXT_SHADOW_STACK

  /* shadow stack saves ret address only, need less space */

  stack->ss_size= stack_size >> 5;

  /* align shadow stack to 8 bytes. */

  stack->ss_size = (stack->ss_size + 7) & ~7;

  /* issue syscall to create shadow stack for the new fcontext */

  /* SHADOW_STACK_SET_TOKEN option will put "restore token" on the new shadow stack */

  stack->ss_base = (void *)syscall(__NR_map_shadow_stack, 0, stack->ss_size, SHADOW_STACK_SET_TOKEN);

  if (stack->ss_base == MAP_FAILED) {

    zend_throw_exception_ex(NULL, 0, "Fiber shadow stack allocate failed: mmap failed: %s (%d)", strerror(errno), errno);

    return NULL;

  }

#endif

#ifdef VALGRIND_STACK_REGISTER

  uintptr_t base = (uintptr_t) stack->pointer;

  stack->valgrind_stack_id = VALGRIND_STACK_REGISTER(base, base + stack->size);

#endif

#ifdef __SANITIZE_ADDRESS__

  stack->asan_pointer = stack->pointer;

  stack->asan_size = stack->size;

#endif

  return stack;

}

static void zend_fiber_stack_free(zend_fiber_stack *stack)

{

#ifdef VALGRIND_STACK_DEREGISTER

  VALGRIND_STACK_DEREGISTER(stack->valgrind_stack_id);

#endif

  const size_t page_size = zend_fiber_get_page_size();

  void *pointer = (void *) ((uintptr_t) stack->pointer - ZEND_FIBER_GUARD_PAGES * page_size);

#ifdef __SANITIZE_ADDRESS__

  /* If another mmap happens after unmapping, it may trigger the stale stack red zones

   * so we have to unpoison it before unmapping. */

  ASAN_UNPOISON_MEMORY_REGION(pointer, stack->size + ZEND_FIBER_GUARD_PAGES * page_size);

#endif

#ifdef ZEND_WIN32

  VirtualFree(pointer, 0, MEM_RELEASE);

#else

  munmap(pointer, stack->size + ZEND_FIBER_GUARD_PAGES * page_size);

#endif

#if !defined(ZEND_FIBER_UCONTEXT) && BOOST_CONTEXT_SHADOW_STACK

  munmap(stack->ss_base, stack->ss_size);

#endif

  efree(stack);

}

#ifdef ZEND_CHECK_STACK_LIMIT

ZEND_API void* zend_fiber_stack_limit(zend_fiber_stack *stack)

{

  zend_ulong reserve = EG(reserved_stack_size);

#ifdef __APPLE__

  /* On Apple Clang, the stack probing function ___chkstk_darwin incorrectly

   * probes a location that is twice the entered function's stack usage away

   * from the stack pointer, when using an alternative stack.

   * https://openradar.appspot.com/radar?id=5497722702397440

   */

  reserve = reserve * 2;

#endif

  /* stack->pointer is the end of the stack */

  return (int8_t*)stack->pointer + reserve;

}

ZEND_API void* zend_fiber_stack_base(zend_fiber_stack *stack)

{

  return (void*)((uintptr_t)stack->pointer + stack->size);

}

#endif

#ifdef ZEND_FIBER_UCONTEXT

static ZEND_NORETURN void zend_fiber_trampoline(void)

#else

static ZEND_NORETURN void zend_fiber_trampoline(boost_context_data data)

#endif

{

  /* Initialize transfer struct with a copy of passed data. */

#ifdef ZEND_FIBER_UCONTEXT

  zend_fiber_transfer transfer = *transfer_data;

#else

  zend_fiber_transfer transfer = *data.transfer;

#endif

  zend_fiber_context *from = transfer.context;

#ifdef __SANITIZE_ADDRESS__

  __sanitizer_finish_switch_fiber(NULL, &from->stack->asan_pointer, &from->stack->asan_size);

#endif

#ifndef ZEND_FIBER_UCONTEXT

  /* Get the context that resumed us and update its handle to allow for symmetric coroutines. */

  from->handle = data.handle;

#endif

  /* Ensure that previous fiber will be cleaned up (needed by symmetric coroutines). */

  if (from->status == ZEND_FIBER_STATUS_DEAD) {

    zend_fiber_destroy_context(from);

  }

  zend_fiber_context *context = EG(current_fiber_context);

  context->function(&transfer);

  context->status = ZEND_FIBER_STATUS_DEAD;

  /* Final context switch, the fiber must not be resumed afterwards! */

  zend_fiber_switch_context(&transfer);

  /* Abort here because we are in an inconsistent program state. */

  abort();

}

ZEND_API void zend_fiber_switch_block(void)

{

  ++zend_fiber_switch_blocking;

}

ZEND_API void zend_fiber_switch_unblock(void)

{

  ZEND_ASSERT(zend_fiber_switch_blocking && "Fiber switching was not blocked");

  --zend_fiber_switch_blocking;

}

ZEND_API bool zend_fiber_switch_blocked(void)

{

  return zend_fiber_switch_blocking;

}

ZEND_API zend_result zend_fiber_init_context(zend_fiber_context *context, void *kind, zend_fiber_coroutine coroutine, size_t stack_size)

{

  context->stack = zend_fiber_stack_allocate(stack_size);

  if (UNEXPECTED(!context->stack)) {

    return FAILURE;

  }

#ifdef ZEND_FIBER_UCONTEXT

  ucontext_t *handle = &context->stack->ucontext;

  getcontext(handle);

  handle->uc_stack.ss_size = context->stack->size;

  handle->uc_stack.ss_sp = context->stack->pointer;

  handle->uc_stack.ss_flags = 0;

  handle->uc_link = NULL;

  makecontext(handle, (void (*)(void)) zend_fiber_trampoline, 0);

  context->handle = handle;

#else

  // Stack grows down, calculate the top of the stack. make_fcontext then shifts pointer to lower 16-byte boundary.

  void *stack = (void *) ((uintptr_t) context->stack->pointer + context->stack->size);

#if BOOST_CONTEXT_SHADOW_STACK

  // pass the shadow stack pointer to make_fcontext

  // i.e., link the new shadow stack with the new fcontext

  // TODO should be a better way?

  *((unsigned long*) (stack - 8)) = (unsigned long)context->stack->ss_base + context->stack->ss_size;

#endif

  context->handle = make_fcontext(stack, context->stack->size, zend_fiber_trampoline);

  ZEND_ASSERT(context->handle != NULL && "make_fcontext() never returns NULL");

#endif

  context->kind = kind;

  context->function = coroutine;

  // Set status in case memory has not been zeroed.

  context->status = ZEND_FIBER_STATUS_INIT;

  zend_observer_fiber_init_notify(context);

  return SUCCESS;

}

ZEND_API void zend_fiber_destroy_context(zend_fiber_context *context)

{

  zend_observer_fiber_destroy_notify(context);

  if (context->cleanup) {

    context->cleanup(context);

  }

  zend_fiber_stack_free(context->stack);

}

ZEND_API void zend_fiber_switch_context(zend_fiber_transfer *transfer)

{

  zend_fiber_context *from = EG(current_fiber_context);

  zend_fiber_context *to = transfer->context;

  zend_fiber_vm_state state;

  ZEND_ASSERT(to && to->handle && to->status != ZEND_FIBER_STATUS_DEAD && "Invalid fiber context");

  ZEND_ASSERT(from && "From fiber context must be present");

  ZEND_ASSERT(to != from && "Cannot switch into the running fiber context");

  /* Assert that all error transfers hold a Throwable value. */

  ZEND_ASSERT((

    !(transfer->flags & ZEND_FIBER_TRANSFER_FLAG_ERROR) ||

    (Z_TYPE(transfer->value) == IS_OBJECT && (

      zend_is_unwind_exit(Z_OBJ(transfer->value)) ||

      zend_is_graceful_exit(Z_OBJ(transfer->value)) ||

      instanceof_function(Z_OBJCE(transfer->value), zend_ce_throwable)

    ))

  ) && "Error transfer requires a throwable value");

  zend_observer_fiber_switch_notify(from, to);

  zend_fiber_capture_vm_state(&state);

  to->status = ZEND_FIBER_STATUS_RUNNING;

  if (EXPECTED(from->status == ZEND_FIBER_STATUS_RUNNING)) {

    from->status = ZEND_FIBER_STATUS_SUSPENDED;

  }

  /* Update transfer context with the current fiber before switching. */

  transfer->context = from;

  EG(current_fiber_context) = to;

#ifdef __SANITIZE_ADDRESS__

  void *fake_stack = NULL;

  __sanitizer_start_switch_fiber(

    from->status != ZEND_FIBER_STATUS_DEAD ? &fake_stack : NULL,

    to->stack->asan_pointer,

    to->stack->asan_size);

#endif

#ifdef ZEND_FIBER_UCONTEXT

  transfer_data = transfer;

  swapcontext(from->handle, to->handle);

  /* Copy transfer struct because it might live on the other fiber's stack that will eventually be destroyed. */

  *transfer = *transfer_data;

#else

  boost_context_data data = jump_fcontext(to->handle, transfer);

  /* Copy transfer struct because it might live on the other fiber's stack that will eventually be destroyed. */

  *transfer = *data.transfer;

#endif

  to = transfer->context;

#ifndef ZEND_FIBER_UCONTEXT

  /* Get the context that resumed us and update its handle to allow for symmetric coroutines. */

  to->handle = data.handle;

#endif

#ifdef __SANITIZE_ADDRESS__

  __sanitizer_finish_switch_fiber(fake_stack, &to->stack->asan_pointer, &to->stack->asan_size);

#endif

  EG(current_fiber_context) = from;

  zend_fiber_restore_vm_state(&state);

  /* Destroy prior context if it has been marked as dead. */

  if (to->status == ZEND_FIBER_STATUS_DEAD) {

    zend_fiber_destroy_context(to);

  }

}

static void zend_fiber_cleanup(zend_fiber_context *context)

{

  zend_fiber *fiber = zend_fiber_from_context(context);

  zend_vm_stack current_stack = EG(vm_stack);

  EG(vm_stack) = fiber->vm_stack;

  zend_vm_stack_destroy();

  EG(vm_stack) = current_stack;

  fiber->execute_data = NULL;

  fiber->stack_bottom = NULL;

  fiber->caller = NULL;

}

static ZEND_STACK_ALIGNED void zend_fiber_execute(zend_fiber_transfer *transfer)

{

  ZEND_ASSERT(Z_TYPE(transfer->value) == IS_NULL && "Initial transfer value to fiber context must be NULL");

  ZEND_ASSERT(!transfer->flags && "No flags should be set on initial transfer");

  zend_fiber *fiber = EG(active_fiber);

  /* Determine the current error_reporting ini setting. */

  zend_long error_reporting = zend_ini_long_literal("error_reporting");

  /* If error_reporting is 0 and not explicitly set to 0, zend_ini_str returns a null pointer. */

  if (!error_reporting && !zend_ini_str_literal("error_reporting")) {

    error_reporting = E_ALL;

  }

  EG(vm_stack) = NULL;

  zend_first_try {

    zend_vm_stack stack = zend_vm_stack_new_page(ZEND_FIBER_VM_STACK_SIZE, NULL);

    EG(vm_stack) = stack;

    EG(vm_stack_top) = stack->top + ZEND_CALL_FRAME_SLOT;

    EG(vm_stack_end) = stack->end;

    EG(vm_stack_page_size) = ZEND_FIBER_VM_STACK_SIZE;

    fiber->execute_data = (zend_execute_data *) stack->top;

    fiber->stack_bottom = fiber->execute_data;

    memset(fiber->execute_data, 0, sizeof(zend_execute_data));

    fiber->execute_data->func = &zend_fiber_function;

    fiber->stack_bottom->prev_execute_data = EG(current_execute_data);

    EG(current_execute_data) = fiber->execute_data;

    EG(jit_trace_num) = 0;

    EG(error_reporting) = error_reporting;

#ifdef ZEND_CHECK_STACK_LIMIT

    EG(stack_base) = zend_fiber_stack_base(fiber->context.stack);

    EG(stack_limit) = zend_fiber_stack_limit(fiber->context.stack);

#endif

    fiber->fci.retval = &fiber->result;

    zend_call_function(&fiber->fci, &fiber->fci_cache);

    /* Cleanup callback and unset field to prevent GC / duplicate dtor issues. */

    zval_ptr_dtor(&fiber->fci.function_name);

    ZVAL_UNDEF(&fiber->fci.function_name);

    if (EG(exception)) {

      if (!(fiber->flags & ZEND_FIBER_FLAG_DESTROYED)

        || !(zend_is_graceful_exit(EG(exception)) || zend_is_unwind_exit(EG(exception)))

      ) {

        fiber->flags |= ZEND_FIBER_FLAG_THREW;

        transfer->flags = ZEND_FIBER_TRANSFER_FLAG_ERROR;

        ZVAL_OBJ_COPY(&transfer->value, EG(exception));

      }

      zend_clear_exception();

    }

  } zend_catch {

    fiber->flags |= ZEND_FIBER_FLAG_BAILOUT;

    transfer->flags = ZEND_FIBER_TRANSFER_FLAG_BAILOUT;

  } zend_end_try();

  fiber->context.cleanup = &zend_fiber_cleanup;

  fiber->vm_stack = EG(vm_stack);

  transfer->context = fiber->caller;

}

/* Handles forwarding of result / error from a transfer into the running fiber. */

static zend_always_inline void zend_fiber_delegate_transfer_result(

  zend_fiber_transfer *transfer, INTERNAL_FUNCTION_PARAMETERS

) {

  if (transfer->flags & ZEND_FIBER_TRANSFER_FLAG_ERROR) {

    /* Use internal throw to skip the Throwable-check that would fail for (graceful) exit. */

    zend_throw_exception_internal(Z_OBJ(transfer->value));

    RETURN_THROWS();

  }

  if (return_value != NULL) {

    RETURN_COPY_VALUE(&transfer->value);

  } else {

    zval_ptr_dtor(&transfer->value);

  }

}

static zend_always_inline zend_fiber_transfer zend_fiber_switch_to(

  zend_fiber_context *context, zval *value, bool exception

) {

  zend_fiber_transfer transfer = {

    .context = context,

    .flags = exception ? ZEND_FIBER_TRANSFER_FLAG_ERROR : 0,

  };

  if (value) {

    ZVAL_COPY(&transfer.value, value);

  } else {

    ZVAL_NULL(&transfer.value);

  }

  zend_fiber_switch_context(&transfer);

  /* Forward bailout into current fiber. */

  if (UNEXPECTED(transfer.flags & ZEND_FIBER_TRANSFER_FLAG_BAILOUT)) {

    EG(active_fiber) = NULL;

    zend_bailout();

  }

  return transfer;

}

static zend_always_inline zend_fiber_transfer zend_fiber_resume_internal(zend_fiber *fiber, zval *value, bool exception)

{

  zend_fiber *previous = EG(active_fiber);

  if (previous) {

    previous->execute_data = EG(current_execute_data);

  }

  fiber->caller = EG(current_fiber_context);

  EG(active_fiber) = fiber;

  zend_fiber_transfer transfer = zend_fiber_switch_to(fiber->previous, value, exception);

  EG(active_fiber) = previous;

  return transfer;

}

static zend_always_inline zend_fiber_transfer zend_fiber_suspend_internal(zend_fiber *fiber, zval *value)

{

  ZEND_ASSERT(!(fiber->flags & ZEND_FIBER_FLAG_DESTROYED));

  ZEND_ASSERT(fiber->context.status == ZEND_FIBER_STATUS_RUNNING || fiber->context.status == ZEND_FIBER_STATUS_SUSPENDED);

  ZEND_ASSERT(fiber->caller != NULL);

  zend_fiber_context *caller = fiber->caller;

  fiber->previous = EG(current_fiber_context);

  fiber->caller = NULL;

  fiber->execute_data = EG(current_execute_data);

  return zend_fiber_switch_to(caller, value, false);

}

ZEND_API zend_result zend_fiber_start(zend_fiber *fiber, zval *return_value)

{

  ZEND_ASSERT(fiber->context.status == ZEND_FIBER_STATUS_INIT);

  if (zend_fiber_init_context(&fiber->context, zend_ce_fiber, zend_fiber_execute, EG(fiber_stack_size)) == FAILURE) {

    return FAILURE;

  }

  fiber->previous = &fiber->context;

  zend_fiber_transfer transfer = zend_fiber_resume_internal(fiber, NULL, false);

  zend_fiber_delegate_transfer_result(&transfer, EG(current_execute_data), return_value);

  return SUCCESS;

}

ZEND_API void zend_fiber_resume(zend_fiber *fiber, zval *value, zval *return_value)

{

  ZEND_ASSERT(fiber->context.status == ZEND_FIBER_STATUS_SUSPENDED && fiber->caller == NULL);

  fiber->stack_bottom->prev_execute_data = EG(current_execute_data);

  zend_fiber_transfer transfer = zend_fiber_resume_internal(fiber, value, /* exception */ false);

  zend_fiber_delegate_transfer_result(&transfer, EG(current_execute_data), return_value);

}

ZEND_API void zend_fiber_resume_exception(zend_fiber *fiber, zval *exception, zval *return_value)

{

  ZEND_ASSERT(fiber->context.status == ZEND_FIBER_STATUS_SUSPENDED && fiber->caller == NULL);

  fiber->stack_bottom->prev_execute_data = EG(current_execute_data);

  zend_fiber_transfer transfer = zend_fiber_resume_internal(fiber, exception, /* exception */ true);

  zend_fiber_delegate_transfer_result(&transfer, EG(current_execute_data), return_value);

}

ZEND_API void zend_fiber_suspend(zend_fiber *fiber, zval *value, zval *return_value)

{

  fiber->stack_bottom->prev_execute_data = NULL;

  zend_fiber_transfer transfer = zend_fiber_suspend_internal(fiber, value);

  zend_fiber_delegate_transfer_result(&transfer, EG(current_execute_data), return_value);

}

static zend_object *zend_fiber_object_create(zend_class_entry *ce)

{

  zend_fiber *fiber = emalloc(sizeof(zend_fiber));

  memset(fiber, 0, sizeof(zend_fiber));

  zend_object_std_init(&fiber->std, ce);

  return &fiber->std;

}

static void zend_fiber_object_destroy(zend_object *object)

{

  zend_fiber *fiber = (zend_fiber *) object;

  if (fiber->context.status != ZEND_FIBER_STATUS_SUSPENDED) {

    return;

  }

  zend_object *exception = EG(exception);

  EG(exception) = NULL;

  zval graceful_exit;

  ZVAL_OBJ(&graceful_exit, zend_create_graceful_exit());

  fiber->flags |= ZEND_FIBER_FLAG_DESTROYED;

  zend_fiber_transfer transfer = zend_fiber_resume_internal(fiber, &graceful_exit, true);

  zval_ptr_dtor(&graceful_exit);

  if (transfer.flags & ZEND_FIBER_TRANSFER_FLAG_ERROR) {

    EG(exception) = Z_OBJ(transfer.value);

    if (!exception && EG(current_execute_data) && EG(current_execute_data)->func

        && ZEND_USER_CODE(EG(current_execute_data)->func->common.type)) {

      zend_rethrow_exception(EG(current_execute_data));

    }

    zend_exception_set_previous(EG(exception), exception);

    if (!EG(current_execute_data)) {

      zend_exception_error(EG(exception), E_ERROR);

    }

  } else {

    zval_ptr_dtor(&transfer.value);

    EG(exception) = exception;

  }

}

static void zend_fiber_object_free(zend_object *object)

{

  zend_fiber *fiber = (zend_fiber *) object;

  zval_ptr_dtor(&fiber->fci.function_name);

  zval_ptr_dtor(&fiber->result);

  zend_object_std_dtor(&fiber->std);

}

static HashTable *zend_fiber_object_gc(zend_object *object, zval **table, int *num)

{

  zend_fiber *fiber = (zend_fiber *) object;

  zend_get_gc_buffer *buf = zend_get_gc_buffer_create();

  zend_get_gc_buffer_add_zval(buf, &fiber->fci.function_name);

  zend_get_gc_buffer_add_zval(buf, &fiber->result);

  if (fiber->context.status != ZEND_FIBER_STATUS_SUSPENDED || fiber->caller != NULL) {

    zend_get_gc_buffer_use(buf, table, num);

    return NULL;

  }

  HashTable *lastSymTable = NULL;

  zend_execute_data *ex = fiber->execute_data;

  for (; ex; ex = ex->prev_execute_data) {

    HashTable *symTable;

    if (ZEND_CALL_INFO(ex) & ZEND_CALL_GENERATOR) {

      /* The generator object is stored in ex->return_value */

      zend_generator *generator = (zend_generator*)ex->return_value;

      /* There are two cases to consider:

       * - If the generator is currently running, the Generator's GC

       *   handler will ignore it because it is not collectable. However,

       *   in this context the generator is suspended in Fiber::suspend()

       *   and may be collectable, so we can inspect it.

       * - If the generator is not running, the Generator's GC handler

       *   will inspect it. In this case we have to skip the frame.

       */

      if (!(generator->flags & ZEND_GENERATOR_CURRENTLY_RUNNING)) {

        continue;

      }

      symTable = zend_generator_frame_gc(buf, generator);

    } else {

      symTable = zend_unfinished_execution_gc_ex(ex, ex->func && ZEND_USER_CODE(ex->func->type) ? ex->call : NULL, buf, false);

    }

    if (symTable) {

      if (lastSymTable) {

        zval *val;

        ZEND_HASH_FOREACH_VAL(lastSymTable, val) {

          if (EXPECTED(Z_TYPE_P(val) == IS_INDIRECT)) {

            val = Z_INDIRECT_P(val);

          }

          zend_get_gc_buffer_add_zval(buf, val);

        } ZEND_HASH_FOREACH_END();

      }

      lastSymTable = symTable;

    }

  }

  zend_get_gc_buffer_use(buf, table, num);

  return lastSymTable;

}

ZEND_METHOD(Fiber, __construct)

{

  zend_fcall_info fci;

  zend_fcall_info_cache fcc;

  ZEND_PARSE_PARAMETERS_START(1, 1)

    Z_PARAM_FUNC(fci, fcc)

  ZEND_PARSE_PARAMETERS_END();

  zend_fiber *fiber = (zend_fiber *) Z_OBJ_P(ZEND_THIS);

  if (UNEXPECTED(fiber->context.status != ZEND_FIBER_STATUS_INIT || Z_TYPE(fiber->fci.function_name) != IS_UNDEF)) {

    zend_throw_error(zend_ce_fiber_error, "Cannot call constructor twice");

    RETURN_THROWS();

  }

  fiber->fci = fci;

  fiber->fci_cache = fcc;

  // Keep a reference to closures or callable objects while the fiber is running.

  Z_TRY_ADDREF(fiber->fci.function_name);

}

ZEND_METHOD(Fiber, start)

{

  zend_fiber *fiber = (zend_fiber *) Z_OBJ_P(ZEND_THIS);

  ZEND_PARSE_PARAMETERS_START(0, -1)

    Z_PARAM_VARIADIC_WITH_NAMED(fiber->fci.params, fiber->fci.param_count, fiber->fci.named_params);

  ZEND_PARSE_PARAMETERS_END();

  if (UNEXPECTED(zend_fiber_switch_blocked())) {

    zend_throw_error(zend_ce_fiber_error, "Cannot switch fibers in current execution context");

    RETURN_THROWS();

  }

  if (fiber->context.status != ZEND_FIBER_STATUS_INIT) {

    zend_throw_error(zend_ce_fiber_error, "Cannot start a fiber that has already been started");

    RETURN_THROWS();

  }

  if (zend_fiber_init_context(&fiber->context, zend_ce_fiber, zend_fiber_execute, EG(fiber_stack_size)) == FAILURE) {

    RETURN_THROWS();

  }

  fiber->previous = &fiber->context;

  zend_fiber_transfer transfer = zend_fiber_resume_internal(fiber, NULL, false);

  zend_fiber_delegate_transfer_result(&transfer, INTERNAL_FUNCTION_PARAM_PASSTHRU);

}

ZEND_METHOD(Fiber, suspend)

{

  zval *value = NULL;

  ZEND_PARSE_PARAMETERS_START(0, 1)

    Z_PARAM_OPTIONAL

    Z_PARAM_ZVAL(value);

  ZEND_PARSE_PARAMETERS_END();

  zend_fiber *fiber = EG(active_fiber);