/src/php-src/ext/opcache/zend_shared_alloc.c

Source
/*
   +----------------------------------------------------------------------+
   | Zend OPcache                                                         |
   +----------------------------------------------------------------------+
   | Copyright © The PHP Group 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: Andi Gutmans <andi@php.net>                                 |
   |          Zeev Suraski <zeev@php.net>                                 |
   |          Stanislav Malyshev <stas@zend.com>                          |
   |          Dmitry Stogov <dmitry@php.net>                              |
   +----------------------------------------------------------------------+
*/

#if defined(__linux__)
# include <php_config.h>
# if defined(HAVE_MEMFD_CREATE)
#  include <sys/mman.h>
# endif
#endif

#include <errno.h>
#include "ZendAccelerator.h"
#include "zend_shared_alloc.h"
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#include <fcntl.h>
#ifndef ZEND_WIN32
# include <sys/types.h>
# include <signal.h>
# include <sys/stat.h>
# include <stdio.h>
#endif

#ifdef HAVE_MPROTECT
# include "sys/mman.h"
#endif

#define SEM_FILENAME_PREFIX ".ZendSem."
#define S_H(s) g_shared_alloc_handler->s

/* True globals */
/* old/new mapping. We can use true global even for ZTS because its usage
   is wrapped with exclusive lock anyway */
static const zend_shared_memory_handlers *g_shared_alloc_handler = NULL;
static const char *g_shared_model;
/* pointer to globals allocated in SHM and shared across processes */
ZEND_EXT_API zend_smm_shared_globals *smm_shared_globals;

#ifdef ZTS
static MUTEX_T zts_protect_lock;
static uint32_t zts_unprotected_threads;
#endif

#ifndef ZEND_WIN32
#ifdef ZTS
static MUTEX_T zts_lock;
#endif
int lock_file = -1;
static char lockfile_name[MAXPATHLEN];
#endif

static const zend_shared_memory_handler_entry handler_table[] = {
#ifdef USE_MMAP
  { "mmap", &zend_alloc_mmap_handlers },
#endif
#ifdef USE_SHM
  { "shm", &zend_alloc_shm_handlers },
#endif
#ifdef USE_SHM_OPEN
  { "posix", &zend_alloc_posix_handlers },
#endif
#ifdef ZEND_WIN32
  { "win32", &zend_alloc_win32_handlers },
#endif
  { NULL, NULL}
};

#ifndef ZEND_WIN32
void zend_shared_alloc_create_lock(char *lockfile_path)
{
  int val;

#ifdef ZTS
  zts_lock = tsrm_mutex_alloc();
#endif

#if defined(__linux__) && defined(HAVE_MEMFD_CREATE)
  /* on Linux, we can use a memfd instead of a "real" file, so
   * we can do this without a writable filesystem and without
   * needing to clean up */
  /* note: FreeBSD has memfd_create(), too, but fcntl(F_SETLKW)
   * on it fails with EBADF, therefore we use this only on
   * Linux */
  lock_file = memfd_create("opcache_lock", MFD_CLOEXEC);
  if (lock_file >= 0)
    return;
#endif

#ifdef O_TMPFILE
  lock_file = open(lockfile_path, O_RDWR | O_TMPFILE | O_EXCL | O_CLOEXEC, 0666);
  /* lack of O_TMPFILE support results in many possible errors
   * use it only when open returns a non-negative integer */
  if (lock_file >= 0) {
    return;
  }
#endif

  snprintf(lockfile_name, sizeof(lockfile_name), "%s/%sXXXXXX", lockfile_path, SEM_FILENAME_PREFIX);
  lock_file = mkstemp(lockfile_name);
  if (lock_file == -1) {
    zend_accel_error_noreturn(ACCEL_LOG_FATAL, "Unable to create opcache lock file in %s: %s (%d)", lockfile_path, strerror(errno), errno);
  }

  if (fchmod(lock_file, 0666) == -1) {
    zend_accel_error(ACCEL_LOG_WARNING, "Unable to change opcache lock file permissions in %s: %s (%d)", lockfile_path, strerror(errno), errno);
  }

  val = fcntl(lock_file, F_GETFD, 0);
  val |= FD_CLOEXEC;
  fcntl(lock_file, F_SETFD, val);

  unlink(lockfile_name);
}
#endif

static void no_memory_bailout(size_t allocate_size, const char *error)
{
  zend_accel_error_noreturn(ACCEL_LOG_FATAL, "Unable to allocate shared memory segment of %zu bytes: %s: %s (%d)", allocate_size, error?error:"unknown", strerror(errno), errno );
}

static void copy_shared_segments(void *to, void *from, int count, int size)
{
  zend_shared_segment **shared_segments_v = (zend_shared_segment **)to;
  void *shared_segments_to_p = ((char *)to + count*(sizeof(void *)));
  void *shared_segments_from_p = from;
  int i;

  for (i = 0; i < count; i++) {
    shared_segments_v[i] =  shared_segments_to_p;
    memcpy(shared_segments_to_p, shared_segments_from_p, size);
    shared_segments_to_p = ((char *)shared_segments_to_p + size);
    shared_segments_from_p = ((char *)shared_segments_from_p + size);
  }
}

static int zend_shared_alloc_try(const zend_shared_memory_handler_entry *he, size_t requested_size, zend_shared_segment ***shared_segments_p, int *shared_segments_count, const char **error_in)
{
  int res;
  g_shared_alloc_handler = he->handler;
  g_shared_model = he->name;
  ZSMMG(shared_segments) = NULL;
  ZSMMG(shared_segments_count) = 0;

  res = S_H(create_segments)(requested_size, shared_segments_p, shared_segments_count, error_in);

  if (res) {
    /* this model works! */
    return res;
  }
  if (*shared_segments_p) {
    int i;
    /* cleanup */
    for (i = 0; i < *shared_segments_count; i++) {
      if ((*shared_segments_p)[i]->p && (*shared_segments_p)[i]->p != (void *)-1) {
        S_H(detach_segment)((*shared_segments_p)[i]);
      }
    }
    free(*shared_segments_p);
    *shared_segments_p = NULL;
  }
  g_shared_alloc_handler = NULL;
  return ALLOC_FAILURE;
}

int zend_shared_alloc_startup(size_t requested_size, size_t reserved_size)
{
  zend_shared_segment **tmp_shared_segments;
  size_t shared_segments_array_size;
  zend_smm_shared_globals tmp_shared_globals, *p_tmp_shared_globals;
  const char *error_in = NULL;
  const zend_shared_memory_handler_entry *he;
  int res = ALLOC_FAILURE;
  int i;

#ifdef ZTS
  zts_protect_lock = tsrm_mutex_alloc();
  zts_unprotected_threads = 0;
#endif

  /* shared_free must be valid before we call zend_shared_alloc()
   * - make it temporarily point to a local variable
   */
  smm_shared_globals = &tmp_shared_globals;
  ZSMMG(shared_free) = requested_size - reserved_size; /* goes to tmp_shared_globals.shared_free */

#ifndef ZEND_WIN32
  zend_shared_alloc_create_lock(ZCG(accel_directives).lockfile_path);
#else
  zend_shared_alloc_create_lock();
#endif

  if (ZCG(accel_directives).memory_model && ZCG(accel_directives).memory_model[0]) {
    const char *model = ZCG(accel_directives).memory_model;
    /* "cgi" is really "shm"... */
    if (strncmp(ZCG(accel_directives).memory_model, "cgi", sizeof("cgi")) == 0) {
      model = "shm";
    }

    for (he = handler_table; he->name; he++) {
      if (strcmp(model, he->name) == 0) {
        res = zend_shared_alloc_try(he, requested_size, &ZSMMG(shared_segments), &ZSMMG(shared_segments_count), &error_in);
        if (res) {
          /* this model works! */
          break;
        }
      }
    }
  }

  if (res == FAILED_REATTACHED) {
    smm_shared_globals = NULL;
    return res;
  }
#if ENABLE_FILE_CACHE_FALLBACK
  if (ALLOC_FALLBACK == res) {
    smm_shared_globals = NULL;
    return ALLOC_FALLBACK;
  }
#endif

  if (!g_shared_alloc_handler) {
    /* try memory handlers in order */
    if (handler_table->name == NULL) {
      return NO_SHM_BACKEND;
    }
    for (he = handler_table; he->name; he++) {
      res = zend_shared_alloc_try(he, requested_size, &ZSMMG(shared_segments), &ZSMMG(shared_segments_count), &error_in);
      if (res) {
        /* this model works! */
        break;
      }
    }
  }

  if (!g_shared_alloc_handler) {
    no_memory_bailout(requested_size, error_in);
    return ALLOC_FAILURE;
  }

  if (res == SUCCESSFULLY_REATTACHED) {
    return res;
  }
#if ENABLE_FILE_CACHE_FALLBACK
  if (ALLOC_FALLBACK == res) {
    smm_shared_globals = NULL;
    return ALLOC_FALLBACK;
  }
#endif

  for (i = 0; i < ZSMMG(shared_segments_count); i++) {
    ZSMMG(shared_segments)[i]->end = ZSMMG(shared_segments)[i]->size;
  }

  shared_segments_array_size = ZSMMG(shared_segments_count) * S_H(segment_type_size)();

  /* move shared_segments and shared_free to shared memory */
  ZCG(locked) = 1; /* no need to perform a real lock at this point */

  p_tmp_shared_globals = (zend_smm_shared_globals *) zend_shared_alloc(sizeof(zend_smm_shared_globals));
  if (!p_tmp_shared_globals) {
    zend_accel_error_noreturn(ACCEL_LOG_FATAL, "Insufficient shared memory!");
    return ALLOC_FAILURE;
  }
  memset(p_tmp_shared_globals, 0, sizeof(zend_smm_shared_globals));

  tmp_shared_segments = zend_shared_alloc(shared_segments_array_size + ZSMMG(shared_segments_count) * sizeof(void *));
  if (!tmp_shared_segments) {
    zend_accel_error_noreturn(ACCEL_LOG_FATAL, "Insufficient shared memory!");
    return ALLOC_FAILURE;
  }

  copy_shared_segments(tmp_shared_segments, ZSMMG(shared_segments)[0], ZSMMG(shared_segments_count), S_H(segment_type_size)());

  *p_tmp_shared_globals = tmp_shared_globals;
  smm_shared_globals = p_tmp_shared_globals;

  free(ZSMMG(shared_segments));
  ZSMMG(shared_segments) = tmp_shared_segments;

  ZSMMG(shared_memory_state).positions = (size_t *)zend_shared_alloc(sizeof(size_t) * ZSMMG(shared_segments_count));
  if (!ZSMMG(shared_memory_state).positions) {
    zend_accel_error_noreturn(ACCEL_LOG_FATAL, "Insufficient shared memory!");
    return ALLOC_FAILURE;
  }

  if (reserved_size) {
    i = ZSMMG(shared_segments_count) - 1;
    if (ZSMMG(shared_segments)[i]->size - ZSMMG(shared_segments)[i]->pos >= reserved_size) {
      ZSMMG(shared_segments)[i]->end = ZSMMG(shared_segments)[i]->size - reserved_size;
      ZSMMG(reserved) = (char*)ZSMMG(shared_segments)[i]->p + ZSMMG(shared_segments)[i]->end;
      ZSMMG(reserved_size) = reserved_size;
    } else {
      zend_accel_error_noreturn(ACCEL_LOG_FATAL, "Insufficient shared memory!");
      return ALLOC_FAILURE;
    }
  }

  ZCG(locked) = 0;

  return res;
}

void zend_shared_alloc_shutdown(void)
{
  zend_shared_segment **tmp_shared_segments;
  zend_shared_segment *shared_segments_buf[16];
  size_t shared_segments_array_size;
  zend_smm_shared_globals tmp_shared_globals;
  int i;

  tmp_shared_globals = *smm_shared_globals;
  smm_shared_globals = &tmp_shared_globals;
  shared_segments_array_size = ZSMMG(shared_segments_count) * (S_H(segment_type_size)() + sizeof(void *));
  if (shared_segments_array_size > 16) {
    tmp_shared_segments = malloc(shared_segments_array_size);
  } else {
    tmp_shared_segments = shared_segments_buf;
  }
  copy_shared_segments(tmp_shared_segments, ZSMMG(shared_segments)[0], ZSMMG(shared_segments_count), S_H(segment_type_size)());
  ZSMMG(shared_segments) = tmp_shared_segments;

  for (i = 0; i < ZSMMG(shared_segments_count); i++) {
    S_H(detach_segment)(ZSMMG(shared_segments)[i]);
  }
  if (shared_segments_array_size > 16) {
    free(ZSMMG(shared_segments));
  }
  ZSMMG(shared_segments) = NULL;
  g_shared_alloc_handler = NULL;
#ifndef ZEND_WIN32
  close(lock_file);

# ifdef ZTS
  tsrm_mutex_free(zts_lock);
# endif
#endif
#ifdef ZTS
  tsrm_mutex_free(zts_protect_lock);
#endif
}

static size_t zend_shared_alloc_get_largest_free_block(void)
{
  int i;
  size_t largest_block_size = 0;

  for (i = 0; i < ZSMMG(shared_segments_count); i++) {
    size_t block_size = ZSMMG(shared_segments)[i]->end - ZSMMG(shared_segments)[i]->pos;

    if (block_size>largest_block_size) {
      largest_block_size = block_size;
    }
  }
  return largest_block_size;
}

#define MIN_FREE_MEMORY 64*1024

#define SHARED_ALLOC_FAILED() do {   \
    zend_accel_error(ACCEL_LOG_WARNING, "Not enough free shared space to allocate %zu bytes (%zu bytes free)", size, ZSMMG(shared_free)); \
    if (zend_shared_alloc_get_largest_free_block() < MIN_FREE_MEMORY) { \
      ZSMMG(memory_exhausted) = 1; \
    } \
  } while (0)

void *zend_shared_alloc(size_t size)
{
  int i;
  size_t block_size = ZEND_ALIGNED_SIZE(size);

#if 1
  if (!ZCG(locked)) {
    ZEND_ASSERT(0 && "Shared memory lock not obtained");
    zend_accel_error_noreturn(ACCEL_LOG_ERROR, "Shared memory lock not obtained");
  }
#endif
  if (block_size > ZSMMG(shared_free)) { /* No hope to find a big-enough block */
    SHARED_ALLOC_FAILED();
    return NULL;
  }
  for (i = 0; i < ZSMMG(shared_segments_count); i++) {
    if (ZSMMG(shared_segments)[i]->end - ZSMMG(shared_segments)[i]->pos >= block_size) { /* found a valid block */
      void *retval = (void *) (((char *) ZSMMG(shared_segments)[i]->p) + ZSMMG(shared_segments)[i]->pos);

      ZSMMG(shared_segments)[i]->pos += block_size;
      ZSMMG(shared_free) -= block_size;
      ZEND_ASSERT(((uintptr_t)retval & 0x7) == 0); /* should be 8 byte aligned */
      return retval;
    }
  }
  SHARED_ALLOC_FAILED();
  return NULL;
}

static zend_always_inline zend_ulong zend_rotr3(zend_ulong key)
{
  return (key >> 3) | (key << ((sizeof(key) * 8) - 3));
}

int zend_shared_memdup_size(void *source, size_t size)
{
  void *old_p;
  zend_ulong key = (zend_ulong)source;

  key = zend_rotr3(key);
  if ((old_p = zend_hash_index_find_ptr(&ZCG(xlat_table), key)) != NULL) {
    /* we already duplicated this pointer */
    return 0;
  }
  zend_hash_index_add_new_ptr(&ZCG(xlat_table), key, source);
  return ZEND_ALIGNED_SIZE(size);
}

static zend_always_inline void *_zend_shared_memdup(void *source, size_t size, bool get_xlat, bool set_xlat, bool free_source)
{
  void *old_p, *retval;
  zend_ulong key;

  if (get_xlat) {
    key = (zend_ulong)source;
    key = zend_rotr3(key);
    if ((old_p = zend_hash_index_find_ptr(&ZCG(xlat_table), key)) != NULL) {
      /* we already duplicated this pointer */
      return old_p;
    }
  }
  retval = ZCG(mem);
  ZCG(mem) = (void*)(((char*)ZCG(mem)) + ZEND_ALIGNED_SIZE(size));
  memcpy(retval, source, size);
  if (set_xlat) {
    if (!get_xlat) {
      key = (zend_ulong)source;
      key = zend_rotr3(key);
    }
    zend_hash_index_add_new_ptr(&ZCG(xlat_table), key, retval);
  }
  if (free_source) {
    efree(source);
  }
  return retval;
}

void *zend_shared_memdup_get_put_free(void *source, size_t size)
{
  return _zend_shared_memdup(source, size, true, true, true);
}

void *zend_shared_memdup_put_free(void *source, size_t size)
{
  return _zend_shared_memdup(source, size, false, true, true);
}

void *zend_shared_memdup_free(void *source, size_t size)
{
  return _zend_shared_memdup(source, size, false, false, true);
}

void *zend_shared_memdup_get_put(void *source, size_t size)
{
  return _zend_shared_memdup(source, size, true, true, false);
}

void *zend_shared_memdup_put(void *source, size_t size)
{
  return _zend_shared_memdup(source, size, false, true, false);
}

void *zend_shared_memdup(void *source, size_t size)
{
  return _zend_shared_memdup(source, size, false, false, false);
}

void zend_shared_alloc_safe_unlock(void)
{
  if (ZCG(locked)) {
    zend_shared_alloc_unlock();
  }
}

void zend_shared_alloc_lock(void)
{
  ZEND_ASSERT(!ZCG(locked));

#ifndef ZEND_WIN32
  struct flock mem_write_lock;

  mem_write_lock.l_type = F_WRLCK;
  mem_write_lock.l_whence = SEEK_SET;
  mem_write_lock.l_start = 0;
  mem_write_lock.l_len = 1;

#ifdef ZTS
  tsrm_mutex_lock(zts_lock);
#endif

#if 0
  /* this will happen once per process, and will un-globalize mem_write_lock */
  if (mem_write_lock.l_pid == -1) {
    mem_write_lock.l_pid = getpid();
  }
#endif

  while (1) {
    if (fcntl(lock_file, F_SETLKW, &mem_write_lock) == -1) {
      if (errno == EINTR) {
        continue;
      }
      zend_accel_error_noreturn(ACCEL_LOG_ERROR, "Cannot create lock - %s (%d)", strerror(errno), errno);
    }
    break;
  }
#else
  zend_shared_alloc_lock_win32();
#endif

  ZCG(locked) = 1;
}

void zend_shared_alloc_unlock(void)
{
  ZEND_ASSERT(ZCG(locked));

#ifndef ZEND_WIN32
  struct flock mem_write_unlock;

  mem_write_unlock.l_type = F_UNLCK;
  mem_write_unlock.l_whence = SEEK_SET;
  mem_write_unlock.l_start = 0;
  mem_write_unlock.l_len = 1;
#endif

  ZCG(locked) = 0;

#ifndef ZEND_WIN32
  if (fcntl(lock_file, F_SETLK, &mem_write_unlock) == -1) {
    zend_accel_error_noreturn(ACCEL_LOG_ERROR, "Cannot remove lock - %s (%d)", strerror(errno), errno);
  }
#ifdef ZTS
  tsrm_mutex_unlock(zts_lock);
#endif
#else
  zend_shared_alloc_unlock_win32();
#endif
}

void zend_shared_alloc_init_xlat_table(void)
{
  /* Prepare translation table */
  zend_hash_init(&ZCG(xlat_table), 128, NULL, NULL, 0);
}

void zend_shared_alloc_destroy_xlat_table(void)
{
  /* Destroy translation table */
  zend_hash_destroy(&ZCG(xlat_table));
}

void zend_shared_alloc_clear_xlat_table(void)
{
  zend_hash_clean(&ZCG(xlat_table));
}

uint32_t zend_shared_alloc_checkpoint_xlat_table(void)
{
  return ZCG(xlat_table).nNumUsed;
}

void zend_shared_alloc_restore_xlat_table(uint32_t checkpoint)
{
  zend_hash_discard(&ZCG(xlat_table), checkpoint);
}

void zend_shared_alloc_register_xlat_entry(const void *key_pointer, const void *value)
{
  zend_ulong key = (zend_ulong)key_pointer;

  key = zend_rotr3(key);
  zend_hash_index_add_new_ptr(&ZCG(xlat_table), key, (void*)value);
}

void *zend_shared_alloc_get_xlat_entry(const void *key_pointer)
{
  void *retval;
  zend_ulong key = (zend_ulong)key_pointer;

  key = zend_rotr3(key);
  if ((retval = zend_hash_index_find_ptr(&ZCG(xlat_table), key)) == NULL) {
    return NULL;
  }
  return retval;
}

size_t zend_shared_alloc_get_free_memory(void)
{
  return ZSMMG(shared_free);
}

void zend_shared_alloc_save_state(void)
{
  int i;

  for (i = 0; i < ZSMMG(shared_segments_count); i++) {
    ZSMMG(shared_memory_state).positions[i] = ZSMMG(shared_segments)[i]->pos;
  }
  ZSMMG(shared_memory_state).shared_free = ZSMMG(shared_free);
}

void zend_shared_alloc_restore_state(void)
{
  int i;

  for (i = 0; i < ZSMMG(shared_segments_count); i++) {
    ZSMMG(shared_segments)[i]->pos = ZSMMG(shared_memory_state).positions[i];
  }
  ZSMMG(shared_free) = ZSMMG(shared_memory_state).shared_free;
  ZSMMG(memory_exhausted) = 0;
  ZSMMG(wasted_shared_memory) = 0;
}

const char *zend_accel_get_shared_model(void)
{
  return g_shared_model;
}

void zend_accel_shared_protect(bool protected)
{
#if defined(HAVE_MPROTECT) || defined(ZEND_WIN32)
  int i;

  if (!smm_shared_globals) {
    return;
  }

# ifdef ZTS
  /* Memory protection is process-wide, so overlapping writers must be tracked across threads. */
  tsrm_mutex_lock(zts_protect_lock);
  if (protected) {
    if (ZCG(unprotect_depth) && --ZCG(unprotect_depth) == 0) {
      ZEND_ASSERT(zts_unprotected_threads > 0);
      zts_unprotected_threads--;
    }
    if (zts_unprotected_threads) {
      tsrm_mutex_unlock(zts_protect_lock);
      return;
    }
  } else if (ZCG(unprotect_depth)++ == 0) {
    zts_unprotected_threads++;
  }
# endif

# ifdef HAVE_MPROTECT
  const int mode = protected ? PROT_READ : PROT_READ|PROT_WRITE;

  for (i = 0; i < ZSMMG(shared_segments_count); i++) {
    mprotect(ZSMMG(shared_segments)[i]->p, ZSMMG(shared_segments)[i]->end, mode);
  }
# elif defined(ZEND_WIN32)
  const int mode = protected ? PAGE_READONLY : PAGE_READWRITE;

  for (i = 0; i < ZSMMG(shared_segments_count); i++) {
    DWORD oldProtect;
    if (!VirtualProtect(ZSMMG(shared_segments)[i]->p, ZSMMG(shared_segments)[i]->end, mode, &oldProtect)) {
      zend_accel_error_noreturn(ACCEL_LOG_ERROR, "Failed to protect memory");
    }
  }
# endif

# ifdef ZTS
  tsrm_mutex_unlock(zts_protect_lock);
# endif
#endif
}

bool zend_accel_in_shm(void *ptr)
{
  int i;

  if (!smm_shared_globals) {
    return false;
  }

  for (i = 0; i < ZSMMG(shared_segments_count); i++) {
    if ((char*)ptr >= (char*)ZSMMG(shared_segments)[i]->p &&
        (char*)ptr < (char*)ZSMMG(shared_segments)[i]->p + ZSMMG(shared_segments)[i]->end) {
      return true;
    }
  }
  return false;
}

Coverage Report

Created: 2026-09-14 06:25