/src/php-src/Zend/zend_call_stack.c

Source
/*
   +----------------------------------------------------------------------+
   | 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: Arnaud Le Blanc <arnaud.lb@gmail.com>                       |
   +----------------------------------------------------------------------+
*/

/* Inspired from Chromium's stack_util.cc */

#include "zend.h"
#include "zend_globals.h"
#include "zend_portability.h"
#include "zend_call_stack.h"
#include <stdint.h>
#ifdef ZEND_WIN32
# include <processthreadsapi.h>
# include <memoryapi.h>
#else /* ZEND_WIN32 */
# include <sys/resource.h>
# ifdef HAVE_UNISTD_H
#  include <unistd.h>
# endif
# ifdef HAVE_SYS_TYPES_H
#  include <sys/types.h>
# endif
#endif /* ZEND_WIN32 */
#if (defined(HAVE_PTHREAD_GETATTR_NP) && defined(HAVE_PTHREAD_ATTR_GETSTACK)) || \
    defined(__FreeBSD__) || defined(__APPLE__) || defined(__OpenBSD__) || \
    defined(__NetBSD__) || defined(__DragonFly__) || defined(__sun) || \
    defined(_AIX)
# include <pthread.h>
#endif
#if defined(__FreeBSD__) || defined(__DragonFly__)
# include <pthread_np.h>
# include <sys/mman.h>
# include <sys/sysctl.h>
# include <sys/user.h>
#endif
#ifdef __OpenBSD__
typedef int boolean_t;
# include <tib.h>
# include <pthread_np.h>
# include <sys/sysctl.h>
# include <sys/user.h>
#endif
#ifdef __NetBSD__
# include <sys/sysctl.h>
# include <sys/syscall.h>
#endif
#ifdef __HAIKU__
# include <kernel/OS.h>
#endif
#ifdef __linux__
#include <sys/syscall.h>
#endif
#ifdef __sun
# include <sys/lwp.h>
# ifdef HAVE_LIBPROC_H
#  define _STRUCTURED_PROC 1
#  include <sys/procfs.h>
#  include <libproc.h>
# endif
#include <thread.h>
#endif

#ifdef HAVE_VALGRIND
# include <valgrind/valgrind.h>
#endif

#ifdef ZEND_CHECK_STACK_LIMIT

/* Called once per process or thread */
ZEND_API void zend_call_stack_init(void) {
  if (!zend_call_stack_get(&EG(call_stack))) {
    EG(call_stack) = (zend_call_stack){0};
  }

  switch (EG(max_allowed_stack_size)) {
    case ZEND_MAX_ALLOWED_STACK_SIZE_DETECT: {
      void *base = EG(call_stack).base;
      size_t size = EG(call_stack).max_size;
      if (UNEXPECTED(base == (void*)0)) {
        base = zend_call_stack_position();
        size = zend_call_stack_default_size();
        /* base is not the actual stack base */
        size -= 32 * 1024;
      }
      EG(stack_base) = base;
      EG(stack_limit) = zend_call_stack_limit(base, size, EG(reserved_stack_size));
      break;
    }
    case ZEND_MAX_ALLOWED_STACK_SIZE_UNCHECKED: {
      EG(stack_base) = (void*)0;
      EG(stack_limit) = (void*)0;
      break;
    }
    default: {
      ZEND_ASSERT(EG(max_allowed_stack_size) > 0);
      void *base = EG(call_stack).base;
      if (UNEXPECTED(base == (void*)0)) {
        base = zend_call_stack_position();
      }
      EG(stack_base) = base;
      EG(stack_limit) = zend_call_stack_limit(base, EG(max_allowed_stack_size), EG(reserved_stack_size));
      break;
    }
  }
}

#ifdef __linux__
static bool zend_call_stack_is_main_thread(void) {
# ifdef HAVE_GETTID
  return getpid() == gettid();
# else
  return getpid() == syscall(SYS_gettid);
# endif
}

# if defined(HAVE_PTHREAD_GETATTR_NP) && defined(HAVE_PTHREAD_ATTR_GETSTACK)
static bool zend_call_stack_get_linux_pthread(zend_call_stack *stack)
{
  pthread_attr_t attr;
  int error;
  void *addr;
  size_t max_size;

  /* pthread_getattr_np() will return bogus values for the main thread with
   * musl or with some old glibc versions */
  ZEND_ASSERT(!zend_call_stack_is_main_thread());

  error = pthread_getattr_np(pthread_self(), &attr);
  if (UNEXPECTED(error)) {
    return false;
  }

  error = pthread_attr_getstack(&attr, &addr, &max_size);
  if (UNEXPECTED(error)) {
    pthread_attr_destroy(&attr);
    return false;
  }

#  if defined(__GLIBC__) && (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 8))
  {
    size_t guard_size;
    /* In glibc prior to 2.8, addr and size include the guard pages */
    error = pthread_attr_getguardsize(&attr, &guard_size);
    if (UNEXPECTED(error)) {
      pthread_attr_destroy(&attr);
      return false;
    }

    addr = (int8_t*)addr + guard_size;
    max_size -= guard_size;
  }
#  endif /* glibc < 2.8 */

  stack->base = (int8_t*)addr + max_size;
  stack->max_size = max_size;

  pthread_attr_destroy(&attr);

  return true;
}
# else /* defined(HAVE_PTHREAD_GETATTR_NP) && defined(HAVE_PTHREAD_ATTR_GETSTACK) */
static bool zend_call_stack_get_linux_pthread(zend_call_stack *stack)
{
  return false;
}
# endif /* defined(HAVE_PTHREAD_GETATTR_NP) && defined(HAVE_PTHREAD_ATTR_GETSTACK) */

static bool zend_call_stack_get_linux_proc_maps(zend_call_stack *stack)
{
  FILE *f;
  char buffer[4096];
  uintptr_t addr_on_stack = (uintptr_t) zend_call_stack_position();
  uintptr_t start, end, prev_end = 0;
  size_t max_size;
  bool found = false;
  struct rlimit rlim;
  int error;

  /* This method is relevant only for the main thread */
  ZEND_ASSERT(zend_call_stack_is_main_thread());

  /* Scan the process memory mappings to find the one containing the stack.
   *
   * The end of the stack mapping is the base of the stack. The start is
   * adjusted by the kernel as the stack grows. The maximum stack size is
   * determined by RLIMIT_STACK and the previous mapping.
   *
   *
   *                   ^ Higher addresses  ^
   *                   :                   :
   *                   :                   :
   *   Mapping end --> |-------------------| <-- Stack base (stack start)
   *                   |                   |   ^
   *                   | Stack Mapping     |   | Stack size
   *                   |                   |   v
   * Mapping start --> |-------------------| <-- Current stack end
   * (adjusted         :                   :
   *  downwards as the .                   .
   *  stack grows)     :                   :
   *                   |-------------------|
   *                   | Some Mapping      | The previous mapping may prevent
   *                   |-------------------| stack growth
   *                   :                   :
   *                   :                   :
   *                   v Lower addresses   v
   */

  f = fopen("/proc/self/maps", "r");
  if (!f) {
    return false;
  }

  while (fgets(buffer, sizeof(buffer), f) && sscanf(buffer, "%" SCNxPTR "-%" SCNxPTR, &start, &end) == 2) {
    if (start <= addr_on_stack && end >= addr_on_stack) {
      found = true;
      break;
    }
    prev_end = end;
  }

  fclose(f);

  if (!found) {
    return false;
  }

  error = getrlimit(RLIMIT_STACK, &rlim);
  if (error || rlim.rlim_cur == RLIM_INFINITY) {
    return false;
  }

  max_size = rlim.rlim_cur;

#ifdef HAVE_VALGRIND
  /* Under Valgrind, the last page is not usable */
  if (RUNNING_ON_VALGRIND) {
    max_size -= zend_get_page_size();
  }
#endif

  /* Previous mapping may prevent the stack from growing */
  if (end - max_size < prev_end) {
    max_size = prev_end - end;
  }

  stack->base = (void*)end;
  stack->max_size = max_size;

  return true;
}

static bool zend_call_stack_get_linux(zend_call_stack *stack)
{
  if (zend_call_stack_is_main_thread()) {
    return zend_call_stack_get_linux_proc_maps(stack);
  }

  return zend_call_stack_get_linux_pthread(stack);
}
#else /* __linux__ */
static bool zend_call_stack_get_linux(zend_call_stack *stack)
{
  return false;
}
#endif /* __linux__ */

#if defined(__FreeBSD__) || defined(__DragonFly__)
static bool zend_call_stack_is_main_thread(void)
{
  int is_main = pthread_main_np();
  return is_main == -1 || is_main == 1;
}

# if defined(HAVE_PTHREAD_ATTR_GET_NP) && defined(HAVE_PTHREAD_ATTR_GETSTACK)
static bool zend_call_stack_get_freebsd_pthread(zend_call_stack *stack)
{
  pthread_attr_t attr;
  int error;
  void *addr;
  size_t max_size;

  /* pthread will return bogus values for the main thread */
  ZEND_ASSERT(!zend_call_stack_is_main_thread());

  pthread_attr_init(&attr);

  error = pthread_attr_get_np(pthread_self(), &attr);
  if (error) {
    goto fail;
  }

  error = pthread_attr_getstack(&attr, &addr, &max_size);
  if (error) {
    goto fail;
  }

  stack->base = (int8_t*)addr + max_size;
  stack->max_size = max_size;

  pthread_attr_destroy(&attr);
  return true;

fail:
  pthread_attr_destroy(&attr);
  return false;
}
# else /* defined(HAVE_PTHREAD_ATTR_GET_NP) && defined(HAVE_PTHREAD_ATTR_GETSTACK) */
static bool zend_call_stack_get_freebsd_pthread(zend_call_stack *stack)
{
  return false;
}
# endif /* defined(HAVE_PTHREAD_ATTR_GET_NP) && defined(HAVE_PTHREAD_ATTR_GETSTACK) */

static bool zend_call_stack_get_freebsd_sysctl(zend_call_stack *stack)
{
  void *stack_base;
  int mib[2] = {CTL_KERN, KERN_USRSTACK};
  size_t len = sizeof(stack_base);
  struct rlimit rlim;
  size_t numguards = 0;

  /* This method is relevant only for the main thread */
  ZEND_ASSERT(zend_call_stack_is_main_thread());

  if (sysctl(mib, sizeof(mib)/sizeof(*mib), &stack_base, &len, NULL, 0) != 0) {
    return false;
  }

  if (getrlimit(RLIMIT_STACK, &rlim) != 0) {
    return false;
  }

  if (rlim.rlim_cur == RLIM_INFINITY) {
    return false;
  }

  len = sizeof(numguards);
  /* For most of the cases, we do not necessarily need to do so as, by default, it is `1` page, but is user writable */
  if (sysctlbyname("security.bsd.stack_guard_page", &numguards, &len, NULL, 0) != 0) {
    return false;
  }

  size_t guard_size = numguards * getpagesize();

  stack->base = stack_base;
  stack->max_size = rlim.rlim_cur - guard_size;

  return true;
}

static bool zend_call_stack_get_freebsd(zend_call_stack *stack)
{
  if (zend_call_stack_is_main_thread()) {
    return zend_call_stack_get_freebsd_sysctl(stack);
  }

  return zend_call_stack_get_freebsd_pthread(stack);
}
#else
static bool zend_call_stack_get_freebsd(zend_call_stack *stack)
{
  return false;
}
#endif /* __FreeBSD__ */

#ifdef ZEND_WIN32
static bool zend_call_stack_get_win32(zend_call_stack *stack)
{
  ULONG_PTR low_limit, high_limit;
  MEMORY_BASIC_INFORMATION guard_region = {0}, uncommitted_region = {0};
  size_t result_size, page_size;

  /* The stack consists of three regions: committed, guard, and uncommitted.
   * Memory is committed when the guard region is accessed. If only one page
   * is left in the uncommitted region, a stack overflow error is raised
   * instead.
   *
   * The total usable stack size is the size of the committed and uncommitted
   * regions less one page.
   *
   * http://blogs.msdn.com/b/satyem/archive/2012/08/13/thread-s-stack-memory-management.aspx
   * https://learn.microsoft.com/en-us/windows/win32/procthread/thread-stack-size
   *
   *                ^  Higher addresses  ^
   *                :                    :
   *                :                    :
   * high_limit --> |--------------------|
   *            ^   |                    |
   *            |   | Committed region   |
   *            |   |                    |
   *            |   |------------------- | <-- guard_region.BaseAddress
   *   reserved |   |                    |     + guard_region.RegionSize
   *       size |   | Guard region       |
   *            |   |                    |
   *            |   |--------------------| <-- guard_region.BaseAddress,
   *            |   |                    |     uncommitted_region.BaseAddress
   *            |   | Uncommitted region |     + uncommitted_region.RegionSize
   *            v   |                    |
   * low_limit  --> |------------------- | <-- uncommitted_region.BaseAddress
   *                :                    :
   *                :                    :
   *                v  Lower addresses   v
   */

  GetCurrentThreadStackLimits(&low_limit, &high_limit);

  result_size = VirtualQuery((void*)low_limit,
      &uncommitted_region, sizeof(uncommitted_region));
  ZEND_ASSERT(result_size >= sizeof(uncommitted_region));

  result_size = VirtualQuery((int8_t*)uncommitted_region.BaseAddress + uncommitted_region.RegionSize,
      &guard_region, sizeof(guard_region));
  ZEND_ASSERT(result_size >= sizeof(uncommitted_region));

  stack->base = (void*)high_limit;
  stack->max_size = (uintptr_t)high_limit - (uintptr_t)low_limit;

  ZEND_ASSERT(stack->max_size > guard_region.RegionSize);
  stack->max_size -= guard_region.RegionSize;

  /* The uncommitted region does not shrink below 1 page */
  page_size = zend_get_page_size();
  ZEND_ASSERT(stack->max_size > page_size);
  stack->max_size -= page_size;

  return true;
}
#else /* ZEND_WIN32 */
static bool zend_call_stack_get_win32(zend_call_stack *stack)
{
  return false;
}
#endif /* ZEND_WIN32 */

#if defined(__APPLE__) && defined(HAVE_PTHREAD_GET_STACKADDR_NP)
static bool zend_call_stack_get_macos(zend_call_stack *stack)
{
  void *base = pthread_get_stackaddr_np(pthread_self());
  size_t max_size;

#if !defined(__aarch64__)
  if (pthread_main_np())
  {
    /* pthread_get_stacksize_np() returns a too low value for the main
     * thread in OSX 10.9, 10.10:
     * https://mail.openjdk.org/pipermail/hotspot-dev/2013-October/011353.html
     * https://github.com/rust-lang/rust/issues/43347
     */

    /* Stack size is 8MiB by default for main threads
     * https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/Multithreading/CreatingThreads/CreatingThreads.html */
    max_size = 8 * 1024 * 1024;
  }
  else
#endif
  {
    max_size = pthread_get_stacksize_np(pthread_self());
  }

  stack->base = base;
  stack->max_size = max_size;

  return true;
}
#else /* defined(__APPLE__) && defined(HAVE_PTHREAD_GET_STACKADDR_NP) */
static bool zend_call_stack_get_macos(zend_call_stack *stack)
{
  return false;
}
#endif /* defined(__APPLE__) && defined(HAVE_PTHREAD_GET_STACKADDR_NP) */

#if defined(__OpenBSD__)
#if defined(HAVE_PTHREAD_STACKSEG_NP)
static bool zend_call_stack_get_openbsd_pthread(zend_call_stack *stack)
{
  stack_t ss;

  if (pthread_stackseg_np(pthread_self(), &ss) != 0) {
    return false;
  }

  stack->base = (char *)ss.ss_sp - ss.ss_size;
  stack->max_size = ss.ss_size - sysconf(_SC_PAGE_SIZE);

  return true;
}
#else
static bool zend_call_stack_get_openbsd_pthread(zend_call_stack *stack)
{
  return false;
}
#endif /* defined(HAVE_PTHREAD_STACKSEG_NP) */

static bool zend_call_stack_get_openbsd_vm(zend_call_stack *stack)
{
  struct _ps_strings ps;
  struct rlimit rlim;
  int mib[2] = {CTL_VM, VM_PSSTRINGS };
  size_t len = sizeof(ps), pagesize;

  if (sysctl(mib, 2, &ps, &len, NULL, 0) != 0) {
    return false;
  }

  if (getrlimit(RLIMIT_STACK, &rlim) != 0) {
    return false;
  }

  if (rlim.rlim_cur == RLIM_INFINITY) {
    return false;
  }

  pagesize = sysconf(_SC_PAGE_SIZE);

  stack->base = (void *)((uintptr_t)ps.val + (pagesize - 1) & ~(pagesize - 1));
  stack->max_size = rlim.rlim_cur - pagesize;

  return true;
}

static bool zend_call_stack_get_openbsd(zend_call_stack *stack)
{
  // TIB_THREAD_INITIAL_STACK is private and here we avoid using pthread's api (ie pthread_main_np)
  if (!TIB_GET()->tib_thread || (TIB_GET()->tib_thread_flags & 0x002) != 0) {
    return zend_call_stack_get_openbsd_vm(stack);
  }

  return zend_call_stack_get_openbsd_pthread(stack);
}

#else
static bool zend_call_stack_get_openbsd(zend_call_stack *stack)
{
  return false;
}
#endif /* defined(__OpenBSD__) */
#if defined(__HAIKU__)
static bool zend_call_stack_get_haiku(zend_call_stack *stack)
{
  thread_id id;
  thread_info ti;
  size_t guard_size;

  // unlikely, main thread ought to be always available but we never know
  if ((id = find_thread(NULL)) == B_NAME_NOT_FOUND || get_thread_info(id, &ti) != B_OK) {
    return false;
  }

  // USER_STACK_GUARD_SIZE
  guard_size = sysconf(_SC_PAGESIZE) * 4;

  stack->base = ti.stack_end;
  stack->max_size = ((size_t)ti.stack_end - (size_t)ti.stack_base) - guard_size;

  return true;
}
#else
static bool zend_call_stack_get_haiku(zend_call_stack *stack)
{
  return false;
}
#endif /* defined(__HAIKU__) */

#if defined(__NetBSD__)
# ifdef HAVE_PTHREAD_GETATTR_NP
static bool zend_call_stack_get_netbsd_pthread(zend_call_stack *stack)
{
  pthread_attr_t attr;
  int error;
  void *addr;
  size_t max_size, guard_size;

  error = pthread_getattr_np(pthread_self(), &attr);
  if (error) {
    return false;
  }

  error = pthread_attr_getstack(&attr, &addr, &max_size);
  if (error) {
    pthread_attr_destroy(&attr);
    return false;
  }

  error = pthread_attr_getguardsize(&attr, &guard_size);
  if (error) {
    pthread_attr_destroy(&attr);
    return false;
  }

  addr = (char *)addr + guard_size;
  max_size -= guard_size;

  stack->base = (char *)addr + max_size;
  stack->max_size = max_size;

  pthread_attr_destroy(&attr);
  return true;
}
# else
static bool zend_call_stack_get_netbsd_pthread(zend_call_stack *stack)
{
  return false;
}
# endif /* HAVE_PTHREAD_GETATTR_NP */
static bool zend_call_stack_get_netbsd_vm(zend_call_stack *stack, void **ptr)
{
  /**
   * NetBSD supports procfs in a similar fashion as Linux
   * however NetBSD's mid/long term plan is to remove it completely.
   */
  char *start, *end;
  struct kinfo_vmentry *entry;
  size_t len, max_size;
  uintptr_t addr_on_stack = (uintptr_t) zend_call_stack_position();
  int mib[5] = { CTL_VM, VM_PROC, VM_PROC_MAP, getpid(), sizeof(struct kinfo_vmentry) };
  bool found = false;
  struct rlimit rlim;

  if (sysctl(mib, 5, NULL, &len, NULL, 0) != 0) {
    return false;
  }

  // kinfo_getvmmap uses the same formula, only we do not want to rely on libkvm
  len = len * 4 / 3 ;
  *ptr = malloc(len);

  if (sysctl(mib, 5, *ptr, &len, NULL, 0) != 0) {
    return false;
  }

  start = (char *)*ptr;
  end = start + len;

  while (start < end) {
    entry = (struct kinfo_vmentry *)start;
    if (entry->kve_start <= addr_on_stack && entry->kve_end >= addr_on_stack) {
      found = true;
      break;
    }

    start += sizeof(struct kinfo_vmentry);
  }

  if (!found) {
    return false;
  }

  if (getrlimit(RLIMIT_STACK, &rlim) || rlim.rlim_cur == RLIM_INFINITY) {
    return false;
  }

  max_size = rlim.rlim_cur;

  stack->base = (void *)entry->kve_end;
  stack->max_size = max_size;

  return true;
}


static bool zend_call_stack_get_netbsd(zend_call_stack *stack)
{
  if (syscall(SYS__lwp_self) == 1) {
    void *ptr = NULL;
    bool r = zend_call_stack_get_netbsd_vm(stack, &ptr);
    free(ptr);
    return r;
  }

  return zend_call_stack_get_netbsd_pthread(stack);
}
#else
static bool zend_call_stack_get_netbsd(zend_call_stack *stack)
{
  return false;
}
#endif /* defined(__NetBSD__) */

#if defined(__sun)
static bool zend_call_stack_get_solaris_pthread(zend_call_stack *stack)
{
  stack_t s;
  if (thr_stksegment(&s) < 0) {
    return false;
  }

  stack->max_size = s.ss_size;
  stack->base = s.ss_sp;
  return true;
}

#ifdef HAVE_LIBPROC_H
static bool zend_call_stack_get_solaris_proc_maps(zend_call_stack *stack)
{
  uintptr_t addr_on_stack = (uintptr_t) zend_call_stack_position();
  bool found = false, r = false;
  struct ps_prochandle *proc;
  prmap_t *map, *orig;
  struct rlimit rlim;
  char path[PATH_MAX];
  size_t size;
  ssize_t len = -1;
  pid_t pid;
  int error, fd;

  pid = getpid();
  proc = Pgrab(pid, PGRAB_RDONLY, &error);
  if (!proc) {
    return false;
  }

  size = (1 << 20);
  snprintf(path, sizeof(path), "/proc/%d/map", (int)pid);

  if ((fd = open(path, O_RDONLY)) == -1) {
    Prelease(proc, 0);
    return false;
  }

  orig = malloc(size);
  if (!orig) {
    Prelease(proc, 0);
    close(fd);
    return false;
  }

  while (size > 0 && (len = pread(fd, orig, size, 0)) == size) {
    prmap_t *tmp;
    size <<= 1;
    tmp = realloc(orig, size);
    if (!tmp) {
      goto end;
    }
    orig = tmp;
  }

  for (map = orig; len > 0; ++map) {
    if ((uintptr_t)map->pr_vaddr <= addr_on_stack && (uintptr_t)map->pr_vaddr + map->pr_size >= addr_on_stack) {
      found = true;
      break;
    }
    len -= sizeof(*map);
  }

  if (!found) {
    goto end;
  }

  error = getrlimit(RLIMIT_STACK, &rlim);
  if (error || rlim.rlim_cur == RLIM_INFINITY) {
    goto end;
  }

  stack->base = (void *)map->pr_vaddr + map->pr_size;
  stack->max_size = rlim.rlim_cur;
  r = true;

end:
  free(orig);
  Prelease(proc, 0);
  close(fd);
  return r;
}
#endif

static bool zend_call_stack_get_solaris(zend_call_stack *stack)
{
#ifdef HAVE_LIBPROC_H
  if (_lwp_self() == 1) {
    return zend_call_stack_get_solaris_proc_maps(stack);
  }
#endif
  return zend_call_stack_get_solaris_pthread(stack);
}
#else
static bool zend_call_stack_get_solaris(zend_call_stack *stack)
{
  return false;
}
#endif /* defined(__sun) */

#if defined(_AIX)
static bool zend_call_stack_get_aix_pthread(zend_call_stack *stack)
{
#ifdef HAVE_PTHREAD_GETTHRDS_NP
  pthread_t pt = pthread_self();
  struct __pthrdsinfo thread_info = {0};
  /*
   * We don't need the register buffer since we only call the function
   * on our own thread, and since the register buffer is only used for
   * suspended threads...
   */
  int regsz = 0;

  if (pthread_getthrds_np(&pt, PTHRDSINFO_QUERY_ALL, &thread_info,
        sizeof(thread_info), NULL, &regsz)) {
    return false;
  }

  /*
   * These can be null in rare situations, allegedly with user-provided
   * stacks with pthread (according to OpenJDK)
   */
  if (!(thread_info.__pi_stackend && thread_info.__pi_stackaddr)) {
    return false;
  }

  /*
   * The top of the stack (stackend) is not page aligned, there's some
   * internal stuff above it. Thankfully, we don't need page alignment.
   *
   * The size is a little weird. The stacksize field for child threads
   * is smaller than subtracting the bottom (stackaddr) from the top;
   * it's about 0x888 to 0x1888 above stackaddr. I'm assuming it rounds
   * the bottom of the stack to page alignment? The main thread size is
   * the same as end - addr, but it is variable between systems; also
   * assuming there's stuff at the top of the stack that gets taken off,
   * regardless of maximum declared size.
   *
   * A somewhat crude diagram is available here:
   * https://www.ibm.com/docs/en/aix/7.2.0?topic=tuning-thread-environment-variables
   *
   * pthread->pt_stk.st_limit is __pi_stackend,
   * above that is internal pthread junk close to the end of page
   * pthread->pt_stk.st_base is __pi_stackaddr,
   * below that is the red zone
   */
  stack->base = thread_info.__pi_stackend;
  stack->max_size = thread_info.__pi_stackend - thread_info.__pi_stackaddr;
  return true;
#else
  /* pthread likely not linked in; default NTS build behaviour */
  return false;
#endif
}

static bool zend_call_stack_get_aix(zend_call_stack *stack)
{
  /*
   * While we could use /proc on AIX (and the implementation basically
   * like the Solaris one, as the procfs is similar), it doesn't work on
   * PASE. The pthread API works even on the main thread, so we should
   * use it when we have pthread linked (always with ZTS, maybe not with
   * NTS builds).
   */
  return zend_call_stack_get_aix_pthread(stack);
}
#else
static bool zend_call_stack_get_aix(zend_call_stack *stack)
{
  return false;
}
#endif /* defined(_AIX) */

/** Get the stack information for the calling thread */
ZEND_API bool zend_call_stack_get(zend_call_stack *stack)
{
  if (zend_call_stack_get_linux(stack)) {
    return true;
  }

  if (zend_call_stack_get_freebsd(stack)) {
    return true;
  }

  if (zend_call_stack_get_win32(stack)) {
    return true;
  }

  if (zend_call_stack_get_macos(stack)) {
    return true;
  }

  if (zend_call_stack_get_openbsd(stack)) {
    return true;
  }

  if (zend_call_stack_get_netbsd(stack)) {
    return true;
  }

  if (zend_call_stack_get_haiku(stack)) {
    return true;
  }

  if (zend_call_stack_get_solaris(stack)) {
    return true;
  }

  if (zend_call_stack_get_aix(stack)) {
    return true;
  }

  return false;
}

#endif /* ZEND_CHECK_STACK_LIMIT */

Coverage Report

Created: 2026-10-28 06:20