/* Thread library support for -fsplit-stack.  *//* Copyright (C) 2009-2026 Free Software Foundation, Inc.   Contributed by Ian Lance Taylor <iant@google.com>. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it underthe terms of the GNU General Public License as published by the FreeSoftware Foundation; either version 3, or (at your option) any laterversion. GCC is distributed in the hope that it will be useful, but WITHOUT ANYWARRANTY; without even the implied warranty of MERCHANTABILITY orFITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public Licensefor more details. Under Section 7 of GPL version 3, you are granted additionalpermissions described in the GCC Runtime Library Exception, version3.1, as published by the Free Software Foundation. You should have received a copy of the GNU General Public License anda copy of the GCC Runtime Library Exception along with this program;see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see<http://www.gnu.org/licenses/>.  */ #include "tconfig.h"#include "tsystem.h"#include "coretypes.h"#include "tm.h"#include "libgcc_tm.h" /* If inhibit_libc is defined, we cannot compile this file.  The   effect is that people will not be able to use -fsplit-stack.  That   is much better than failing the build particularly since people   will want to define inhibit_libc while building a compiler which   can build glibc.  */ #ifndef inhibit_libc #include <errno.h>#include <signal.h>#include <pthread.h> #include "generic-morestack.h" /* We declare the pthread functions we need as weak, so that   libgcc_s.so does not need to be linked against -lpthread.  */ extern int pthread_once (pthread_once_t *, void (*) (void))  __attribute__ ((weak)); extern int pthread_key_create (pthread_key_t *, void (*) (void *))  __attribute__ ((weak)); extern int pthread_setspecific (pthread_key_t, const void *)  __attribute__ ((weak)); extern int pthread_sigmask (int, const sigset_t *, sigset_t *)  __attribute__ ((weak)); /* The key for the list of stack segments to free when the thread   exits.  This is created by pthread_key_create.  */ static pthread_key_t segment_list_key; /* Used to only run create_key once.  */ static pthread_once_t create_key_once = PTHREAD_ONCE_INIT; /* Release all the segments for a thread.  This is the destructor   function used by pthread_key_create, and is called when a thread   exits.  */ static voidfree_segments (void* arg){  /* We must block signals in case the signal handler tries to split     the stack.  We leave them blocked while the thread exits.  */  if (pthread_sigmask)    {      sigset_t mask;       sigfillset (&mask);      pthread_sigmask (SIG_BLOCK, &mask, NULL);    }   __morestack_release_segments ((struct stack_segment **) arg, 1);} /* Set up the key for the list of segments.  This is called via   pthread_once.  */ static voidcreate_key (void){  int err;   err = pthread_key_create (&segment_list_key, free_segments);  if (err != 0)    {      static const char msg[] = "pthread_key_create failed: errno ";      __morestack_fail (msg, sizeof msg - 1, err);    }} /* Pass information from the pthread_create wrapper to   stack_split_initialize_thread.  */ struct pthread_create_args{  void *(*start_routine) (void *);  void *arg;}; /* Initialize a thread.  This is called via pthread_create.  It calls   a target dependent function to set up any required stack guard.  */ static void* stack_split_initialize_thread (void *)  __attribute__ ((no_split_stack)); static void *stack_split_initialize_thread (void *varg){  struct pthread_create_args *args = (struct pthread_create_args *) varg;  int err;  void *(*start_routine) (void *);  void *arg;   __stack_split_initialize ();   err = pthread_setspecific (segment_list_key, (void *) &__morestack_segments);  if (err != 0)    {      static const char msg[] = "pthread_setspecific failed: errno ";      __morestack_fail (msg, sizeof msg - 1, err);    }   start_routine = args->start_routine;  arg = args->arg;  free (args);  return (*start_routine) (arg);} /* This function wraps calls to pthread_create to make sure that the   stack guard is initialized for new threads.  FIXME: This hack will   not be necessary if glibc supports -fsplit-stack directly.  */ int __wrap_pthread_create (pthread_t *, const pthread_attr_t *,			   void *(*start_routine) (void *), void *)  __attribute__ ((visibility ("hidden"))); extern int __real_pthread_create (pthread_t *, const pthread_attr_t *,				  void *(*start_routine) (void *), void *)  __attribute__ ((weak)); int__wrap_pthread_create (pthread_t *tid, const pthread_attr_t *attr,		       void *(*start_routine) (void *), void *arg){  int err;  struct pthread_create_args* args;   err = pthread_once (&create_key_once, create_key);  if (err != 0)    {      static const char msg[] = "pthread_once failed: errno ";      __morestack_fail (msg, sizeof msg - 1, err);    }   args = malloc (sizeof (struct pthread_create_args));  if (args == NULL)    return EAGAIN;  args->start_routine = start_routine;  args->arg = arg;  return __real_pthread_create (tid, attr, stack_split_initialize_thread, args);} #endif /* !defined (inhibit_libc) */