/* Thread library support for -fsplit-stack.  */
/* Copyright (C) 2009-2024 Free Software Foundation, Inc.
  Contributed by Ian Lance Taylor <[email protected]>.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC 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
for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a 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 void
free_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 void
create_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) */

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