blob: 1f2a202f5ea23b26172dfed3e17bd7a725893b2f [file] [log] [blame]
/* Thread library support for -fsplit-stack. */
/* Copyright (C) 2009-2021 Free Software Foundation, Inc.
Contributed by Ian Lance Taylor <>.
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
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
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
<>. */
#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 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));
__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) */