libgcc/generic-morestack-thread.c

   1 /* Thread library support for -fsplit-stack.  */
   2 /* Copyright (C) 2009-2021 Free Software Foundation, Inc.
   3    Contributed by Ian Lance Taylor <iant@google.com>.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 Under Section 7 of GPL version 3, you are granted additional
  18 permissions described in the GCC Runtime Library Exception, version
  19 3.1, as published by the Free Software Foundation.
  20
  21 You should have received a copy of the GNU General Public License and
  22 a copy of the GCC Runtime Library Exception along with this program;
  23 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 <http://www.gnu.org/licenses/>.  */
  25
  26 #include "tconfig.h"
  27 #include "tsystem.h"
  28 #include "coretypes.h"
  29 #include "tm.h"
  30 #include "libgcc_tm.h"
  31
  32 /* If inhibit_libc is defined, we cannot compile this file.  The
  33    effect is that people will not be able to use -fsplit-stack.  That
  34    is much better than failing the build particularly since people
  35    will want to define inhibit_libc while building a compiler which
  36    can build glibc.  */
  37
  38 #ifndef inhibit_libc
  39
  40 #include <errno.h>
  41 #include <signal.h>
  42 #include <pthread.h>
  43
  44 #include "generic-morestack.h"
  45
  46 /* We declare the pthread functions we need as weak, so that
  47    libgcc_s.so does not need to be linked against -lpthread.  */
  48
  49 extern int pthread_once (pthread_once_t *, void (*) (void))
  50   __attribute__ ((weak));
  51
  52 extern int pthread_key_create (pthread_key_t *, void (*) (void *))
  53   __attribute__ ((weak));
  54
  55 extern int pthread_setspecific (pthread_key_t, const void *)
  56   __attribute__ ((weak));
  57
  58 extern int pthread_sigmask (int, const sigset_t *, sigset_t *)
  59   __attribute__ ((weak));
  60
  61 /* The key for the list of stack segments to free when the thread
  62    exits.  This is created by pthread_key_create.  */
  63
  64 static pthread_key_t segment_list_key;
  65
  66 /* Used to only run create_key once.  */
  67
  68 static pthread_once_t create_key_once = PTHREAD_ONCE_INIT;
  69
  70 /* Release all the segments for a thread.  This is the destructor
  71    function used by pthread_key_create, and is called when a thread
  72    exits.  */
  73
  74 static void
  75 free_segments (void* arg)
  76 {
  77   /* We must block signals in case the signal handler tries to split
  78      the stack.  We leave them blocked while the thread exits.  */
  79   if (pthread_sigmask)
  80     {
  81       sigset_t mask;
  82
  83       sigfillset (&mask);
  84       pthread_sigmask (SIG_BLOCK, &mask, NULL);
  85     }
  86
  87   __morestack_release_segments ((struct stack_segment **) arg, 1);
  88 }
  89
  90 /* Set up the key for the list of segments.  This is called via
  91    pthread_once.  */
  92
  93 static void
  94 create_key (void)
  95 {
  96   int err;
  97
  98   err = pthread_key_create (&segment_list_key, free_segments);
  99   if (err != 0)
 100     {
 101       static const char msg[] = "pthread_key_create failed: errno ";
 102       __morestack_fail (msg, sizeof msg - 1, err);
 103     }
 104 }
 105
 106 /* Pass information from the pthread_create wrapper to
 107    stack_split_initialize_thread.  */
 108
 109 struct pthread_create_args
 110 {
 111   void *(*start_routine) (void *);
 112   void *arg;
 113 };
 114
 115 /* Initialize a thread.  This is called via pthread_create.  It calls
 116    a target dependent function to set up any required stack guard.  */
 117
 118 static void* stack_split_initialize_thread (void *)
 119   __attribute__ ((no_split_stack));
 120
 121 static void *
 122 stack_split_initialize_thread (void *varg)
 123 {
 124   struct pthread_create_args *args = (struct pthread_create_args *) varg;
 125   int err;
 126   void *(*start_routine) (void *);
 127   void *arg;
 128
 129   __stack_split_initialize ();
 130
 131   err = pthread_setspecific (segment_list_key, (void *) &__morestack_segments);
 132   if (err != 0)
 133     {
 134       static const char msg[] = "pthread_setspecific failed: errno ";
 135       __morestack_fail (msg, sizeof msg - 1, err);
 136     }
 137
 138   start_routine = args->start_routine;
 139   arg = args->arg;
 140   free (args);
 141   return (*start_routine) (arg);
 142 }
 143
 144 /* This function wraps calls to pthread_create to make sure that the
 145    stack guard is initialized for new threads.  FIXME: This hack will
 146    not be necessary if glibc supports -fsplit-stack directly.  */
 147
 148 int __wrap_pthread_create (pthread_t *, const pthread_attr_t *,
 149                            void *(*start_routine) (void *), void *)
 150   __attribute__ ((visibility ("hidden")));
 151
 152 extern int __real_pthread_create (pthread_t *, const pthread_attr_t *,
 153                                   void *(*start_routine) (void *), void *)
 154   __attribute__ ((weak));
 155
 156 int
 157 __wrap_pthread_create (pthread_t *tid, const pthread_attr_t *attr,
 158                        void *(*start_routine) (void *), void *arg)
 159 {
 160   int err;
 161   struct pthread_create_args* args;
 162
 163   err = pthread_once (&create_key_once, create_key);
 164   if (err != 0)
 165     {
 166       static const char msg[] = "pthread_once failed: errno ";
 167       __morestack_fail (msg, sizeof msg - 1, err);
 168     }
 169
 170   args = malloc (sizeof (struct pthread_create_args));
 171   if (args == NULL)
 172     return EAGAIN;
 173   args->start_routine = start_routine;
 174   args->arg = arg;
 175   return __real_pthread_create (tid, attr, stack_split_initialize_thread, args);
 176 }
 177
 178 #endif /* !defined (inhibit_libc) */