sysdeps/nptl/unwind-forcedunwind.c

   1 /* Copyright (C) 2003-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Jakub Jelinek <jakub@redhat.com>.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If
  17    not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include <dlfcn.h>
  20 #include <stdio.h>
  21 #include <unwind.h>
  22 #include <pthreadP.h>
  23 #include <sysdep.h>
  24 #include <gnu/lib-names.h>
  25 #include <unwind-resume.h>
  26
  27 static void *libgcc_s_handle;
  28 void (*__libgcc_s_resume) (struct _Unwind_Exception *exc)
  29   attribute_hidden __attribute__ ((noreturn));
  30 static _Unwind_Reason_Code (*libgcc_s_personality) PERSONALITY_PROTO;
  31 static _Unwind_Reason_Code (*libgcc_s_forcedunwind)
  32   (struct _Unwind_Exception *, _Unwind_Stop_Fn, void *);
  33 static _Unwind_Word (*libgcc_s_getcfa) (struct _Unwind_Context *);
  34
  35 void
  36 __attribute_noinline__
  37 pthread_cancel_init (void)
  38 {
  39   void *resume;
  40   void *personality;
  41   void *forcedunwind;
  42   void *getcfa;
  43   void *handle;
  44
  45   if (__glibc_likely (libgcc_s_handle != NULL))
  46     {
  47       /* Force gcc to reload all values.  */
  48       asm volatile ("" ::: "memory");
  49       return;
  50     }
  51
  52   handle = __libc_dlopen (LIBGCC_S_SO);
  53
  54   if (handle == NULL
  55       || (resume = __libc_dlsym (handle, "_Unwind_Resume")) == NULL
  56       || (personality = __libc_dlsym (handle, "__gcc_personality_v0")) == NULL
  57       || (forcedunwind = __libc_dlsym (handle, "_Unwind_ForcedUnwind"))
  58          == NULL
  59       || (getcfa = __libc_dlsym (handle, "_Unwind_GetCFA")) == NULL
  60 #ifdef ARCH_CANCEL_INIT
  61       || ARCH_CANCEL_INIT (handle)
  62 #endif
  63       )
  64     __libc_fatal (LIBGCC_S_SO " must be installed for pthread_cancel to work\n");
  65
  66   PTR_MANGLE (resume);
  67   __libgcc_s_resume = resume;
  68   PTR_MANGLE (personality);
  69   libgcc_s_personality = personality;
  70   PTR_MANGLE (forcedunwind);
  71   libgcc_s_forcedunwind = forcedunwind;
  72   PTR_MANGLE (getcfa);
  73   libgcc_s_getcfa = getcfa;
  74   /* Make sure libgcc_s_handle is written last.  Otherwise,
  75      pthread_cancel_init might return early even when the pointer the
  76      caller is interested in is not initialized yet.  */
  77   atomic_write_barrier ();
  78   libgcc_s_handle = handle;
  79 }
  80
  81 void
  82 __libc_freeres_fn_section
  83 __unwind_freeres (void)
  84 {
  85   void *handle = libgcc_s_handle;
  86   if (handle != NULL)
  87     {
  88       libgcc_s_handle = NULL;
  89       __libc_dlclose (handle);
  90     }
  91 }
  92
  93 #if !HAVE_ARCH_UNWIND_RESUME
  94 void
  95 _Unwind_Resume (struct _Unwind_Exception *exc)
  96 {
  97   if (__glibc_unlikely (libgcc_s_handle == NULL))
  98     pthread_cancel_init ();
  99   else
 100     atomic_read_barrier ();
 101
 102   void (*resume) (struct _Unwind_Exception *exc) = __libgcc_s_resume;
 103   PTR_DEMANGLE (resume);
 104   resume (exc);
 105 }
 106 #endif
 107
 108 _Unwind_Reason_Code
 109 __gcc_personality_v0 PERSONALITY_PROTO
 110 {
 111   if (__glibc_unlikely (libgcc_s_handle == NULL))
 112     pthread_cancel_init ();
 113   else
 114     atomic_read_barrier ();
 115
 116   __typeof (libgcc_s_personality) personality = libgcc_s_personality;
 117   PTR_DEMANGLE (personality);
 118   return (*personality) PERSONALITY_ARGS;
 119 }
 120
 121 _Unwind_Reason_Code
 122 _Unwind_ForcedUnwind (struct _Unwind_Exception *exc, _Unwind_Stop_Fn stop,
 123                       void *stop_argument)
 124 {
 125   if (__glibc_unlikely (libgcc_s_handle == NULL))
 126     pthread_cancel_init ();
 127   else
 128     atomic_read_barrier ();
 129
 130   _Unwind_Reason_Code (*forcedunwind)
 131     (struct _Unwind_Exception *, _Unwind_Stop_Fn, void *)
 132     = libgcc_s_forcedunwind;
 133   PTR_DEMANGLE (forcedunwind);
 134   return forcedunwind (exc, stop, stop_argument);
 135 }
 136
 137 _Unwind_Word
 138 _Unwind_GetCFA (struct _Unwind_Context *context)
 139 {
 140   if (__glibc_unlikely (libgcc_s_handle == NULL))
 141     pthread_cancel_init ();
 142   else
 143     atomic_read_barrier ();
 144
 145   _Unwind_Word (*getcfa) (struct _Unwind_Context *) = libgcc_s_getcfa;
 146   PTR_DEMANGLE (getcfa);
 147   return getcfa (context);
 148 }