sysdeps/unix/sysv/linux/arm/unwind-forcedunwind.c

   1 /* Copyright (C) 2003-2015 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.  If not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <dlfcn.h>
  20 #include <stdio.h>
  21 #include <unwind.h>
  22 #include <pthreadP.h>
  23
  24 static void *libgcc_s_handle;
  25 static void (*libgcc_s_resume) (struct _Unwind_Exception *exc)
  26   __attribute_used__;
  27 static _Unwind_Reason_Code (*libgcc_s_personality)
  28   (_Unwind_State, struct _Unwind_Exception *, struct _Unwind_Context *);
  29 static _Unwind_Reason_Code (*libgcc_s_forcedunwind)
  30   (struct _Unwind_Exception *, _Unwind_Stop_Fn, void *);
  31 static _Unwind_Word (*libgcc_s_getcfa) (struct _Unwind_Context *);
  32
  33 void
  34 __attribute_noinline__
  35 pthread_cancel_init (void)
  36 {
  37   void *resume, *personality, *forcedunwind, *getcfa;
  38   void *handle;
  39
  40   if (__builtin_expect (libgcc_s_handle != NULL, 1))
  41     {
  42       /* Force gcc to reload all values.  */
  43       asm volatile ("" ::: "memory");
  44       return;
  45     }
  46
  47   handle = __libc_dlopen ("libgcc_s.so.1");
  48
  49   if (handle == NULL
  50       || (resume = __libc_dlsym (handle, "_Unwind_Resume")) == NULL
  51       || (personality = __libc_dlsym (handle, "__gcc_personality_v0")) == NULL
  52       || (forcedunwind = __libc_dlsym (handle, "_Unwind_ForcedUnwind"))
  53          == NULL
  54       || (getcfa = __libc_dlsym (handle, "_Unwind_GetCFA")) == NULL
  55 #ifdef ARCH_CANCEL_INIT
  56       || ARCH_CANCEL_INIT (handle)
  57 #endif
  58       )
  59     __libc_fatal ("libgcc_s.so.1 must be installed for pthread_cancel to work\n");
  60
  61   libgcc_s_resume = resume;
  62   libgcc_s_personality = personality;
  63   libgcc_s_forcedunwind = forcedunwind;
  64   libgcc_s_getcfa = getcfa;
  65   /* Make sure libgcc_s_getcfa is written last.  Otherwise,
  66      pthread_cancel_init might return early even when the pointer the
  67      caller is interested in is not initialized yet.  */
  68   atomic_write_barrier ();
  69   libgcc_s_handle = handle;
  70 }
  71
  72 void
  73 __libc_freeres_fn_section
  74 __unwind_freeres (void)
  75 {
  76   void *handle = libgcc_s_handle;
  77   if (handle != NULL)
  78     {
  79       libgcc_s_handle = NULL;
  80       __libc_dlclose (handle);
  81     }
  82 }
  83
  84 /* It's vitally important that _Unwind_Resume not have a stack frame; the
  85    ARM unwinder relies on register state at entrance.  So we write this in
  86    assembly.  */
  87
  88 #define STR1(S) #S
  89 #define STR(S)  STR1(S)
  90
  91 asm (
  92 "       .globl  _Unwind_Resume\n"
  93 "       .type   _Unwind_Resume, %function\n"
  94 "_Unwind_Resume:\n"
  95 "       .cfi_sections .debug_frame\n"
  96 "       " CFI_STARTPROC "\n"
  97 "       push    {r4, r5, r6, lr}\n"
  98 "       " CFI_ADJUST_CFA_OFFSET (16)" \n"
  99 "       " CFI_REL_OFFSET (r4, 0) "\n"
 100 "       " CFI_REL_OFFSET (r5, 4) "\n"
 101 "       " CFI_REL_OFFSET (r6, 8) "\n"
 102 "       " CFI_REL_OFFSET (lr, 12) "\n"
 103 "       " CFI_REMEMBER_STATE "\n"
 104 "       ldr     r4, 1f\n"
 105 "       ldr     r5, 2f\n"
 106 "3:     add     r4, pc, r4\n"
 107 "       ldr     r3, [r4, r5]\n"
 108 "       mov     r6, r0\n"
 109 "       cmp     r3, #0\n"
 110 "       beq     4f\n"
 111 "5:     mov     r0, r6\n"
 112 "       pop     {r4, r5, r6, lr}\n"
 113 "       " CFI_ADJUST_CFA_OFFSET (-16) "\n"
 114 "       " CFI_RESTORE (r4) "\n"
 115 "       " CFI_RESTORE (r5) "\n"
 116 "       " CFI_RESTORE (r6) "\n"
 117 "       " CFI_RESTORE (lr) "\n"
 118 "       bx      r3\n"
 119 "       " CFI_RESTORE_STATE "\n"
 120 "4:     bl      pthread_cancel_init\n"
 121 "       ldr     r3, [r4, r5]\n"
 122 "       b       5b\n"
 123 "       " CFI_ENDPROC "\n"
 124 "       .align 2\n"
 125 "1:     .word   _GLOBAL_OFFSET_TABLE_ - 3b - " STR (PC_OFS) "\n"
 126 "2:     .word   libgcc_s_resume(GOTOFF)\n"
 127 "       .size   _Unwind_Resume, .-_Unwind_Resume\n"
 128 );
 129
 130 _Unwind_Reason_Code
 131 __gcc_personality_v0 (_Unwind_State state,
 132                       struct _Unwind_Exception *ue_header,
 133                       struct _Unwind_Context *context)
 134 {
 135   if (__builtin_expect (libgcc_s_personality == NULL, 0))
 136     pthread_cancel_init ();
 137
 138   return libgcc_s_personality (state, ue_header, context);
 139 }
 140
 141 _Unwind_Reason_Code
 142 _Unwind_ForcedUnwind (struct _Unwind_Exception *exc, _Unwind_Stop_Fn stop,
 143                       void *stop_argument)
 144 {
 145   if (__builtin_expect (libgcc_s_forcedunwind == NULL, 0))
 146     pthread_cancel_init ();
 147
 148   return libgcc_s_forcedunwind (exc, stop, stop_argument);
 149 }
 150
 151 _Unwind_Word
 152 _Unwind_GetCFA (struct _Unwind_Context *context)
 153 {
 154   if (__builtin_expect (libgcc_s_getcfa == NULL, 0))
 155     pthread_cancel_init ();
 156
 157   return libgcc_s_getcfa (context);
 158 }