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

/* Copyright (C) 2003-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Jakub Jelinek <jakub@redhat.com>.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library.  If not, see
   <http://www.gnu.org/licenses/>.  */

#include <dlfcn.h>
#include <stdio.h>
#include <unwind.h>
#include <pthreadP.h>

static void *libgcc_s_handle;
static void (*libgcc_s_resume) (struct _Unwind_Exception *exc);
static _Unwind_Reason_Code (*libgcc_s_personality)
  (_Unwind_State, struct _Unwind_Exception *, struct _Unwind_Context *);
static _Unwind_Reason_Code (*libgcc_s_forcedunwind)
  (struct _Unwind_Exception *, _Unwind_Stop_Fn, void *);
static _Unwind_Word (*libgcc_s_getcfa) (struct _Unwind_Context *);

void
__attribute_noinline__
pthread_cancel_init (void)
{
  void *resume, *personality, *forcedunwind, *getcfa;
  void *handle;

  if (__builtin_expect (libgcc_s_handle != NULL, 1))
    {
      /* Force gcc to reload all values.  */
      asm volatile ("" ::: "memory");
      return;
    }

  handle = __libc_dlopen ("libgcc_s.so.1");

  if (handle == NULL
      || (resume = __libc_dlsym (handle, "_Unwind_Resume")) == NULL
      || (personality = __libc_dlsym (handle, "__gcc_personality_v0")) == NULL
      || (forcedunwind = __libc_dlsym (handle, "_Unwind_ForcedUnwind"))
	 == NULL
      || (getcfa = __libc_dlsym (handle, "_Unwind_GetCFA")) == NULL
#ifdef ARCH_CANCEL_INIT
      || ARCH_CANCEL_INIT (handle)
#endif
      )
    __libc_fatal ("libgcc_s.so.1 must be installed for pthread_cancel to work\n");

  libgcc_s_resume = resume;
  libgcc_s_personality = personality;
  libgcc_s_forcedunwind = forcedunwind;
  libgcc_s_getcfa = getcfa;
  /* Make sure libgcc_s_getcfa is written last.  Otherwise,
     pthread_cancel_init might return early even when the pointer the
     caller is interested in is not initialized yet.  */
  atomic_write_barrier ();
  libgcc_s_handle = handle;
}

void
__libc_freeres_fn_section
__unwind_freeres (void)
{
  void *handle = libgcc_s_handle;
  if (handle != NULL)
    {
      libgcc_s_handle = NULL;
      __libc_dlclose (handle);
    }
}

/* It's vitally important that _Unwind_Resume not have a stack frame; the
   ARM unwinder relies on register state at entrance.  So we write this in
   assembly.  */

#define STR1(S) #S
#define STR(S)  STR1(S)

asm (
"	.globl	_Unwind_Resume\n"
"	.type	_Unwind_Resume, %function\n"
"_Unwind_Resume:\n"
"	.cfi_sections .debug_frame\n"
"	" CFI_STARTPROC "\n"
"	push	{r4, r5, r6, lr}\n"
"	" CFI_ADJUST_CFA_OFFSET (16)" \n"
"	" CFI_REL_OFFSET (r4, 0) "\n"
"	" CFI_REL_OFFSET (r5, 4) "\n"
"	" CFI_REL_OFFSET (r6, 8) "\n"
"	" CFI_REL_OFFSET (lr, 12) "\n"
"	" CFI_REMEMBER_STATE "\n"
"	ldr	r4, 1f\n"
"	ldr	r5, 2f\n"
"3:	add	r4, pc, r4\n"
"	ldr	r3, [r4, r5]\n"
"	mov	r6, r0\n"
"	cmp	r3, #0\n"
"	beq	4f\n"
"5:	mov	r0, r6\n"
"	pop	{r4, r5, r6, lr}\n"
"	" CFI_ADJUST_CFA_OFFSET (-16) "\n"
"	" CFI_RESTORE (r4) "\n"
"	" CFI_RESTORE (r5) "\n"
"	" CFI_RESTORE (r6) "\n"
"	" CFI_RESTORE (lr) "\n"
"	bx	r3\n"
"	" CFI_RESTORE_STATE "\n"
"4:	bl	pthread_cancel_init\n"
"	ldr	r3, [r4, r5]\n"
"	b	5b\n"
"	" CFI_ENDPROC "\n"
"	.align 2\n"
"1:	.word	_GLOBAL_OFFSET_TABLE_ - 3b - " STR (PC_OFS) "\n"
"2:	.word	libgcc_s_resume(GOTOFF)\n"
"	.size	_Unwind_Resume, .-_Unwind_Resume\n"
);

_Unwind_Reason_Code
__gcc_personality_v0 (_Unwind_State state,
		      struct _Unwind_Exception *ue_header,
		      struct _Unwind_Context *context)
{
  if (__builtin_expect (libgcc_s_personality == NULL, 0))
    pthread_cancel_init ();

  return libgcc_s_personality (state, ue_header, context);
}

_Unwind_Reason_Code
_Unwind_ForcedUnwind (struct _Unwind_Exception *exc, _Unwind_Stop_Fn stop,
		      void *stop_argument)
{
  if (__builtin_expect (libgcc_s_forcedunwind == NULL, 0))
    pthread_cancel_init ();

  return libgcc_s_forcedunwind (exc, stop, stop_argument);
}

_Unwind_Word
_Unwind_GetCFA (struct _Unwind_Context *context)
{
  if (__builtin_expect (libgcc_s_getcfa == NULL, 0))
    pthread_cancel_init ();

  return libgcc_s_getcfa (context);
}