unwind functions (blacklist candidates)

[honggyukim]

gcc/libgcc/config/arm/libunwind.S

• UNWIND_WRAPPER in arm mode
• UNWIND_WRAPPER in thumb mode

$ gcc/libgcc/config/arm/libunwind.S
    ...
UNWIND_WRAPPER _Unwind_RaiseException 1
UNWIND_WRAPPER _Unwind_Resume 1
UNWIND_WRAPPER _Unwind_Resume_or_Rethrow 1
UNWIND_WRAPPER _Unwind_ForcedUnwind 3
UNWIND_WRAPPER _Unwind_Backtrace 2
    ...

gcc/libgcc/config/ia64/unwind-ia64.c

$ gcc/libgcc/config/ia64/unwind-ia64.c
    ...
#include "unwind.inc"

#if defined (USE_GAS_SYMVER) && defined (SHARED) && defined (USE_LIBUNWIND_EXCEPTIONS)
alias (_Unwind_Backtrace);
alias (_Unwind_DeleteException);
alias (_Unwind_FindEnclosingFunction);
alias (_Unwind_ForcedUnwind);
alias (_Unwind_GetBSP);
alias (_Unwind_GetCFA);
alias (_Unwind_GetGR);
alias (_Unwind_GetIP);
alias (_Unwind_GetLanguageSpecificData);
alias (_Unwind_GetRegionStart);
alias (_Unwind_RaiseException);
alias (_Unwind_Resume);
alias (_Unwind_Resume_or_Rethrow);
alias (_Unwind_SetGR);
alias (_Unwind_SetIP);
#endif
    ...

gcc/libgcc/unwind.inc

$ gcc/libgcc/unwind.inc
    ...
/* Resume propagation of an existing exception.  This is used after
   e.g. executing cleanup code, and not to implement rethrowing.  */

void LIBGCC2_UNWIND_ATTRIBUTE
_Unwind_Resume (struct _Unwind_Exception *exc)
{
  struct _Unwind_Context this_context, cur_context;
  _Unwind_Reason_Code code;
  unsigned long frames;

  uw_init_context (&this_context);
  cur_context = this_context;

  /* Choose between continuing to process _Unwind_RaiseException
     or _Unwind_ForcedUnwind.  */
  if (exc->private_1 == 0)
    code = _Unwind_RaiseException_Phase2 (exc, &cur_context, &frames);
  else
    code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context, &frames);

  gcc_assert (code == _URC_INSTALL_CONTEXT);

  uw_install_context (&this_context, &cur_context, frames);
}
    ...
/* Perform stack backtrace through unwind data.  */

_Unwind_Reason_Code LIBGCC2_UNWIND_ATTRIBUTE
_Unwind_Backtrace(_Unwind_Trace_Fn trace, void * trace_argument)
{
  struct _Unwind_Context context;
  _Unwind_Reason_Code code;

  uw_init_context (&context);

  while (1)
    {
      _Unwind_FrameState fs;

      /* Set up fs to describe the FDE for the caller of context.  */
      code = uw_frame_state_for (&context, &fs);
      if (code != _URC_NO_REASON && code != _URC_END_OF_STACK)
        return _URC_FATAL_PHASE1_ERROR;

      /* Call trace function.  */
      if ((*trace) (&context, trace_argument) != _URC_NO_REASON)
        return _URC_FATAL_PHASE1_ERROR;

      /* We're done at end of stack.  */
      if (code == _URC_END_OF_STACK)
        break;

      /* Update context to describe the same frame as fs.  */
      uw_update_context (&context, &fs);
    }

  return code;
}
    ...

[honggyukim]

glibc-2.26/sysdeps/arm/backtrace.c

$ cat glibc-2.26/sysdeps/arm/backtrace.c
    ...
static void
init (void)
{
  libgcc_handle = __libc_dlopen ("libgcc_s.so.1");

  if (libgcc_handle == NULL)
    return;

  unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
  unwind_vrs_get = __libc_dlsym (libgcc_handle, "_Unwind_VRS_Get");
  if (unwind_vrs_get == NULL)
    unwind_backtrace = NULL;
}
    ...
int
__backtrace (void **array, int size)
{
  struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };

  if (size <= 0)
    return 0;

#ifdef SHARED
  __libc_once_define (static, once);

  __libc_once (once, init);
  if (unwind_backtrace == NULL)
    return 0;
#endif

  unwind_backtrace (backtrace_helper, &arg);

  if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
    --arg.cnt;
  return arg.cnt != -1 ? arg.cnt : 0;
}
weak_alias (__backtrace, backtrace)
libc_hidden_def (__backtrace)
    ...