gcc/testsuite/c-c++-common/strub-defer-O3.c

/* { dg-do run } */
/* { dg-options "-fstrub=strict -O3" } */
/* { dg-require-effective-target strub } */

/* Check that a strub function called by another strub function defers the
   strubbing to its caller at -O3.  */

#ifndef EXPECT_DEFERRAL
/* Other strub-defer*.c tests override this macro.  */
# define EXPECT_DEFERRAL
#endif

const char test_string[] = "\x55\xde\xad\xbe\xef\xc0\x1d\xca\xfe\x55\xaa";

/* Pad before and after the string on the stack, so that it's not overwritten by
   regular stack use.  */
#define PAD 7

static inline __attribute__ ((__always_inline__, __strub__ ("callable")))
char *
leak_string (void)
{
  /* We use this variable to avoid any stack red zone.  Stack scrubbing covers
     it, but __builtin_stack_address, that we take as a reference, doesn't, so
     if e.g. callable() were to store the string in the red zone, we wouldn't
     find it because it would be outside the range we searched.  */
  typedef void __attribute__ ((__strub__ ("callable"))) callable_t (char *);
  callable_t *f = 0;

  char s[2 * PAD + 1][sizeof (test_string)];
  __builtin_strcpy (s[PAD], test_string);
  asm ("" : "+m" (s), "+r" (f));

  if (__builtin_expect (!f, 1))
    return (char*)__builtin_stack_address ();

  f (s[PAD]);
  return 0;
}

static inline __attribute__ ((__always_inline__, __strub__ ("callable")))
int
look_for_string (char *e)
{
  char *p = (char*)__builtin_stack_address ();

  if (p == e)
    __builtin_abort ();

  if (p > e)
    {
      char *q = p;
      p = e;
      e = q;
    }

  for (char *re = e - sizeof (test_string); p < re; p++)
    for (int i = 0; p[i] == test_string[i]; i++)
      if (i == sizeof (test_string) - 1)
	return i;

  return 0;
}

static __attribute__ ((__strub__ ("at-calls"), __noinline__, __noclone__))
char *
at_calls ()
{
  return leak_string ();
}

static __attribute__ ((__strub__ ("at-calls")))
char *
deferred_at_calls ()
{
  char *ret;
  int i = 1;
  /* Since these test check stack contents above the top of the stack, an
     unexpected asynchronous signal or interrupt might overwrite the bits we
     expect to find and cause spurious fails.  Tolerate one such overall
     spurious fail by retrying.  */
  while (EXPECT_DEFERRAL !look_for_string ((ret = at_calls ())))
    if (!i--) __builtin_abort ();
  return ret;
}

static __attribute__ ((__strub__ ("internal")))
char *
deferred_internal ()
{
  int i = 1;
  char *ret;
  while (EXPECT_DEFERRAL !look_for_string ((ret = at_calls ())))
    if (!i--) __builtin_abort ();
  return ret;
}

int main ()
{
  int i = 1;
  /* These calls should not be subject to spurious fails: whether or not some
     asynchronous event overwrites the scrubbed stack space, the string won't
     remain there.  Unless the asynchronous event happens to write the string
     where we look for it, but what are the odds?  Anyway, it doesn't hurt to
     retry, even if just for symmetry.  */
  while (look_for_string (deferred_at_calls ()))
    if (!i--) __builtin_abort ();
  while (look_for_string (deferred_internal ()))
    if (!i--) __builtin_abort ();
  __builtin_exit (0);
}