gdb/testsuite/gdb.arch/amd64-invalid-stack-top.c

/* This testcase is part of GDB, the GNU debugger.

   Copyright 2014-2021 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program 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 General Public License for more details.

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

#include <sys/mman.h>
#include <unistd.h>
#include <assert.h>

void *global_invalid_ptr = NULL;

void
func2 (void)
{
  /* Replace the current stack pointer and frame pointer with the invalid
     pointer.  */
  asm ("mov %0, %%rsp\n\tmov %0, %%rbp" : : "r" (global_invalid_ptr));

  /* Create a label for a breakpoint.  */
  asm (".global breakpt\nbreakpt:");
}

void
func1 (void *ptr)
{
  global_invalid_ptr = ptr;
  func2 ();
}

/* Finds and returns an invalid pointer, mmaps in a page, grabs a pointer
   to it then unmaps the page again.  This is almost certainly "undefined"
   behaviour, but should be good enough for this small test program.  */

static void *
make_invalid_ptr (void)
{
  int page_size, ans;
  void *ptr;
  
  page_size = getpagesize ();
  ptr =  mmap (0, page_size, PROT_NONE,
	       MAP_PRIVATE | MAP_ANONYMOUS,
	       -1, 0);
  assert (ptr != MAP_FAILED);
  ans = munmap (ptr, page_size);
  assert (ans == 0);

  return ptr;
}

int 
main (void)
{
  void *invalid_ptr;

  invalid_ptr = make_invalid_ptr ();
  func1 (invalid_ptr);
  
  return 0;
}