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      1 /* This test program is part of GDB, the GNU debugger.
      2 
      3    Copyright 2015-2024 Free Software Foundation, Inc.
      4 
      5    This program is free software; you can redistribute it and/or modify
      6    it under the terms of the GNU General Public License as published by
      7    the Free Software Foundation; either version 3 of the License, or
      8    (at your option) any later version.
      9 
     10    This program 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
     13    GNU General Public License for more details.
     14 
     15    You should have received a copy of the GNU General Public License
     16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
     17 
     18 /* This is the test program loaded into GDB by the py-unwind test.  */
     19 
     20 #include <stdint.h>
     21 #include <stdio.h>
     22 #include <stdlib.h>
     23 
     24 static void *
     25 swap_value (void **location, void *new_value)
     26 {
     27   void *old_value = *location;
     28   *location = new_value;
     29   return old_value;
     30 }
     31 
     32 static void
     33 bad_layout(void **variable_ptr, void *fp)
     34 {
     35   fprintf (stderr, "First variable should be allocated one word below "
     36            "the frame.  Got variable's address %p, frame at %p instead.\n",
     37            variable_ptr, fp);
     38   abort();
     39 }
     40 
     41 #define MY_FRAME (__builtin_frame_address (0))
     42 
     43 static void
     44 corrupt_frame_inner (void)
     45 {
     46   /* Save outer frame address, then corrupt the unwind chain by
     47      setting the outer frame address in it to self.  This is
     48      ABI-specific: the first word of the frame contains previous frame
     49      address in amd64.  */
     50   void *previous_fp = swap_value ((void **) MY_FRAME, MY_FRAME);
     51 
     52   /* Verify the compiler allocates the first local variable one word
     53      below frame.  This is where the test unwinder expects to find the
     54      correct outer frame address.  */
     55   if (&previous_fp + 1 != (void **) MY_FRAME)
     56     bad_layout (&previous_fp + 1, MY_FRAME);
     57 
     58   /* Now restore it so that we can return.  The test sets the
     59      breakpoint just before this happens, and GDB will not be able to
     60      show the backtrace without JIT reader.  */
     61   swap_value ((void **) MY_FRAME, previous_fp); /* break backtrace-broken */
     62 }
     63 
     64 static void
     65 corrupt_frame_outer (void)
     66 {
     67   /* See above for the explanation of the code here.  This function
     68      corrupts its frame, too, and then calls the inner one.  */
     69   void *previous_fp = swap_value ((void **) MY_FRAME, MY_FRAME);
     70   if (&previous_fp + 1 != (void **) MY_FRAME)
     71     bad_layout (&previous_fp, MY_FRAME);
     72   corrupt_frame_inner ();
     73   swap_value ((void **) MY_FRAME, previous_fp);
     74 }
     75 
     76 int
     77 main ()
     78 {
     79   corrupt_frame_outer ();
     80   return 0;
     81 }
     82