1  /* _longjmp_unwind -- Clean up stack frames unwound by longjmp.  Hurd version.
       2     Copyright (C) 1995-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library 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 GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <jmpbuf-unwind.h>
      20  #include <hurd/userlink.h>
      21  #include <hurd/signal.h>
      22  #include <hurd/sigpreempt.h>
      23  #include <assert.h>
      24  #include <stdint.h>
      25  #include <pointer_guard.h>
      26  
      27  #ifndef _JMPBUF_UNWINDS
      28  #error "<jmpbuf-unwind.h> fails to define _JMPBUF_UNWINDS"
      29  #endif
      30  
      31  static inline uintptr_t
      32  demangle_ptr (uintptr_t x)
      33  {
      34    PTR_DEMANGLE (x);
      35    return x;
      36  }
      37  
      38  /* This function is called by `longjmp' (with its arguments) to restore
      39     active resources to a sane state before the frames code using them are
      40     jumped out of.  */
      41  
      42  void
      43  _longjmp_unwind (jmp_buf env, int val)
      44  {
      45    struct hurd_sigstate *ss = _hurd_self_sigstate ();
      46    struct hurd_userlink *link;
      47  
      48    /* All access to SS->active_resources must take place inside a critical
      49       section where signal handlers cannot run.  */
      50    __spin_lock (&ss->lock);
      51    assert (! __spin_lock_locked (&ss->critical_section_lock));
      52    __spin_lock (&ss->critical_section_lock);
      53  
      54    /* Remove local signal preemptors being unwound past.  */
      55    while (ss->preemptors
      56  	 && _JMPBUF_UNWINDS (env[0].__jmpbuf, ss->preemptors, demangle_ptr))
      57      ss->preemptors = ss->preemptors->next;
      58  
      59    __spin_unlock (&ss->lock);
      60  
      61    /* Iterate over the current thread's list of active resources.
      62       Process the head portion of the list whose links reside
      63       in stack frames being unwound by this jump.  */
      64  
      65    for (link = ss->active_resources;
      66         link && _JMPBUF_UNWINDS (env[0].__jmpbuf, link, demangle_ptr);
      67         link = link->thread.next)
      68      /* Remove this link from the resource's users list,
      69         since the frame using the resource is being unwound.
      70         This call returns nonzero if that was the last user.  */
      71      if (_hurd_userlink_unlink (link))
      72        /* One of the frames being unwound by the longjmp was the last user
      73  	 of its resource.  Call the cleanup function to deallocate it.  */
      74        (*link->cleanup) (link->cleanup_data, env, val);
      75  
      76    _hurd_critical_section_unlock (ss);
      77  }