sysdeps/mach/hurd/jmp-unwind.c

   1 /* _longjmp_unwind -- Clean up stack frames unwound by longjmp.  Hurd version.
   2    Copyright (C) 1995-2024 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 }