Fix getpass fflush_unlocked namespace (bug 18540).
[glibc.git] / hurd / sigunwind.c
blob3a62fb5fb9486b826d277accfe180a18c6db2f16
1 /* longjmp cleanup function for unwinding past signal handlers.
2 Copyright (C) 1995-2015 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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.
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.
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 <http://www.gnu.org/licenses/>. */
19 #include <hurd.h>
20 #include <thread_state.h>
21 #include <jmpbuf-unwind.h>
22 #include <assert.h>
23 #include <stdint.h>
26 /* _hurd_setup_sighandler puts a link on the `active resources' chain so that
27 _longjmp_unwind will call this function with the `struct sigcontext *'
28 describing the context interrupted by the signal, when `longjmp' is jumping
29 to an environment that unwinds past the interrupted frame. */
31 void
32 _hurdsig_longjmp_from_handler (void *data, jmp_buf env, int val)
34 struct sigcontext *scp = data;
35 struct hurd_sigstate *ss = _hurd_self_sigstate ();
36 int onstack;
37 inline void cleanup (void)
39 /* Destroy the MiG reply port used by the signal handler, and restore
40 the reply port in use by the thread when interrupted. */
41 mach_port_t *reply_port =
42 (mach_port_t *) __hurd_threadvar_location (_HURD_THREADVAR_MIG_REPLY);
43 if (*reply_port)
45 mach_port_t port = *reply_port;
46 /* Assigning MACH_PORT_DEAD here tells libc's mig_get_reply_port
47 not to get another reply port, but avoids mig_dealloc_reply_port
48 trying to deallocate it after the receive fails (which it will,
49 because the reply port will be bogus, regardless). */
50 *reply_port = MACH_PORT_DEAD;
51 __mach_port_destroy (__mach_task_self (), port);
53 *reply_port = scp->sc_reply_port;
56 __spin_lock (&ss->lock);
57 /* We should only ever be called from _longjmp_unwind (in jmp-unwind.c),
58 which calls us inside a critical section. */
59 assert (__spin_lock_locked (&ss->critical_section_lock));
60 /* Are we on the alternate signal stack now? */
61 onstack = (ss->sigaltstack.ss_flags & SS_ONSTACK);
62 __spin_unlock (&ss->lock);
64 if (onstack && ! scp->sc_onstack)
66 /* We are unwinding off the signal stack. We must use sigreturn to
67 do it robustly. Mutate the sigcontext so that when sigreturn
68 resumes from that context, it will be as if `__longjmp (ENV, VAL)'
69 were done. */
71 struct hurd_userlink *link;
73 inline uintptr_t demangle_ptr (uintptr_t x)
75 # ifdef PTR_DEMANGLE
76 PTR_DEMANGLE (x);
77 # endif
78 return x;
81 /* Continue _longjmp_unwind's job of running the unwind
82 forms for frames being unwound, since we will not
83 return to its loop like this one, which called us. */
84 for (link = ss->active_resources;
85 link && _JMPBUF_UNWINDS (env[0].__jmpbuf, link, demangle_ptr);
86 link = link->thread.next)
87 if (_hurd_userlink_unlink (link))
89 if (link->cleanup == &_hurdsig_longjmp_from_handler)
91 /* We are unwinding past another signal handler invocation.
92 Just finish the cleanup for this (inner) one, and then
93 swap SCP to restore to the outer context. */
94 cleanup ();
95 scp = link->cleanup_data;
97 else
98 (*link->cleanup) (link->cleanup_data, env, val);
101 #define sc_machine_thread_state paste(sc_,machine_thread_state)
102 #define paste(a,b) paste1(a,b)
103 #define paste1(a,b) a##b
105 /* There are no more unwind forms to be run!
106 Now we can just have the sigreturn do the longjmp for us. */
107 _hurd_longjmp_thread_state
108 ((struct machine_thread_state *) &scp->sc_machine_thread_state,
109 env, val);
111 /* Restore to the same current signal mask. If sigsetjmp saved the
112 mask, longjmp has already restored it as desired; if not, we
113 should leave it as it is. */
114 scp->sc_mask = ss->blocked;
116 /* sigreturn expects the link added by _hurd_setup_sighandler
117 to still be there, but _longjmp_unwind removed it just before
118 calling us. Put it back now so sigreturn can find it. */
119 link = (void *) &scp[1];
120 assert (! link->resource.next && ! link->resource.prevp);
121 assert (link->thread.next == ss->active_resources);
122 assert (link->thread.prevp == &ss->active_resources);
123 if (link->thread.next)
124 link->thread.next->thread.prevp = &link->thread.next;
125 ss->active_resources = link;
127 /* We must momentarily exit the critical section so that sigreturn
128 does not get upset with us. But we don't want signal handlers
129 running right now, because we are presently in the bogus state of
130 having run all the unwind forms back to ENV's frame, but our SP is
131 still inside those unwound frames. */
132 __spin_lock (&ss->lock);
133 __spin_unlock (&ss->critical_section_lock);
134 ss->blocked = ~(sigset_t) 0 & ~_SIG_CANT_MASK;
135 __spin_unlock (&ss->lock);
137 /* Restore to the modified signal context that now
138 performs `longjmp (ENV, VAL)'. */
139 __sigreturn (scp);
140 assert (! "sigreturn returned!");
143 /* We are not unwinding off the alternate signal stack. So nothing
144 really funny is going on here. We can just clean up this handler
145 frame and let _longjmp_unwind continue unwinding. */
146 cleanup ();
147 ss->intr_port = scp->sc_intr_port;