1 /* Copyright (C) 1991-2021 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18 register int *sp asm ("%esp");
19
20 #include <hurd.h>
21 #include <hurd/signal.h>
22 #include <hurd/threadvar.h>
23 #include <hurd/msg.h>
24 #include <stdlib.h>
25 #include <string.h>
26
27 /* This is run on the thread stack after restoring it, to be able to
28 unlock SS off sigstack. */
29 static void
__sigreturn2(int * usp)30 __sigreturn2 (int *usp)
31 {
32 struct hurd_sigstate *ss = _hurd_self_sigstate ();
33 _hurd_sigstate_unlock (ss);
34
35 sp = usp;
36 #define A(line) asm volatile (#line)
37 /* The members in the sigcontext are arranged in this order
38 so we can pop them easily. */
39
40 /* Pop the segment registers (except %cs and %ss, done last). */
41 A (popl %gs);
42 A (popl %fs);
43 A (popl %es);
44 A (popl %ds);
45 /* Pop the general registers. */
46 A (popa);
47 /* Pop the processor flags. */
48 A (popf);
49 /* Return to the saved PC. */
50 A (ret);
51
52 /* Firewall. */
53 A (hlt);
54 #undef A
55 }
56
57 int
__sigreturn(struct sigcontext * scp)58 __sigreturn (struct sigcontext *scp)
59 {
60 struct hurd_sigstate *ss;
61 struct hurd_userlink *link = (void *) &scp[1];
62 mach_port_t *reply_port;
63
64 if (scp == NULL || (scp->sc_mask & _SIG_CANT_MASK))
65 {
66 errno = EINVAL;
67 return -1;
68 }
69
70 ss = _hurd_self_sigstate ();
71 _hurd_sigstate_lock (ss);
72
73 /* Remove the link on the `active resources' chain added by
74 _hurd_setup_sighandler. Its purpose was to make sure
75 that we got called; now we have, it is done. */
76 _hurd_userlink_unlink (link);
77
78 /* Restore the set of blocked signals, and the intr_port slot. */
79 ss->blocked = scp->sc_mask;
80 ss->intr_port = scp->sc_intr_port;
81
82 /* Check for pending signals that were blocked by the old set. */
83 if (_hurd_sigstate_pending (ss) & ~ss->blocked)
84 {
85 /* There are pending signals that just became unblocked. Wake up the
86 signal thread to deliver them. But first, squirrel away SCP where
87 the signal thread will notice it if it runs another handler, and
88 arrange to have us called over again in the new reality. */
89 ss->context = scp;
90 _hurd_sigstate_unlock (ss);
91 __msg_sig_post (_hurd_msgport, 0, 0, __mach_task_self ());
92 /* If a pending signal was handled, sig_post never returned.
93 If it did return, the pending signal didn't run a handler;
94 proceed as usual. */
95 _hurd_sigstate_lock (ss);
96 ss->context = NULL;
97 }
98
99 if (scp->sc_onstack)
100 ss->sigaltstack.ss_flags &= ~SS_ONSTACK;
101
102 /* Destroy the MiG reply port used by the signal handler, and restore the
103 reply port in use by the thread when interrupted. */
104 reply_port = &__hurd_local_reply_port;
105 if (*reply_port)
106 {
107 mach_port_t port = *reply_port;
108
109 /* Assigning MACH_PORT_DEAD here tells libc's mig_get_reply_port not to
110 get another reply port, but avoids mig_dealloc_reply_port trying to
111 deallocate it after the receive fails (which it will, because the
112 reply port will be bogus, whether we do this or not). */
113 *reply_port = MACH_PORT_DEAD;
114
115 __mach_port_destroy (__mach_task_self (), port);
116 }
117 *reply_port = scp->sc_reply_port;
118
119 if (scp->sc_fpused)
120 /* Restore the FPU state. Mach conveniently stores the state
121 in the format the i387 `frstor' instruction uses to restore it. */
122 asm volatile ("frstor %0" : : "m" (scp->sc_fpsave));
123
124 {
125 /* There are convenient instructions to pop state off the stack, so we
126 copy the registers onto the user's stack, switch there, pop and
127 return. */
128
129 int *usp = (int *) scp->sc_uesp;
130
131 *--usp = scp->sc_eip;
132 *--usp = scp->sc_efl;
133 memcpy (usp -= 12, &scp->sc_i386_thread_state, 12 * sizeof (int));
134
135 /* Pass usp to __sigreturn2 so it can unwind itself easily. */
136 *(usp-1) = (int) usp;
137 --usp;
138 /* Bogus return address for __sigreturn2 */
139 *--usp = 0;
140 *--usp = (int) __sigreturn2;
141
142 /* Restore thread stack */
143 sp = usp;
144 /* Return into __sigreturn2. */
145 asm volatile ("ret");
146 /* Firewall. */
147 asm volatile ("hlt");
148 }
149
150 /* NOTREACHED */
151 return -1;
152 }
153
154 weak_alias (__sigreturn, sigreturn)
155