1 /* Copyright (C) 1991-2023 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/msg.h>
23 #include <stdlib.h>
24 #include <string.h>
25
26 /* This is run on the thread stack after restoring it, to be able to
27 unlock SS off sigstack. */
28 static void
29 __sigreturn2 (int *usp, struct sigcontext *scp)
30 {
31 mach_port_t reply_port;
32 struct hurd_sigstate *ss;
33
34 /* We know the sigstate must be initialized by the call below, but the
35 compiler does not. Help it out a little bit by eliding the check that
36 _hurd_self_sigstate makes otherwise. */
37 ss = THREAD_GETMEM (THREAD_SELF, _hurd_sigstate);
38 _hurd_sigstate_unlock (ss);
39
40 /* Destroy the MiG reply port used by the signal handler, and restore the
41 reply port in use by the thread when interrupted.
42
43 We cannot use the original reply port for our RPCs that we do here, since
44 we could unexpectedly receive/consume a reply message meant for the user
45 (in particular, msg_sig_post_reply), and also since we would deallocate
46 the port if *our* RPC fails, which we don't want to do since the user
47 still has the old name. And so, temporarily set MACH_PORT_DEAD as our
48 reply name, and make sure destroying the port is the very last RPC we
49 do. */
50 reply_port = THREAD_GETMEM (THREAD_SELF, reply_port);
51 THREAD_SETMEM (THREAD_SELF, reply_port, MACH_PORT_DEAD);
52 if (__glibc_likely (MACH_PORT_VALID (reply_port)))
53 (void) __mach_port_mod_refs (__mach_task_self (), reply_port,
54 MACH_PORT_RIGHT_RECEIVE, -1);
55 THREAD_SETMEM (THREAD_SELF, reply_port, scp->sc_reply_port);
56
57 sp = usp;
58 #define A(line) asm volatile (#line)
59 /* The members in the sigcontext are arranged in this order
60 so we can pop them easily. */
61
62 /* Pop the segment registers (except %cs and %ss, done last). */
63 A (popl %gs);
64 A (popl %fs);
65 A (popl %es);
66 A (popl %ds);
67 /* Pop the general registers. */
68 A (popa);
69 /* Pop the processor flags. */
70 A (popf);
71 /* Return to the saved PC. */
72 A (ret);
73
74 /* Firewall. */
75 A (hlt);
76 #undef A
77 __builtin_unreachable ();
78 }
79
80 int
81 __sigreturn (struct sigcontext *scp)
82 {
83 struct hurd_sigstate *ss;
84 struct hurd_userlink *link = (void *) &scp[1];
85
86 if (__glibc_unlikely (scp == NULL || (scp->sc_mask & _SIG_CANT_MASK)))
87 return __hurd_fail (EINVAL);
88
89 ss = _hurd_self_sigstate ();
90 _hurd_sigstate_lock (ss);
91
92 /* Remove the link on the `active resources' chain added by
93 _hurd_setup_sighandler. Its purpose was to make sure
94 that we got called; now we have, it is done. */
95 _hurd_userlink_unlink (link);
96
97 /* Restore the set of blocked signals, and the intr_port slot. */
98 ss->blocked = scp->sc_mask;
99 ss->intr_port = scp->sc_intr_port;
100
101 /* Check for pending signals that were blocked by the old set. */
102 if (_hurd_sigstate_pending (ss) & ~ss->blocked)
103 {
104 /* There are pending signals that just became unblocked. Wake up the
105 signal thread to deliver them. But first, squirrel away SCP where
106 the signal thread will notice it if it runs another handler, and
107 arrange to have us called over again in the new reality. */
108 ss->context = scp;
109 _hurd_sigstate_unlock (ss);
110 __msg_sig_post (_hurd_msgport, 0, 0, __mach_task_self ());
111 /* If a pending signal was handled, sig_post never returned.
112 If it did return, the pending signal didn't run a handler;
113 proceed as usual. */
114 _hurd_sigstate_lock (ss);
115 ss->context = NULL;
116 }
117
118 if (scp->sc_onstack)
119 ss->sigaltstack.ss_flags &= ~SS_ONSTACK;
120
121 if (scp->sc_fpused)
122 /* Restore the FPU state. Mach conveniently stores the state
123 in the format the i387 `frstor' instruction uses to restore it. */
124 asm volatile ("frstor %0" : : "m" (scp->sc_fpsave));
125
126 {
127 /* There are convenient instructions to pop state off the stack, so we
128 copy the registers onto the user's stack, switch there, pop and
129 return. */
130
131 int usp_arg, *usp = (int *) scp->sc_uesp;
132
133 *--usp = scp->sc_eip;
134 *--usp = scp->sc_efl;
135 memcpy (usp -= 12, &scp->sc_i386_thread_state, 12 * sizeof (int));
136 usp_arg = (int) usp;
137
138 *--usp = (int) scp;
139 /* Pass usp to __sigreturn2 so it can unwind itself easily. */
140 *--usp = usp_arg;
141 /* Bogus return address for __sigreturn2 */
142 *--usp = 0;
143 *--usp = (int) __sigreturn2;
144
145 /* Restore thread stack */
146 sp = usp;
147 /* Return into __sigreturn2. */
148 asm volatile ("ret");
149 /* Firewall. */
150 asm volatile ("hlt");
151 }
152
153 /* NOTREACHED */
154 return -1;
155 }
156
157 weak_alias (__sigreturn, sigreturn)