signalcontext.c revision 330897 
1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2003 Marcel Moolenaar
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30__FBSDID("$FreeBSD: stable/11/lib/libc/amd64/gen/signalcontext.c 330897 2018-03-14 03:19:51Z eadler $");
31
32#include <sys/types.h>
33#include <sys/ucontext.h>
34#include <signal.h>
35#include <stdlib.h>
36#include <strings.h>
37
38typedef void (*handler_t)(uint64_t, uint64_t, uint64_t);
39
40/* Prototypes */
41static void sigctx_wrapper(ucontext_t *ucp, handler_t func, uint64_t *args);
42
43__weak_reference(__signalcontext, signalcontext);
44
45int
46__signalcontext(ucontext_t *ucp, int sig, __sighandler_t *func)
47{
48	uint64_t *args;
49	siginfo_t *sig_si;
50	ucontext_t *sig_uc;
51	uint64_t sp;
52
53	/* Bail out if we don't have a valid ucontext pointer. */
54	if (ucp == NULL)
55		abort();
56
57	/*
58	 * Build a signal frame and copy the arguments of signal handler
59	 * 'func' onto the stack and do the funky stack alignment.
60	 * This means that we need an 8-byte-odd alignment since the ABI expects
61	 * the return address to be pushed, thus breaking the 16 byte alignment.
62	 */
63	sp = (ucp->uc_mcontext.mc_rsp - 128 - sizeof(ucontext_t)) & ~15UL;
64	sig_uc = (ucontext_t *)sp;
65	bcopy(ucp, sig_uc, sizeof(*sig_uc));
66	sp = (sp - sizeof(siginfo_t)) & ~15UL;
67	sig_si = (siginfo_t *)sp;
68	bzero(sig_si, sizeof(*sig_si));
69	sig_si->si_signo = sig;
70	sp -= 3 * sizeof(uint64_t);
71	args = (uint64_t *)sp;
72	args[0] = sig;
73	args[1] = (intptr_t)sig_si;
74	args[2] = (intptr_t)sig_uc;
75	sp -= 16;
76
77	/*
78	 * Setup the ucontext of the signal handler.
79	 */
80	bzero(&ucp->uc_mcontext, sizeof(ucp->uc_mcontext));
81	ucp->uc_mcontext.mc_fpformat = _MC_FPFMT_NODEV;
82	ucp->uc_mcontext.mc_ownedfp = _MC_FPOWNED_NONE;
83	ucp->uc_link = sig_uc;
84	sigdelset(&ucp->uc_sigmask, sig);
85
86	ucp->uc_mcontext.mc_len = sizeof(mcontext_t);
87	ucp->uc_mcontext.mc_rdi = (register_t)ucp;
88	ucp->uc_mcontext.mc_rsi = (register_t)func;
89	ucp->uc_mcontext.mc_rdx = (register_t)args;
90	ucp->uc_mcontext.mc_rbp = (register_t)sp;
91	ucp->uc_mcontext.mc_rbx = (register_t)sp;
92	ucp->uc_mcontext.mc_rsp = (register_t)sp;
93	ucp->uc_mcontext.mc_rip = (register_t)sigctx_wrapper;
94	return (0);
95}
96
97static void
98sigctx_wrapper(ucontext_t *ucp, handler_t func, uint64_t *args)
99{
100
101	(*func)(args[0], args[1], args[2]);
102	if (ucp->uc_link == NULL)
103		exit(0);
104	setcontext((const ucontext_t *)ucp->uc_link);
105	/* should never get here */
106	abort();
107	/* NOTREACHED */
108}
109