1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
4 */
5
6#include <stdarg.h>
7#include <stdio.h>
8#include <stdlib.h>
9#include <unistd.h>
10#include <errno.h>
11#include <signal.h>
12#include <string.h>
13#include <termios.h>
14#include <sys/wait.h>
15#include <sys/mman.h>
16#include <sys/utsname.h>
17#include <sys/random.h>
18#include <init.h>
19#include <os.h>
20
21void stack_protections(unsigned long address)
22{
23	if (mprotect((void *) address, UM_THREAD_SIZE,
24		    PROT_READ | PROT_WRITE | PROT_EXEC) < 0)
25		panic("protecting stack failed, errno = %d", errno);
26}
27
28int raw(int fd)
29{
30	struct termios tt;
31	int err;
32
33	CATCH_EINTR(err = tcgetattr(fd, &tt));
34	if (err < 0)
35		return -errno;
36
37	cfmakeraw(&tt);
38
39	CATCH_EINTR(err = tcsetattr(fd, TCSADRAIN, &tt));
40	if (err < 0)
41		return -errno;
42
43	/*
44	 * XXX tcsetattr could have applied only some changes
45	 * (and cfmakeraw() is a set of changes)
46	 */
47	return 0;
48}
49
50void setup_machinename(char *machine_out)
51{
52	struct utsname host;
53
54	uname(&host);
55#ifdef UML_CONFIG_UML_X86
56# ifndef UML_CONFIG_64BIT
57	if (!strcmp(host.machine, "x86_64")) {
58		strcpy(machine_out, "i686");
59		return;
60	}
61# else
62	if (!strcmp(host.machine, "i686")) {
63		strcpy(machine_out, "x86_64");
64		return;
65	}
66# endif
67#endif
68	strcpy(machine_out, host.machine);
69}
70
71void setup_hostinfo(char *buf, int len)
72{
73	struct utsname host;
74
75	uname(&host);
76	snprintf(buf, len, "%s %s %s %s %s", host.sysname, host.nodename,
77		 host.release, host.version, host.machine);
78}
79
80/*
81 * We cannot use glibc's abort(). It makes use of tgkill() which
82 * has no effect within UML's kernel threads.
83 * After that glibc would execute an invalid instruction to kill
84 * the calling process and UML crashes with SIGSEGV.
85 */
86static inline void __attribute__ ((noreturn)) uml_abort(void)
87{
88	sigset_t sig;
89
90	fflush(NULL);
91
92	if (!sigemptyset(&sig) && !sigaddset(&sig, SIGABRT))
93		sigprocmask(SIG_UNBLOCK, &sig, 0);
94
95	for (;;)
96		if (kill(getpid(), SIGABRT) < 0)
97			exit(127);
98}
99
100ssize_t os_getrandom(void *buf, size_t len, unsigned int flags)
101{
102	return getrandom(buf, len, flags);
103}
104
105/*
106 * UML helper threads must not handle SIGWINCH/INT/TERM
107 */
108void os_fix_helper_signals(void)
109{
110	signal(SIGWINCH, SIG_IGN);
111	signal(SIGINT, SIG_DFL);
112	signal(SIGTERM, SIG_DFL);
113}
114
115void os_dump_core(void)
116{
117	int pid;
118
119	signal(SIGSEGV, SIG_DFL);
120
121	/*
122	 * We are about to SIGTERM this entire process group to ensure that
123	 * nothing is around to run after the kernel exits.  The
124	 * kernel wants to abort, not die through SIGTERM, so we
125	 * ignore it here.
126	 */
127
128	signal(SIGTERM, SIG_IGN);
129	kill(0, SIGTERM);
130	/*
131	 * Most of the other processes associated with this UML are
132	 * likely sTopped, so give them a SIGCONT so they see the
133	 * SIGTERM.
134	 */
135	kill(0, SIGCONT);
136
137	/*
138	 * Now, having sent signals to everyone but us, make sure they
139	 * die by ptrace.  Processes can survive what's been done to
140	 * them so far - the mechanism I understand is receiving a
141	 * SIGSEGV and segfaulting immediately upon return.  There is
142	 * always a SIGSEGV pending, and (I'm guessing) signals are
143	 * processed in numeric order so the SIGTERM (signal 15 vs
144	 * SIGSEGV being signal 11) is never handled.
145	 *
146	 * Run a waitpid loop until we get some kind of error.
147	 * Hopefully, it's ECHILD, but there's not a lot we can do if
148	 * it's something else.  Tell os_kill_ptraced_process not to
149	 * wait for the child to report its death because there's
150	 * nothing reasonable to do if that fails.
151	 */
152
153	while ((pid = waitpid(-1, NULL, WNOHANG | __WALL)) > 0)
154		os_kill_ptraced_process(pid, 0);
155
156	uml_abort();
157}
158
159void um_early_printk(const char *s, unsigned int n)
160{
161	printf("%.*s", n, s);
162}
163
164static int quiet_info;
165
166static int __init quiet_cmd_param(char *str, int *add)
167{
168	quiet_info = 1;
169	return 0;
170}
171
172__uml_setup("quiet", quiet_cmd_param,
173"quiet\n"
174"    Turns off information messages during boot.\n\n");
175
176/*
177 * The os_info/os_warn functions will be called by helper threads. These
178 * have a very limited stack size and using the libc formatting functions
179 * may overflow the stack.
180 * So pull in the kernel vscnprintf and use that instead with a fixed
181 * on-stack buffer.
182 */
183int vscnprintf(char *buf, size_t size, const char *fmt, va_list args);
184
185void os_info(const char *fmt, ...)
186{
187	char buf[256];
188	va_list list;
189	int len;
190
191	if (quiet_info)
192		return;
193
194	va_start(list, fmt);
195	len = vscnprintf(buf, sizeof(buf), fmt, list);
196	fwrite(buf, len, 1, stderr);
197	va_end(list);
198}
199
200void os_warn(const char *fmt, ...)
201{
202	char buf[256];
203	va_list list;
204	int len;
205
206	va_start(list, fmt);
207	len = vscnprintf(buf, sizeof(buf), fmt, list);
208	fwrite(buf, len, 1, stderr);
209	va_end(list);
210}
211