util.c

  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, PROT_READ | PROT_WRITE) < 0)
 24		panic("protecting stack failed, errno = %d", errno);
 25}
 26
 27int raw(int fd)
 28{
 29	struct termios tt;
 30	int err;
 31
 32	CATCH_EINTR(err = tcgetattr(fd, &tt));
 33	if (err < 0)
 34		return -errno;
 35
 36	cfmakeraw(&tt);
 37
 38	CATCH_EINTR(err = tcsetattr(fd, TCSADRAIN, &tt));
 39	if (err < 0)
 40		return -errno;
 41
 42	/*
 43	 * XXX tcsetattr could have applied only some changes
 44	 * (and cfmakeraw() is a set of changes)
 45	 */
 46	return 0;
 47}
 48
 49void setup_machinename(char *machine_out)
 50{
 51	struct utsname host;
 52
 53	uname(&host);
 54#if IS_ENABLED(CONFIG_UML_X86)
 55# if !IS_ENABLED(CONFIG_64BIT)
 56	if (!strcmp(host.machine, "x86_64")) {
 57		strcpy(machine_out, "i686");
 58		return;
 59	}
 60# else
 61	if (!strcmp(host.machine, "i686")) {
 62		strcpy(machine_out, "x86_64");
 63		return;
 64	}
 65# endif
 66#endif
 67	strcpy(machine_out, host.machine);
 68}
 69
 70void setup_hostinfo(char *buf, int len)
 71{
 72	struct utsname host;
 73
 74	uname(&host);
 75	snprintf(buf, len, "%s %s %s %s %s", host.sysname, host.nodename,
 76		 host.release, host.version, host.machine);
 77}
 78
 79/*
 80 * We cannot use glibc's abort(). It makes use of tgkill() which
 81 * has no effect within UML's kernel threads.
 82 * After that glibc would execute an invalid instruction to kill
 83 * the calling process and UML crashes with SIGSEGV.
 84 */
 85static inline void __attribute__ ((noreturn)) uml_abort(void)
 86{
 87	sigset_t sig;
 88
 89	fflush(NULL);
 90
 91	if (!sigemptyset(&sig) && !sigaddset(&sig, SIGABRT))
 92		sigprocmask(SIG_UNBLOCK, &sig, 0);
 93
 94	for (;;)
 95		if (kill(getpid(), SIGABRT) < 0)
 96			exit(127);
 97}
 98
 99ssize_t os_getrandom(void *buf, size_t len, unsigned int flags)
100{
101	return getrandom(buf, len, flags);
102}
103
104/*
105 * UML helper threads must not handle SIGWINCH/INT/TERM
106 */
107void os_fix_helper_signals(void)
108{
109	signal(SIGWINCH, SIG_IGN);
110	signal(SIGINT, SIG_DFL);
111	signal(SIGTERM, SIG_DFL);
112}
113
114void os_dump_core(void)
115{
116	int pid;
117
118	signal(SIGSEGV, SIG_DFL);
119
120	/*
121	 * We are about to SIGTERM this entire process group to ensure that
122	 * nothing is around to run after the kernel exits.  The
123	 * kernel wants to abort, not die through SIGTERM, so we
124	 * ignore it here.
125	 */
126
127	signal(SIGTERM, SIG_IGN);
128	kill(0, SIGTERM);
129	/*
130	 * Most of the other processes associated with this UML are
131	 * likely sTopped, so give them a SIGCONT so they see the
132	 * SIGTERM.
133	 */
134	kill(0, SIGCONT);
135
136	/*
137	 * Now, having sent signals to everyone but us, make sure they
138	 * die by ptrace.  Processes can survive what's been done to
139	 * them so far - the mechanism I understand is receiving a
140	 * SIGSEGV and segfaulting immediately upon return.  There is
141	 * always a SIGSEGV pending, and (I'm guessing) signals are
142	 * processed in numeric order so the SIGTERM (signal 15 vs
143	 * SIGSEGV being signal 11) is never handled.
144	 *
145	 * Run a waitpid loop until we get some kind of error.
146	 * Hopefully, it's ECHILD, but there's not a lot we can do if
147	 * it's something else.  Tell os_kill_ptraced_process not to
148	 * wait for the child to report its death because there's
149	 * nothing reasonable to do if that fails.
150	 */
151
152	while ((pid = waitpid(-1, NULL, WNOHANG | __WALL)) > 0)
153		os_kill_ptraced_process(pid, 0);
154
155	uml_abort();
156}
157
158void um_early_printk(const char *s, unsigned int n)
159{
160	printf("%.*s", n, s);
161}
162
163static int quiet_info;
164
165static int __init quiet_cmd_param(char *str, int *add)
166{
167	quiet_info = 1;
168	return 0;
169}
170
171__uml_setup("quiet", quiet_cmd_param,
172"quiet\n"
173"    Turns off information messages during boot.\n\n");
174
175/*
176 * The os_info/os_warn functions will be called by helper threads. These
177 * have a very limited stack size and using the libc formatting functions
178 * may overflow the stack.
179 * So pull in the kernel vscnprintf and use that instead with a fixed
180 * on-stack buffer.
181 */
182int vscnprintf(char *buf, size_t size, const char *fmt, va_list args);
183
184void os_info(const char *fmt, ...)
185{
186	char buf[256];
187	va_list list;
188	int len;
189
190	if (quiet_info)
191		return;
192
193	va_start(list, fmt);
194	len = vscnprintf(buf, sizeof(buf), fmt, list);
195	fwrite(buf, len, 1, stderr);
196	va_end(list);
197}
198
199void os_warn(const char *fmt, ...)
200{
201	char buf[256];
202	va_list list;
203	int len;
204
205	va_start(list, fmt);
206	len = vscnprintf(buf, sizeof(buf), fmt, list);
207	fwrite(buf, len, 1, stderr);
208	va_end(list);
209}