1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
4  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
5  */
6 
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 <sys/resource.h>
14 #include <sys/personality.h>
15 #include <as-layout.h>
16 #include <init.h>
17 #include <kern_util.h>
18 #include <os.h>
19 #include <um_malloc.h>
20 #include "internal.h"
21 
22 #define STACKSIZE (8 * 1024 * 1024)
23 
24 long elf_aux_hwcap;
25 
26 static void __init set_stklim(void)
27 {
28 	struct rlimit lim;
29 
30 	if (getrlimit(RLIMIT_STACK, &lim) < 0) {
31 		perror("getrlimit");
32 		exit(1);
33 	}
34 	if ((lim.rlim_cur == RLIM_INFINITY) || (lim.rlim_cur > STACKSIZE)) {
35 		lim.rlim_cur = STACKSIZE;
36 		if (setrlimit(RLIMIT_STACK, &lim) < 0) {
37 			perror("setrlimit");
38 			exit(1);
39 		}
40 	}
41 }
42 
43 static void last_ditch_exit(int sig)
44 {
45 	uml_cleanup();
46 	exit(1);
47 }
48 
49 static void __init install_fatal_handler(int sig)
50 {
51 	struct sigaction action;
52 
53 	/* All signals are enabled in this handler ... */
54 	sigemptyset(&action.sa_mask);
55 
56 	/*
57 	 * ... including the signal being handled, plus we want the
58 	 * handler reset to the default behavior, so that if an exit
59 	 * handler is hanging for some reason, the UML will just die
60 	 * after this signal is sent a second time.
61 	 */
62 	action.sa_flags = SA_RESETHAND | SA_NODEFER;
63 	action.sa_restorer = NULL;
64 	action.sa_handler = last_ditch_exit;
65 	if (sigaction(sig, &action, NULL) < 0) {
66 		os_warn("failed to install handler for signal %d "
67 			"- errno = %d\n", sig, errno);
68 		exit(1);
69 	}
70 }
71 
72 #define UML_LIB_PATH	":" OS_LIB_PATH "/uml"
73 
74 static void __init setup_env_path(void)
75 {
76 	char *new_path = NULL;
77 	char *old_path = NULL;
78 	int path_len = 0;
79 
80 	old_path = getenv("PATH");
81 	/*
82 	 * if no PATH variable is set or it has an empty value
83 	 * just use the default + /usr/lib/uml
84 	 */
85 	if (!old_path || (path_len = strlen(old_path)) == 0) {
86 		if (putenv("PATH=:/bin:/usr/bin/" UML_LIB_PATH))
87 			perror("couldn't putenv");
88 		return;
89 	}
90 
91 	/* append /usr/lib/uml to the existing path */
92 	path_len += strlen("PATH=" UML_LIB_PATH) + 1;
93 	new_path = malloc(path_len);
94 	if (!new_path) {
95 		perror("couldn't malloc to set a new PATH");
96 		return;
97 	}
98 	snprintf(new_path, path_len, "PATH=%s" UML_LIB_PATH, old_path);
99 	if (putenv(new_path)) {
100 		perror("couldn't putenv to set a new PATH");
101 		free(new_path);
102 	}
103 }
104 
105 int __init main(int argc, char **argv, char **envp)
106 {
107 	char **new_argv;
108 	int ret, i, err;
109 
110 	/* Disable randomization and re-exec if it was changed successfully */
111 	ret = personality(PER_LINUX | ADDR_NO_RANDOMIZE);
112 	if (ret >= 0 && (ret & (PER_LINUX | ADDR_NO_RANDOMIZE)) !=
113 			 (PER_LINUX | ADDR_NO_RANDOMIZE)) {
114 		char buf[4096] = {};
115 		ssize_t ret;
116 
117 		ret = readlink("/proc/self/exe", buf, sizeof(buf));
118 		if (ret < 0 || ret >= sizeof(buf)) {
119 			perror("readlink failure");
120 			exit(1);
121 		}
122 		execve(buf, argv, envp);
123 	}
124 
125 	set_stklim();
126 
127 	setup_env_path();
128 
129 	setsid();
130 
131 	new_argv = malloc((argc + 1) * sizeof(char *));
132 	if (new_argv == NULL) {
133 		perror("Mallocing argv");
134 		exit(1);
135 	}
136 	for (i = 0; i < argc; i++) {
137 		new_argv[i] = strdup(argv[i]);
138 		if (new_argv[i] == NULL) {
139 			perror("Mallocing an arg");
140 			exit(1);
141 		}
142 	}
143 	new_argv[argc] = NULL;
144 
145 	/*
146 	 * Allow these signals to bring down a UML if all other
147 	 * methods of control fail.
148 	 */
149 	install_fatal_handler(SIGINT);
150 	install_fatal_handler(SIGTERM);
151 
152 #ifdef CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
153 	scan_elf_aux(envp);
154 #endif
155 
156 	change_sig(SIGPIPE, 0);
157 	ret = linux_main(argc, argv, envp);
158 
159 	/*
160 	 * Disable SIGPROF - I have no idea why libc doesn't do this or turn
161 	 * off the profiling time, but UML dies with a SIGPROF just before
162 	 * exiting when profiling is active.
163 	 */
164 	change_sig(SIGPROF, 0);
165 
166 	/*
167 	 * This signal stuff used to be in the reboot case.  However,
168 	 * sometimes a timer signal can come in when we're halting (reproducably
169 	 * when writing out gcov information, presumably because that takes
170 	 * some time) and cause a segfault.
171 	 */
172 
173 	/* stop timers and set timer signal to be ignored */
174 	os_timer_disable();
175 
176 	/* disable SIGIO for the fds and set SIGIO to be ignored */
177 	err = deactivate_all_fds();
178 	if (err)
179 		os_warn("deactivate_all_fds failed, errno = %d\n", -err);
180 
181 	/*
182 	 * Let any pending signals fire now.  This ensures
183 	 * that they won't be delivered after the exec, when
184 	 * they are definitely not expected.
185 	 */
186 	unblock_signals();
187 
188 	os_info("\n");
189 	/* Reboot */
190 	if (ret) {
191 		execvp(new_argv[0], new_argv);
192 		perror("Failed to exec kernel");
193 		ret = 1;
194 	}
195 	return uml_exitcode;
196 }
197 
198 extern void *__real_malloc(int);
199 extern void __real_free(void *);
200 
201 /* workaround for -Wmissing-prototypes warnings */
202 void *__wrap_malloc(int size);
203 void *__wrap_calloc(int n, int size);
204 void __wrap_free(void *ptr);
205 
206 void *__wrap_malloc(int size)
207 {
208 	void *ret;
209 
210 	if (!kmalloc_ok)
211 		return __real_malloc(size);
212 	else if (size <= UM_KERN_PAGE_SIZE)
213 		/* finding contiguous pages can be hard*/
214 		ret = uml_kmalloc(size, UM_GFP_KERNEL);
215 	else ret = vmalloc(size);
216 
217 	/*
218 	 * glibc people insist that if malloc fails, errno should be
219 	 * set by malloc as well. So we do.
220 	 */
221 	if (ret == NULL)
222 		errno = ENOMEM;
223 
224 	return ret;
225 }
226 
227 void *__wrap_calloc(int n, int size)
228 {
229 	void *ptr = __wrap_malloc(n * size);
230 
231 	if (ptr == NULL)
232 		return NULL;
233 	memset(ptr, 0, n * size);
234 	return ptr;
235 }
236 
237 void __wrap_free(void *ptr)
238 {
239 	unsigned long addr = (unsigned long) ptr;
240 
241 	/*
242 	 * We need to know how the allocation happened, so it can be correctly
243 	 * freed.  This is done by seeing what region of memory the pointer is
244 	 * in -
245 	 * 	physical memory - kmalloc/kfree
246 	 *	kernel virtual memory - vmalloc/vfree
247 	 * 	anywhere else - malloc/free
248 	 * If kmalloc is not yet possible, then either high_physmem and/or
249 	 * end_vm are still 0 (as at startup), in which case we call free, or
250 	 * we have set them, but anyway addr has not been allocated from those
251 	 * areas. So, in both cases __real_free is called.
252 	 *
253 	 * CAN_KMALLOC is checked because it would be bad to free a buffer
254 	 * with kmalloc/vmalloc after they have been turned off during
255 	 * shutdown.
256 	 * XXX: However, we sometimes shutdown CAN_KMALLOC temporarily, so
257 	 * there is a possibility for memory leaks.
258 	 */
259 
260 	if ((addr >= uml_physmem) && (addr < high_physmem)) {
261 		if (kmalloc_ok)
262 			kfree(ptr);
263 	}
264 	else if ((addr >= start_vm) && (addr < end_vm)) {
265 		if (kmalloc_ok)
266 			vfree(ptr);
267 	}
268 	else __real_free(ptr);
269 }
270