xref: /linux/arch/um/os-Linux/main.c (revision 36ec807b627b4c0a0a382f0ae48eac7187d14b2b)
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 <as-layout.h>
15 #include <init.h>
16 #include <kern_util.h>
17 #include <os.h>
18 #include <um_malloc.h>
19 #include "internal.h"
20 
21 #define PGD_BOUND (4 * 1024 * 1024)
22 #define STACKSIZE (8 * 1024 * 1024)
23 #define THREAD_NAME_LEN (256)
24 
25 long elf_aux_hwcap;
26 
27 static void set_stklim(void)
28 {
29 	struct rlimit lim;
30 
31 	if (getrlimit(RLIMIT_STACK, &lim) < 0) {
32 		perror("getrlimit");
33 		exit(1);
34 	}
35 	if ((lim.rlim_cur == RLIM_INFINITY) || (lim.rlim_cur > STACKSIZE)) {
36 		lim.rlim_cur = STACKSIZE;
37 		if (setrlimit(RLIMIT_STACK, &lim) < 0) {
38 			perror("setrlimit");
39 			exit(1);
40 		}
41 	}
42 }
43 
44 static void last_ditch_exit(int sig)
45 {
46 	uml_cleanup();
47 	exit(1);
48 }
49 
50 static void install_fatal_handler(int sig)
51 {
52 	struct sigaction action;
53 
54 	/* All signals are enabled in this handler ... */
55 	sigemptyset(&action.sa_mask);
56 
57 	/*
58 	 * ... including the signal being handled, plus we want the
59 	 * handler reset to the default behavior, so that if an exit
60 	 * handler is hanging for some reason, the UML will just die
61 	 * after this signal is sent a second time.
62 	 */
63 	action.sa_flags = SA_RESETHAND | SA_NODEFER;
64 	action.sa_restorer = NULL;
65 	action.sa_handler = last_ditch_exit;
66 	if (sigaction(sig, &action, NULL) < 0) {
67 		os_warn("failed to install handler for signal %d "
68 			"- errno = %d\n", sig, errno);
69 		exit(1);
70 	}
71 }
72 
73 #define UML_LIB_PATH	":" OS_LIB_PATH "/uml"
74 
75 static void setup_env_path(void)
76 {
77 	char *new_path = NULL;
78 	char *old_path = NULL;
79 	int path_len = 0;
80 
81 	old_path = getenv("PATH");
82 	/*
83 	 * if no PATH variable is set or it has an empty value
84 	 * just use the default + /usr/lib/uml
85 	 */
86 	if (!old_path || (path_len = strlen(old_path)) == 0) {
87 		if (putenv("PATH=:/bin:/usr/bin/" UML_LIB_PATH))
88 			perror("couldn't putenv");
89 		return;
90 	}
91 
92 	/* append /usr/lib/uml to the existing path */
93 	path_len += strlen("PATH=" UML_LIB_PATH) + 1;
94 	new_path = malloc(path_len);
95 	if (!new_path) {
96 		perror("couldn't malloc to set a new PATH");
97 		return;
98 	}
99 	snprintf(new_path, path_len, "PATH=%s" UML_LIB_PATH, old_path);
100 	if (putenv(new_path)) {
101 		perror("couldn't putenv to set a new PATH");
102 		free(new_path);
103 	}
104 }
105 
106 int __init main(int argc, char **argv, char **envp)
107 {
108 	char **new_argv;
109 	int ret, i, err;
110 
111 	set_stklim();
112 
113 	setup_env_path();
114 
115 	setsid();
116 
117 	new_argv = malloc((argc + 1) * sizeof(char *));
118 	if (new_argv == NULL) {
119 		perror("Mallocing argv");
120 		exit(1);
121 	}
122 	for (i = 0; i < argc; i++) {
123 		new_argv[i] = strdup(argv[i]);
124 		if (new_argv[i] == NULL) {
125 			perror("Mallocing an arg");
126 			exit(1);
127 		}
128 	}
129 	new_argv[argc] = NULL;
130 
131 	/*
132 	 * Allow these signals to bring down a UML if all other
133 	 * methods of control fail.
134 	 */
135 	install_fatal_handler(SIGINT);
136 	install_fatal_handler(SIGTERM);
137 
138 #ifdef CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
139 	scan_elf_aux(envp);
140 #endif
141 
142 	change_sig(SIGPIPE, 0);
143 	ret = linux_main(argc, argv);
144 
145 	/*
146 	 * Disable SIGPROF - I have no idea why libc doesn't do this or turn
147 	 * off the profiling time, but UML dies with a SIGPROF just before
148 	 * exiting when profiling is active.
149 	 */
150 	change_sig(SIGPROF, 0);
151 
152 	/*
153 	 * This signal stuff used to be in the reboot case.  However,
154 	 * sometimes a timer signal can come in when we're halting (reproducably
155 	 * when writing out gcov information, presumably because that takes
156 	 * some time) and cause a segfault.
157 	 */
158 
159 	/* stop timers and set timer signal to be ignored */
160 	os_timer_disable();
161 
162 	/* disable SIGIO for the fds and set SIGIO to be ignored */
163 	err = deactivate_all_fds();
164 	if (err)
165 		os_warn("deactivate_all_fds failed, errno = %d\n", -err);
166 
167 	/*
168 	 * Let any pending signals fire now.  This ensures
169 	 * that they won't be delivered after the exec, when
170 	 * they are definitely not expected.
171 	 */
172 	unblock_signals();
173 
174 	os_info("\n");
175 	/* Reboot */
176 	if (ret) {
177 		execvp(new_argv[0], new_argv);
178 		perror("Failed to exec kernel");
179 		ret = 1;
180 	}
181 	return uml_exitcode;
182 }
183 
184 extern void *__real_malloc(int);
185 
186 /* workaround for -Wmissing-prototypes warnings */
187 void *__wrap_malloc(int size);
188 void *__wrap_calloc(int n, int size);
189 void __wrap_free(void *ptr);
190 
191 void *__wrap_malloc(int size)
192 {
193 	void *ret;
194 
195 	if (!kmalloc_ok)
196 		return __real_malloc(size);
197 	else if (size <= UM_KERN_PAGE_SIZE)
198 		/* finding contiguous pages can be hard*/
199 		ret = uml_kmalloc(size, UM_GFP_KERNEL);
200 	else ret = vmalloc(size);
201 
202 	/*
203 	 * glibc people insist that if malloc fails, errno should be
204 	 * set by malloc as well. So we do.
205 	 */
206 	if (ret == NULL)
207 		errno = ENOMEM;
208 
209 	return ret;
210 }
211 
212 void *__wrap_calloc(int n, int size)
213 {
214 	void *ptr = __wrap_malloc(n * size);
215 
216 	if (ptr == NULL)
217 		return NULL;
218 	memset(ptr, 0, n * size);
219 	return ptr;
220 }
221 
222 extern void __real_free(void *);
223 
224 extern unsigned long high_physmem;
225 
226 void __wrap_free(void *ptr)
227 {
228 	unsigned long addr = (unsigned long) ptr;
229 
230 	/*
231 	 * We need to know how the allocation happened, so it can be correctly
232 	 * freed.  This is done by seeing what region of memory the pointer is
233 	 * in -
234 	 * 	physical memory - kmalloc/kfree
235 	 *	kernel virtual memory - vmalloc/vfree
236 	 * 	anywhere else - malloc/free
237 	 * If kmalloc is not yet possible, then either high_physmem and/or
238 	 * end_vm are still 0 (as at startup), in which case we call free, or
239 	 * we have set them, but anyway addr has not been allocated from those
240 	 * areas. So, in both cases __real_free is called.
241 	 *
242 	 * CAN_KMALLOC is checked because it would be bad to free a buffer
243 	 * with kmalloc/vmalloc after they have been turned off during
244 	 * shutdown.
245 	 * XXX: However, we sometimes shutdown CAN_KMALLOC temporarily, so
246 	 * there is a possibility for memory leaks.
247 	 */
248 
249 	if ((addr >= uml_physmem) && (addr < high_physmem)) {
250 		if (kmalloc_ok)
251 			kfree(ptr);
252 	}
253 	else if ((addr >= start_vm) && (addr < end_vm)) {
254 		if (kmalloc_ok)
255 			vfree(ptr);
256 	}
257 	else __real_free(ptr);
258 }
259