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
set_stklim(void)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
last_ditch_exit(int sig)43 static void last_ditch_exit(int sig)
44 {
45 uml_cleanup();
46 exit(1);
47 }
48
install_fatal_handler(int sig)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
setup_env_path(void)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
main(int argc,char ** argv,char ** envp)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
__wrap_malloc(int size)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
__wrap_calloc(int n,int size)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
__wrap_free(void * ptr)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