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Linux/arch/um/os-Linux/main.c

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  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 
 20 #define PGD_BOUND (4 * 1024 * 1024)
 21 #define STACKSIZE (8 * 1024 * 1024)
 22 #define THREAD_NAME_LEN (256)
 23 
 24 long elf_aux_hwcap;
 25 
 26 static void 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 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 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 extern void scan_elf_aux( char **envp);
106 
107 int __init main(int argc, char **argv, char **envp)
108 {
109         char **new_argv;
110         int ret, i, err;
111 
112         set_stklim();
113 
114         setup_env_path();
115 
116         setsid();
117 
118         new_argv = malloc((argc + 1) * sizeof(char *));
119         if (new_argv == NULL) {
120                 perror("Mallocing argv");
121                 exit(1);
122         }
123         for (i = 0; i < argc; i++) {
124                 new_argv[i] = strdup(argv[i]);
125                 if (new_argv[i] == NULL) {
126                         perror("Mallocing an arg");
127                         exit(1);
128                 }
129         }
130         new_argv[argc] = NULL;
131 
132         /*
133          * Allow these signals to bring down a UML if all other
134          * methods of control fail.
135          */
136         install_fatal_handler(SIGINT);
137         install_fatal_handler(SIGTERM);
138 
139 #ifdef CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
140         scan_elf_aux(envp);
141 #endif
142 
143         change_sig(SIGPIPE, 0);
144         ret = linux_main(argc, argv);
145 
146         /*
147          * Disable SIGPROF - I have no idea why libc doesn't do this or turn
148          * off the profiling time, but UML dies with a SIGPROF just before
149          * exiting when profiling is active.
150          */
151         change_sig(SIGPROF, 0);
152 
153         /*
154          * This signal stuff used to be in the reboot case.  However,
155          * sometimes a timer signal can come in when we're halting (reproducably
156          * when writing out gcov information, presumably because that takes
157          * some time) and cause a segfault.
158          */
159 
160         /* stop timers and set timer signal to be ignored */
161         os_timer_disable();
162 
163         /* disable SIGIO for the fds and set SIGIO to be ignored */
164         err = deactivate_all_fds();
165         if (err)
166                 os_warn("deactivate_all_fds failed, errno = %d\n", -err);
167 
168         /*
169          * Let any pending signals fire now.  This ensures
170          * that they won't be delivered after the exec, when
171          * they are definitely not expected.
172          */
173         unblock_signals();
174 
175         os_info("\n");
176         /* Reboot */
177         if (ret) {
178                 execvp(new_argv[0], new_argv);
179                 perror("Failed to exec kernel");
180                 ret = 1;
181         }
182         return uml_exitcode;
183 }
184 
185 extern void *__real_malloc(int);
186 
187 void *__wrap_malloc(int size)
188 {
189         void *ret;
190 
191         if (!kmalloc_ok)
192                 return __real_malloc(size);
193         else if (size <= UM_KERN_PAGE_SIZE)
194                 /* finding contiguous pages can be hard*/
195                 ret = uml_kmalloc(size, UM_GFP_KERNEL);
196         else ret = vmalloc(size);
197 
198         /*
199          * glibc people insist that if malloc fails, errno should be
200          * set by malloc as well. So we do.
201          */
202         if (ret == NULL)
203                 errno = ENOMEM;
204 
205         return ret;
206 }
207 
208 void *__wrap_calloc(int n, int size)
209 {
210         void *ptr = __wrap_malloc(n * size);
211 
212         if (ptr == NULL)
213                 return NULL;
214         memset(ptr, 0, n * size);
215         return ptr;
216 }
217 
218 extern void __real_free(void *);
219 
220 extern unsigned long high_physmem;
221 
222 void __wrap_free(void *ptr)
223 {
224         unsigned long addr = (unsigned long) ptr;
225 
226         /*
227          * We need to know how the allocation happened, so it can be correctly
228          * freed.  This is done by seeing what region of memory the pointer is
229          * in -
230          *      physical memory - kmalloc/kfree
231          *      kernel virtual memory - vmalloc/vfree
232          *      anywhere else - malloc/free
233          * If kmalloc is not yet possible, then either high_physmem and/or
234          * end_vm are still 0 (as at startup), in which case we call free, or
235          * we have set them, but anyway addr has not been allocated from those
236          * areas. So, in both cases __real_free is called.
237          *
238          * CAN_KMALLOC is checked because it would be bad to free a buffer
239          * with kmalloc/vmalloc after they have been turned off during
240          * shutdown.
241          * XXX: However, we sometimes shutdown CAN_KMALLOC temporarily, so
242          * there is a possibility for memory leaks.
243          */
244 
245         if ((addr >= uml_physmem) && (addr < high_physmem)) {
246                 if (kmalloc_ok)
247                         kfree(ptr);
248         }
249         else if ((addr >= start_vm) && (addr < end_vm)) {
250                 if (kmalloc_ok)
251                         vfree(ptr);
252         }
253         else __real_free(ptr);
254 }
255 

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