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

DEFINITIONS

1. set_stklim
2. last_ditch_exit
3. install_fatal_handler
4. setup_env_path
5. main
6. __wrap_malloc
7. __wrap_calloc
8. __wrap_free

   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 }