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main.c

/*
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <sys/resource.h>
#include "as-layout.h"
#include "init.h"
#include "kern_constants.h"
#include "kern_util.h"
#include "os.h"
#include "um_malloc.h"

#define PGD_BOUND (4 * 1024 * 1024)
#define STACKSIZE (8 * 1024 * 1024)
#define THREAD_NAME_LEN (256)

static void set_stklim(void)
{
      struct rlimit lim;

      if (getrlimit(RLIMIT_STACK, &lim) < 0) {
            perror("getrlimit");
            exit(1);
      }
      if ((lim.rlim_cur == RLIM_INFINITY) || (lim.rlim_cur > STACKSIZE)) {
            lim.rlim_cur = STACKSIZE;
            if (setrlimit(RLIMIT_STACK, &lim) < 0) {
                  perror("setrlimit");
                  exit(1);
            }
      }
}

static __init void do_uml_initcalls(void)
{
      initcall_t *call;

      call = &__uml_initcall_start;
      while (call < &__uml_initcall_end) {
            (*call)();
            call++;
      }
}

static void last_ditch_exit(int sig)
{
      uml_cleanup();
      exit(1);
}

static void install_fatal_handler(int sig)
{
      struct sigaction action;

      /* All signals are enabled in this handler ... */
      sigemptyset(&action.sa_mask);

      /*
       * ... including the signal being handled, plus we want the
       * handler reset to the default behavior, so that if an exit
       * handler is hanging for some reason, the UML will just die
       * after this signal is sent a second time.
       */
      action.sa_flags = SA_RESETHAND | SA_NODEFER;
      action.sa_restorer = NULL;
      action.sa_handler = last_ditch_exit;
      if (sigaction(sig, &action, NULL) < 0) {
            printf("failed to install handler for signal %d - errno = %d\n",
                   errno);
            exit(1);
      }
}

#define UML_LIB_PATH    ":/usr/lib/uml"

static void setup_env_path(void)
{
      char *new_path = NULL;
      char *old_path = NULL;
      int path_len = 0;

      old_path = getenv("PATH");
      /*
       * if no PATH variable is set or it has an empty value
       * just use the default + /usr/lib/uml
       */
      if (!old_path || (path_len = strlen(old_path)) == 0) {
            putenv("PATH=:/bin:/usr/bin/" UML_LIB_PATH);
            return;
      }

      /* append /usr/lib/uml to the existing path */
      path_len += strlen("PATH=" UML_LIB_PATH) + 1;
      new_path = malloc(path_len);
      if (!new_path) {
            perror("coudn't malloc to set a new PATH");
            return;
      }
      snprintf(new_path, path_len, "PATH=%s" UML_LIB_PATH, old_path);
      putenv(new_path);
}

extern int uml_exitcode;

extern void scan_elf_aux( char **envp);

int __init main(int argc, char **argv, char **envp)
{
      char **new_argv;
      int ret, i, err;

      set_stklim();

      setup_env_path();

      new_argv = malloc((argc + 1) * sizeof(char *));
      if (new_argv == NULL) {
            perror("Mallocing argv");
            exit(1);
      }
      for (i = 0; i < argc; i++) {
            new_argv[i] = strdup(argv[i]);
            if (new_argv[i] == NULL) {
                  perror("Mallocing an arg");
                  exit(1);
            }
      }
      new_argv[argc] = NULL;

      /*
       * Allow these signals to bring down a UML if all other
       * methods of control fail.
       */
      install_fatal_handler(SIGINT);
      install_fatal_handler(SIGTERM);
      install_fatal_handler(SIGHUP);

      scan_elf_aux(envp);

      do_uml_initcalls();
      ret = linux_main(argc, argv);

      /*
       * Disable SIGPROF - I have no idea why libc doesn't do this or turn
       * off the profiling time, but UML dies with a SIGPROF just before
       * exiting when profiling is active.
       */
      change_sig(SIGPROF, 0);

      /*
       * This signal stuff used to be in the reboot case.  However,
       * sometimes a SIGVTALRM can come in when we're halting (reproducably
       * when writing out gcov information, presumably because that takes
       * some time) and cause a segfault.
       */

      /* stop timers and set SIGVTALRM to be ignored */
      disable_timer();

      /* disable SIGIO for the fds and set SIGIO to be ignored */
      err = deactivate_all_fds();
      if (err)
            printf("deactivate_all_fds failed, errno = %d\n", -err);

      /*
       * Let any pending signals fire now.  This ensures
       * that they won't be delivered after the exec, when
       * they are definitely not expected.
       */
      unblock_signals();

      /* Reboot */
      if (ret) {
            printf("\n");
            execvp(new_argv[0], new_argv);
            perror("Failed to exec kernel");
            ret = 1;
      }
      printf("\n");
      return uml_exitcode;
}

extern void *__real_malloc(int);

void *__wrap_malloc(int size)
{
      void *ret;

      if (!kmalloc_ok)
            return __real_malloc(size);
      else if (size <= UM_KERN_PAGE_SIZE)
            /* finding contiguous pages can be hard*/
            ret = kmalloc(size, UM_GFP_KERNEL);
      else ret = vmalloc(size);

      /*
       * glibc people insist that if malloc fails, errno should be
       * set by malloc as well. So we do.
       */
      if (ret == NULL)
            errno = ENOMEM;

      return ret;
}

void *__wrap_calloc(int n, int size)
{
      void *ptr = __wrap_malloc(n * size);

      if (ptr == NULL)
            return NULL;
      memset(ptr, 0, n * size);
      return ptr;
}

extern void __real_free(void *);

extern unsigned long high_physmem;

void __wrap_free(void *ptr)
{
      unsigned long addr = (unsigned long) ptr;

      /*
       * We need to know how the allocation happened, so it can be correctly
       * freed.  This is done by seeing what region of memory the pointer is
       * in -
       *    physical memory - kmalloc/kfree
       *    kernel virtual memory - vmalloc/vfree
       *    anywhere else - malloc/free
       * If kmalloc is not yet possible, then either high_physmem and/or
       * end_vm are still 0 (as at startup), in which case we call free, or
       * we have set them, but anyway addr has not been allocated from those
       * areas. So, in both cases __real_free is called.
       *
       * CAN_KMALLOC is checked because it would be bad to free a buffer
       * with kmalloc/vmalloc after they have been turned off during
       * shutdown.
       * XXX: However, we sometimes shutdown CAN_KMALLOC temporarily, so
       * there is a possibility for memory leaks.
       */

      if ((addr >= uml_physmem) && (addr < high_physmem)) {
            if (kmalloc_ok)
                  kfree(ptr);
      }
      else if ((addr >= start_vm) && (addr < end_vm)) {
            if (kmalloc_ok)
                  vfree(ptr);
      }
      else __real_free(ptr);
}

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