/*
   * Handling of different ABIs (personalities).
   *
   * We group personalities into execution domains which have their
   * own handlers for kernel entry points, signal mapping, etc...
   *
   * 2001-05-06	Complete rewrite,  Christoph Hellwig (hch@infradead.org)
   */

  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/kmod.h>
  #include <linux/module.h>
  #include <linux/personality.h>
  #include <linux/sched.h>
  #include <linux/syscalls.h>
  #include <linux/sysctl.h>
  #include <linux/types.h>
  
  
  static void default_handler(int, struct pt_regs *);
  
  static struct exec_domain *exec_domains = &default_exec_domain;
  static DEFINE_RWLOCK(exec_domains_lock);
  
  
  static u_long ident_map[32] = {
  	0,	1,	2,	3,	4,	5,	6,	7,
  	8,	9,	10,	11,	12,	13,	14,	15,
  	16,	17,	18,	19,	20,	21,	22,	23,
  	24,	25,	26,	27,	28,	29,	30,	31
  };
  
  struct exec_domain default_exec_domain = {
  	.name		= "Linux",		/* name */
  	.handler	= default_handler,	/* lcall7 causes a seg fault. */
  	.pers_low	= 0, 			/* PER_LINUX personality. */
  	.pers_high	= 0,			/* PER_LINUX personality. */
  	.signal_map	= ident_map,		/* Identity map signals. */
  	.signal_invmap	= ident_map,		/*  - both ways. */
  };
  
  
  static void
  default_handler(int segment, struct pt_regs *regp)
  {
  	set_personality(0);
  
  	if (current_thread_info()->exec_domain->handler != default_handler)
  		current_thread_info()->exec_domain->handler(segment, regp);
  	else
  		send_sig(SIGSEGV, current, 1);
  }
  
  static struct exec_domain *
  lookup_exec_domain(u_long personality)
  {
  	struct exec_domain *	ep;
  	u_long			pers = personality(personality);
  		
  	read_lock(&exec_domains_lock);
  	for (ep = exec_domains; ep; ep = ep->next) {
  		if (pers >= ep->pers_low && pers <= ep->pers_high)
  			if (try_module_get(ep->module))
  				goto out;
  	}
  
  #ifdef CONFIG_KMOD
  	read_unlock(&exec_domains_lock);
  	request_module("personality-%ld", pers);
  	read_lock(&exec_domains_lock);
  
  	for (ep = exec_domains; ep; ep = ep->next) {
  		if (pers >= ep->pers_low && pers <= ep->pers_high)
  			if (try_module_get(ep->module))
  				goto out;
  	}
  #endif
  
  	ep = &default_exec_domain;
  out:
  	read_unlock(&exec_domains_lock);
  	return (ep);
  }
  
  int
  register_exec_domain(struct exec_domain *ep)
  {
  	struct exec_domain	*tmp;
  	int			err = -EBUSY;
  
  	if (ep == NULL)
  		return -EINVAL;
  
  	if (ep->next != NULL)
  		return -EBUSY;
  
  	write_lock(&exec_domains_lock);
  	for (tmp = exec_domains; tmp; tmp = tmp->next) {
  		if (tmp == ep)
  			goto out;
  	}
  
  	ep->next = exec_domains;
  	exec_domains = ep;
  	err = 0;
  
  out:
  	write_unlock(&exec_domains_lock);
  	return (err);
  }
  
  int
  unregister_exec_domain(struct exec_domain *ep)
  {
  	struct exec_domain	**epp;
  
  	epp = &exec_domains;
  	write_lock(&exec_domains_lock);
  	for (epp = &exec_domains; *epp; epp = &(*epp)->next) {
  		if (ep == *epp)
  			goto unregister;
  	}
  	write_unlock(&exec_domains_lock);
  	return -EINVAL;
  
  unregister:
  	*epp = ep->next;
  	ep->next = NULL;
  	write_unlock(&exec_domains_lock);
  	return 0;
  }
  
  int
  __set_personality(u_long personality)
  {
  	struct exec_domain	*ep, *oep;
  
  	ep = lookup_exec_domain(personality);
  	if (ep == current_thread_info()->exec_domain) {
  		current->personality = personality;

  		module_put(ep->module);

  		return 0;
  	}
  
  	if (atomic_read(&current->fs->count) != 1) {
  		struct fs_struct *fsp, *ofsp;
  
  		fsp = copy_fs_struct(current->fs);
  		if (fsp == NULL) {
  			module_put(ep->module);
  			return -ENOMEM;
  		}
  
  		task_lock(current);
  		ofsp = current->fs;
  		current->fs = fsp;
  		task_unlock(current);
  
  		put_fs_struct(ofsp);
  	}
  
  	/*
  	 * At that point we are guaranteed to be the sole owner of
  	 * current->fs.
  	 */
  
  	current->personality = personality;
  	oep = current_thread_info()->exec_domain;
  	current_thread_info()->exec_domain = ep;
  	set_fs_altroot();
  
  	module_put(oep->module);
  	return 0;
  }
  
  int
  get_exec_domain_list(char *page)
  {
  	struct exec_domain	*ep;
  	int			len = 0;
  
  	read_lock(&exec_domains_lock);
  	for (ep = exec_domains; ep && len < PAGE_SIZE - 80; ep = ep->next)
  		len += sprintf(page + len, "%d-%d\t%-16s\t[%s]
  ",
  			       ep->pers_low, ep->pers_high, ep->name,
  			       module_name(ep->module));
  	read_unlock(&exec_domains_lock);
  	return (len);
  }
  
  asmlinkage long
  sys_personality(u_long personality)
  {
  	u_long old = current->personality;
  
  	if (personality != 0xffffffff) {
  		set_personality(personality);
  		if (current->personality != personality)
  			return -EINVAL;
  	}
  
  	return (long)old;
  }
  
  
  EXPORT_SYMBOL(register_exec_domain);
  EXPORT_SYMBOL(unregister_exec_domain);
  EXPORT_SYMBOL(__set_personality);