exec.c

		spin_unlock(&oldsighand->siglock);
		write_unlock_irq(&tasklist_lock);

		__cleanup_sighand(oldsighand);
	}

	BUG_ON(!thread_group_leader(tsk));
	return 0;
}

/*
 * These functions flushes out all traces of the currently running executable
 * so that a new one can be started
 */
static void flush_old_files(struct files_struct * files)
{
	long j = -1;
	struct fdtable *fdt;

	spin_lock(&files->file_lock);
	for (;;) {
		unsigned long set, i;

		j++;
		i = j * __NFDBITS;
		fdt = files_fdtable(files);
		if (i >= fdt->max_fds)
			break;
		set = fdt->close_on_exec->fds_bits[j];
		if (!set)
			continue;
		fdt->close_on_exec->fds_bits[j] = 0;
		spin_unlock(&files->file_lock);
		for ( ; set ; i++,set >>= 1) {
			if (set & 1) {
				sys_close(i);
			}
		}
		spin_lock(&files->file_lock);

	}
	spin_unlock(&files->file_lock);
}

char *get_task_comm(char *buf, struct task_struct *tsk)
{
	/* buf must be at least sizeof(tsk->comm) in size */
	task_lock(tsk);
	strncpy(buf, tsk->comm, sizeof(tsk->comm));
	task_unlock(tsk);
	return buf;
}
EXPORT_SYMBOL_GPL(get_task_comm);

void set_task_comm(struct task_struct *tsk, char *buf)
{
	task_lock(tsk);

	/*
	 * Threads may access current->comm without holding
	 * the task lock, so write the string carefully.
	 * Readers without a lock may see incomplete new
	 * names but are safe from non-terminating string reads.
	 */
	memset(tsk->comm, 0, TASK_COMM_LEN);
	wmb();
	strlcpy(tsk->comm, buf, sizeof(tsk->comm));
	task_unlock(tsk);
	perf_event_comm(tsk);
}

int flush_old_exec(struct linux_binprm * bprm)
{
	int retval;

	/*
	 * Make sure we have a private signal table and that
	 * we are unassociated from the previous thread group.
	 */
	retval = de_thread(current);
	if (retval)
		goto out;

	set_mm_exe_file(bprm->mm, bprm->file);

	/*
	 * Release all of the old mmap stuff
	 */
	acct_arg_size(bprm, 0);
	retval = exec_mmap(bprm->mm);
	if (retval)
		goto out;

	bprm->mm = NULL;		/* We're using it now */

	set_fs(USER_DS);
	current->flags &= ~(PF_RANDOMIZE | PF_KTHREAD);
	flush_thread();
	current->personality &= ~bprm->per_clear;

	return 0;

out:
	return retval;
}
EXPORT_SYMBOL(flush_old_exec);

void setup_new_exec(struct linux_binprm * bprm)
{
	int i, ch;
	const char *name;
	char tcomm[sizeof(current->comm)];

	arch_pick_mmap_layout(current->mm);

	/* This is the point of no return */
	current->sas_ss_sp = current->sas_ss_size = 0;

	if (current_euid() == current_uid() && current_egid() == current_gid())
		set_dumpable(current->mm, 1);
	else
		set_dumpable(current->mm, suid_dumpable);

	name = bprm->filename;

	/* Copies the binary name from after last slash */
	for (i=0; (ch = *(name++)) != '\0';) {
		if (ch == '/')
			i = 0; /* overwrite what we wrote */
		else
			if (i < (sizeof(tcomm) - 1))
				tcomm[i++] = ch;
	}
	tcomm[i] = '\0';
	set_task_comm(current, tcomm);

	/* Set the new mm task size. We have to do that late because it may
	 * depend on TIF_32BIT which is only updated in flush_thread() on
	 * some architectures like powerpc
	 */
	current->mm->task_size = TASK_SIZE;

	/* install the new credentials */
	if (bprm->cred->uid != current_euid() ||
	    bprm->cred->gid != current_egid()) {
		current->pdeath_signal = 0;
	} else if (file_permission(bprm->file, MAY_READ) ||
		   bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
		set_dumpable(current->mm, suid_dumpable);
	}

	/*
	 * Flush performance counters when crossing a
	 * security domain:
	 */
	if (!get_dumpable(current->mm))
		perf_event_exit_task(current);

	/* An exec changes our domain. We are no longer part of the thread
	   group */

	current->self_exec_id++;
			
	flush_signal_handlers(current, 0);
	flush_old_files(current->files);
}
EXPORT_SYMBOL(setup_new_exec);

/*
 * Prepare credentials and lock ->cred_guard_mutex.
 * install_exec_creds() commits the new creds and drops the lock.
 * Or, if exec fails before, free_bprm() should release ->cred and
 * and unlock.
 */
int prepare_bprm_creds(struct linux_binprm *bprm)
{
	if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
		return -ERESTARTNOINTR;

	bprm->cred = prepare_exec_creds();
	if (likely(bprm->cred))
		return 0;

	mutex_unlock(&current->signal->cred_guard_mutex);
	return -ENOMEM;
}

void free_bprm(struct linux_binprm *bprm)
{
	free_arg_pages(bprm);
	if (bprm->cred) {
		mutex_unlock(&current->signal->cred_guard_mutex);
		abort_creds(bprm->cred);
	}
	kfree(bprm);
}

/*
 * install the new credentials for this executable
 */
void install_exec_creds(struct linux_binprm *bprm)
{
	security_bprm_committing_creds(bprm);

	commit_creds(bprm->cred);
	bprm->cred = NULL;
	/*
	 * cred_guard_mutex must be held at least to this point to prevent
	 * ptrace_attach() from altering our determination of the task's
	 * credentials; any time after this it may be unlocked.
	 */
	security_bprm_committed_creds(bprm);
	mutex_unlock(&current->signal->cred_guard_mutex);
}
EXPORT_SYMBOL(install_exec_creds);

/*
 * determine how safe it is to execute the proposed program
 * - the caller must hold ->cred_guard_mutex to protect against
 *   PTRACE_ATTACH
 */
int check_unsafe_exec(struct linux_binprm *bprm)
{
	struct task_struct *p = current, *t;
	unsigned n_fs;
	int res = 0;

	bprm->unsafe = tracehook_unsafe_exec(p);

	n_fs = 1;
	spin_lock(&p->fs->lock);
	rcu_read_lock();
	for (t = next_thread(p); t != p; t = next_thread(t)) {
		if (t->fs == p->fs)
			n_fs++;
	}
	rcu_read_unlock();

	if (p->fs->users > n_fs) {
		bprm->unsafe |= LSM_UNSAFE_SHARE;
	} else {
		res = -EAGAIN;
		if (!p->fs->in_exec) {
			p->fs->in_exec = 1;
			res = 1;
		}
	}
	spin_unlock(&p->fs->lock);

	return res;
}

/* 
 * Fill the binprm structure from the inode. 
 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
 *
 * This may be called multiple times for binary chains (scripts for example).
 */
int prepare_binprm(struct linux_binprm *bprm)
{
	umode_t mode;
	struct inode * inode = bprm->file->f_path.dentry->d_inode;
	int retval;

	mode = inode->i_mode;
	if (bprm->file->f_op == NULL)
		return -EACCES;

	/* clear any previous set[ug]id data from a previous binary */
	bprm->cred->euid = current_euid();
	bprm->cred->egid = current_egid();

	if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
		/* Set-uid? */
		if (mode & S_ISUID) {
			bprm->per_clear |= PER_CLEAR_ON_SETID;
			bprm->cred->euid = inode->i_uid;
		}

		/* Set-gid? */
		/*
		 * If setgid is set but no group execute bit then this
		 * is a candidate for mandatory locking, not a setgid
		 * executable.
		 */
		if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
			bprm->per_clear |= PER_CLEAR_ON_SETID;
			bprm->cred->egid = inode->i_gid;
		}
	}

	/* fill in binprm security blob */
	retval = security_bprm_set_creds(bprm);
	if (retval)
		return retval;
	bprm->cred_prepared = 1;

	memset(bprm->buf, 0, BINPRM_BUF_SIZE);
	return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
}

EXPORT_SYMBOL(prepare_binprm);

/*
 * Arguments are '\0' separated strings found at the location bprm->p
 * points to; chop off the first by relocating brpm->p to right after
 * the first '\0' encountered.
 */
int remove_arg_zero(struct linux_binprm *bprm)
{
	int ret = 0;
	unsigned long offset;
	char *kaddr;
	struct page *page;

	if (!bprm->argc)
		return 0;

	do {
		offset = bprm->p & ~PAGE_MASK;
		page = get_arg_page(bprm, bprm->p, 0);
		if (!page) {
			ret = -EFAULT;
			goto out;
		}
		kaddr = kmap_atomic(page, KM_USER0);

		for (; offset < PAGE_SIZE && kaddr[offset];
				offset++, bprm->p++)
			;

		kunmap_atomic(kaddr, KM_USER0);
		put_arg_page(page);

		if (offset == PAGE_SIZE)
			free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
	} while (offset == PAGE_SIZE);

	bprm->p++;
	bprm->argc--;
	ret = 0;

out:
	return ret;
}
EXPORT_SYMBOL(remove_arg_zero);

/*
 * cycle the list of binary formats handler, until one recognizes the image
 */
int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
{
	unsigned int depth = bprm->recursion_depth;
	int try,retval;
	struct linux_binfmt *fmt;

	retval = security_bprm_check(bprm);
	if (retval)
		return retval;

	retval = audit_bprm(bprm);
	if (retval)
		return retval;

	retval = -ENOENT;
	for (try=0; try<2; try++) {
		read_lock(&binfmt_lock);
		list_for_each_entry(fmt, &formats, lh) {
			int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
			if (!fn)
				continue;
			if (!try_module_get(fmt->module))
				continue;
			read_unlock(&binfmt_lock);
			retval = fn(bprm, regs);
			/*
			 * Restore the depth counter to its starting value
			 * in this call, so we don't have to rely on every
			 * load_binary function to restore it on return.
			 */
			bprm->recursion_depth = depth;
			if (retval >= 0) {
				if (depth == 0)
					tracehook_report_exec(fmt, bprm, regs);
				put_binfmt(fmt);
				allow_write_access(bprm->file);
				if (bprm->file)
					fput(bprm->file);
				bprm->file = NULL;
				current->did_exec = 1;
				proc_exec_connector(current);
				return retval;
			}
			read_lock(&binfmt_lock);
			put_binfmt(fmt);
			if (retval != -ENOEXEC || bprm->mm == NULL)
				break;
			if (!bprm->file) {
				read_unlock(&binfmt_lock);
				return retval;
			}
		}
		read_unlock(&binfmt_lock);
		if (retval != -ENOEXEC || bprm->mm == NULL) {
			break;
#ifdef CONFIG_MODULES
		} else {
#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
			if (printable(bprm->buf[0]) &&
			    printable(bprm->buf[1]) &&
			    printable(bprm->buf[2]) &&
			    printable(bprm->buf[3]))
				break; /* -ENOEXEC */
			request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
#endif
		}
	}
	return retval;
}

EXPORT_SYMBOL(search_binary_handler);

/*
 * sys_execve() executes a new program.
 */
static int do_execve_common(const char *filename,
				struct user_arg_ptr argv,
				struct user_arg_ptr envp,
				struct pt_regs *regs)
{
	struct linux_binprm *bprm;
	struct file *file;
	struct files_struct *displaced;
	bool clear_in_exec;
	int retval;

	retval = unshare_files(&displaced);
	if (retval)
		goto out_ret;

	retval = -ENOMEM;
	bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
	if (!bprm)
		goto out_files;

	retval = prepare_bprm_creds(bprm);
	if (retval)
		goto out_free;

	retval = check_unsafe_exec(bprm);
	if (retval < 0)
		goto out_free;
	clear_in_exec = retval;
	current->in_execve = 1;

	file = open_exec(filename);
	retval = PTR_ERR(file);
	if (IS_ERR(file))
		goto out_unmark;

	sched_exec();

	bprm->file = file;
	bprm->filename = filename;
	bprm->interp = filename;

	retval = bprm_mm_init(bprm);
	if (retval)
		goto out_file;

	bprm->argc = count(argv, MAX_ARG_STRINGS);
	if ((retval = bprm->argc) < 0)
		goto out;

	bprm->envc = count(envp, MAX_ARG_STRINGS);
	if ((retval = bprm->envc) < 0)
		goto out;

	retval = prepare_binprm(bprm);
	if (retval < 0)
		goto out;

	retval = copy_strings_kernel(1, &bprm->filename, bprm);
	if (retval < 0)
		goto out;

	bprm->exec = bprm->p;
	retval = copy_strings(bprm->envc, envp, bprm);
	if (retval < 0)
		goto out;

	retval = copy_strings(bprm->argc, argv, bprm);
	if (retval < 0)
		goto out;

	retval = search_binary_handler(bprm,regs);
	if (retval < 0)
		goto out;

	/* execve succeeded */
	current->fs->in_exec = 0;
	current->in_execve = 0;
	acct_update_integrals(current);
	free_bprm(bprm);
	if (displaced)
		put_files_struct(displaced);
	return retval;

out:
	if (bprm->mm) {
		acct_arg_size(bprm, 0);
		mmput(bprm->mm);
	}

out_file:
	if (bprm->file) {
		allow_write_access(bprm->file);
		fput(bprm->file);
	}

out_unmark:
	if (clear_in_exec)
		current->fs->in_exec = 0;
	current->in_execve = 0;

out_free:
	free_bprm(bprm);

out_files:
	if (displaced)
		reset_files_struct(displaced);
out_ret:
	return retval;
}

int do_execve(const char *filename,
	const char __user *const __user *__argv,
	const char __user *const __user *__envp,
	struct pt_regs *regs)
{
	struct user_arg_ptr argv = { .ptr.native = __argv };
	struct user_arg_ptr envp = { .ptr.native = __envp };
	return do_execve_common(filename, argv, envp, regs);
}

#ifdef CONFIG_COMPAT
int compat_do_execve(char *filename,
	compat_uptr_t __user *__argv,
	compat_uptr_t __user *__envp,
	struct pt_regs *regs)
{
	struct user_arg_ptr argv = {
		.is_compat = true,
		.ptr.compat = __argv,
	};
	struct user_arg_ptr envp = {
		.is_compat = true,
		.ptr.compat = __envp,
	};
	return do_execve_common(filename, argv, envp, regs);
}
#endif

void set_binfmt(struct linux_binfmt *new)
{
	struct mm_struct *mm = current->mm;

	if (mm->binfmt)
		module_put(mm->binfmt->module);

	mm->binfmt = new;
	if (new)
		__module_get(new->module);
}

EXPORT_SYMBOL(set_binfmt);

static int expand_corename(struct core_name *cn)
{
	char *old_corename = cn->corename;

	cn->size = CORENAME_MAX_SIZE * atomic_inc_return(&call_count);
	cn->corename = krealloc(old_corename, cn->size, GFP_KERNEL);

	if (!cn->corename) {
		kfree(old_corename);
		return -ENOMEM;
	}

	return 0;
}

static int cn_printf(struct core_name *cn, const char *fmt, ...)
{
	char *cur;
	int need;
	int ret;
	va_list arg;

	va_start(arg, fmt);
	need = vsnprintf(NULL, 0, fmt, arg);
	va_end(arg);

	if (likely(need < cn->size - cn->used - 1))
		goto out_printf;

	ret = expand_corename(cn);
	if (ret)
		goto expand_fail;

out_printf:
	cur = cn->corename + cn->used;
	va_start(arg, fmt);
	vsnprintf(cur, need + 1, fmt, arg);
	va_end(arg);
	cn->used += need;
	return 0;

expand_fail:
	return ret;
}

static int cn_print_exe_file(struct core_name *cn)
{
	struct file *exe_file;
	char *pathbuf, *path, *p;
	int ret;

	exe_file = get_mm_exe_file(current->mm);
	if (!exe_file)
		return cn_printf(cn, "(unknown)");

	pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
	if (!pathbuf) {
		ret = -ENOMEM;
		goto put_exe_file;
	}

	path = d_path(&exe_file->f_path, pathbuf, PATH_MAX);
	if (IS_ERR(path)) {
		ret = PTR_ERR(path);
		goto free_buf;
	}

	for (p = path; *p; p++)
		if (*p == '/')
			*p = '!';

	ret = cn_printf(cn, "%s", path);

free_buf:
	kfree(pathbuf);
put_exe_file:
	fput(exe_file);
	return ret;
}

/* format_corename will inspect the pattern parameter, and output a
 * name into corename, which must have space for at least
 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
 */
static int format_corename(struct core_name *cn, long signr)
{
	const struct cred *cred = current_cred();
	const char *pat_ptr = core_pattern;
	int ispipe = (*pat_ptr == '|');
	int pid_in_pattern = 0;
	int err = 0;

	cn->size = CORENAME_MAX_SIZE * atomic_read(&call_count);
	cn->corename = kmalloc(cn->size, GFP_KERNEL);
	cn->used = 0;

	if (!cn->corename)
		return -ENOMEM;

	/* Repeat as long as we have more pattern to process and more output
	   space */
	while (*pat_ptr) {
		if (*pat_ptr != '%') {
			if (*pat_ptr == 0)
				goto out;
			err = cn_printf(cn, "%c", *pat_ptr++);
		} else {
			switch (*++pat_ptr) {
			/* single % at the end, drop that */
			case 0:
				goto out;
			/* Double percent, output one percent */
			case '%':
				err = cn_printf(cn, "%c", '%');
				break;
			/* pid */
			case 'p':
				pid_in_pattern = 1;
				err = cn_printf(cn, "%d",
					      task_tgid_vnr(current));
				break;
			/* uid */
			case 'u':
				err = cn_printf(cn, "%d", cred->uid);
				break;
			/* gid */
			case 'g':
				err = cn_printf(cn, "%d", cred->gid);
				break;
			/* signal that caused the coredump */
			case 's':
				err = cn_printf(cn, "%ld", signr);
				break;
			/* UNIX time of coredump */
			case 't': {
				struct timeval tv;
				do_gettimeofday(&tv);
				err = cn_printf(cn, "%lu", tv.tv_sec);
				break;
			}
			/* hostname */
			case 'h':
				down_read(&uts_sem);
				err = cn_printf(cn, "%s",
					      utsname()->nodename);
				up_read(&uts_sem);
				break;
			/* executable */
			case 'e':
				err = cn_printf(cn, "%s", current->comm);
				break;
			case 'E':
				err = cn_print_exe_file(cn);
				break;
			/* core limit size */
			case 'c':
				err = cn_printf(cn, "%lu",
					      rlimit(RLIMIT_CORE));
				break;
			default:
				break;
			}
			++pat_ptr;
		}

		if (err)
			return err;
	}

	/* Backward compatibility with core_uses_pid:
	 *
	 * If core_pattern does not include a %p (as is the default)
	 * and core_uses_pid is set, then .%pid will be appended to
	 * the filename. Do not do this for piped commands. */
	if (!ispipe && !pid_in_pattern && core_uses_pid) {
		err = cn_printf(cn, ".%d", task_tgid_vnr(current));
		if (err)
			return err;
	}
out:
	return ispipe;
}

static int zap_process(struct task_struct *start, int exit_code)
{
	struct task_struct *t;
	int nr = 0;

	start->signal->flags = SIGNAL_GROUP_EXIT;
	start->signal->group_exit_code = exit_code;
	start->signal->group_stop_count = 0;

	t = start;
	do {
		task_clear_group_stop_pending(t);
		if (t != current && t->mm) {
			sigaddset(&t->pending.signal, SIGKILL);
			signal_wake_up(t, 1);
			nr++;
		}
	} while_each_thread(start, t);

	return nr;
}

static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
				struct core_state *core_state, int exit_code)
{
	struct task_struct *g, *p;
	unsigned long flags;
	int nr = -EAGAIN;

	spin_lock_irq(&tsk->sighand->siglock);
	if (!signal_group_exit(tsk->signal)) {
		mm->core_state = core_state;
		nr = zap_process(tsk, exit_code);
	}
	spin_unlock_irq(&tsk->sighand->siglock);
	if (unlikely(nr < 0))
		return nr;

	if (atomic_read(&mm->mm_users) == nr + 1)
		goto done;
	/*
	 * We should find and kill all tasks which use this mm, and we should
	 * count them correctly into ->nr_threads. We don't take tasklist
	 * lock, but this is safe wrt:
	 *
	 * fork:
	 *	None of sub-threads can fork after zap_process(leader). All
	 *	processes which were created before this point should be
	 *	visible to zap_threads() because copy_process() adds the new
	 *	process to the tail of init_task.tasks list, and lock/unlock
	 *	of ->siglock provides a memory barrier.
	 *
	 * do_exit:
	 *	The caller holds mm->mmap_sem. This means that the task which
	 *	uses this mm can't pass exit_mm(), so it can't exit or clear
	 *	its ->mm.
	 *
	 * de_thread:
	 *	It does list_replace_rcu(&leader->tasks, &current->tasks),
	 *	we must see either old or new leader, this does not matter.
	 *	However, it can change p->sighand, so lock_task_sighand(p)
	 *	must be used. Since p->mm != NULL and we hold ->mmap_sem
	 *	it can't fail.
	 *
	 *	Note also that "g" can be the old leader with ->mm == NULL
	 *	and already unhashed and thus removed from ->thread_group.
	 *	This is OK, __unhash_process()->list_del_rcu() does not
	 *	clear the ->next pointer, we will find the new leader via
	 *	next_thread().
	 */
	rcu_read_lock();
	for_each_process(g) {
		if (g == tsk->group_leader)
			continue;
		if (g->flags & PF_KTHREAD)
			continue;
		p = g;
		do {
			if (p->mm) {
				if (unlikely(p->mm == mm)) {
					lock_task_sighand(p, &flags);
					nr += zap_process(p, exit_code);
					unlock_task_sighand(p, &flags);
				}
				break;
			}
		} while_each_thread(g, p);
	}
	rcu_read_unlock();
done:
	atomic_set(&core_state->nr_threads, nr);
	return nr;
}

static int coredump_wait(int exit_code, struct core_state *core_state)
{
	struct task_struct *tsk = current;
	struct mm_struct *mm = tsk->mm;
	struct completion *vfork_done;
	int core_waiters = -EBUSY;

	init_completion(&core_state->startup);
	core_state->dumper.task = tsk;
	core_state->dumper.next = NULL;

	down_write(&mm->mmap_sem);
	if (!mm->core_state)
		core_waiters = zap_threads(tsk, mm, core_state, exit_code);
	up_write(&mm->mmap_sem);

	if (unlikely(core_waiters < 0))
		goto fail;

	/*
	 * Make sure nobody is waiting for us to release the VM,
	 * otherwise we can deadlock when we wait on each other
	 */
	vfork_done = tsk->vfork_done;
	if (vfork_done) {
		tsk->vfork_done = NULL;
		complete(vfork_done);
	}

	if (core_waiters)
		wait_for_completion(&core_state->startup);
fail:
	return core_waiters;
}

static void coredump_finish(struct mm_struct *mm)
{
	struct core_thread *curr, *next;
	struct task_struct *task;

	next = mm->core_state->dumper.next;
	while ((curr = next) != NULL) {
		next = curr->next;
		task = curr->task;
		/*
		 * see exit_mm(), curr->task must not see
		 * ->task == NULL before we read ->next.
		 */
		smp_mb();
		curr->task = NULL;
		wake_up_process(task);
	}

	mm->core_state = NULL;
}

/*
 * set_dumpable converts traditional three-value dumpable to two flags and
 * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
 * these bits are not changed atomically.  So get_dumpable can observe the
 * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
 * return either old dumpable or new one by paying attention to the order of
 * modifying the bits.
 *
 * dumpable |   mm->flags (binary)
 * old  new | initial interim  final
 * ---------+-----------------------
 *  0    1  |   00      01      01
 *  0    2  |   00      10(*)   11
 *  1    0  |   01      00      00
 *  1    2  |   01      11      11
 *  2    0  |   11      10(*)   00
 *  2    1  |   11      11      01
 *
 * (*) get_dumpable regards interim value of 10 as 11.
 */
void set_dumpable(struct mm_struct *mm, int value)
{
	switch (value) {
	case 0:
		clear_bit(MMF_DUMPABLE, &mm->flags);
		smp_wmb();
		clear_bit(MMF_DUMP_SECURELY, &mm->flags);
		break;
	case 1:
		set_bit(MMF_DUMPABLE, &mm->flags);
		smp_wmb();
		clear_bit(MMF_DUMP_SECURELY, &mm->flags);
		break;
	case 2:
		set_bit(MMF_DUMP_SECURELY, &mm->flags);
		smp_wmb();
		set_bit(MMF_DUMPABLE, &mm->flags);
		break;
	}
}

static int __get_dumpable(unsigned long mm_flags)
{
	int ret;

	ret = mm_flags & MMF_DUMPABLE_MASK;
	return (ret >= 2) ? 2 : ret;
}

int get_dumpable(struct mm_struct *mm)
{
	return __get_dumpable(mm->flags);
}

static void wait_for_dump_helpers(struct file *file)
{
	struct pipe_inode_info *pipe;

	pipe = file->f_path.dentry->d_inode->i_pipe;

	pipe_lock(pipe);
	pipe->readers++;
	pipe->writers--;

	while ((pipe->readers > 1) && (!signal_pending(current))) {
		wake_up_interruptible_sync(&pipe->wait);
		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
		pipe_wait(pipe);
	}

	pipe->readers--;
	pipe->writers++;
	pipe_unlock(pipe);

}


/*
 * umh_pipe_setup
 * helper function to customize the process used
 * to collect the core in userspace.  Specifically
 * it sets up a pipe and installs it as fd 0 (stdin)
 * for the process.  Returns 0 on success, or
 * PTR_ERR on failure.
 * Note that it also sets the core limit to 1.  This
 * is a special value that we use to trap recursive
 * core dumps
 */
static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
{