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Commit a0a7ec30 authored by JANAK DESAI's avatar JANAK DESAI Committed by Linus Torvalds
Browse files

[PATCH] unshare system call -v5: unshare vm 



If vm structure is being shared, allocate a new one and copy information from
the current, shared, structure.

Signed-off-by: default avatarJanak Desai <janak@us.ibm.com>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Cc: Andi Kleen <ak@muc.de>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 741a2951

kernel/fork.c

+56 −31
Original line number Diff line number Diff line
@@ -446,6 +446,55 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm) 
	}

}



/*

 * Allocate a new mm structure and copy contents from the

 * mm structure of the passed in task structure.

 */

static struct mm_struct *dup_mm(struct task_struct *tsk)

{

	struct mm_struct *mm, *oldmm = current->mm;

	int err;



	if (!oldmm)

		return NULL;



	mm = allocate_mm();

	if (!mm)

		goto fail_nomem;



	memcpy(mm, oldmm, sizeof(*mm));



	if (!mm_init(mm))

		goto fail_nomem;



	if (init_new_context(tsk, mm))

		goto fail_nocontext;



	err = dup_mmap(mm, oldmm);

	if (err)

		goto free_pt;



	mm->hiwater_rss = get_mm_rss(mm);

	mm->hiwater_vm = mm->total_vm;



	return mm;



free_pt:

	mmput(mm);



fail_nomem:

	return NULL;



fail_nocontext:

	/*

	 * If init_new_context() failed, we cannot use mmput() to free the mm

	 * because it calls destroy_context()

	 */

	mm_free_pgd(mm);

	free_mm(mm);

	return NULL;

}



static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)

{

	struct mm_struct * mm, *oldmm;
@@ -473,43 +522,17 @@ static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 
	}



	retval = -ENOMEM;

	mm = allocate_mm();

	mm = dup_mm(tsk);

	if (!mm)

		goto fail_nomem;



	/* Copy the current MM stuff.. */

	memcpy(mm, oldmm, sizeof(*mm));

	if (!mm_init(mm))

		goto fail_nomem;



	if (init_new_context(tsk,mm))

		goto fail_nocontext;



	retval = dup_mmap(mm, oldmm);

	if (retval)

		goto free_pt;



	mm->hiwater_rss = get_mm_rss(mm);

	mm->hiwater_vm = mm->total_vm;



good_mm:

	tsk->mm = mm;

	tsk->active_mm = mm;

	return 0;



free_pt:

	mmput(mm);

fail_nomem:

	return retval;



fail_nocontext:

	/*

	 * If init_new_context() failed, we cannot use mmput() to free the mm

	 * because it calls destroy_context()

	 */

	mm_free_pgd(mm);

	free_mm(mm);

	return retval;

}



static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
@@ -1423,18 +1446,20 @@ static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct ** 
}



/*

 * Unsharing of vm for tasks created with CLONE_VM is not supported yet

 * Unshare vm if it is being shared

 */

static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)

{

	struct mm_struct *mm = current->mm;



	if ((unshare_flags & CLONE_VM) &&

	    (mm && atomic_read(&mm->mm_users) > 1))

		return -EINVAL;

	    (mm && atomic_read(&mm->mm_users) > 1)) {

		*new_mmp = dup_mm(current);

		if (!*new_mmp)

			return -ENOMEM;

	}



	return 0;



}



/*