linux-kernel - Re: [RFC] fs, proc: Introduce the /proc/<pid>/map

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Date:	Thu, 25 Aug 2011 19:01:47 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Vasiliy Kulikov <segoon@...nwall.com>,
	Nathan Lynch <ntl@...ox.com>,
	Oren Laadan <orenl@...columbia.edu>,
	Daniel Lezcano <dlezcano@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	linux-kernel@...r.kernel.org,
	James Bottomley <jbottomley@...allels.com>,
	LINUXFS-ML <linux-fsdevel@...r.kernel.org>,
	containers@...ts.osdl.org, Zan Lynx <zlynx@....org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [RFC] fs, proc: Introduce the /proc/<pid>/map_files/ directory v2

Hello,

On Thu, Aug 25, 2011 at 12:29:44PM +0400, Cyrill Gorcunov wrote:
>  | lr-x------ 1 cyrill cyrill 64 Aug  9 15:25 0x3d73a00000 -> /lib64/ld-2.5.so
>  | lr-x------ 1 cyrill cyrill 64 Aug  9 15:25 0x3d73c1b000 -> /lib64/ld-2.5.so
>  | lr-x------ 1 cyrill cyrill 64 Aug  9 15:25 0x3d73c1c000 -> /lib64/ld-2.5.so
>  | lr-x------ 1 cyrill cyrill 64 Aug  9 15:25 0x3d73e00000 -> /lib64/libc-2.5.so
>  | lr-x------ 1 cyrill cyrill 64 Aug  9 15:25 0x3d73f4e000 -> /lib64/libc-2.5.so

I would prefer if the filename included both start and end addresses
so that it matches the first column of /proc/PID/maps and ls'ing the
directory is more useful.  What do other people think?

> +static int map_files_d_revalidate(struct dentry *dentry, struct nameidata *nd)
> +{
> +	struct task_struct *task;
> +	struct vm_area_struct *vma;
> +	struct mm_struct *mm;
> +	struct inode *inode;
> +
> +	if (nd && nd->flags & LOOKUP_RCU)
> +		return -ECHILD;
> +
> +	inode = dentry->d_inode;
> +	task = get_proc_task(inode);
> +	if (!task)
> +		goto out;
> +
> +	mm = get_task_mm(task);
> +	put_task_struct(task);
> +	if (!mm)
> +		goto out;
> +
> +	down_read(&mm->mmap_sem);
> +	vma = find_exact_vma(mm, PROC_I(inode)->vm_start);
> +	up_read(&mm->mmap_sem);
> +	mmput(mm);
> +
> +	if (vma)
> +		return 1;

Hmm... don't we need the same credential update as
tid_fd_revalidate()?  If the task seteuid's, we want the permissions
to change accordingly, right?

Thanks.

-- 
tejun
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