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From: Nikita Danilov <nikita@clusterfs.com>
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Date: Wed, 4 Apr 2007 15:18:41 +0400
To: Matt Mackall <mpm@selenic.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 12/13] maps: Add /proc/pid/pagemap interface
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Matt Mackall writes:
 > Add /proc/pid/pagemap interface
 > 
 > This interface provides a mapping for each page in an address space to
 > its physical page frame number, allowing precise determination of what
 > pages are mapped and what pages are shared between processes.

[...]

 >  
 > +#ifdef CONFIG_PROC_PAGEMAP
 > +struct pagemapread {
 > +	struct mm_struct *mm;
 > +	unsigned long next;
 > +	unsigned long *buf;
 > +	unsigned long pos;
 > +	size_t count;
 > +	int index;
 > +	char __user *out;
 > +};
 > +
 > +static int flush_pagemap(struct pagemapread *pm)
 > +{
 > +	int n = min(pm->count, pm->index * sizeof(unsigned long));
 > +	if (copy_to_user(pm->out, pm->buf, n))
 > +		return -EFAULT;

This pushes binary data to the user space. Wasn't /proc supposed to be
ascii-based to avoid compatibility problems (e.g., size of unsigned long
changing, endianness, etc.)?

Nikita.