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Re: PAGE_ALIGN + PAGE_SHIFT from userspace

To: Daniel Laird <>
Subject: Re: PAGE_ALIGN + PAGE_SHIFT from userspace
From: Thiemo Seufer <>
Date: Mon, 18 Dec 2006 12:47:00 +0000
In-reply-to: <>
Original-recipient: rfc822;
References: <>
User-agent: Mutt/1.5.13 (2006-08-11)
Daniel Laird wrote:
> Hi All,
> I was using linux on my MIPS and it was all going well.  I am just
> porting to 2.6.19 and am having a couple of issues.
> My first issue is that i used to mmap a buffer from user space.  I used to
> use a PAGE_ALIGN macro when doing this:
> /** to align the pointer to the (next) page boundary */
> #define PAGE_ALIGN(addr)      (((addr) + PAGE_SIZE - 1) & PAGE_MASK)
> this worked as PAGE_SIZE and PAGE_MASK were available in page.h.

It didn't work reliably since the pagesize is a kernel configuration option.

> This have now been moved inside the #ifdef KERNEL guard in the header file. 
> Meaning these are no longer available.
> Are these available somewhere else?
> Should I be doing something different to mmap?

Use the libc's sysconf(_SC_PAGESIZE) function.


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