lkml.org 
[lkml]   [2001]   [May]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: pte_page
mingo@elte.hu said:
> On Wed, 30 May 2001 mdaljeet@in.ibm.com wrote:
> > I use the 'pgt_offset', 'pmd_offset', 'pte_offset' and 'pte_page'
> > inside a module to get the physical address of a user space virtual
> > address. The physical address returned by 'pte_page' is not page
> > aligned whereas the virtual address was page aligned. Can somebody
> > tell me the reason?
>
> __pa(page_address(pte_page(pte))) is the address you want. [or
> pte_val(*pte) & (PAGE_SIZE-1) on x86 but this is platform-dependent.]

Does this work on x86 non-kmapped highmem user pages too? (i.e. is
page->virtual valid for every potential user page.)

-- Pete

> > Also, can i use these functions to get the physical address of a
> > kernel virtual address using init_mm?
>
> nope. Eg. on x86 these functions only walk normal 4K page pagetables, they
> do not walk 4MB pages correctly. (which are set up on pentiums and better
> CPUs, unless mem=nopentium is specified.)
>
> a kernel virtual address can be decoded by simply doing __pa(kaddr). If
> the page is a highmem page [and you have the struct page pointer] then you
> can do [(page-mem_map) << PAGE_SHIFT] to get the physical address, but
> only on systems where mem_map[] starts at physical address 0.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:54    [W:0.032 / U:0.124 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site