* x86_64: Question about fixmaps
@ 2015-04-14 13:16 Alexander Kuleshov
2015-04-15 0:28 ` Andy Lutomirski
0 siblings, 1 reply; 2+ messages in thread
From: Alexander Kuleshov @ 2015-04-14 13:16 UTC (permalink / raw)
To: linux-kernel
Hello All,
I'm reading x86_64 source code and trying to understand where are
fixmaps space in the virtual memory space. If I understand correctly
(but i'm really not sure about it), fixmap space is after vsyscall
space. As Documentation/x86/x86_64/mm.txt says vsyscall virtual space
is:
ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls
With 'earlyprintk' i got FIXADDR_START and FIXADDR_TOP and they are:
FIXADDR_START - 0xffffffffff779000L
FIXADDR_TOP - 0xffffffffff7ff000L
with these addressess FIXADDR_START/FIXADDR_TOP overlap vsyscalls
area. Is it correct case that fixmaps are in vsyscal virtual memory
space or I'm wrong somewhere?
Thank you.
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: x86_64: Question about fixmaps
2015-04-14 13:16 x86_64: Question about fixmaps Alexander Kuleshov
@ 2015-04-15 0:28 ` Andy Lutomirski
0 siblings, 0 replies; 2+ messages in thread
From: Andy Lutomirski @ 2015-04-15 0:28 UTC (permalink / raw)
To: Alexander Kuleshov, linux-kernel
On 04/14/2015 06:16 AM, Alexander Kuleshov wrote:
> Hello All,
>
> I'm reading x86_64 source code and trying to understand where are
> fixmaps space in the virtual memory space. If I understand correctly
> (but i'm really not sure about it), fixmap space is after vsyscall
> space. As Documentation/x86/x86_64/mm.txt says vsyscall virtual space
> is:
>
> ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls
>
> With 'earlyprintk' i got FIXADDR_START and FIXADDR_TOP and they are:
>
> FIXADDR_START - 0xffffffffff779000L
> FIXADDR_TOP - 0xffffffffff7ff000L
>
> with these addressess FIXADDR_START/FIXADDR_TOP overlap vsyscalls
> area. Is it correct case that fixmaps are in vsyscal virtual memory
> space or I'm wrong somewhere?
It's the other way around. vsyscalls are in the fixmap. I should fix
the docs.
--Andy
^ permalink raw reply [flat|nested] 2+ messages in thread
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