how can I have access to the memory as in flat mode?

how can I have access to the memory as in flat mode?

[Frederic Marmond]

Hi,

few days ago, i posted mails to try to know better about linear memory 
in linux.
perhapse you've already answer me, but I could'nt see mails from the list...
So, I managed to make my prog work by using /dev/mem
it's very ugly, but it worked.

Is there any other way to access somewhere?
In fact the exact problem is:

on a embeded system, the mac-adress of  eth0 and eth1 are stored in a 
flash memory, mapped somewhere.
The 'standard' driver (natsemi) doesn't know this, and try to access to 
the 'normal' pci network card.
So, i have to read the mac adress by hand, and modify the value returned 
by the 'standard' driver.

I know the adress, but I've got seg-faults when trying to access it from 
the driver (readb, (unsigned char*)0xf8000, ...)

any help?

Fred

Re: how can I have access to the memory as in flat mode?

[h-peter recktenwald]

On Sun, 23 Jun 2002 17:13:51 +0200
Frederic Marmond <fmarmond@eprocess.fr> wrote:

> 
> Hi,
> 
> few days ago, i posted mails to try to know better about linear memory 
> in linux.
> perhapse you've already answer me, but I could'nt see mails from the list...
> So, I managed to make my prog work by using /dev/mem
> it's very ugly, but it worked.
> 
> Is there any other way to access somewhere?
> In fact the exact problem is:
> 
> on a embeded system, the mac-adress of  eth0 and eth1 are stored in a 
> flash memory, mapped somewhere.
> The 'standard' driver (natsemi) doesn't know this, and try to access to 
> the 'normal' pci network card.
> So, i have to read the mac adress by hand, and modify the value returned 
> by the 'standard' driver.
> 
> I know the adress, but I've got seg-faults when trying to access it from 
> the driver (readb, (unsigned char*)0xf8000, ...)
				^^^^^^^^^^^^

i'm most probably the least experieced on this access mode, thus only 
guessing, i.e. the way how i would start trying:

is your code running in kernel mode (e.g. module)?
otherwise that address would not be accessible, 1st GB owned by kernel.

in kernel mode you might try sys_open on /dev/kmem and set the 'file pointer' 
to the mentioned mmap-ed(?) address, then read w. 
	sys_read fd,memory-address,number-of-byte-to-read

which might even work from user space (by a 'normal' program) when called 
with 'root' access privileges.

> 
> any help?

???? - I'd yet never try any of those...


regards,
	hp

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