Re: Walking all the physical memory in an x86 system

[linux-os]

On Tue, 30 Nov 2004, Alan Cox wrote:

> On Maw, 2004-11-30 at 17:34, Jan Engelhardt wrote:
> > 	unsigned short p;
> > 	fd = open("/dev/mem", O_RDONLY | O_BINARY);
> > 	lseek(fd, 0x400, SEEK_SET);
> > 	read(fd, &p, 2);
>
> You want ports for that not mem, has always been the case since back
> before Linux existed.

At offset 0 in the BIOS segment of 0x40, real address 0x400, are
the addresses of up to 4 ports for the serial communications
devices, followed by up to 4 port addresses of any parallel
communications devices found by the BIOS upon startup. This
is likely what he meant. The code shown will return the address
of the first RS-232 device (usually a 8250 UART) found.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.9 on an i686 machine (5537.79 BogoMips).
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