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SubjectRe: ptrace question ...
On Tue, Jun 01, 1999 at 04:01:25PM +0200, Jamie Lokier wrote:

> Ralf Baechle wrote:
> > Is there any reason why we don't attempt to handle requests for addresses
> > with MAP_NR(page) >= MAP_NR(high_memory) correctly? I've got a pending
> > bug report for the MIPS port where somebody complains that the respective
> > code for MIPS prevents accessing the hardware directly from GDB.
>
> Yes: if you remove the test, accessing the hardware still doesn't work!

Obviously. However that code was written even before Linux 1.0 and
at that time there was no ioremap that is all memory mappaple devices
were permanently accessible.

> > *(unsigned long *) (page + (addr & ~PAGE_MASK)) = data;
>
> This line only works for pages where MAP_NR(page) < MAP_NR(high_memory).
> To access other hardware addresses from kernel space requires a call
> to ioremap() first.
>
> Well ok, _some_ addresses will still work if the phase of your moon is
> right, but not reliably.

Will make it work right ...

> However I don't know why the test isn't simply `page < high_memory'.

In Linux 1.0 it basically was.

Ralf

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