Wright, David wrote:
On the other hand, there's nothing to prevent the
ambitious developer from writing their own
/dev/crash driver that *does* have a write operation
in it, is there?
-- David Wright, Egenera, Inc.
Nope. Or removing the restriction from the /dev/mem driver,
which runs into the per-arch devmem_is_allowed() function.
Here's the "arch/i386/mm/init.c" version:
/*
* devmem_is_allowed() checks to see if /dev/mem access to a certain address is
* valid. The argument is a physical page number.
*
* On x86, access has to be given to the first megabyte of ram because that area
* contains bios code and data regions used by X and dosemu and similar apps.
* Access has to be given to non-kernel-ram areas as well, these contain the PCI
* mmio resources as well as potential bios/acpi data regions.
*/
int devmem_is_allowed(unsigned long pagenr)
{
if (pagenr <= 256)
return 1;
if (!page_is_ram(pagenr))
return 1;
return 0;
}
Dave
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