Strange virtual/physical address of global data

From: Timur Tabi (ttabi@interactivesi.com)
Date: Wed Sep 20 2000 - 12:55:50 EST

I wrote a little module to test virt_to_phys:

unsigned long test_data;

int init_module(void)
{
    void *virt = &test_data;
    unsigned long phys = virt_to_phys(virt);

When I run this and check the valur of virt and phys, it appears that phys is
outside the range of physical memory! That is, if I have 512MB of RAM, then
phys is equal to about 520M. However, if I make test_data a local variable:

int init_module(void)
{
    unsigned long test_data;
    void *virt = &test_data;
    unsigned long phys = virt_to_phys(virt);

Then I get a number which makes sense (less than 512M)

Could someone explain this to me? 

-- 
Timur Tabi - ttabi@interactivesi.com
Interactive Silicon - http://www.interactivesi.com

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