write protect kernel page problem

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Hi,

I'm using the following code in an attempt to write protect
a kernel page dependent on a particular address:

char *ptr;
unsigned long addr;
pgd_t *kpgd;
pmd_t *kpmd;
pte_t *kpte;
pte_t pte;

ptr = kmalloc(sizeof(int),GFP_ATOMIC);
addr = (unsigned long)ptr;
kpgd = pgd_offset_k(addr);
kpmd = pmd_offset(kpgd,addr);
kpte = pte_offset(kpmd,addr);
pte = *kpte;
pte = pte_wrprotect(pte);
set_pte(kpte,pte);
flush_tlb_all();

Using 2.2.14 and have edited linux/arch/i386/mm/init.c to remove
the use of the 4MB kernel page tables. Everything seems to work
until the set_pte(kpte,pte) call. I crash the kernel at that point.

I followed a similar thread on this list concerning a 2.3.x
kernel, but am still a bit confused as to the problem I'm creating
here. Any thoughts or suggestions would be most appreciated.

Please cc to me, as I am not currently on the list.

thanks.

-joel
jkholl@cs.wm.edu

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