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SubjectRe: [PATCH] New phys_addr() syscall
On Sun, Jul 19, 1998 at 03:53:24PM +1000, Richard.Gooch@atnf.csiro.au wrote:
> +asmlinkage int sys_phys_addr(unsigned long *address)
> +{
> + int error = 0;
> + unsigned long addr;
> + pte_t *pte;
> +
> + error = copy_from_user (&addr, address, sizeof addr);
> + if (error < 0) return error;
> + pte = pte_offset (pmd_offset (pgd_offset (current->mm, addr), addr),
> + addr);
> + if ( !pte_present (*pte) ) return -EINVAL;
> + addr = __pa (pte_page (*pte)) + (addr & (PAGE_SIZE-1));
> + return copy_to_user (address, &addr, sizeof addr) ? -EFAULT : 0;
> +}

There is no point in copying to and from memory. An error return will
be a non-page-aligned value > -PAGE_SIZE. Just get the pa of address
and return the result.


r~

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