Re: [PATCH] New phys_addr() syscall
Richard Henderson (rth@dot.cygnus.com)
Mon, 20 Jul 1998 01:46:10 -0700
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~
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.altern.org/andrebalsa/doc/lkml-faq.html