Re: [PATCH] New phys_addr() syscall
Richard Gooch (Richard.Gooch@atnf.CSIRO.AU)
Tue, 21 Jul 1998 16:47:13 +1000
Richard Henderson writes:
> 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.
Aside: I've switched to an ioctl(2) interface on /proc/*/mem.
The problem is that the return value is an int, which is only 32
bits. Won't this be a problem for 64 machines with over 4 GBytes of
RAM?
Regards,
Richard....
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