Re: Regarding implementation of copy_from_user() and copy_to_user()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Sun, May 17, 2009 at 3:18 PM, seshikanth varma
<seshikanthvarma@xxxxxxxxx> wrote:
> Hi All,
> I am trying to understand the implementation of copy_from_user() and
> copy_to_user() implementation in linux. I know the basics of asm format. But
> i don't know what is
> .section .fixup
> .previous
> .align 4
> Can u please point me to a detailed documentation of asm details involving
> the above?

Google for "inline assembly" and "assembly in C".

> Thanks,
> Seshikanth
>
>  320 * Tell gcc we read from memory instead of writing: this is because
>  321 * we do not write to any memory gcc knows about, so there are no
>  322 * aliasing issues.
>  323 */
>  324#define __put_user_asm(x, addr, err, itype, rtype, ltype, errret)
> \
>  325        __asm__ __volatile__(
> \
>  326                "1:     mov"itype" %"rtype"1,%2\n"
> \
>  327                "2:\n"
> \
>  328                ".section .fixup,\"ax\"\n"
> \
>  329                "3:     movl %3,%0\n"
> \
>  330                "       jmp 2b\n"
> \
>  331                ".previous\n"
> \
>  332                ".section __ex_table,\"a\"\n"
> \
>  333                "       .align 4\n"
> \
>  334                "       .long 1b,3b\n"
> \
>  335                ".previous"
> \
>  336                : "=r"(err)
> \
>  337                : ltype (x), "m"(__m(addr)), "i"(errret), "0"(err))
>  338
>  339
>
> --
> Regards,
> Seshikanth
>



-- 
Regards,
Sandeep.





 	
“To learn is to change. Education is a process that changes the learner.”

--
To unsubscribe from this list: send an email with
"unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx
Please read the FAQ at http://kernelnewbies.org/FAQ



[Index of Archives]     [Newbies FAQ]     [Linux Kernel Mentors]     [Linux Kernel Development]     [IETF Annouce]     [Git]     [Networking]     [Security]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux RAID]     [Linux SCSI]     [Linux ACPI]
  Powered by Linux