Re: [KJ PATCH] Replacing memcpy(dest,src,PAGE_SIZE) with copy_page(dest,src) in arch/i386/kernel/machine_kexec.c

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

 



Eric W. Biederman wrote:
> Shani Moideen <[email protected]> writes:
> 
>> Hi,
>> Replacing memcpy(dest,src,PAGE_SIZE) with copy_page(dest,src) in
>> arch/i386/kernel/machine_kexec.c.
> 
> Please no.
> 
> People get creative in copy_page (especially mmx_copy_page),
> and this code path need something simple and stupid, that
> will work every time, especially when things are messed up
> elsewhere.
> 

memcpy() is pretty creative, too.  If you want something really dumb and
robust, you should probably create an inline:

/*
 * Eric sez: his code path need something simple and stupid, that
 * will work every time, especially when things are messed up
 * elsewhere.
 */
static inline void braindead_copy_page(void *dst, void *src)
{
	unsigned long ctr = PAGE_SIZE >> 2;

	asm volatile("cld; rep; movsl"
			: "+D" (dst), "+S" (src), "+c" (ctr)
			: : "memory");
}

(FWIW, the "cld" is supposed to be redundant, as DF=0 is supposed to be
guaranteed by the ABI.)

	-hpa
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux