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

Re: [patch v2 02/10] kdump: Make kimage_load_crash_segment() weak



On Wed, Jul 27, 2011 at 02:55:06PM +0200, Michael Holzheu wrote:
> From: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>
> 
> On s390 we do not create page tables at all for the crashkernel memory.
> This requires a s390 specific version for kimage_load_crash_segment().
> Therefore this patch declares this function as "__weak". The s390 version is
> very simple. It just copies the kexec segment to real memory without using
> page tables:
> 
> int kimage_load_crash_segment(struct kimage *image,
>                               struct kexec_segment *segment)
> {
>         return copy_from_user_real((void *) segment->mem, segment->buf,
>                                    segment->bufsz);
> }
> 
> There are two main advantages of not creating page tables for the
> crashkernel memory:
> 
> a) It saves memory. We have scenarios in mind, where crashkernel
>    memory can be very large and saving page table space is important.
> b) We protect the crashkernel memory from being overwritten.
> 
> Signed-off-by: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>
> ---
>  kernel/kexec.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -842,8 +842,8 @@ out:
>  	return result;
>  }
>  
> -static int kimage_load_crash_segment(struct kimage *image,
> -					struct kexec_segment *segment)
> +int __weak kimage_load_crash_segment(struct kimage *image,
> +				     struct kexec_segment *segment)

A comment here why we are making it weak should help in increasing
the code readability.

Thanks
Vivek

>  {
>  	/* For crash dumps kernels we simply copy the data from
>  	 * user space to it's destination.
--
To unsubscribe from this list: send the line "unsubscribe linux-s390" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Kernel Newbies]     [Share Photos]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Photo]     [Yosemite]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Samba]     [Linux Media]     [Device Mapper]     [Linux Resources]


Add to Google Powered by Linux