Re: [PATCH v2 04/16] x86/efi: Generating random number in EFI stub

joeyli
2015-08-27T04:07:09Z

Hi Matt,

Thanks for your reviewing and sorry for my delay.

On Thu, Aug 20, 2015 at 03:12:21PM +0100, Matt Fleming wrote:
> On Tue, 11 Aug, at 02:16:24PM, Lee, Chun-Yi wrote:
> > This patch adds the codes for generating random number array as the
> > HMAC key that will used by later EFI stub codes.
> >
> > The original codes in efi_random copied from aslr and add the codes
> > to accept input entropy and EFI debugging. In later patch will add
> > the codes to get random number by EFI protocol. The separate codes
> > can avoid impacting aslr function.
>
> Is there some way we can share the code between aslr and the EFI boot
> stub? People may not review both files when making changes and so bug
> fixes to one might not appear in the other.
>
> --
> Matt Fleming, Intel Open Source Technology Center

The origin design is base on get_random_long() from aslr, so I direct
copy it to efi_random.c then modified it.
There have some reasons I didn't share the code with aslr:

- There have some debug_puttstr() for debugging in aslr, but those
debugging log do not work in EFI stub, and I want put efi_print
for debugging purpose. I don't want affect the code in aslr, so
I choice copy get_random_long() to efi_random.c specific for EFI stub.

- In subsequent patches add EFI random protocol support to
get_random_longh().

In next version, I will try to extract shared code to misc.c to reuse them
between aslr and efi_random.

Thanks a lot!
Joey Lee