Re: [PATCH v9 08/11] x86/boot/64: Adapt assembly for PIE support

Thomas Garnier
2019-10-29T21:30:11Z

On Fri, Aug 9, 2019 at 10:29 AM Borislav Petkov <bp@alien8.de> wrote:
>
> chOn Tue, Jul 30, 2019 at 12:12:52PM -0700, Thomas Garnier wrote:
> > Change the assembly code to use only relative references of symbols for the
> > kernel to be PIE compatible.
> >
> > Early at boot, the kernel is mapped at a temporary address while preparing
> > the page table. To know the changes needed for the page table with KASLR,
>
> These manipulations need to be done regardless of whether KASLR is
> enabled or not. You're basically accomodating them to PIE.
>
> > the boot code calculate the difference between the expected address of the
>
> calculates
>
> > kernel and the one chosen by KASLR. It does not work with PIE because all
> > symbols in code are relatives. Instead of getting the future relocated
> > virtual address, you will get the current temporary mapping.
>
> Please avoid "you", "we" etc personal pronouns in commit messages.
>
> > Instructions were changed to have absolute 64-bit references.
>
> From Documentation/process/submitting-patches.rst:
>
> "Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
> instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
> to do frotz", as if you are giving orders to the codebase to change
> its behaviour."

Sorry for the late reply, busy couple months.

I will integrate your feedback in v10. Thanks.

>
> Thx.
>
> --
> Regards/Gruss,
> Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.