On Tue, Aug 06, 2019 at 05:43:47PM +0200, Borislav Petkov wrote:

On Tue, Jul 30, 2019 at 12:12:44PM -0700, Thomas Garnier wrote:

quoted

These patches make some of the changes necessary to build the kernel as
Position Independent Executable (PIE) on x86_64. Another patchset will
add the PIE option and larger architecture changes.

Yeah, about this: do we have a longer writeup about the actual benefits
of all this and why we should take this all? After all, after looking
at the first couple of asm patches, it is posing restrictions to how
we deal with virtual addresses in asm (only RIP-relative addressing in
64-bit mode, MOVs with 64-bit immediates, etc, for example) and I'm
willing to bet money that some future unrelated change will break PIE
sooner or later.

Possibly objtool can help here; it should be possible to teach it about
these rules, and then it will yell when violated. That should avoid
regressions.