Re: [PATCH v3 0/3] Detect changed compiler dependencies for full rebuild

Kees Cook
2025-05-08T15:56:11Z

On Wed, May 07, 2025 at 02:02:42PM +0200, Nicolas Schier wrote:
> On Sat, 03 May 2025, Kees Cook wrote:
>
> > v3: move to include/generated, add touch helper
> > v2: https://lore.kernel.org/lkml/20250502224512.it.706-kees@kernel.org/
> > v1: https://lore.kernel.org/lkml/20250501193839.work.525-kees@kernel.org/
> >
> > Hi,
> >
> > This is my attempt to introduce dependencies that track the various
> > compiler behaviors that may globally change the build that aren't
> > represented by either compiler flags nor the compiler version
> > (CC_VERSION_TEXT). Namely, this is to detect when the contents of a
> > file the compiler uses changes. We have 3 such situations currently in
> > the tree:
> >
> > - If any of the GCC plugins change, we need to rebuild everything that
> > was built with them, as they may have changed their behavior and those
> > behaviors may need to be synchronized across all translation units.
> > (The most obvious of these is the randstruct GCC plugin, but is true
> > for most of them.)
> >
> > - If the randstruct seed itself changes (whether for GCC plugins or
> > Clang), the entire tree needs to be rebuilt since the randomization of
> > structures may change between compilation units if not.
> >
> > - If the integer-wrap-ignore.scl file for Clang's integer wrapping
> > sanitizer changes, a full rebuild is needed as the coverage for wrapping
> > types may have changed, once again cause behavior differences between
> > compilation units.
>
> I am unsure if it is too much detail, but I'd like to see some of these
> infos in include/linux/compiler-version.h, too.

Yeah, that's a good idea. No reason to make people dig for the commit
logs, etc -- it should be immediately discoverable. I've updated the
patches to include the (slight rephrased) text above.

Thanks!

--
Kees Cook