On Mon, Dec 16, 2019 at 9:21 AM Stephen Smalley <sds@xxxxxxxxxxxxx> wrote: > On 12/14/19 1:50 PM, Dan Aloni wrote: > > On Fri, Dec 13, 2019 at 03:28:38PM -0500, Stephen Smalley wrote: > >> I would have expected that two kernels built with the same config > >> with this enabled would have yielded different struct layouts in > >> pahole vmlinux output, but that doesn't appear to be the case. They > >> do have different seeds. Am I doing something wrong? > >> Also, does DEBUG_INFO_BTF effectively undermine/negate the benefits of this > >> change if enabled? > > > > There's currently a long-standing bug with the GCC plugin where the > > generated debug info is in declaration order, not build order (see: > > [1]). So, to verify it, try looking at the generated machine code. > > Thanks for that clarification; I can see in the code that the struct > layout has changed between the two kernel builds. This likely falls under the category of stupid questions, but I'm assuming it passed the test suite w/o problems and the system generally ran as expected? I've also heard some comments about performance concerns, have you done any testing? I'm guessing that isn't a major concern here because I don't recall any of the structs marked in this patch going through any optimizations, but I could be forgetting something (or missing a performance concern with RANDSTRUCT). -- paul moore www.paul-moore.com
