Kees Could you comment on the feasibility of this alternative from the Control Flow Integrity perspective. My proposal is to change the proc_handler to void* and back in the same release. So there would not be a kernel released with a void* proc_handler. > > However, there is an alternative way to do this that allows chunking. We > > first define the proc_handler as a void pointer (casting it where it is > > being used) [1]. Then we could do the constification by subsystem (like > > Jakub proposes). Finally we can "revert the void pointer change so we > > don't have one size fit all pointer as our proc_handler [2]. > > > > Here are some comments about the alternative: > > 1. We would need to make the first argument const in all the derived > > proc_handlers [3] > > 2. There would be no undefined behavior for two reasons: > > 2.1. There is no case where we change the first argument. We know > > this because there are no compile errors after we make it const. > > 2.2. We would always go from non-const to const. This is the case > > because all the stuff that is unchanged in non-const. > > 3. If the idea sticks, it should go into mainline as one patchset. I > > would not like to have a void* proc_handler in a kernel release. > > 4. I think this is a "win/win" solution were the constification goes > > through and it is divided in such a way that it is reviewable. > > > > I would really like to hear what ppl think about this "heretic" > > alternative. @Thomas, @Luis, @Kees @Jakub? > > Thanks for that alternative, I'm not a big fan though. > > Besides the wonky syntax, Control Flow Integrity should trap on > this construct. Functions are called through different pointers than > their actual types which is exactly what CFI is meant to prevent. > > Maybe people find it easier to review when using > "--word-diff" and/or "-U0" with git diff/show. > There is really nothing going an besides adding a few "const"s. > > But if the consensus prefers this solution, I'll be happy to adopt it. > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/joel.granados/linux.git/commit/?h=jag/constfy_treewide_alternative&id=4a383503b1ea650d4e12c1f5838974e879f5aa6f > > [2] https://git.kernel.org/pub/scm/linux/kernel/git/joel.granados/linux.git/commit/?h=jag/constfy_treewide_alternative&id=a3be65973d27ec2933b9e81e1bec60be3a9b460d > > [3] proc_dostring, proc_dobool, proc_dointvec.... > > > Thomas Best -- Joel Granados
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