On Thu, Oct 24, 2019 at 10:35:46AM +0100, Matthias Maennich wrote: > On Wed, Oct 23, 2019 at 12:22:22PM +0000, Luis Chamberlain wrote: > > On Fri, Oct 18, 2019 at 10:31:39AM +0100, Matthias Maennich wrote: > > > The introduction of the symbol namespace patches changed the way symbols are > > > named in the ksymtab entries. That caused userland tools to fail (such as > > > kmod's depmod). As depmod is used as part of the kernel build it was worth > > > having another look whether this name change can be avoided. > > > > Why have this as a default feature? What about having an option to > > disable this feature? The benefit being that without a full swing of > > tests to avoid regressions its not clear what other issues may creep > > up. With this as optional, those wanting the mechanism can enable it > > and happilly find the issues for those more conservative. > > The strongest argument against that is, that the 'conservative' people > would constantly break things for the more 'adventurous' ones. They > would introduce namespace requirements by just using symbols without > correctly adjusting the imports. > > Second, vmlinux and modules would have to be compiled in the same > configuration. Otherwise they are incompatible and we would likely have > to maintain code in the module loader to catch issues caused by that. > In general, I think for the adoption of this feature and one of its > purposes - making unexpected use of symbols across the tree visible > already at review time - we should not make this an optional one. > Enforcing the imports at module load time is optional (there is an > option). > > And finally, having that code configurable for both options introduces > quite some complexity in kernel/module.c, modpost and > include/linux/export.h that would make the code hard to maintain and > complex to test. Hence that would likely introduce more issues. > > I know the feature came with some rough edges. Sorry about that. I > think, we got most of them worked out pretty well (big thanks to > Masahiro and Jessica and others helping with that). Now the actual > change to the surface exposed to userland tools is much smaller and the > feature itself less intrusive. This logic makes sense, the complexity over module loading is already high and supporting yet another division would be a burden for review and maintenace. However I'd feel much more inclined to support such decisions when and if we had a series of test cases to prevent possible regressions. Since effort with testing will move forward, I'm happy with the status quo. Luis
