On Mon, May 15, 2023 at 05:39:25PM -0400, Peter Xu wrote: > On Mon, May 15, 2023 at 08:32:32PM +0100, Lorenzo Stoakes wrote: > > As well as fixing the repro described in [1] this also continues to pass > > uffd unit tests. > > Side note on testing, not directly relevant to the patch itself.. > > I'm wondering whether do we have tests somewhere to just test vma > operations on split and merge, then verify it using smap or whatever. > > The uffd unit test in this case is probably not gonna trigger anything > because we always mostly register with a whole vma over the testing ranges, > so not immediately helpful. > > The trick here is we have quite a few ops that will call vma merge/split in > different ways, but logically we can still category them into: (1) add/del > vmas, or (2) modify vma flags, so at least for case (2) we can have a > framework to cover all the cases (mbind, mprotect, uffd reg/unreg, mlock, > etc.), the difference will be the flags we'll be looking at for different > cases, however how vmas merge/split should be somehow in the same pattern. > I totally agree we need more testing on this. We do have some basic self-tests for various things but I don't think we test this specifically or certainly not in the way I'd prefer (somehow pull vma_merge() + friends into userland and instrument with heavy unit tests). I do intend to try to do something with this soon. Something with /proc/$pid/[s]maps could be a good straightforward thing, I will try to write some small test (we already have a little repro for the reported issue) for this anyway. > -- > Peter Xu >
