On Thursday, 21.06.2018 at 07:46, Adam Steen wrote: > > > Mirage-Skeleton Hello World Tutorial, I now find this causes as " > > > > > > mprotect W^X violation" on OpenBSD. > > > > That's err, odd. Do you get a "Warning: phdr[N] requests WRITE and EXEC > > > > permissions" when running ukvm-bin? > > Yes.
Right, so your ELF is requesting such a segment, in which case the failure is expected (without manually disabling W^X for the ukvm-bin). > > When you write "causes a mprotect W^X violation", how does that actually > > > > manifest itself at run-time? Does ukvm-bin get killed? Or some other way? > > ukvm-bin gets killed by the kernel. > > "ukvm-bin: hello.ukvm: Warning: phdr[0] requests WRITE and EXEC permissions" > "ukvm-bin: hello.ukbm: Not Supported" The second error would be from the mprotect() returning ENOTSUP, which is due to the W^X policy, and ukvm-bin is correctly aborting in that case. > Looks like I will have to dig a little deeper, I do recall something like > this happening soon after i got things working on a custom kernel. I am awol > again next week, but will try to nail down exactly what caused the issue. > > Thanks for the confirmation about linux and a starting point with "readelf -l" As I wrote initially, this looks like something in the MirageOS build on OpenBSD is generating a segment with W & X on it. You can double-confirm by e.g. building the same unikernel on Linux and seeing if it runs on OpenBSD. If it changed recently then it's possible that either a) you were previously running a kernel that did not enforce this or b) the build toolchain changed and/or due to a) you did not notice that it's producing W & X segments in the first place. I'd ask around on the OpenBSD lists and/or check the various clang / ld manual pages for any options that might affect this. -mato
