l4linux and sysenter

[Ryan Brown]

Thanks for the ptrace fix, that really helped with debugging.
We were seeing programs crash at the first system call when using some
versions of glibc, but not others. It seems the difference is that the
working glibc's are compiled without vdso support.
When glibc tries to use the vdso for system calls, it crashes at the
sysenter instruction.
If we start l4linux with vdso32=0, the program is able to run.
Is sysenter expected to work under l4linux? It looks like it requires using
msr's, so perhaps l4linux isn't able to setup sysenter? Should it be
installing the int80 vdso function instead?

While investigating the vdso stuff to I also became curious. How difficult
would it be to set up an l4 specific vdso? I assume just using l4 ipc
directly would be more efficient than using int80?

Thanks,

Ryan Brown
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