ktrace: Teach kernel to write v0 format

[dchagin]

Summary

To preserve ABI stability force kernel to write v0 format if
ktrace p_osrel is old.

[kib]

This does not make sense to me. You are basing the output format on the osrel of the binary that is being traced. So 1) it does not solve my issue when I have fresh HEAD and take the ktrace dump on it and move it to stable/13 2) if more than one process is traced, and their binaries have mixed osrel, you get the mix of the record types in the output

[dchagin]

In D35851#814336, @kib wrote:

This does not make sense to me. You are basing the output format on the osrel of the binary that is being traced. So 1) it does not solve my issue when I have fresh HEAD and take the ktrace dump on it and move it to stable/13 2) if more than one process is traced, and their binaries have mixed osrel, you get the mix of the record types in the output

this is a quick hack to demonstrate a solution, I haven't even had time to test it, as the world is still builds. If this approach is ok for you, I will complete the fix, otherwise I will do as you suggested earlier

sys/kern/kern_ktrace.c

1223

it should be if (td->td_proc->p_osrel > P_OSREL_KTRACE_VERSIONED)

[kib]

In D35851#814341, @dchagin wrote:

In D35851#814336, @kib wrote:

This does not make sense to me. You are basing the output format on the osrel of the binary that is being traced. So 1) it does not solve my issue when I have fresh HEAD and take the ktrace dump on it and move it to stable/13 2) if more than one process is traced, and their binaries have mixed osrel, you get the mix of the record types in the output

this is a quick hack to demonstrate a solution, I haven't even had time to test it, as the world is still builds. If this approach is ok for you, I will complete the fix, otherwise I will do as you suggested earlier

I do not think that my response above can be read as my agreement with the approach