Hi,
This series corrects a number of issues with NT_PRFPREG regset, most importantly an FCSR access API regression introduced with the addition of MSA support, and then a few smaller issues with the get/set handlers.
I have decided to factor out non-MSA and MSA context helpers as the first step to avoid the issue with excessive indentation that would inevitably happen if the regression fix was applied to current code as it stands. It shouldn't be a big deal with backporting as this code hasn't changed much since the regression, and it will make any future bacports easier. Only a call to `init_fp_ctx' will have to be trivially resolved (though arguably commit ac9ad83bc318 ("MIPS: prevent FP context set via ptrace being discarded"), which has added `init_fp_ctx', would be good to backport as far as possible instead).
These changes have been verified by examining the register state recorded in core dumps manually with GDB, as well as by running the GDB test suite. No user of ptrace(2) PTRACE_GETREGSET and PTRACE_SETREGSET requests is known for the MIPS port, so this part remains not covered, however it is assumed to remain consistent with how the creation of core file works.
See individual patch descriptions for further details.
Maciej