Query regarding syscall decoders

[Sahil Siddiq]

Hi,

Two new syscalls, listmount and statmount, were added to the linux
kernel [1][2][3]. I have never written a syscall decoder and this seems to
be a challenging task. I would like to try my hand at this.

I was going through several syscall decoders in strace and I have got a
question. Several decoders (eg: getpriority) return RVAL_DECODED, while
some decoders (eg: getrusage) return 0 unconditionally.

When should a decoder return RVAL_DECODED and when is "return 0"
appropriate?

Regards,
Sahil

[1] https://lwn.net/Articles/950569/
[2] https://lwn.net/ml/linux-kernel/20231101-urenkel-banal-b232d7a3cbe8@brauner/
[3] https://www.phoronix.com/news/Linux-6.8-statmount-listmount