Hi Sebastian,
Thanks for the feedback!
Em 18/06/2025 04:08, Sebastian Andrzej Siewior escreveu:
On 2025-06-17 15:34:17 [-0300], André Almeida wrote:
This patch adds a new robust_list() syscall. The current syscall can't be expanded to cover the following use case, so a new one is needed. This new syscall allows users to set multiple robust lists per process and to have either 32bit or 64bit pointers in the list.
Thank you for the reminder. It was on my list, it slipped. Two questions:
- there was a bot warning for v3 but this v4 is a RESEND. It the warning addressed in any way?
Ops, I forgot to address them. I will do it for v5.
- You say 64bit x86-64 does not have the problem due the compat syscall. Arm64 has this problem. New arm64 do not provide arm32 facility. You introduce the syscall here. Why not introduce the compat syscall instead? I'm sorry if this has been answered somewhere below but this was one question I had while I initially skimmed over the patches.
The main target for this new syscall is Arm64, that can't handle 32 pointers in the current syscall, so this new interface allows the robust list mechanism to know if it needs to do 64 or 32 bit pointer arithmetic operations to walk in the list.
Introducing a compat syscall won't fix this, giving that it only works in x86-64. We need an entry point for Arm64 that can handle 32 bit pointers.
I hope that it's clear now, let me know if you have more questions :)
Sebastian