Messages in this thread | | | Subject | Re: Sealed memfd & no-fault mmap | From | Ming Lin <> | Date | Thu, 3 Jun 2021 13:07:56 -0700 |
| |
On 6/3/2021 6:01 AM, Simon Ser wrote:
> > Regarding the requirements for Wayland: > > - The baseline requirement is being able to avoid SIGBUS for read-only mappings > of shm files. > - Wayland clients can expand their shm files. However the compositor doesn't > need to immediately access the new expanded region. The client will tell the > compositor what the new shm file size is, and the compositor will re-map it. > - Ideally, MAP_NOSIGBUS would work on PROT_WRITE + MAP_SHARED mappings (of > course, the no-SIGBUS behavior would be restricted to that mapping). The > use-case is writing back to client buffers e.g. for screen capture. From the > earlier discussions it seems like this would be complicated to implement. > This means we'll need to come up with a new libwayland API to allow > compositors to opt-in to the read-only mappings. This is sub-optimal but > seems doable. > - Ideally, MAP_SIGBUS wouldn't be restricted to shm. There are use-cases for > using it on ordinary files too, e.g. for sharing ICC profiles. But from the > earlier replies it seems very unlikely that this will become possible, and > making it work only on shm files would already be fantastic.
In the new version of the patches, MAP_NOSIGBUS is not restricted to shmem. It can be used on ordinary files.
| |