On 2024-10-21, Christian Brauner <brauner@xxxxxxxxxx> wrote: > On Thu, 10 Oct 2024 07:40:33 +1100, Aleksa Sarai wrote: > > This is something that I've been thinking about for a while. We had a > > discussion at LPC 2020 about this[1] but the proposals suggested there > > never materialised. > > > > In short, it is quite difficult for userspace to detect the feature > > capability of syscalls at runtime. This is something a lot of programs > > want to do, but they are forced to create elaborate scenarios to try to > > figure out if a feature is supported without causing damage to the > > system. For the vast majority of cases, each individual feature also > > needs to be tested individually (because syscall results are > > all-or-nothing), so testing even a single syscall's feature set can > > easily inflate the startup time of programs. > > > > [...] > > I think the copy_struct_to_user() is useful especially now that we'll gain > another user with pidfd_info. Once we start extending pidfd_info, it might be necessary to add some more helpers to make it easier to figure out what bits to set in the returned request mask. > --- > > Applied to the vfs.usercopy branch of the vfs/vfs.git tree. > Patches in the vfs.usercopy branch should appear in linux-next soon. > > Please report any outstanding bugs that were missed during review in a > new review to the original patch series allowing us to drop it. > > It's encouraged to provide Acked-bys and Reviewed-bys even though the > patch has now been applied. If possible patch trailers will be updated. > > Note that commit hashes shown below are subject to change due to rebase, > trailer updates or similar. If in doubt, please check the listed branch. > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git > branch: vfs.usercopy > > [01/10] uaccess: add copy_struct_to_user helper > https://git.kernel.org/vfs/vfs/c/424a55a4a908 > [02/10] sched_getattr: port to copy_struct_to_user > https://git.kernel.org/vfs/vfs/c/112cca098a70 -- Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH <https://www.cyphar.com/>
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