> On Mar 31, 2019, at 3:17 PM, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > >> On Sun, Mar 31, 2019 at 2:10 PM Christian Brauner <christian@xxxxxxxxxx> wrote: >> >> I don't think that we want or can make them equivalent since that would >> mean we depend on procfs. > > Sure we can. > > If /proc is enabled, then you always do that dance YOU ALREADY WROTE > THE CODE FOR to do the stupid ioctl. > > And if /procfs isn't enabled, then you don't do that. > > Ta-daa. Done. No stupid ioctl, and now /proc and pidfd_open() return > the same damn thing. > > And guess what? If /proc isn't enabled, then obviously pidfd_open() > gives you the /proc-less thing, but at least there is no crazy "two > different file descriptors for the same thing" situation, because then > the /proc one doesn't exist. > I wish we could do this, and, in a clean design, it would be a no-brainer. But /proc has too much baggage. Just to mention two such things, there’s “net” and “../sys”. This crud is why we have all kinds of crazy rules that prevent programs in sandboxes from making a new mounts and mounting /proc in it. If we make it possible to clone a new process and this access /proc without having /proc mounted, we’ll open up a big can of worms. Maybe we could have a sanitized view of /proc and make a pidfd be a directory fd pointing at that.
