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cdda1f26e7
A common pattern when using pid fds is having to get information about the process, which currently requires /proc being mounted, resolving the fd to a pid, and then do manual string parsing of /proc/N/status and friends. This needs to be reimplemented over and over in all userspace projects (e.g.: I have reimplemented resolving in systemd, dbus, dbus-daemon, polkit so far), and requires additional care in checking that the fd is still valid after having parsed the data, to avoid races. Having a programmatic API that can be used directly removes all these requirements, including having /proc mounted. As discussed at LPC24, add an ioctl with an extensible struct so that more parameters can be added later if needed. Start with returning pid/tgid/ppid and creds unconditionally, and cgroupid optionally. Signed-off-by: Luca Boccassi <luca.boccassi@gmail.com> Link: https://lore.kernel.org/r/20241010155401.2268522-1-luca.boccassi@gmail.com Signed-off-by: Christian Brauner <brauner@kernel.org>