• Iago López Galeiras's avatar
    fs, proc: introduce CONFIG_PROC_CHILDREN · 2e13ba54
    Iago López Galeiras authored
    Commit 81841161 ("fs, proc: introduce /proc/<pid>/task/<tid>/children
    entry") introduced the children entry for checkpoint restore and the
    file is only available on kernels configured with CONFIG_EXPERT and
    CONFIG_CHECKPOINT_RESTORE.
    
    This is available in most distributions (Fedora, Debian, Ubuntu, CoreOS)
    because they usually enable CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE.
    But Arch does not enable CONFIG_EXPERT or CONFIG_CHECKPOINT_RESTORE.
    
    However, the children proc file is useful outside of checkpoint restore.
    I would like to use it in rkt.  The rkt process exec() another program
    it does not control, and that other program will fork()+exec() a child
    process.  I would like to find the pid of the child process from an
    external tool without iterating in /proc over all processes to find
    which one has a parent pid equal to rkt.
    
    This commit introduces CONFIG_PROC_CHILDREN and makes
    CONFIG_CHECKPOINT_RESTORE select it.  This allows enabling
    /proc/<pid>/task/<tid>/children without needing to enable
    CONFIG_CHECKPOINT_RESTORE and CONFIG_EXPERT.
    
    Alban tested that /proc/<pid>/task/<tid>/children is present when the
    kernel is configured with CONFIG_PROC_CHILDREN=y but without
    CONFIG_CHECKPOINT_RESTORE
    Signed-off-by: default avatarIago López Galeiras <iago@endocode.com>
    Tested-by: default avatarAlban Crequy <alban@endocode.com>
    Reviewed-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Pavel Emelyanov <xemul@parallels.com>
    Cc: Serge Hallyn <serge.hallyn@canonical.com>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: Alexander Viro <viro@zeniv.linux.org.uk>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Djalal Harouni <djalal@endocode.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    2e13ba54
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