eventfd: present id to userspace via fdinfo
authorMasatake YAMATO <yamato@redhat.com>
Tue, 14 May 2019 22:45:19 +0000 (15:45 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 15 May 2019 02:52:51 +0000 (19:52 -0700)
commitb556db17b0e7c439bb6113b6dc7185bd0b1bbbb4
tree1888389de67f8da7ace9de06fcc4f7432fae9c95
parent1fd402df4586bcc239298081449ce58a78211626
eventfd: present id to userspace via fdinfo

Finding endpoints of an IPC channel is one of essential task to
understand how a user program works.  Procfs and netlink socket provide
enough hints to find endpoints for IPC channels like pipes, unix
sockets, and pseudo terminals.  However, there is no simple way to find
endpoints for an eventfd file from userland.  An inode number doesn't
hint.  Unlike pipe, all eventfd files share the same inode object.

To provide the way to find endpoints of an eventfd file, this patch adds
"eventfd-id" field to /proc/PID/fdinfo of eventfd as identifier.
Integers managed by an IDA are used as ids.

A tool like lsof can utilize the information to print endpoints.

Link: http://lkml.kernel.org/r/20190327181823.20222-1-yamato@redhat.com
Signed-off-by: Masatake YAMATO <yamato@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/eventfd.c