The patch titled
Subject: eventfd: present id to userspace via fdinfo
has been added to the -mm tree. Its filename is
eventfd-prepare-id-to-userspace-via-fdinfo.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/eventfd-prepare-id-to-userspace-via-fdinfo.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/eventfd-prepare-id-to-userspace-via-fdinfo.patch
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------------------------------------------------------
From: Masatake YAMATO <yamato@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx
Signed-off-by: Masatake YAMATO <yamato@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/eventfd.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/fs/eventfd.c~eventfd-prepare-id-to-userspace-via-fdinfo
+++ a/fs/eventfd.c
@@ -21,6 +21,9 @@
#include <linux/eventfd.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
+#include <linux/idr.h>
+
+DEFINE_IDA(eventfd_ida);
struct eventfd_ctx {
struct kref kref;
@@ -35,6 +38,7 @@ struct eventfd_ctx {
*/
__u64 count;
unsigned int flags;
+ int id;
};
/**
@@ -69,6 +73,8 @@ EXPORT_SYMBOL_GPL(eventfd_signal);
static void eventfd_free_ctx(struct eventfd_ctx *ctx)
{
+ if (ctx->id >= 0)
+ ida_simple_remove(&eventfd_ida, ctx->id);
kfree(ctx);
}
@@ -297,6 +303,7 @@ static void eventfd_show_fdinfo(struct s
seq_printf(m, "eventfd-count: %16llx\n",
(unsigned long long)ctx->count);
spin_unlock_irq(&ctx->wqh.lock);
+ seq_printf(m, "eventfd-id: %d\n", ctx->id);
}
#endif
@@ -400,6 +407,7 @@ static int do_eventfd(unsigned int count
init_waitqueue_head(&ctx->wqh);
ctx->count = count;
ctx->flags = flags;
+ ctx->id = ida_simple_get(&eventfd_ida, 0, 0, GFP_KERNEL);
fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
_
Patches currently in -mm which might be from yamato@xxxxxxxxxx are
eventfd-prepare-id-to-userspace-via-fdinfo.patch
