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Date: Tue, 31 May 2022 14:25:15 -0700
From: Kalesh Singh <kaleshsingh@...gle.com>
To: unlisted-recipients:; (no To-header on input)
Cc: ilkos@...gle.com, tjmercier@...gle.com, surenb@...gle.com,
kernel-team@...roid.com, Kalesh Singh <kaleshsingh@...gle.com>,
Jonathan Corbet <corbet@....net>,
Sumit Semwal <sumit.semwal@...aro.org>,
"Christian König" <christian.koenig@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
David Hildenbrand <david@...hat.com>,
Christoph Anton Mitterer <mail@...istoph.anton.mitterer.name>,
Johannes Weiner <hannes@...xchg.org>,
Colin Cross <ccross@...gle.com>,
Mike Rapoport <rppt@...nel.org>,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Randy Dunlap <rdunlap@...radead.org>,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-media@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org
Subject: [PATCH 2/2] procfs: Add 'path' to /proc/<pid>/fdinfo/
In order to identify the type of memory a process has pinned through
its open fds, add the file path to fdinfo output. This allows
identifying memory types based on common prefixes. e.g. "/memfd...",
"/dmabuf...", "/dev/ashmem...".
Access to /proc/<pid>/fdinfo is governed by PTRACE_MODE_READ_FSCREDS
the same as /proc/<pid>/maps which also exposes the file path of
mappings; so the security permissions for accessing path is consistent
with that of /proc/<pid>/maps.
Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
---
Changes from rfc:
- Split adding 'size' and 'path' into a separate patches, per Christian
- Fix indentation (use tabs) in documentaion, per Randy
Documentation/filesystems/proc.rst | 14 ++++++++++++--
fs/proc/fd.c | 4 ++++
2 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 779c05528e87..591f12d30d97 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -1886,14 +1886,16 @@ if precise results are needed.
3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
---------------------------------------------------------------
This file provides information associated with an opened file. The regular
-files have at least five fields -- 'pos', 'flags', 'mnt_id', 'ino', and 'size'.
+files have at least six fields -- 'pos', 'flags', 'mnt_id', 'ino', 'size',
+and 'path'.
The 'pos' represents the current offset of the opened file in decimal
form [see lseek(2) for details], 'flags' denotes the octal O_xxx mask the
file has been created with [see open(2) for details] and 'mnt_id' represents
mount ID of the file system containing the opened file [see 3.5
/proc/<pid>/mountinfo for details]. 'ino' represents the inode number of
-the file, and 'size' represents the size of the file in bytes.
+the file, 'size' represents the size of the file in bytes, and 'path'
+represents the file path.
A typical output is::
@@ -1902,6 +1904,7 @@ A typical output is::
mnt_id: 19
ino: 63107
size: 0
+ path: /dev/null
All locks associated with a file descriptor are shown in its fdinfo too::
@@ -1920,6 +1923,7 @@ Eventfd files
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:[eventfd]
eventfd-count: 5a
where 'eventfd-count' is hex value of a counter.
@@ -1934,6 +1938,7 @@ Signalfd files
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:[signalfd]
sigmask: 0000000000000200
where 'sigmask' is hex value of the signal mask associated
@@ -1949,6 +1954,7 @@ Epoll files
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:[eventpoll]
tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
where 'tfd' is a target file descriptor number in decimal form,
@@ -1968,6 +1974,7 @@ For inotify files the format is the following::
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:inotify
inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
where 'wd' is a watch descriptor in decimal form, i.e. a target file
@@ -1992,6 +1999,7 @@ For fanotify files the format is::
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:[fanotify]
fanotify flags:10 event-flags:0
fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
@@ -2018,6 +2026,7 @@ Timerfd files
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:[timerfd]
clockid: 0
ticks: 0
settime flags: 01
@@ -2042,6 +2051,7 @@ DMA Buffer files
mnt_id: 9
ino: 63107
size: 32768
+ path: /dmabuf:
count: 2
exp_name: system-heap
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 464bc3f55759..8889a8ba09d4 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -60,6 +60,10 @@ static int seq_show(struct seq_file *m, void *v)
seq_printf(m, "ino:\t%lu\n", file_inode(file)->i_ino);
seq_printf(m, "size:\t%lli\n", (long long)file_inode(file)->i_size);
+ seq_puts(m, "path:\t");
+ seq_file_path(m, file, "\n");
+ seq_putc(m, '\n');
+
/* show_fd_locks() never deferences files so a stale value is safe */
show_fd_locks(m, file, files);
if (seq_has_overflowed(m))
--
2.36.1.255.ge46751e96f-goog
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