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Diffstat (limited to 'Documentation/filesystems/proc.rst')
| -rw-r--r-- | Documentation/filesystems/proc.rst | 40 |
1 files changed, 29 insertions, 11 deletions
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index db6167befb7b..c102b62023cd 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -23,13 +23,13 @@ fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 1 Collecting System Information 1.1 Process-Specific Subdirectories 1.2 Kernel data - 1.3 IDE devices in /proc/ide - 1.4 Networking info in /proc/net - 1.5 SCSI info - 1.6 Parallel port info in /proc/parport - 1.7 TTY info in /proc/tty - 1.8 Miscellaneous kernel statistics in /proc/stat - 1.9 Ext4 file system parameters + 1.3 Networking info in /proc/net + 1.4 SCSI info + 1.5 Parallel port info in /proc/parport + 1.6 TTY info in /proc/tty + 1.7 Miscellaneous kernel statistics in /proc/stat + 1.8 Ext4 file system parameters + 1.9 /proc/consoles - Shows registered system consoles 2 Modifying System Parameters @@ -52,6 +52,7 @@ fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 4 Configuring procfs 4.1 Mount options + 4.2 Mount restrictions 5 Filesystem behavior @@ -118,7 +119,7 @@ PTRACE_MODE_ATTACH permissions; CAP_PERFMON capability does not grant access to /proc/PID/mem for other processes. Note that an open file descriptor to /proc/<pid> or to any of its -contained files or subdirectories does not prevent <pid> being reused +contained files or subdirectories does not prevent <pid> from being reused for some other process in the event that <pid> exits. Operations on open /proc/<pid> file descriptors corresponding to dead processes never act on any new process that the kernel may, through chance, have @@ -512,7 +513,7 @@ In some kernel configurations, the semantics of pages part of a larger allocation (e.g., THP) can differ: a page is accounted as "private" if all pages part of the corresponding large allocation are *certainly* mapped in the same process, even if the page is mapped multiple times in that process. A -page is accounted as "shared" if any page page of the larger allocation +page is accounted as "shared" if any page of the larger allocation is *maybe* mapped in a different process. In some cases, a large allocation might be treated as "maybe mapped by multiple processes" even though this is no longer the case. @@ -607,6 +608,7 @@ encoded manner. The codes are the following: um userfaultfd missing tracking uw userfaultfd wr-protect tracking ui userfaultfd minor fault + ur userfaultfd read-write-protect tracking ss shadow/guarded control stack page sl sealed lf lock on fault pages @@ -2211,7 +2213,7 @@ the process is maintaining. Example output:: | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls The name of a link represents the virtual memory bounds of a mapping, i.e. -vm_area_struct::vm_start-vm_area_struct::vm_end. +vm_area_struct::vm_start - vm_area_struct::vm_end. The main purpose of the map_files is to retrieve a set of memory mapped files in a fast way instead of parsing /proc/<pid>/maps or @@ -2425,7 +2427,9 @@ prohibited by hidepid=. If you use some daemon like identd which needs to learn information about processes information, just add identd to this group. subset=pid hides all top level files and directories in the procfs that -are not related to tasks. +are not related to tasks. This option cannot be changed on an existing +procfs instance because overmounts that existed before the change could +otherwise remain reachable after the top level procfs entries are hidden. pidns= specifies a pid namespace (either as a string path to something like `/proc/$pid/ns/pid`, or a file descriptor when using `FSCONFIG_SET_FD`) that @@ -2434,6 +2438,20 @@ will use the calling process's active pid namespace. Note that the pid namespace of an existing procfs instance cannot be modified (attempting to do so will give an `-EBUSY` error). +4.2 Mount restrictions +-------------------------- + +If user namespaces are in use, the kernel additionally checks the instances of +procfs available to the mounter and will not allow procfs to be mounted if: + + 1. This mount is not fully visible unless the new procfs is going to be + mounted with subset=pid option. + + a. Its root directory is not the root directory of the filesystem. + b. If any file or non-empty procfs directory is hidden by another mount. + + 2. A new mount overrides the readonly option or any option from atime family. + Chapter 5: Filesystem behavior ============================== |