Merge tag 'docs-5.0' of git://git.lwn.net/linux

[mirror_ubuntu-eoan-kernel.git] / Documentation / filesystems / proc.txt

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 12a5e6e693b6e4f516ffb85d78677aff53ab81b0..66cad5c86171f1bd6b5dffb2878d618dc2d1fbbf 100644 (file)
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -125,6 +125,13 @@ process running on the system, which is named after the process ID (PID).
 The link  self  points  to  the  process reading the file system. Each process
 subdirectory has the entries listed in Table 1-1.
 
+Note that an open a file descriptor to /proc/<pid> or to any of its
+contained files or subdirectories does not prevent <pid> 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
+also assigned the process ID <pid>. Instead, operations on these FDs
+usually fail with ESRCH.
 
 Table 1-1: Process specific entries in /proc
 ..............................................................................
@@ -182,6 +189,7 @@ read the file /proc/PID/status:
   VmSwap:        0 kB
   HugetlbPages:          0 kB
   CoreDumping:    0
+  THP_enabled:   1
   Threads:        1
   SigQ:   0/28578
   SigPnd: 0000000000000000
@@ -193,8 +201,10 @@ read the file /proc/PID/status:
   CapPrm: 0000000000000000
   CapEff: 0000000000000000
   CapBnd: ffffffffffffffff
+  CapAmb: 0000000000000000
   NoNewPrivs:     0
   Seccomp:        0
+  Speculation_Store_Bypass:       thread vulnerable
   voluntary_ctxt_switches:        0
   nonvoluntary_ctxt_switches:     1
 
@@ -214,7 +224,7 @@ asynchronous manner and the value may not be very precise. To see a precise
 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
 It's slow but very precise.
 
-Table 1-2: Contents of the status files (as of 4.8)
+Table 1-2: Contents of the status files (as of 4.19)
 ..............................................................................
  Field                       Content
  Name                        filename of the executable
@@ -256,6 +266,8 @@ Table 1-2: Contents of the status files (as of 4.8)
  HugetlbPages                size of hugetlb memory portions
  CoreDumping                 process's memory is currently being dumped
                              (killing the process may lead to a corrupted core)
+ THP_enabled                process is allowed to use THP (returns 0 when
+                            PR_SET_THP_DISABLE is set on the process
  Threads                     number of threads
  SigQ                        number of signals queued/max. number for queue
  SigPnd                      bitmap of pending signals for the thread
@@ -267,8 +279,10 @@ Table 1-2: Contents of the status files (as of 4.8)
  CapPrm                      bitmap of permitted capabilities
  CapEff                      bitmap of effective capabilities
  CapBnd                      bitmap of capabilities bounding set
+ CapAmb                      bitmap of ambient capabilities
  NoNewPrivs                  no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
  Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
+ Speculation_Store_Bypass    speculative store bypass mitigation status
  Cpus_allowed                mask of CPUs on which this process may run
  Cpus_allowed_list           Same as previous, but in "list format"
  Mems_allowed                mask of memory nodes allowed to this process
@@ -425,6 +439,7 @@ SwapPss:               0 kB
 KernelPageSize:        4 kB
 MMUPageSize:           4 kB
 Locked:                0 kB
+THPeligible:           0
 VmFlags: rd ex mr mw me dw
 
 the first of these lines shows the same information as is displayed for the
@@ -462,6 +477,8 @@ replaced by copy-on-write) part of the underlying shmem object out on swap.
 "SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
 does not take into account swapped out page of underlying shmem objects.
 "Locked" indicates whether the mapping is locked in memory or not.
+"THPeligible" indicates whether the mapping is eligible for THP pages - 1 if
+true, 0 otherwise.
 
 "VmFlags" field deserves a separate description. This member represents the kernel
 flags associated with the particular virtual memory area in two letter encoded
@@ -496,7 +513,9 @@ manner. The codes are the following:
 
 Note that there is no guarantee that every flag and associated mnemonic will
 be present in all further kernel releases. Things get changed, the flags may
-be vanished or the reverse -- new added.
+be vanished or the reverse -- new added. Interpretation of their meaning
+might change in future as well. So each consumer of these flags has to
+follow each specific kernel version for the exact semantic.
 
 This file is only present if the CONFIG_MMU kernel configuration option is
 enabled.