Check in gVisor.

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+This document tracks what is implemented in procfs. Refer to
+Documentation/filesystems/proc.txt in the Linux project for information about
+procfs generally.
+
+**NOTE**: This document is not guaranteed to be up to date. If you find an
+inconsistency, please file a bug.
+
+[TOC]
+## Kernel data
+
+The following files are implemented:
+
+| File /proc/               | Content                                          |
+| :------------------------ | :----------------------------------------------- |
+| [cpuinfo](#cpuinfo)       | Info about the CPU                               |
+| [filesystem](#filesystem) | Supported filesystems                            |
+| [loadavg](#loadavg)       | Load average of last 1, 5 & 15 minutes           |
+| [meminfo](#meminfo)       | Overall memory info                              |
+| [stat](#stat)             | Overall kernel statistics                        |
+| [sys](#sys)               | Change parameters within the kernel              |
+| [uptime](#uptime)         | Wall clock since boot, combined idle time of all |
+:                           : cpus                                             :
+| [version](#version)       | Kernel version                                   |
+
+### cpuinfo
+
+```bash
+$ cat /proc/cpuinfo
+processor   : 0
+vendor_id   : GenuineIntel
+cpu family  : 6
+model       : 45
+model name  : unknown
+stepping    : unknown
+cpu MHz     : 1234.588
+fpu     : yes
+fpu_exception   : yes
+cpuid level : 13
+wp      : yes
+flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx xsaveopt
+bogomips    : 1234.59
+clflush size    : 64
+cache_alignment : 64
+address sizes   : 46 bits physical, 48 bits virtual
+power management:
+
+...
+```
+
+Notable divergences:
+
+Field name       | Notes
+:--------------- | :---------------------------------------
+model name       | Always unknown
+stepping         | Always unknown
+fpu              | Always yes
+fpu_exception    | Always yes
+wp               | Always yes
+bogomips         | Bogus value (matches cpu MHz)
+clflush size     | Always 64
+cache_alignment  | Always 64
+address sizes    | Always 46 bits physical, 48 bits virtual
+power management | Always blank
+
+Otherwise fields are derived from the SentryCPUIDSpec proto config.
+
+### filesystem
+
+```bash
+$ cat /proc/filesystem
+nodev   9p
+nodev   devtmpfs
+nodev   proc
+nodev   ramdiskfs
+nodev   sysfs
+nodev   tmpfs
+```
+
+Notable divergences:
+
+Filesystem | Notes
+:--------- | :--------------------------------------------------------
+ramdiskfs  | No Linux equivalent, see the SentryRamdiskFS proto config
+
+### loadavg
+
+```bash
+$ cat /proc/loadavg
+0.00 0.00 0.00 0/0 0
+```
+
+Column                                | Notes
+:------------------------------------ | :----------
+CPU.IO utilization in last 1 minute   | Always zero
+CPU.IO utilization in last 5 minutes  | Always zero
+CPU.IO utilization in last 10 minutes | Always zero
+Num currently running processes       | Always zero
+Total num processes                   | Always zero
+
+TODO: Populate the columns with accurate statistics.
+### meminfo
+
+```bash
+$ cat /proc/meminfo
+MemTotal:        2097152 kB
+MemFree:         2083540 kB
+MemAvailable:    2083540 kB
+Buffers:               0 kB
+Cached:             4428 kB
+SwapCache:             0 kB
+Active:            10812 kB
+Inactive:           2216 kB
+Active(anon):       8600 kB
+Inactive(anon):        0 kB
+Active(file):       2212 kB
+Inactive(file):     2216 kB
+Unevictable:           0 kB
+Mlocked:               0 kB
+SwapTotal:             0 kB
+SwapFree:              0 kB
+Dirty:                 0 kB
+Writeback:             0 kB
+AnonPages:          8600 kB
+Mapped:             4428 kB
+Shmem:                 0 kB
+
+```
+
+Notable divergences:
+
+Field name        | Notes
+:---------------- | :--------------------------------------------------------
+Buffers           | Always zero, no block devices
+SwapCache         | Always zero, no swap
+Inactive(anon)    | Always zero, see SwapCache
+Unevictable       | Always zero TODO
+Mlocked           | Always zero TODO
+SwapTotal         | Always zero, no swap
+SwapFree          | Always zero, no swap
+Dirty             | Always zero TODO
+Writeback         | Always zero TODO
+MemAvailable      | Uses the same value as MemFree since there is no swap.
+Slab              | Missing
+SReclaimable      | Missing
+SUnreclaim        | Missing
+KernelStack       | Missing
+PageTables        | Missing
+NFS_Unstable      | Missing
+Bounce            | Missing
+WritebackTmp      | Missing
+CommitLimit       | Missing
+Committed_AS      | Missing
+VmallocTotal      | Missing
+VmallocUsed       | Missing
+VmallocChunk      | Missing
+HardwareCorrupted | Missing
+AnonHugePages     | Missing
+ShmemHugePages    | Missing
+ShmemPmdMapped    | Missing
+HugePages_Total   | Missing
+HugePages_Free    | Missing
+HugePages_Rsvd    | Missing
+HugePages_Surp    | Missing
+Hugepagesize      | Missing
+DirectMap4k       | Missing
+DirectMap2M       | Missing
+DirectMap1G       | Missing
+
+See [Memory
+Accounting](pkg/sentry/usage/g3doc/memory-accounting.md)
+for general caveats.
+
+### stat
+
+```bash
+$ cat /proc/stat
+cpu  0 0 0 0 0 0 0 0 0 0
+cpu0 0 0 0 0 0 0 0 0 0 0
+cpu1 0 0 0 0 0 0 0 0 0 0
+cpu2 0 0 0 0 0 0 0 0 0 0
+cpu3 0 0 0 0 0 0 0 0 0 0
+cpu4 0 0 0 0 0 0 0 0 0 0
+cpu5 0 0 0 0 0 0 0 0 0 0
+cpu6 0 0 0 0 0 0 0 0 0 0
+cpu7 0 0 0 0 0 0 0 0 0 0
+intr 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+ctxt 0
+btime 1504040968
+processes 0
+procs_running 0
+procs_blokkcked 0
+softirq 0 0 0 0 0 0 0 0 0 0 0
+```
+
+All fields except for `btime` are always zero.
+TODO: Populate with accurate fields.
+
+### sys
+
+```bash
+$ ls /proc/sys
+kernel vm
+```
+
+Directory | Notes
+:-------- | :----------------------------
+abi       | Missing
+debug     | Missing
+dev       | Missing
+fs        | Missing
+kernel    | Contains hostname (only)
+net       | Missing
+user      | Missing
+vm        | Contains mmap_min_addr (only)
+
+### uptime
+
+```bash
+$ cat /proc/uptime
+3204.62 0.00
+```
+
+Column                           | Notes
+:------------------------------- | :----------------------------
+Total num seconds system running | Time since procfs was mounted
+Number of seconds idle           | Always zero
+
+### version
+
+```bash
+$ cat /proc/version
+Linux version 3.11.10 #1 SMP Fri Nov 29 10:47:50 PST 2013
+```
+
+## Process-specific data
+
+The following files are implemented:
+
+File /proc/PID      | Content
+:------------------ | :---------------------------------------------------
+[auxv](#auxv)       | Copy of auxiliary vector for the process
+[cmdline](#cmdline) | Command line arguments
+[comm](#comm)       | Command name associated with the process
+[exe](#exe)         | Symlink to the process's executable
+[fd](#fd)           | Directory containing links to open file descriptors
+[fdinfo](#fdinfo)   | Information associated with open file descriptors
+[gid_map](#gid_map) | Mappings for group IDs inside the user namespace
+[io](#io)           | IO statistics
+[maps](#maps)       | Memory mappings (anon, executables, library files)
+[ns](#ns)           | Directory containing info about supported namespaces
+[stat](#stat)       | Process statistics
+[status](#status)   | Process status in human readable format
+[task](#task)       | Directory containing info about running threads
+[uid_map](#uid_map) | Mappings for user IDs inside the user namespace
+
+### auxv
+
+TODO
+
+### cmdline
+
+TODO
+
+### comm
+
+TODO
+
+### exe
+
+TODO
+
+### fd
+
+TODO
+
+### fdinfo
+
+TODO
+
+### gid_map
+
+TODO
+
+### io
+
+Only has data for rchar, wchar, syscr, and syscw.
+
+TODO: add more detail.
+
+### maps
+
+TODO
+
+### ns
+
+TODO
+
+### stat
+
+Only has data for pid, comm, state, ppid, utime, stime, cutime, cstime,
+num_threads, and exit_signal.
+
+TODO: add more detail.
+
+### status
+
+Statically created, most of the fields have no data.
+
+TODO: add more detail.
+
+### task
+
+TODO
+
+### uid_map
+
+TODO