linux-toradex.git/include/uapi/linux/shm.h, branch v4.16-rc4

License cleanup: add SPDX license identifier to uapi header files with no license

2017-11-02T10:19:54+00:00

Many user space API headers are missing licensing information, which
makes it hard for compliance tools to determine the correct license.

By default are files without license information under the default
license of the kernel, which is GPLV2.  Marking them GPLV2 would exclude
them from being included in non GPLV2 code, which is obviously not
intended. The user space API headers fall under the syscall exception
which is in the kernels COPYING file:

   NOTE! This copyright does *not* cover user programs that use kernel
   services by normal system calls - this is merely considered normal use
   of the kernel, and does *not* fall under the heading of "derived work".

otherwise syscall usage would not be possible.

Update the files which contain no license information with an SPDX
license identifier.  The chosen identifier is 'GPL-2.0 WITH
Linux-syscall-note' which is the officially assigned identifier for the
Linux syscall exception.  SPDX license identifiers are a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.  See the previous patch in this series for the
methodology of how this patch was researched.

Reviewed-by: Kate Stewart 
Reviewed-by: Philippe Ombredanne 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

mm: shm: use new hugetlb size encoding definitions

2017-09-07T00:27:28+00:00

Use the common definitions from hugetlb_encode.h header file for
encoding hugetlb size definitions in shmget system call flags.

In addition, move these definitions from the internal (kernel) to user
(uapi) header file.

Link: http://lkml.kernel.org/r/1501527386-10736-4-git-send-email-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz 
Suggested-by: Matthew Wilcox 
Acked-by: Michal Hocko 
Cc: Andi Kleen 
Cc: Andrea Arcangeli 
Cc: Aneesh Kumar K.V 
Cc: Anshuman Khandual 
Cc: Arnd Bergmann 
Cc: Davidlohr Bueso 
Cc: Michael Kerrisk 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc,shm: document new limits in the uapi header

2014-06-06T23:08:14+00:00

This is useful in the future and allows users to better understand the
reasoning behind the changes.

Also use UL as we're dealing with it anyways.

Signed-off-by: Davidlohr Bueso 
Cc: Michael Kerrisk 
Cc: Manfred Spraul 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc/shm.c: increase the defaults for SHMALL, SHMMAX

2014-06-06T23:08:14+00:00

System V shared memory

a) can be abused to trigger out-of-memory conditions and the standard
   measures against out-of-memory do not work:

    - it is not possible to use setrlimit to limit the size of shm segments.

    - segments can exist without association with any processes, thus
      the oom-killer is unable to free that memory.

b) is typically used for shared information - today often multiple GB.
   (e.g. database shared buffers)

The current default is a maximum segment size of 32 MB and a maximum
total size of 8 GB.  This is often too much for a) and not enough for
b), which means that lots of users must change the defaults.

This patch increases the default limits (nearly) to the maximum, which
is perfect for case b).  The defaults are used after boot and as the
initial value for each new namespace.

Admins/distros that need a protection against a) should reduce the
limits and/or enable shm_rmid_forced.

Unix has historically required setting these limits for shared memory,
and Linux inherited such behavior.  The consequence of this is added
complexity for users and administrators.  One very common example are
Database setup/installation documents and scripts, where users must
manually calculate the values for these limits.  This also requires
(some) knowledge of how the underlying memory management works, thus
causing, in many occasions, the limits to just be flat out wrong.
Disabling these limits sooner could have saved companies a lot of time,
headaches and money for support.  But it's never too late, simplify
users life now.

Further notes:
- The patch only changes default, overrides behave as before:
        # sysctl kernel.shmall=33554432
  would recreate the previous limit for SHMMAX (for the current namespace).

- Disabling sysv shm allocation is possible with:
        # sysctl kernel.shmall=0
  (not a new feature, also per-namespace)

- The limits are intentionally set to a value slightly less than ULONG_MAX,
  to avoid triggering overflows in user space apps.
  [not unreasonable, see http://marc.info/?l=linux-mm&m=139638334330127]

Signed-off-by: Manfred Spraul 
Signed-off-by: Davidlohr Bueso 
Reported-by: Davidlohr Bueso 
Acked-by: Michael Kerrisk 
Acked-by: KOSAKI Motohiro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

uapi: Use __kernel_ulong_t in shmid64_ds/shminfo64/shm_info

2014-01-20T22:45:25+00:00

Both x32 and x86-64 use the same struct shmid64_ds/shminfo64/shm_info for
system calls.  But x32 long is 32-bit. This patch replaces unsigned long
with __kernel_ulong_t in struct shmid64_ds/shminfo64/shm_info.

Signed-off-by: H.J. Lu 
Link: http://lkml.kernel.org/r/1388182464-28428-8-git-send-email-hjl.tools@gmail.com
Signed-off-by: H. Peter Anvin

UAPI: (Scripted) Disintegrate include/linux

2012-10-13T09:46:48+00:00

Signed-off-by: David Howells 
Acked-by: Arnd Bergmann 
Acked-by: Thomas Gleixner 
Acked-by: Michael Kerrisk 
Acked-by: Paul E. McKenney 
Acked-by: Dave Jones