fs, kernel: permit disabling the uselib syscall

uselib hasn't been used since libc5; glibc does not use it.  Support
turning it off.

When disabled, also omit the load_elf_library implementation from
binfmt_elf.c, which only uselib invokes.

bloat-o-meter:
add/remove: 0/4 grow/shrink: 0/1 up/down: 0/-785 (-785)
function                                     old     new   delta
padzero                                       39      36      -3
uselib_flags                                  20       -     -20
sys_uselib                                   168       -    -168
SyS_uselib                                   168       -    -168
load_elf_library                             426       -    -426

The new CONFIG_USELIB defaults to `y'.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SubmittingPatches: add style recommendation to use imperative descriptions

Most commit messages use this style, and the recommendation frequently
comes up in discussions (especially in response to patches that don't
use it), but that recommendation doesn't actually appear anywhere in
Documentation.  Add this style guideline to SubmittingPatches, using the
description from git's SubmittingPatches.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Rob Landley <rob@landley.net>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SubmittingPatches: add recommendation for mailing list references

SubmittingPatches already mentions referencing bugs fixed by a commit,
but doesn't mention citing relevant mailing list discussions.  Add a
note to that effect, along with a recommendation to use the
https://lkml.kernel.org/ redirector.

Portions based on text from git's SubmittingPatches.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Rob Landley <rob@landley.net>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SubmittingPatches: document the use of git

Most of the mechanical portions of SubmittingPatches exist to help patch
submitters replicate the output of git.  Mention this explicitly, both
as a reminder that git will help with this process, and as signposting
to let git users know what they can safely skip.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Rob Landley <rob@landley.net>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
err.h: use bool for IS_ERR and IS_ERR_OR_NULL

Use the more natural return of bool for these tests.

No difference observed in .o files produced by gcc for x86.

Remove the dentry description of kernel pointers left over from the 90's
and 2002's cleanup move of parts of fs.h to err.h.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
samples/seccomp/Makefile: do not build tests if cross-compiling for MIPS

The Makefile is designed to use the host toolchain so it may be unsafe
to build the tests if the kernel has been configured and built for
another architecture.  This fixes a build problem when the kernel has
been configured and built for the MIPS architecture but the host is not
MIPS (cross-compiled).  The MIPS syscalls are only defined if one of the
following is true:

 1) _MIPS_SIM == _MIPS_SIM_ABI64
 2) _MIPS_SIM == _MIPS_SIM_ABI32
 3) _MIPS_SIM == _MIPS_SIM_NABI32

Of course, none of these make sense on a non-MIPS toolchain and the
following build problem occurs when building on a non-MIPS host.

  linux/usr/include/linux/kexec.h:50: userspace cannot reference function or variable defined in the kernel
  samples/seccomp/bpf-direct.c: In function `emulator':
  samples/seccomp/bpf-direct.c:76:17: error: `__NR_write' undeclared (first use in this function)

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
xattr: guard against simultaneous glibc header inclusion

If the glibc xattr.h header is included after the uapi header,
compilation fails due to an enum re-using a #define from the uapi
header.

Protect against this by guarding the define and enum inclusions against
each other.

(See https://lists.debian.org/debian-glibc/2014/03/msg00029.html
and https://sourceware.org/glibc/wiki/Synchronizing_Headers
for more information.)

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Allan McRae <allan@archlinux.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/syscall.c: unexport task_current_syscall()

It is only used by procfs and procfs cannot be a module.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kernel: audit/fix non-modular users of module_init in core code

Code that is obj-y (always built-in) or dependent on a bool Kconfig
(built-in or absent) can never be modular.  So using module_init as an
alias for __initcall can be somewhat misleading.

Fix these up now, so that we can relocate module_init from init.h into
module.h in the future.  If we don't do this, we'd have to add module.h
to obviously non-modular code, and that would be a worse thing.

The audit targets the following module_init users for change:
 kernel/user.c                  obj-y
 kernel/kexec.c                 bool KEXEC (one instance per arch)
 kernel/profile.c               bool PROFILING
 kernel/hung_task.c             bool DETECT_HUNG_TASK
 kernel/sched/stats.c           bool SCHEDSTATS
 kernel/user_namespace.c        bool USER_NS

Note that direct use of __initcall is discouraged, vs.  one of the
priority categorized subgroups.  As __initcall gets mapped onto
device_initcall, our use of subsys_initcall (which makes sense for these
files) will thus change this registration from level 6-device to level
4-subsys (i.e.  slightly earlier).  However no observable impact of that
difference has been observed during testing.

Also, two instances of missing ";" at EOL are fixed in kexec.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kernel/resource.c: make reallocate_resource() static

sparse says:

kernel/resource.c:518:5: warning:
 symbol 'reallocate_resource' was not declared. Should it be static?

Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
vsprintf: remove %n handling

All in-kernel users of %n in format strings have now been removed and
the %n directive is ignored.  Remove the handling of %n so that it is
treated the same as any other invalid format string directive.  Keep a
warning in place to deter new instances of %n in format strings.

Signed-off-by: Ryan Mallon <rmallon@gmail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
printk: remove duplicated check for log level

The check for the exact log level is already done in printk_get_level.
We do not need to duplicate it in printk_skip_level.

Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
printk: remove obsolete check for log level "c"

The kernel log level "c" was removed in commit 61e99ab8e35a ("printk:
remove the now unnecessary "C" annotation for KERN_CONT").  It is no
longer detected in printk_get_level().  Hence we do not need to check it
in vprintk_emit.

Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
printk: add comment about tricky check for text buffer size

There is no check for potential "text_len" overflow.  It is not needed
because only valid level is detected.  It took me some time to
understand why.  It would deserve a comment ;-)

Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
printk: use also the last bytes in the ring buffer

It seems that we have newer used the last byte in the ring buffer.  In
fact, we have newer used the last 4 bytes because of padding.

First problem is in the check for free space.  The exact number of free
bytes is enough to store the length of data.

Second problem is in the check where the ring buffer is rotated.  The
left side counts the first unused index.  It is unused, so it might be
the same as the size of the buffer.

Note that the first problem has to be fixed together with the second
one.  Otherwise, the buffer is rotated even when there is enough space
on the end of the buffer.  Then the beginning of the buffer is rewritten
and valid entries get corrupted.

Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
printk: do not compute the size of the message twice

This is just a tiny optimization.  It removes duplicate computation of
the message size.

Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/printk.h: remove double asmlinkage in printk_emit

The double asmlinkage was introduced in commit 7ff9554bb578 ("printk:
convert byte-buffer to variable-length record buffer").

Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
printk: fix one circular lockdep warning about console_lock

Fix a warning about possible circular locking dependency.

If do in following sequence:

    enter suspend ->  resume ->  plug-out CPUx (echo 0 > cpux/online)

lockdep will show warning as following:

  ======================================================
  [ INFO: possible circular locking dependency detected ]
  3.10.0 #2 Tainted: G           O
  -------------------------------------------------------
  sh/1271 is trying to acquire lock:
  (console_lock){+.+.+.}, at: console_cpu_notify+0x20/0x2c
  but task is already holding lock:
  (cpu_hotplug.lock){+.+.+.}, at: cpu_hotplug_begin+0x2c/0x58
  which lock already depends on the new lock.

  the existing dependency chain (in reverse order) is:
  -> #2 (cpu_hotplug.lock){+.+.+.}:
    lock_acquire+0x98/0x12c
    mutex_lock_nested+0x50/0x3d8
    cpu_hotplug_begin+0x2c/0x58
    _cpu_up+0x24/0x154
    cpu_up+0x64/0x84
    smp_init+0x9c/0xd4
    kernel_init_freeable+0x78/0x1c8
    kernel_init+0x8/0xe4
    ret_from_fork+0x14/0x2c

  -> #1 (cpu_add_remove_lock){+.+.+.}:
    lock_acquire+0x98/0x12c
    mutex_lock_nested+0x50/0x3d8
    disable_nonboot_cpus+0x8/0xe8
    suspend_devices_and_enter+0x214/0x448
    pm_suspend+0x1e4/0x284
    try_to_suspend+0xa4/0xbc
    process_one_work+0x1c4/0x4fc
    worker_thread+0x138/0x37c
    kthread+0xa4/0xb0
    ret_from_fork+0x14/0x2c

  -> #0 (console_lock){+.+.+.}:
    __lock_acquire+0x1b38/0x1b80
    lock_acquire+0x98/0x12c
    console_lock+0x54/0x68
    console_cpu_notify+0x20/0x2c
    notifier_call_chain+0x44/0x84
    __cpu_notify+0x2c/0x48
    cpu_notify_nofail+0x8/0x14
    _cpu_down+0xf4/0x258
    cpu_down+0x24/0x40
    store_online+0x30/0x74
    dev_attr_store+0x18/0x24
    sysfs_write_file+0x16c/0x19c
    vfs_write+0xb4/0x190
    SyS_write+0x3c/0x70
    ret_fast_syscall+0x0/0x48

  Chain exists of:
     console_lock --> cpu_add_remove_lock --> cpu_hotplug.lock

  Possible unsafe locking scenario:
         CPU0                    CPU1
         ----                    ----
  lock(cpu_hotplug.lock);
                                 lock(cpu_add_remove_lock);
                                 lock(cpu_hotplug.lock);
  lock(console_lock);
    *** DEADLOCK ***

There are three locks involved in two sequence:
a) pm suspend:
	console_lock (@suspend_console())
	cpu_add_remove_lock (@disable_nonboot_cpus())
	cpu_hotplug.lock (@_cpu_down())
b) Plug-out CPUx:
	cpu_add_remove_lock (@(cpu_down())
	cpu_hotplug.lock (@_cpu_down())
	console_lock (@console_cpu_notify()) => Lockdeps prints warning log.

There should be not real deadlock, as flag of console_suspended can
protect this.

Although console_suspend() releases console_sem, it doesn't tell lockdep
about it.  That results in the lockdep warning about circular locking
when doing the following: enter suspend -> resume -> plug-out CPUx (echo
0 > cpux/online)

Fix the problem by telling lockdep we actually released the semaphore in
console_suspend() and acquired it again in console_resume().

Signed-off-by: Jane Li <jiel@marvell.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
MAINTAINERS: add backlight co-maintainers

Bryan Wu and Lee Jones volunteer to maintain backlight drivers and help
to setup git-tree for backlight subsystem.  Thus, I add them as
backlight co-maintainers.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Bryan Wu <cooloney@gmail.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
MAINTAINERS: mark SuperH orphan

Paul Mundt's email address bounces regularly, and he hasn't taken any
SuperH patches for about one year.

Signed-off-by: Geert Uytterhoeven <geert+renesas@linux-m68k.org>
Suggested-by: Paul Bolle <pebolle@tiscali.nl>
Cc: Paul Mundt <paul.mundt@gmail.com>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Simon Horman <horms@verge.net.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>