wait_on_bit: add an acquire memory barrier

There are several places in the kernel where wait_on_bit is not followed
by a memory barrier (for example, in drivers/md/dm-bufio.c:new_read).

On architectures with weak memory ordering, it may happen that memory
accesses that follow wait_on_bit are reordered before wait_on_bit and
they may return invalid data.

Fix this class of bugs by introducing a new function "test_bit_acquire"
that works like test_bit, but has acquire memory ordering semantics.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Will Deacon <will@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

bitops: unify non-atomic bitops prototypes across architectures

Currently, there is a mess with the prototypes of the non-atomic
bitops across the different architectures:

ret bool, int, unsigned long
nr int, long, unsigned int, unsigned long
addr volatile unsigned long *, volatile void *

Thankfully, it doesn't provoke any bugs, but can sometimes make
the compiler angry when it's not handy at all.
Adjust all the prototypes to the following standard:

ret bool retval can be only 0 or 1
nr unsigned long native; signed makes no sense
addr volatile unsigned long * bitmaps are arrays of ulongs

Next, some architectures don't define 'arch_' versions as they don't
support instrumentation, others do. To make sure there is always the
same set of callables present and to ease any potential future
changes, make them all follow the rule:
* architecture-specific files define only 'arch_' versions;
* non-prefixed versions can be defined only in asm-generic files;
and place the non-prefixed definitions into a new file in
asm-generic to be included by non-instrumented architectures.

Finally, add some static assertions in order to prevent people from
making a mess in this room again.
I also used the %__always_inline attribute consistently, so that
they always get resolved to the actual operations.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>

bitops: always define asm-generic non-atomic bitops

Move generic non-atomic bitops from the asm-generic header which
gets included only when there are no architecture-specific
alternatives, to a separate independent file to make them always
available.
Almost no actual code changes, only one comment added to
generic_test_bit() saying that it's an atomic operation itself
and thus `volatile` must always stay there with no cast-aways.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> # comment
Suggested-by: Marco Elver <elver@google.com> # reference to kernel-doc
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>

bitops/non-atomic: make @nr unsigned to avoid any DIV

signed math causes generation of costlier instructions such as DIV when
they could be done by barrerl shifter.

Worse part is this is not caught by things like bloat-o-meter since
instruction length / symbols are typically same size.

e.g.

stock (signed math)
__________________

919b4614 <test_taint>:
919b4614: div r2,r0,0x20
^^^
919b4618: add2 r2,0x920f6050,r2
919b4620: ld_s r2,[r2,0]
919b4622: lsr r0,r2,r0
919b4626: j_s.d [blink]
919b4628: bmsk_s r0,r0,0
919b462a: nop_s

(patched) unsigned math
__________________

919b4614 <test_taint>:
919b4614: lsr r2,r0,0x5 @nr/32
^^^
919b4618: add2 r2,0x920f6050,r2
919b4620: ld_s r2,[r2,0]
919b4622: lsr r0,r2,r0 #test_bit()
919b4626: j_s.d [blink]
919b4628: bmsk_s r0,r0,0
919b462a: nop_s

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

locking/atomic: simplify non-atomic wrappers

Since the non-atomic arch_*() bitops use plain accesses, they are
implicitly instrumnted by the compiler, and we work around this in the
instrumented wrappers to avoid double instrumentation.

It's simpler to avoid the wrappers entirely, and use the preprocessor to
alias the arch_*() bitops to their regular versions, removing the need
for checks in the instrumented wrappers.

Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20210721155813.17082-1-mark.rutland@arm.com

locking/atomic: add generic arch_*() bitops

Now that all architectures provide arch_atomic_long_*(), we can
implement the generic bitops atop these rather than atop
atomic_long_*(), and provide arch_*() forms of the bitops that are safe
to use in noinstr code.

Now that all architectures provide arch_atomic_long_*(), we can
build the generic arch_*() bitops atop these, which can be safely used
in noinstr code. The regular bitop wrappers are built atop these.

As the generic non-atomic bitops use plain accesses, these will be
implicitly instrumented unless they are inlined into noinstr functions
(which is similar to arch_atomic*_read() when based on READ_ONCE()).
The wrappers are modified so that where the underlying arch_*() function
uses a plain access, no explicit instrumentation is added, as this is
redundant and could result in confusing reports.

Since function prototypes get excessively long with both an `arch_`
prefix and `__always_inline` attribute, the return type and function
attributes have been split onto a separate line, matching the style of
the generated atomic headers.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210713105253.7615-6-mark.rutland@arm.com

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is 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.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.

For non */uapi/* files that summary was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139

and resulted in the first patch in this series.

If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930

and resulted in the second patch in this series.

- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:

SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1

and that resulted in the third patch in this series.

- when the two scanners agreed on the detected license(s), that became
the concluded license(s).

- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.

- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).

- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.

- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct

This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

define first set of BIT* macros

define first set of BIT* macros

- move BITOP_MASK and BITOP_WORD from asm-generic/bitops/atomic.h to
include/linux/bitops.h and rename it to BIT_MASK and BIT_WORD
- move BITS_TO_LONGS and BITS_PER_BYTE to bitops.h too and allow easily
define another BITS_TO_something (e.g. in event.c) by BITS_TO_TYPE macro
Remaining (and common) BIT macro will be defined after all occurences and
conflicts will be sorted out in the patches.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

[PATCH] bitops: generic __{,test_and_}{set,clear,change}_bit() and test_bit()

This patch introduces the C-language equivalents of the functions below:

void __set_bit(int nr, volatile unsigned long *addr);
void __clear_bit(int nr, volatile unsigned long *addr);
void __change_bit(int nr, volatile unsigned long *addr);
int __test_and_set_bit(int nr, volatile unsigned long *addr);
int __test_and_clear_bit(int nr, volatile unsigned long *addr);
int __test_and_change_bit(int nr, volatile unsigned long *addr);
int test_bit(int nr, const volatile unsigned long *addr);

In include/asm-generic/bitops/non-atomic.h

This code largely copied from: asm-powerpc/bitops.h

Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>