linux.git/include/linux/bitops.h, branch v4.14.1

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

2017-11-02T10:10:55+00:00

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

bitops: avoid integer overflow in GENMASK(_ULL)

2017-09-09T01:26:48+00:00

GENMASK(_ULL) performs a left-shift of ~0UL(L), which technically
results in an integer overflow.  clang raises a warning if the overflow
occurs in a preprocessor expression.  Clear the low-order bits through a
substraction instead of the left-shift to avoid the overflow.

(akpm: no change in .text size in my testing)

Link: http://lkml.kernel.org/r/20170803212020.24939-1-mka@chromium.org
Signed-off-by: Matthias Kaehlcke 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/vmalloc.c: fix align value calculation error

2016-10-08T01:46:26+00:00

It causes double align requirement for __get_vm_area_node() if parameter
size is power of 2 and VM_IOREMAP is set in parameter flags, for example
size=0x10000 -> fls_long(0x10000)=17 -> align=0x20000

get_count_order_long() is implemented and can be used instead of
fls_long() for fixing the bug, for example size=0x10000 ->
get_count_order_long(0x10000)=16 -> align=0x10000

[akpm@linux-foundation.org: s/get_order_long()/get_count_order_long()/]
[zijun_hu@zoho.com: fixes]
 Link: http://lkml.kernel.org/r/57AABC8B.1040409@zoho.com
[akpm@linux-foundation.org: locate get_count_order_long() next to get_count_order()]
[akpm@linux-foundation.org: move get_count_order[_long] definitions to pick up fls_long()]
[zijun_hu@htc.com: move out get_count_order[_long]() from __KERNEL__ scope]
 Link: http://lkml.kernel.org/r/57B2C4CE.80303@zoho.com
Link: http://lkml.kernel.org/r/fc045ecf-20fa-0722-b3ac-9a6140488fad@zoho.com
Signed-off-by: zijun_hu 
Cc: Tejun Heo 
Cc: Johannes Weiner 
Cc: Minchan Kim 
Cc: David Rientjes 
Signed-off-by: zijun_hu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

md: set MD_CHANGE_PENDING in a atomic region

2016-05-09T16:24:02+00:00

Some code waits for a metadata update by:

1. flagging that it is needed (MD_CHANGE_DEVS or MD_CHANGE_CLEAN)
2. setting MD_CHANGE_PENDING and waking the management thread
3. waiting for MD_CHANGE_PENDING to be cleared

If the first two are done without locking, the code in md_update_sb()
which checks if it needs to repeat might test if an update is needed
before step 1, then clear MD_CHANGE_PENDING after step 2, resulting
in the wait returning early.

So make sure all places that set MD_CHANGE_PENDING are atomicial, and
bit_clear_unless (suggested by Neil) is introduced for the purpose.

Cc: Martin Kepplinger 
Cc: Andrew Morton 
Cc: Denys Vlasenko 
Cc: Sasha Levin 
Cc: 
Reviewed-by: NeilBrown 
Signed-off-by: Guoqing Jiang 
Signed-off-by: Shaohua Li

bitops.h: correctly handle rol32 with 0 byte shift

2015-12-09T18:35:16+00:00

ROL on a 32 bit integer with a shift of 32 or more is undefined and the
result is arch-dependent. Avoid this by handling the trivial case of
roling by 0 correctly.

The trivial solution of checking if shift is 0 breaks gcc's detection
of this code as a ROL instruction, which is unacceptable.

This bug was reported and fixed in GCC
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57157):

	The standard rotate idiom,

	  (x << n) | (x >> (32 - n))

	is recognized by gcc (for concreteness, I discuss only the case that x
	is an uint32_t here).

	However, this is portable C only for n in the range 0 < n < 32. For n
	== 0, we get x >> 32 which gives undefined behaviour according to the
	C standard (6.5.7, Bitwise shift operators). To portably support n ==
	0, one has to write the rotate as something like

	  (x << n) | (x >> ((-n) & 31))

	And this is apparently not recognized by gcc.

Note that this is broken on older GCCs and will result in slower ROL.

Acked-by: Linus Torvalds 
Signed-off-by: Sasha Levin 
Signed-off-by: Linus Torvalds

bitops.h: add sign_extend64()

2015-11-07T01:50:42+00:00

Months back, this was discussed, see https://lkml.org/lkml/2015/1/18/289
The result was the 64-bit version being "likely fine", "valuable" and
"correct".  The discussion fell asleep but since there are possible users,
let's add it.

Signed-off-by: Martin Kepplinger 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Arnaldo Carvalho de Melo 
Cc: Thomas Gleixner 
Cc: "H. Peter Anvin" 
Cc: George Spelvin 
Cc: Rasmus Villemoes 
Cc: Maxime Coquelin 
Cc: Denys Vlasenko 
Cc: Yury Norov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bitops.h: improve sign_extend32()'s documentation

2015-11-07T01:50:42+00:00

It is often overlooked that sign_extend32(), despite its name, is safe to
use for 16 and 8 bit types as well.  This should help prevent sign
extension being done manually some other way.

Signed-off-by: Martin Kepplinger 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Arnaldo Carvalho de Melo 
Cc: Thomas Gleixner 
Cc: "H. Peter Anvin" 
Cc: George Spelvin 
Cc: Rasmus Villemoes 
Cc: Maxime Coquelin 
Cc: Denys Vlasenko 
Cc: Yury Norov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

linux/bitmap: Force inlining of bitmap weight functions

2015-08-05T07:38:08+00:00

With this config:

  http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os

gcc-4.7.2 generates many copies of these tiny functions:

	bitmap_weight (55 copies):
	55                      push   %rbp
	48 89 e5                mov    %rsp,%rbp
	e8 3f 3a 8b 00          callq  __bitmap_weight
	5d                      pop    %rbp
	c3                      retq

	hweight_long (23 copies):
	55                      push   %rbp
	e8 b5 65 8e 00          callq  __sw_hweight64
	48 89 e5                mov    %rsp,%rbp
	5d                      pop    %rbp
	c3                      retq

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122

This patch fixes this via s/inline/__always_inline/

While at it, replaced two "__inline__" with usual "inline"
(the rest of the source file uses the latter).

	    text     data      bss       dec  filename
	86971357 17195880 36659200 140826437  vmlinux.before
	86971120 17195912 36659200 140826232  vmlinux

Signed-off-by: Denys Vlasenko 
Cc: Andrew Morton 
Cc: David Rientjes 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Thomas Graf 
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1438697716-28121-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar

lib: find_*_bit reimplementation

2015-04-17T13:03:53+00:00

This patchset does rework to find_bit function family to achieve better
performance, and decrease size of text.  All rework is done in patch 1.
Patches 2 and 3 are about code moving and renaming.

It was boot-tested on x86_64 and MIPS (big-endian) machines.
Performance tests were ran on userspace with code like this:

	/* addr[] is filled from /dev/urandom */
	start = clock();
	while (ret < nbits)
		ret = find_next_bit(addr, nbits, ret + 1);

	end = clock();
	printf("%ld\t", (unsigned long) end - start);

On Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz measurements are: (for
find_next_bit, nbits is 8M, for find_first_bit - 80K)

	find_next_bit:		find_first_bit:
	new	current		new	current
	26932	43151		14777	14925
	26947	43182		14521	15423
	26507	43824		15053	14705
	27329	43759		14473	14777
	26895	43367		14847	15023
	26990	43693		15103	15163
	26775	43299		15067	15232
	27282	42752		14544	15121
	27504	43088		14644	14858
	26761	43856		14699	15193
	26692	43075		14781	14681
	27137	42969		14451	15061
	...			...

find_next_bit performance gain is 35-40%;
find_first_bit - no measurable difference.

On ARM machine, there is arch-specific implementation for find_bit.

Thanks a lot to George Spelvin and Rasmus Villemoes for hints and
helpful discussions.

This patch (of 3):

New implementations takes less space in source file (see diffstat) and in
object.  For me it's 710 vs 453 bytes of text.  It also shows better
performance.

find_last_bit description fixed due to obvious typo.

[akpm@linux-foundation.org: include linux/bitmap.h, per Rasmus]
Signed-off-by: Yury Norov 
Reviewed-by: Rasmus Villemoes 
Reviewed-by: George Spelvin 
Cc: Alexey Klimov 
Cc: David S. Miller 
Cc: Daniel Borkmann 
Cc: Hannes Frederic Sowa 
Cc: Lai Jiangshan 
Cc: Mark Salter 
Cc: AKASHI Takahiro 
Cc: Thomas Graf 
Cc: Valentin Rothberg 
Cc: Chris Wilson 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bitops: Fix shift overflow in GENMASK macros

2014-11-16T08:55:39+00:00

On some 32 bits architectures, including x86, GENMASK(31, 0) returns 0
instead of the expected ~0UL.

This is the same on some 64 bits architectures with GENMASK_ULL(63, 0).

This is due to an overflow in the shift operand, 1 << 32 for GENMASK,
1 << 64 for GENMASK_ULL.

Reported-by: Eric Paire 
Suggested-by: Rasmus Villemoes 
Signed-off-by: Maxime Coquelin 
Signed-off-by: Peter Zijlstra (Intel) 
Cc:  # v3.13+
Cc: linux@rasmusvillemoes.dk
Cc: gong.chen@linux.intel.com
Cc: John Sullivan 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Theodore Ts'o 
Fixes: 10ef6b0dffe4 ("bitops: Introduce a more generic BITMASK macro")
Link: http://lkml.kernel.org/r/1415267659-10563-1-git-send-email-maxime.coquelin@st.com
Signed-off-by: Ingo Molnar