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linux-next/arch/alpha/lib/ev6-divide.S
Greg Kroah-Hartman b24413180f 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>
2017-11-02 11:10:55 +01:00

264 lines
6.4 KiB
ArmAsm

/* SPDX-License-Identifier: GPL-2.0 */
/*
* arch/alpha/lib/ev6-divide.S
*
* 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
*
* Alpha division..
*/
/*
* The alpha chip doesn't provide hardware division, so we have to do it
* by hand. The compiler expects the functions
*
* __divqu: 64-bit unsigned long divide
* __remqu: 64-bit unsigned long remainder
* __divqs/__remqs: signed 64-bit
* __divlu/__remlu: unsigned 32-bit
* __divls/__remls: signed 32-bit
*
* These are not normal C functions: instead of the normal
* calling sequence, these expect their arguments in registers
* $24 and $25, and return the result in $27. Register $28 may
* be clobbered (assembly temporary), anything else must be saved.
*
* In short: painful.
*
* This is a rather simple bit-at-a-time algorithm: it's very good
* at dividing random 64-bit numbers, but the more usual case where
* the divisor is small is handled better by the DEC algorithm
* using lookup tables. This uses much less memory, though, and is
* nicer on the cache.. Besides, I don't know the copyright status
* of the DEC code.
*/
/*
* My temporaries:
* $0 - current bit
* $1 - shifted divisor
* $2 - modulus/quotient
*
* $23 - return address
* $24 - dividend
* $25 - divisor
*
* $27 - quotient/modulus
* $28 - compare status
*
* Much of the information about 21264 scheduling/coding comes from:
* Compiler Writer's Guide for the Alpha 21264
* abbreviated as 'CWG' in other comments here
* ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
* Scheduling notation:
* E - either cluster
* U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
* L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
* Try not to change the actual algorithm if possible for consistency.
*/
#include <asm/export.h>
#define halt .long 0
/*
* Select function type and registers
*/
#define mask $0
#define divisor $1
#define compare $28
#define tmp1 $3
#define tmp2 $4
#ifdef DIV
#define DIV_ONLY(x,y...) x,##y
#define MOD_ONLY(x,y...)
#define func(x) __div##x
#define modulus $2
#define quotient $27
#define GETSIGN(x) xor $24,$25,x
#define STACK 48
#else
#define DIV_ONLY(x,y...)
#define MOD_ONLY(x,y...) x,##y
#define func(x) __rem##x
#define modulus $27
#define quotient $2
#define GETSIGN(x) bis $24,$24,x
#define STACK 32
#endif
/*
* For 32-bit operations, we need to extend to 64-bit
*/
#ifdef INTSIZE
#define ufunction func(lu)
#define sfunction func(l)
#define LONGIFY(x) zapnot x,15,x
#define SLONGIFY(x) addl x,0,x
#else
#define ufunction func(qu)
#define sfunction func(q)
#define LONGIFY(x)
#define SLONGIFY(x)
#endif
.set noat
.align 4
.globl ufunction
.ent ufunction
ufunction:
subq $30,STACK,$30 # E :
.frame $30,STACK,$23
.prologue 0
7: stq $1, 0($30) # L :
bis $25,$25,divisor # E :
stq $2, 8($30) # L : L U L U
bis $24,$24,modulus # E :
stq $0,16($30) # L :
bis $31,$31,quotient # E :
LONGIFY(divisor) # E : U L L U
stq tmp1,24($30) # L :
LONGIFY(modulus) # E :
bis $31,1,mask # E :
DIV_ONLY(stq tmp2,32($30)) # L : L U U L
beq divisor, 9f /* div by zero */
/*
* In spite of the DIV_ONLY being either a non-instruction
* or an actual stq, the addition of the .align directive
* below ensures that label 1 is going to be nicely aligned
*/
.align 4
#ifdef INTSIZE
/*
* shift divisor left, using 3-bit shifts for
* 32-bit divides as we can't overflow. Three-bit
* shifts will result in looping three times less
* here, but can result in two loops more later.
* Thus using a large shift isn't worth it (and
* s8add pairs better than a sll..)
*/
1: cmpult divisor,modulus,compare # E :
s8addq divisor,$31,divisor # E :
s8addq mask,$31,mask # E :
bne compare,1b # U : U L U L
#else
1: cmpult divisor,modulus,compare # E :
nop # E :
nop # E :
blt divisor, 2f # U : U L U L
addq divisor,divisor,divisor # E :
addq mask,mask,mask # E :
unop # E :
bne compare,1b # U : U L U L
#endif
/* ok, start to go right again.. */
2:
/*
* Keep things nicely bundled... use a nop instead of not
* having an instruction for DIV_ONLY
*/
#ifdef DIV
DIV_ONLY(addq quotient,mask,tmp2) # E :
#else
nop # E :
#endif
srl mask,1,mask # U :
cmpule divisor,modulus,compare # E :
subq modulus,divisor,tmp1 # E :
#ifdef DIV
DIV_ONLY(cmovne compare,tmp2,quotient) # E : Latency 2, extra map slot
nop # E : as part of the cmovne
srl divisor,1,divisor # U :
nop # E : L U L U
nop # E :
cmovne compare,tmp1,modulus # E : Latency 2, extra map slot
nop # E : as part of the cmovne
bne mask,2b # U : U L U L
#else
srl divisor,1,divisor # U :
cmovne compare,tmp1,modulus # E : Latency 2, extra map slot
nop # E : as part of the cmovne
bne mask,2b # U : U L L U
#endif
9: ldq $1, 0($30) # L :
ldq $2, 8($30) # L :
nop # E :
nop # E : U U L L
ldq $0,16($30) # L :
ldq tmp1,24($30) # L :
nop # E :
nop # E :
#ifdef DIV
DIV_ONLY(ldq tmp2,32($30)) # L :
#else
nop # E :
#endif
addq $30,STACK,$30 # E :
ret $31,($23),1 # L0 : L U U L
.end ufunction
EXPORT_SYMBOL(ufunction)
/*
* Uhh.. Ugly signed division. I'd rather not have it at all, but
* it's needed in some circumstances. There are different ways to
* handle this, really. This does:
* -a / b = a / -b = -(a / b)
* -a % b = -(a % b)
* a % -b = a % b
* which is probably not the best solution, but at least should
* have the property that (x/y)*y + (x%y) = x.
*/
.align 4
.globl sfunction
.ent sfunction
sfunction:
subq $30,STACK,$30 # E :
.frame $30,STACK,$23
.prologue 0
bis $24,$25,$28 # E :
SLONGIFY($28) # E :
bge $28,7b # U :
stq $24,0($30) # L :
subq $31,$24,$28 # E :
stq $25,8($30) # L :
nop # E : U L U L
cmovlt $24,$28,$24 /* abs($24) */ # E : Latency 2, extra map slot
nop # E : as part of the cmov
stq $23,16($30) # L :
subq $31,$25,$28 # E : U L U L
stq tmp1,24($30) # L :
cmovlt $25,$28,$25 /* abs($25) */ # E : Latency 2, extra map slot
nop # E :
bsr $23,ufunction # L0: L U L U
ldq $24,0($30) # L :
ldq $25,8($30) # L :
GETSIGN($28) # E :
subq $31,$27,tmp1 # E : U U L L
SLONGIFY($28) # E :
ldq $23,16($30) # L :
cmovlt $28,tmp1,$27 # E : Latency 2, extra map slot
nop # E : U L L U : as part of the cmov
ldq tmp1,24($30) # L :
nop # E : as part of the cmov
addq $30,STACK,$30 # E :
ret $31,($23),1 # L0 : L U U L
.end sfunction
EXPORT_SYMBOL(sfunction)