linux-stable/include/linux/stringhash.h

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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>
2017-11-01 14:07:57 +00:00
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_STRINGHASH_H
#define __LINUX_STRINGHASH_H
#include <linux/compiler.h> /* For __pure */
#include <linux/types.h> /* For u32, u64 */
#include <linux/hash.h>
/*
* Routines for hashing strings of bytes to a 32-bit hash value.
*
* These hash functions are NOT GUARANTEED STABLE between kernel
* versions, architectures, or even repeated boots of the same kernel.
* (E.g. they may depend on boot-time hardware detection or be
* deliberately randomized.)
*
* They are also not intended to be secure against collisions caused by
* malicious inputs; much slower hash functions are required for that.
*
* They are optimized for pathname components, meaning short strings.
* Even if a majority of files have longer names, the dynamic profile of
* pathname components skews short due to short directory names.
* (E.g. /usr/lib/libsesquipedalianism.so.3.141.)
*/
/*
* Version 1: one byte at a time. Example of use:
*
* unsigned long hash = init_name_hash;
* while (*p)
* hash = partial_name_hash(tolower(*p++), hash);
* hash = end_name_hash(hash);
*
* Although this is designed for bytes, fs/hfsplus/unicode.c
* abuses it to hash 16-bit values.
*/
/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
#define init_name_hash(salt) (unsigned long)(salt)
/* partial hash update function. Assume roughly 4 bits per character */
static inline unsigned long
partial_name_hash(unsigned long c, unsigned long prevhash)
{
return (prevhash + (c << 4) + (c >> 4)) * 11;
}
/*
* Finally: cut down the number of bits to a int value (and try to avoid
* losing bits). This also has the property (wanted by the dcache)
* that the msbits make a good hash table index.
*/
<linux/stringhash.h>: fix end_name_hash() for 64bit long The comment claims that this helper will try not to loose bits, but for 64bit long it looses the high bits before hashing 64bit long into 32bit int. Use the helper hash_long() to do the right thing for 64bit long. For 32bit long, there is no change. All the callers of end_name_hash() either assign the result to qstr->hash, which is u32 or return the result as an int value (e.g. full_name_hash()). Change the helper return type to int to conform to its users. [ It took me a while to apply this, because my initial reaction to it was - incorrectly - that it could make for slower code. After having looked more at it, I take back all my complaints about the patch, Amir was right and I was mis-reading things or just being stupid. I also don't worry too much about the possible performance impact of this on 64-bit, since most architectures that actually care about performance end up not using this very much (the dcache code is the most performance-critical, but the word-at-a-time case uses its own hashing anyway). So this ends up being mostly used for filesystems that do their own degraded hashing (usually because they want a case-insensitive comparison function). A _tiny_ worry remains, in that not everybody uses DCACHE_WORD_ACCESS, and then this potentially makes things more expensive on 64-bit architectures with slow or lacking multipliers even for the normal case. That said, realistically the only such architecture I can think of is PA-RISC. Nobody really cares about performance on that, it's more of a "look ma, I've got warts^W an odd machine" platform. So the patch is fine, and all my initial worries were just misplaced from not looking at this properly. - Linus ] Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-05 17:32:18 +00:00
static inline unsigned int end_name_hash(unsigned long hash)
{
<linux/stringhash.h>: fix end_name_hash() for 64bit long The comment claims that this helper will try not to loose bits, but for 64bit long it looses the high bits before hashing 64bit long into 32bit int. Use the helper hash_long() to do the right thing for 64bit long. For 32bit long, there is no change. All the callers of end_name_hash() either assign the result to qstr->hash, which is u32 or return the result as an int value (e.g. full_name_hash()). Change the helper return type to int to conform to its users. [ It took me a while to apply this, because my initial reaction to it was - incorrectly - that it could make for slower code. After having looked more at it, I take back all my complaints about the patch, Amir was right and I was mis-reading things or just being stupid. I also don't worry too much about the possible performance impact of this on 64-bit, since most architectures that actually care about performance end up not using this very much (the dcache code is the most performance-critical, but the word-at-a-time case uses its own hashing anyway). So this ends up being mostly used for filesystems that do their own degraded hashing (usually because they want a case-insensitive comparison function). A _tiny_ worry remains, in that not everybody uses DCACHE_WORD_ACCESS, and then this potentially makes things more expensive on 64-bit architectures with slow or lacking multipliers even for the normal case. That said, realistically the only such architecture I can think of is PA-RISC. Nobody really cares about performance on that, it's more of a "look ma, I've got warts^W an odd machine" platform. So the patch is fine, and all my initial worries were just misplaced from not looking at this properly. - Linus ] Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-05 17:32:18 +00:00
return hash_long(hash, 32);
}
/*
* Version 2: One word (32 or 64 bits) at a time.
* If CONFIG_DCACHE_WORD_ACCESS is defined (meaning <asm/word-at-a-time.h>
* exists, which describes major Linux platforms like x86 and ARM), then
* this computes a different hash function much faster.
*
* If not set, this falls back to a wrapper around the preceding.
*/
extern unsigned int __pure full_name_hash(const void *salt, const char *, unsigned int);
/*
* A hash_len is a u64 with the hash of a string in the low
* half and the length in the high half.
*/
#define hashlen_hash(hashlen) ((u32)(hashlen))
#define hashlen_len(hashlen) ((u32)((hashlen) >> 32))
#define hashlen_create(hash, len) ((u64)(len)<<32 | (u32)(hash))
/* Return the "hash_len" (hash and length) of a null-terminated string */
extern u64 __pure hashlen_string(const void *salt, const char *name);
#endif /* __LINUX_STRINGHASH_H */