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2018-06-13alpha: Remove custom dec_and_lock() implementationSebastian Andrzej Siewior1-2/+0
Alpha provides a custom implementation of dec_and_lock(). The functions is split into two parts: - atomic_add_unless() + return 0 (fast path in assembly) - remaining part including locking (slow path in C) Comparing the result of the alpha implementation with the generic implementation compiled by gcc it looks like the fast path is optimized by avoiding a stack frame (and reloading the GP), register store and all this. This is only done in the slowpath. After marking the slowpath (atomic_dec_and_lock_1()) as "noinline" and doing the slowpath in C (the atomic_add_unless(atomic, -1, 1) part) I noticed differences in the resulting assembly: - the GP is still reloaded - atomic_add_unless() adds more memory barriers compared to the custom assembly - the custom assembly here does "load, sub, beq" while atomic_add_unless() does "load, cmpeq, add, bne". This is okay because it compares against zero after subtraction while the generic code compares against 1 before. I'm not sure if avoiding the stack frame (and GP reloading) brings a lot in terms of performance. Regarding the different barriers, Peter Zijlstra says: |refcount decrement needs to be a RELEASE operation, such that all the |load/stores to the object happen before we decrement the refcount. | |Otherwise things like: | | obj->foo = 5; | refcnt_dec(&obj->ref); | |can be re-ordered, which then allows fun scenarios like: | | CPU0 CPU1 | | refcnt_dec(&obj->ref); | if (dec_and_test(&obj->ref)) | free(obj); | obj->foo = 5; // oops UaF | | |This means (for alpha) that there should be a memory barrier _before_ |the decrement, however the dec_and_lock asm thing only has one _after_, |which, per the above, is too late. | |The generic version using add_unless will result in memory barrier |before and after (because that is the rule for atomic ops with a return |value) which is strictly too many barriers for the refcount story, but |who knows what other ordering requirements code has. Remove the custom alpha implementation of dec_and_lock() and if it is an issue (performance wise) then the fast path could still be inlined. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Richard Henderson <rth@twiddle.net> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: Matt Turner <mattst88@gmail.com> Cc: linux-alpha@vger.kernel.org Link: https://lkml.kernel.org/r/20180606115918.GG12198@hirez.programming.kicks-ass.net Link: https://lkml.kernel.org/r20180612161621.22645-2-bigeasy@linutronix.de
2017-11-02License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseGreg Kroah-Hartman1-0/+1
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>
2017-08-29alpha: Package string routines togetherRichard Henderson1-6/+16
There are direct branches between {str*cpy,str*cat} and stx*cpy. Ensure the branches are within range by merging these objects. Signed-off-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Matt Turner <mattst88@gmail.com>
2017-05-03alpha: make short build log available for division routinesMasahiro Yamada1-2/+2
This enables the Kbuild standard log style as follows: AS arch/alpha/lib/__divlu.o AS arch/alpha/lib/__divqu.o AS arch/alpha/lib/__remlu.o AS arch/alpha/lib/__remqu.o Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-05-03alpha: merge build rules of division routinesMasahiro Yamada1-7/+2
These four objects are generated by the same build rule, with different compile options. The build rules can be merged. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-05-03alpha: add $(src)/ rather than $(obj)/ to make source file pathMasahiro Yamada1-4/+4
$(ev6-y)divide.S is a source file, not a build-time generated file. So, it should be prefixed with $(src)/ rather than $(obj)/. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2012-08-19alpha: Use new generic strncpy_from_user() and strnlen_user()Michael Cree1-2/+0
Similar to x86/sparc/powerpc implementations except: 1) we implement an extremely efficient has_zero()/find_zero() sequence with both prep_zero_mask() and create_zero_mask() no-operations. 2) Our output from prep_zero_mask() differs in that only the lowest eight bits are used to represent the zero bytes nevertheless it can be safely ORed with other similar masks from prep_zero_mask() and forms input to create_zero_mask(), the two fundamental properties prep_zero_mask() must satisfy. Tests on EV67 and EV68 CPUs revealed that the generic code is essentially as fast (to within 0.5% of CPU cycles) of the old Alpha specific code for large quadword-aligned strings, despite the 30% extra CPU instructions executed. In contrast, the generic code for unaligned strings is substantially slower (by more than a factor of 3) than the old Alpha specific code. Signed-off-by: Michael Cree <mcree@orcon.net.nz> Acked-by: Matt Turner <mattst88@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-01-17alpha: change to new Makefile flag variablesmatt mooney1-2/+2
Signed-off-by: matt mooney <mfm@muteddisk.com> Signed-off-by: Matt Turner <mattst88@gmail.com>
2007-10-15kbuild: enable 'make CFLAGS=...' to add additional options to CCSam Ravnborg1-1/+1
The variable CFLAGS is a wellknown variable and the usage by kbuild may result in unexpected behaviour. On top of that several people over time has asked for a way to pass in additional flags to gcc. This patch replace use of CFLAGS with KBUILD_CFLAGS all over the tree and enabling one to use: make CFLAGS=... to specify additional gcc commandline options. One usecase is when trying to find gcc bugs but other use cases has been requested too. Patch was tested on following architectures: alpha, arm, i386, x86_64, mips, sparc, sparc64, ia64, m68k Test was simple to do a defconfig build, apply the patch and check that nothing got rebuild. Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
2007-05-30alpha: cleanup in bitops.hRichard Henderson1-1/+2
Remove 2 functions private to the alpha implemetation, in favor of similar functions in <linux/log2.h>. Provide a more efficient version of the fls64 function for pre-ev67 alphas. Signed-off-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-04-26[STRING]: Move strcasecmp/strncasecmp to lib/string.cDavid S. Miller1-1/+0
We have several platforms using local copies of identical code. Signed-off-by: David S. Miller <davem@davemloft.net>
2005-04-17Linux-2.6.12-rc2v2.6.12-rc2Linus Torvalds1-0/+58
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!