Changes in cpuflags.c

84132633 - x86/cpufeatures: Generate the header based on build config

Wed, 05 Mar 2025 18:47:22 +0000

x86/cpufeatures: Generate the header based on build configIntroduce an AWK script to auto-generate the headerwith required and disabled feature masks based on and the current build config.Thus for any CPU feature with a build config, e.g., X86_FRED, simply add: config X86_DISABLED_FEATURE_FRED def_bool y depends on !X86_FREDto arch/x86/Kconfig.cpufeatures, instead of adding a conditional CPUfeature disable flag, e.g., DISABLE_FRED.Lastly, the generated required and disabled feature masks will be added totheir corresponding feature masks for this particular compile-timeconfiguration. [ Xin: build integration improvements ] [ mingo: Improved changelog and comments ]Signed-off-by: H. Peter Anvin (Intel) Signed-off-by: Xin Li (Intel) Signed-off-by: Borislav Petkov (AMD) Signed-off-by: Ingo Molnar Reviewed-by: Nikolay Borisov Cc: Linus Torvalds Link: https://lore.kernel.org/r/20250305184725.3341760-3-xin@zytor.com List of files: /linux-6.15/arch/x86/boot/cpuflags.c

558fc8e1 - x86/boot: Do not test if AC and ID eflags are changeable on x86_64

Fri, 07 Mar 2025 09:10:03 +0000

x86/boot: Do not test if AC and ID eflags are changeable on x86_64The test for the changeabitily of AC and ID EFLAGS is used todistinguish between i386 and i486 processors (AC) and to testfor CPUID instruction support (ID).Skip these tests on x86_64 processors as they always supports CPUID.Also change the return type of has_eflag() to bool.Signed-off-by: Uros Bizjak Signed-off-by: Ingo Molnar Acked-by: H. Peter Anvin Cc: Linus Torvalds Cc: Brian Gerst Cc: Nathan Chancellor Cc: Nick Desaulniers Link: https://lore.kernel.org/r/20250307091022.181136-1-ubizjak@gmail.com List of files: /linux-6.15/arch/x86/boot/cpuflags.c

60253f10 - x86/boot: Remove x86_32 PIC using %ebx workaround

Fri, 04 Nov 2022 12:45:46 +0000

x86/boot: Remove x86_32 PIC using %ebx workaroundThe currently supported minimum gcc version is 5.1. Before that, thePIC register, when generating Position Independent Code, was considered"fixed" in the sense that it wasn't in the set of registers available tothe compiler's register allocator. Which, on x86-32, is already a verysmall set.What is more, the register allocator was unable to satisfy extended asm"=b" constraints. (Yes, PIC code uses %ebx on 32-bit as the base reg.)With gcc 5.1:"Reuse of the PIC hard register, instead of using a fixed register,was implemented on x86/x86-64 targets. This improves generated PICcode performance as more hard registers can be used. Shared librariescan significantly benefit from this optimization. Currently it isswitched on only for x86/x86-64 targets. As RA infrastructure is alreadyimplemented for PIC register reuse, other targets might follow this inthe future." (from: https://gcc.gnu.org/gcc-5/changes.html)which basically means that the register allocator has a higher degreeof freedom when handling %ebx, including reloading it with the correctvalue before a PIC access.Furthermore: arch/x86/Makefile: # Never want PIC in a 32-bit kernel, prevent breakage with GCC built # with nonstandard options KBUILD_CFLAGS += -fno-pic $ gcc -Wp,-MMD,arch/x86/boot/.cpuflags.o.d ... -fno-pic ... -D__KBUILD_MODNAME=kmod_cpuflags -c -o arch/x86/boot/cpuflags.o arch/x86/boot/cpuflags.cso the 32-bit workaround in cpuid_count() is fixing exactly nothingbecause 32-bit configs don't even allow PIC builds.As to 64-bit builds: they're done using -mcmodel=kernel which producesRIP-relative addressing for PIC builds and thus does not apply hereeither.So get rid of the thing and make cpuid_count() nice and simple.There should be no functional changes resulting from this. [ bp: Expand commit message. ]Signed-off-by: Uros Bizjak Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20221104124546.196077-1-ubizjak@gmail.com List of files: /linux-6.15/arch/x86/boot/cpuflags.c

4b05f815 - x86/tdx: Detect TDX at early kernel decompression time

Tue, 05 Apr 2022 23:29:21 +0000

x86/tdx: Detect TDX at early kernel decompression timeThe early decompression code does port I/O for its console output. But,handling the decompression-time port I/O demands a different approachfrom normal runtime because the IDT required to support #VE based portI/O emulation is not yet set up. Paravirtualizing I/O calls duringthe decompression step is acceptable because the decompression codedoesn't have a lot of call sites to IO instruction.To support port I/O in decompression code, TDX must be detected beforethe decompression code might do port I/O. Detect whether the kernel runsin a TDX guest.Add an early_is_tdx_guest() interface to query the cached TDX gueststatus in the decompression code.TDX is detected with CPUID. Make cpuid_count() accessible outsideboot/cpuflags.c.TDX detection in the main kernel is very similar. Move common bitsinto .The actual port I/O paravirtualization will come later in the series.Signed-off-by: Kuppuswamy Sathyanarayanan Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Reviewed-by: Tony Luck Reviewed-by: Dave Hansen Link: https://lkml.kernel.org/r/20220405232939.73860-13-kirill.shutemov@linux.intel.com List of files: /linux-6.15/arch/x86/boot/cpuflags.c

b2441318 - License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Wed, 01 Nov 2017 14:07:57 +0000

License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseMany source files in the tree are missing licensing information, whichmakes it harder for compliance tools to determine the correct license.By default all files without license information are under the defaultlicense 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 bindingshorthand, which can be used instead of the full boiler plate text.This patch is based on work done by Thomas Gleixner and Kate Stewart andPhilippe Ombredanne.How this work was done:Patches were generated and checked against linux-4.14-rc6 for a subset ofthe 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 caseswhere non-standard license headers were used, and references to licensehad to be inferred by heuristics based on keywords.The analysis to determine which SPDX License Identifier to be applied toa file was done in a spreadsheet of side by side results from of theoutput of two independent scanners (ScanCode & Windriver) producing SPDXtag:value files created by Philippe Ombredanne. Philippe prepared thebase 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 filesassessed. Kate Stewart did a file by file comparison of the scannerresults in the spreadsheet to determine which SPDX license identifier(s)to be applied to the file. She confirmed any determination that was notimmediately 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 licenseidentifiers 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 thespreadsheet to determine the SPDX license identifiers to apply to thesource files by Kate, Philippe, Thomas and, in some cases, confirmationby lawyers working with the Linux Foundation.Kate also obtained a third independent scan of the 4.13 code base fromFOSSology, and compared selected files where the other two scannersdisagreed against that SPDX file, to see if there was new insights. TheWindriver scanner is based on an older version of FOSSology in part, sothey are related.Thomas did random spot checks in about 500 files from the spreadsheetsfor the uapi headers and agreed with SPDX license identifier in thefiles he inspected. For the non-uapi files Thomas did random spot checksin about 15000 files.In initial set of patches against 4.14-rc6, 3 files were found to havecopy/paste license identifier errors, and have been fixed to reflect thecorrect identifier.Additionally Philippe spent 10 hours this week doing a detailed manualinspection and review of the 12,461 patched files from the initial patchversion 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 correctThis produced a worksheet with 20 files needing minor correction. Thisworksheet was then exported into 3 different .csv files for thedifferent types of files to be modified.These .csv files were then reviewed by Greg. Thomas wrote a script toparse the csv files and add the proper SPDX tag to the file, in theformat that the file expected. This script was further refined by Gregbased on the output to detect more types of files automatically and todistinguish between header and source .c files (which need differentcomment types.) Finally Greg ran the script using the .csv files togenerate the patches.Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman List of files: /linux-6.15/arch/x86/boot/cpuflags.c

3677d4c6 - x86/boot: Detect 5-level paging support

Thu, 30 Mar 2017 08:07:25 +0000

x86/boot: Detect 5-level paging supportIn this initial implementation we force-require 5-level paging supportfrom the hardware, when compiled with CONFIG_X86_5LEVEL=y. (The kernelwill panic during boot on CPUs that don't support 5-level paging.)We will implement boot-time switch between 4- and 5-level paging later.Signed-off-by: Kirill A. Shutemov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-arch@vger.kernel.orgCc: linux-mm@kvack.orgLink: http://lkml.kernel.org/r/20170330080731.65421-2-kirill.shutemov@linux.intel.comSigned-off-by: Ingo Molnar List of files: /linux-6.15/arch/x86/boot/cpuflags.c

e4a84be6 - x86/mm: Disallow running with 32-bit PTEs to work around erratum

Fri, 08 Jul 2016 00:19:14 +0000

x86/mm: Disallow running with 32-bit PTEs to work around erratumThe Intel(R) Xeon Phi(TM) Processor x200 Family (codename: KnightsLanding) has an erratum where a processor thread setting the Accessedor Dirty bits may not do so atomically against its checks for thePresent bit. This may cause a thread (which is about to page fault)to set A and/or D, even though the Present bit had already beenatomically cleared.These bits are truly "stray". In the case of the Dirty bit, thethread associated with the stray set was *not* allowed to write tothe page. This means that we do not have to launder the bit(s); wecan simply ignore them.If the PTE is used for storing a swap index or a NUMA migration index,the A bit could be misinterpreted as part of the swap type. The straybits being set cause a software-cleared PTE to be interpreted as aswap entry. In some cases (like when the swap index ends up beingfor a non-existent swapfile), the kernel detects the stray valueand WARN()s about it, but there is no guarantee that the kernel canalways detect it.When we have 64-bit PTEs (64-bit mode or 32-bit PAE), we were ableto move the swap PTE format around to avoid these troublesome bits.But, 32-bit non-PAE is tight on bits. So, disallow it from runningon this hardware. I can't imagine anyone wanting to run 32-bitnon-highmem kernels on this hardware, but disallowing them fromrunning entirely is surely the safe thing to do.Signed-off-by: Dave Hansen Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Toshi Kani Cc: dave.hansen@intel.comCc: linux-mm@kvack.orgCc: mhocko@suse.comLink: http://lkml.kernel.org/r/20160708001914.D0B50110@viggo.jf.intel.comSigned-off-by: Ingo Molnar List of files: /linux-6.15/arch/x86/boot/cpuflags.c

5fbbc25a - x86, boot: Fix word-size assumptions in has_eflag() inline asm

Thu, 30 Jan 2014 11:00:28 +0000

x86, boot: Fix word-size assumptions in has_eflag() inline asmCommit dd78b97367bd575918204cc89107c1479d3fc1a7 ("x86, boot: Move CPUflags out of cpucheck") introduced ambiguous inline asm in thehas_eflag() function. In 16-bit mode want the instruction to be'pushfl', but we just say 'pushf' and hope the compiler does what wewanted.When building with 'clang -m16', it won't, because clang doesn't usethe horrid '.code16gcc' hack that even 'gcc -m16' uses internally.Say what we mean and don't make the compiler make assumptions.[ hpa: ideally we would be able to use the gcc %zN construct here, but that is broken for 64-bit integers in gcc < 4.5. The code with plain "pushf/popf" is fine for 32- or 64-bit mode, but not for 16-bit mode; in 16-bit mode those are 16-bit instructions in .code16 mode, and 32-bit instructions in .code16gcc mode. ]Signed-off-by: David Woodhouse Link: http://lkml.kernel.org/r/1391079628.26079.82.camel@shinybook.infradead.orgSigned-off-by: H. Peter Anvin List of files: /linux-6.15/arch/x86/boot/cpuflags.c

6e6a4932 - x86, boot: Rename get_flags() and check_flags() to *_cpuflags()

Sun, 13 Oct 2013 11:08:56 +0000

x86, boot: Rename get_flags() and check_flags() to *_cpuflags()When a function is used in more than one file it may not be possibleto immediately tell from context what the intended meaning is. Assuch, it is more important that the naming be self-evident. Thus,change get_flags() to get_cpuflags().For consistency, change check_flags() to check_cpuflags() even thoughit is only used in cpucheck.c.Link: http://lkml.kernel.org/r/1381450698-28710-2-git-send-email-keescook@chromium.orgSigned-off-by: H. Peter Anvin List of files: /linux-6.15/arch/x86/boot/cpuflags.c

dd78b973 - x86, boot: Move CPU flags out of cpucheck

Fri, 11 Oct 2013 00:18:13 +0000

x86, boot: Move CPU flags out of cpucheckRefactor the CPU flags handling out of the cpucheck routines so thatthey can be reused by the future ASLR routines (in order to detect CPUfeatures like RDRAND and RDTSC).This reworks has_eflag() and has_fpu() to be used on both 32-bit and64-bit, and refactors the calls to cpuid to make them PIC-safe on 32-bit.Signed-off-by: Kees Cook Link: http://lkml.kernel.org/r/1381450698-28710-2-git-send-email-keescook@chromium.orgSigned-off-by: H. Peter Anvin List of files: /linux-6.15/arch/x86/boot/cpuflags.c