kernel/linux.git/arch/x86/Makefile_32.cpu, branch linux-7.1.y

x86/cpu: Remove M486/M486SX/ELAN support

2026-03-30T09:39:42+00:00

In the x86 architecture we have various complicated hardware emulation facilities on x86-32 to support ancient 32-bit CPUs that very very few people are using with modern kernels. This compatibility glue is sometimes even causing problems that people spend time to resolve, which time could be spent on other things. As Linus recently remarked: > I really get the feeling that it's time to leave i486 support behind. > There's zero real reason for anybody to waste one second of > development effort on this kind of issue. Implement the first step and remove M486/M486SX/ELAN support: CONFIG_M486SX CONFIG_M486 CONFIG_MELAN [ There's no recent M486=y kernel package for any mainstream x86 32-bit distribution available that I've been able to find, so actual users should not be impacted, and any legacy users can keep using older kernels. ] Suggested-by: Linus Torvalds Signed-off-by: Ingo Molnar Reviewed-by: Arnd Bergmann Acked-by: Dave Hansen Cc: Ahmed S. Darwish Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: H. Peter Anvin Cc: John Ogness Link: https://patch.msgid.link/20251214084710.3606385-2-mingo@kernel.org

x86/cpu: Drop unused Kconfig symbol X86_P6_NOP

2026-01-06T16:57:23+00:00

This symbol was removed in early 2025 but 2 dangling references to it were missed. Delete them now. It should be safe to drop the -mtune=generic32 option since gcc 4.3 and later do not cause the problem (see 28f7e66fc1da ("x86: prevent binutils from being "smart" and generating NOPLs for us")). Also, Arnd confirmed this with gcc-8 and gcc-15 (see Link:). Fixes: f388f60ca904 ("x86/cpu: Drop configuration options for early 64-bit CPUs") Signed-off-by: Randy Dunlap Signed-off-by: Dave Hansen Reviewed-by: Nikolay Borisov Link: https://patch.msgid.link/20260106014708.991447-1-rdunlap@infradead.org Link: https://lore.kernel.org/all/c0f0814a-8333-49e1-8e50-740e4c88d94b@app.fastmail.com/

x86/cpu: Drop configuration options for early 64-bit CPUs

2025-02-27T10:19:06+00:00

The x86 CPU selection menu is confusing for a number of reasons: When configuring 32-bit kernels, it shows a small number of early 64-bit microarchitectures (K8, Core 2) but not the regular generic 64-bit target that is the normal default. There is no longer a reason to run 32-bit kernels on production 64-bit systems, so only actual 32-bit CPUs need to be shown here. When configuring 64-bit kernels, the options also pointless as there is no way to pick any CPU from the past 15 years, leaving GENERIC_CPU as the only sensible choice. Address both of the above by removing the obsolete options and making all 64-bit kernels run on both Intel and AMD CPUs from any generation. Testing generic 32-bit kernels on 64-bit hardware remains possible, just not building a 32-bit kernel that requires a 64-bit CPU. Signed-off-by: Arnd Bergmann Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/20250226213714.4040853-5-arnd@kernel.org

x86/build: Do not add -falign flags unconditionally for clang

2021-09-19T01:35:53+00:00

clang does not support -falign-jumps and only recently gained support for -falign-loops. When one of the configuration options that adds these flags is enabled, clang warns and all cc-{disable-warning,option} that follow fail because -Werror gets added to test for the presence of this warning: clang-14: warning: optimization flag '-falign-jumps=0' is not supported [-Wignored-optimization-argument] To resolve this, add a couple of cc-option calls when building with clang; gcc has supported these options since 3.2 so there is no point in testing for their support. -falign-functions was implemented in clang-7, -falign-loops was implemented in clang-14, and -falign-jumps has not been implemented yet. Link: https://lore.kernel.org/r/YSQE2f5teuvKLkON@Ryzen-9-3900X.localdomain/ Link: https://lore.kernel.org/r/20210824022640.2170859-2-nathan@kernel.org/ Reported-by: kernel test robot Reviewed-by: Nick Desaulniers Acked-by: Borislav Petkov Signed-off-by: Nathan Chancellor Signed-off-by: Masahiro Yamada

x86: remove cc-option-yn test for -mtune=

2021-09-02T23:17:20+00:00

As noted in the comment, -mtune= has been supported since GCC 3.4. The minimum required version of GCC to build the kernel (as specified in Documentation/process/changes.rst) is GCC 4.9. tune is not immediately expanded. Instead it defines a macro that will test via cc-option later values for -mtune=. But we can skip the test whether to use -mtune= vs. -mcpu=. Signed-off-by: Nick Desaulniers Reviewed-by: Nathan Chancellor Reviewed-by: Miguel Ojeda Signed-off-by: Masahiro Yamada

x86/math-emu: Limit MATH_EMULATION to 486SX compatibles

2019-10-03T08:51:17+00:00

The FPU emulation code is old and fragile in places, try to limit its use to builds for CPUs that actually use it. As far as I can tell, this is only true for i486sx compatibles, including the Cyrix 486SLC, AMD Am486SX and ÉLAN SC410, UMC U5S amd DM&P VortexSX86, all of which were relatively short-lived and got replaced with i486DX compatible processors soon after introduction, though some of the embedded versions remained available much longer. Signed-off-by: Arnd Bergmann Signed-off-by: Borislav Petkov Reviewed-by: Kees Cook Cc: "H. Peter Anvin" Cc: Andrew Morton Cc: Bill Metzenthen Cc: Ingo Molnar Cc: Masahiro Yamada Cc: Thomas Gleixner Cc: x86-ml Link: https://lkml.kernel.org/r/20191001142344.1274185-2-arnd@arndb.de

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

kbuild: remove cc-option-align

2017-06-25T03:43:00+00:00

Documentation/kbuild/makefiles.txt says the change for align options occurred at GCC 3.0, and Documentation/process/changes.rst says the minimal supported GCC version is 3.2, so it should be safe to hard-code -falign* options. Fix the only user arch/x86/Makefile_32.cpu and remove cc-option-align. Signed-off-by: Masahiro Yamada Acked-by: Ingo Molnar

x86/build: Mostly disable '-maccumulate-outgoing-args'

2017-03-30T09:53:04+00:00

The GCC '-maccumulate-outgoing-args' flag is enabled for most configs, mostly because of issues which are no longer relevant. For most configs, and with most recent versions of GCC, it's no longer needed. Clarify which cases need it, and only enable it for those cases. Also produce a compile-time error for the ftrace graph + mcount + '-Os' case, which will otherwise cause runtime failures. The main benefit of '-maccumulate-outgoing-args' is that it prevents an ugly prologue for functions which have aligned stacks. But removing the option also has some benefits: more readable argument saves, smaller text size, and (presumably) slightly improved performance. Here are the object size savings for 32-bit and 64-bit defconfig kernels: text data bss dec hex filename 10006710 3543328 1773568 15323606 e9d1d6 vmlinux.x86-32.before 9706358 3547424 1773568 15027350 e54c96 vmlinux.x86-32.after text data bss dec hex filename 10652105 4537576 843776 16033457 f4a6b1 vmlinux.x86-64.before 10639629 4537576 843776 16020981 f475f5 vmlinux.x86-64.after That comes out to a 3% text size improvement on x86-32 and a 0.1% text size improvement on x86-64. Signed-off-by: Josh Poimboeuf Cc: Andrew Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Linus Torvalds Cc: Pavel Machek Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20170316193133.zrj6gug53766m6nn@treble Signed-off-by: Ingo Molnar

x86, 386 removal: Remove CONFIG_M386 from Kconfig

2012-11-29T21:23:01+00:00

Remove the CONFIG_M386 symbol from Kconfig so that it cannot be selected. Signed-off-by: H. Peter Anvin Link: http://lkml.kernel.org/r/1354132230-21854-2-git-send-email-hpa@linux.intel.com