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H. Peter Anvin (Intel)Ingo Molnar
H. Peter Anvin (Intel)
authored and
Ingo Molnar
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x86/cpufeatures: Generate the <asm/cpufeaturemasks.h> header based on build config
Introduce an AWK script to auto-generate the <asm/cpufeaturemasks.h> header with required and disabled feature masks based on <asm/cpufeatures.h> 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_FRED to arch/x86/Kconfig.cpufeatures, instead of adding a conditional CPU feature disable flag, e.g., DISABLE_FRED. Lastly, the generated required and disabled feature masks will be added to their corresponding feature masks for this particular compile-time configuration. [ Xin: build integration improvements ] [ mingo: Improved changelog and comments ] Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com> Signed-off-by: Xin Li (Intel) <xin@zytor.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Nikolay Borisov <nik.borisov@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20250305184725.3341760-3-xin@zytor.com
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-12
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‎arch/x86/Makefile‎

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@@ -268,6 +268,21 @@ archscripts: scripts_basic
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archheaders:
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$(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
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###
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# <asm/cpufeaturemasks.h> header generation
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cpufeaturemasks.hdr := arch/x86/include/generated/asm/cpufeaturemasks.h
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cpufeaturemasks.awk := $(srctree)/arch/x86/tools/cpufeaturemasks.awk
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cpufeatures_hdr := $(srctree)/arch/x86/include/asm/cpufeatures.h
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targets += $(cpufeaturemasks.hdr)
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quiet_cmd_gen_featuremasks = GEN $@
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cmd_gen_featuremasks = $(AWK) -f $(cpufeaturemasks.awk) $(cpufeatures_hdr) $(KCONFIG_CONFIG) > $@
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$(cpufeaturemasks.hdr): $(cpufeaturemasks.awk) $(cpufeatures_hdr) $(KCONFIG_CONFIG) FORCE
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$(shell mkdir -p $(dir $@))
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$(call if_changed,gen_featuremasks)
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archprepare: $(cpufeaturemasks.hdr)
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###
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# Kernel objects
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‎arch/x86/boot/cpucheck.c‎

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@@ -22,10 +22,11 @@
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# include "boot.h"
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#endif
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#include <linux/types.h>
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#include <asm/cpufeaturemasks.h>
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#include <asm/intel-family.h>
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#include <asm/processor-flags.h>
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#include <asm/required-features.h>
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#include <asm/msr-index.h>
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#include "string.h"
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#include "msr.h"
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‎arch/x86/boot/cpuflags.c‎

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@@ -3,7 +3,6 @@
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#include "bitops.h"
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#include <asm/processor-flags.h>
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#include <asm/required-features.h>
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#include <asm/msr-index.h>
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#include "cpuflags.h"
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‎arch/x86/boot/mkcpustr.c‎

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@@ -12,8 +12,6 @@
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#include <stdio.h>
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#include "../include/asm/required-features.h"
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#include "../include/asm/disabled-features.h"
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#include "../include/asm/cpufeatures.h"
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#include "../include/asm/vmxfeatures.h"
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#include "../kernel/cpu/capflags.c"
@@ -23,6 +21,7 @@ int main(void)
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int i, j;
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const char *str;
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printf("#include <asm/cpufeaturemasks.h>\n\n");
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printf("static const char x86_cap_strs[] =\n");
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for (i = 0; i < NCAPINTS; i++) {

‎arch/x86/include/asm/Kbuild‎

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@@ -8,6 +8,7 @@ generated-y += syscalls_x32.h
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generated-y += unistd_32_ia32.h
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generated-y += unistd_64_x32.h
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generated-y += xen-hypercalls.h
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generated-y += cpufeaturemasks.h
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generic-y += early_ioremap.h
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generic-y += fprobe.h

‎arch/x86/include/asm/cpufeature.h‎

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@@ -9,6 +9,7 @@
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#include <asm/asm.h>
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#include <linux/bitops.h>
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#include <asm/alternative.h>
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#include <asm/cpufeaturemasks.h>
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enum cpuid_leafs
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{

‎arch/x86/include/asm/cpufeatures.h‎

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@@ -2,14 +2,6 @@
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#ifndef _ASM_X86_CPUFEATURES_H
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#define _ASM_X86_CPUFEATURES_H
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#ifndef _ASM_X86_REQUIRED_FEATURES_H
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#include <asm/required-features.h>
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#endif
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#ifndef _ASM_X86_DISABLED_FEATURES_H
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#include <asm/disabled-features.h>
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#endif
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/*
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* Defines x86 CPU feature bits
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*/

‎arch/x86/kernel/verify_cpu.S‎

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*/
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#include <asm/cpufeatures.h>
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#include <asm/cpufeaturemasks.h>
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#include <asm/msr-index.h>
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#define SSE_MASK \
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(REQUIRED_MASK0 & ((1<<(X86_FEATURE_XMM & 31)) | (1<<(X86_FEATURE_XMM2 & 31))))
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SYM_FUNC_START_LOCAL(verify_cpu)
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pushf # Save caller passed flags
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push $0 # Kill any dangerous flags

‎arch/x86/tools/cpufeaturemasks.awk‎

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#!/usr/bin/awk
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#
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# Convert cpufeatures.h to a list of compile-time masks
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# Note: this blithely assumes that each word has at least one
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# feature defined in it; if not, something else is wrong!
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#
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BEGIN {
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printf "#ifndef _ASM_X86_CPUFEATUREMASKS_H\n";
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printf "#define _ASM_X86_CPUFEATUREMASKS_H\n\n";
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file = 0
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}
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FNR == 1 {
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++file;
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# arch/x86/include/asm/cpufeatures.h
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if (file == 1)
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FS = "[ \t()*+]+";
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# .config
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if (file == 2)
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FS = "=";
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}
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# Create a dictionary of sorts, containing all defined feature bits
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file == 1 && $1 ~ /^#define$/ && $2 ~ /^X86_FEATURE_/ {
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nfeat = $3 * $4 + $5;
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feat = $2;
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sub(/^X86_FEATURE_/, "", feat);
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feats[nfeat] = feat;
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}
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file == 1 && $1 ~ /^#define$/ && $2 == "NCAPINTS" {
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ncapints = int($3);
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}
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# Create a dictionary featstat[REQUIRED|DISABLED, FEATURE_NAME] = on | off
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file == 2 && $1 ~ /^CONFIG_X86_(REQUIRED|DISABLED)_FEATURE_/ {
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on = ($2 == "y");
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if (split($1, fs, "CONFIG_X86_|_FEATURE_") == 3)
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featstat[fs[2], fs[3]] = on;
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}
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END {
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sets[1] = "REQUIRED";
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sets[2] = "DISABLED";
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for (ns in sets) {
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s = sets[ns];
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printf "/*\n";
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printf " * %s features:\n", s;
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printf " *\n";
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fstr = "";
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for (i = 0; i < ncapints; i++) {
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mask = 0;
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for (j = 0; j < 32; j++) {
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feat = feats[i*32 + j];
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if (featstat[s, feat]) {
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nfstr = fstr " " feat;
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if (length(nfstr) > 72) {
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printf " * %s\n", fstr;
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nfstr = " " feat;
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}
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fstr = nfstr;
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mask += (2 ^ j);
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}
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}
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masks[i] = mask;
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}
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printf " * %s\n */\n", fstr;
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for (i = 0; i < ncapints; i++)
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printf "#define %s_MASK%d\t0x%08xU\n", s, i, masks[i];
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printf "#define %s_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != %d)\n\n", s, ncapints;
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}
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printf "#endif /* _ASM_X86_CPUFEATUREMASKS_H */\n";
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}

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