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Commit 9def39be authored by Josh Triplett's avatar Josh Triplett
Browse files

x86: Support compiling out human-friendly processor feature names 



The table mapping CPUID bits to human-readable strings takes up a
non-trivial amount of space, and only exists to support /proc/cpuinfo
and a couple of kernel messages.  Since programs depend on the format of
/proc/cpuinfo, force inclusion of the table when building with /proc
support; otherwise, support omitting that table to save space, in which
case the kernel messages will print features numerically instead.

In addition to saving 1408 bytes out of vmlinux, this also saves 1373
bytes out of the uncompressed setup code, which contributes directly to
the size of bzImage.

Signed-off-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 39f838e0

arch/x86/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -136,6 +136,7 @@ config X86 
	select HAVE_ACPI_APEI if ACPI

	select HAVE_ACPI_APEI_NMI if ACPI

	select ACPI_LEGACY_TABLES_LOOKUP if ACPI

	select X86_FEATURE_NAMES if PROC_FS



config INSTRUCTION_DECODER

	def_bool y
@@ -313,6 +314,17 @@ config SMP 


	  If you don't know what to do here, say N.



config X86_FEATURE_NAMES

	bool "Processor feature human-readable names" if EMBEDDED

	default y

	---help---

	  This option compiles in a table of x86 feature bits and corresponding

	  names.  This is required to support /proc/cpuinfo and a few kernel

	  messages.  You can disable this to save space, at the expense of

	  making those few kernel messages show numeric feature bits instead.



	  If in doubt, say Y.



config X86_X2APIC

	bool "Support x2apic"

	depends on X86_LOCAL_APIC && X86_64 && IRQ_REMAP

arch/x86/boot/Makefile

+5 −2
Original line number Diff line number Diff line
@@ -35,12 +35,14 @@ setup-y += video-vesa.o 
setup-y		+= video-bios.o



targets		+= $(setup-y)

hostprogs-y	:= mkcpustr tools/build

hostprogs-y	:= tools/build

hostprogs-$(CONFIG_X86_FEATURE_NAMES) += mkcpustr



HOST_EXTRACFLAGS += -I$(srctree)/tools/include \

		    -include include/generated/autoconf.h \

	            -D__EXPORTED_HEADERS__



ifdef CONFIG_X86_FEATURE_NAMES

$(obj)/cpu.o: $(obj)/cpustr.h



quiet_cmd_cpustr = CPUSTR  $@
@@ -48,6 +50,7 @@ quiet_cmd_cpustr = CPUSTR $@ 
targets += cpustr.h

$(obj)/cpustr.h: $(obj)/mkcpustr FORCE

	$(call if_changed,cpustr)

endif



# ---------------------------------------------------------------------------

arch/x86/boot/cpu.c

+41 −27
Original line number Diff line number Diff line
@@ -16,7 +16,9 @@ 
 */



#include "boot.h"

#ifdef CONFIG_X86_FEATURE_NAMES

#include "cpustr.h"

#endif



static char *cpu_name(int level)

{
@@ -32,32 +34,13 @@ static char *cpu_name(int level) 
	}

}



int validate_cpu(void)

static void show_cap_strs(u32 *err_flags)

{

	u32 *err_flags;

	int cpu_level, req_level;

	const unsigned char *msg_strs;



	check_cpu(&cpu_level, &req_level, &err_flags);



	if (cpu_level < req_level) {

		printf("This kernel requires an %s CPU, ",

		       cpu_name(req_level));

		printf("but only detected an %s CPU.\n",

		       cpu_name(cpu_level));

		return -1;

	}



	if (err_flags) {

	int i, j;

		puts("This kernel requires the following features "

		     "not present on the CPU:\n");



		msg_strs = (const unsigned char *)x86_cap_strs;



#ifdef CONFIG_X86_FEATURE_NAMES

	const unsigned char *msg_strs = (const unsigned char *)x86_cap_strs;

	for (i = 0; i < NCAPINTS; i++) {

		u32 e = err_flags[i];



		for (j = 0; j < 32; j++) {

			if (msg_strs[0] < i ||

			    (msg_strs[0] == i && msg_strs[1] < j)) {
@@ -77,6 +60,37 @@ int validate_cpu(void) 
			e >>= 1;

		}

	}

#else

	for (i = 0; i < NCAPINTS; i++) {

		u32 e = err_flags[i];

		for (j = 0; j < 32; j++) {

			if (e & 1)

				printf("%d:%d ", i, j);

			e >>= 1;

		}

	}

#endif

}



int validate_cpu(void)

{

	u32 *err_flags;

	int cpu_level, req_level;



	check_cpu(&cpu_level, &req_level, &err_flags);



	if (cpu_level < req_level) {

		printf("This kernel requires an %s CPU, ",

		       cpu_name(req_level));

		printf("but only detected an %s CPU.\n",

		       cpu_name(cpu_level));

		return -1;

	}



	if (err_flags) {

		puts("This kernel requires the following features "

		     "not present on the CPU:\n");

		show_cap_strs(err_flags);

		putchar('\n');

		return -1;

	} else {

arch/x86/include/asm/cpufeature.h

+7 −0
Original line number Diff line number Diff line
@@ -250,8 +250,15 @@ 
#include <asm/asm.h>

#include <linux/bitops.h>



#ifdef CONFIG_X86_FEATURE_NAMES

extern const char * const x86_cap_flags[NCAPINTS*32];

extern const char * const x86_power_flags[32];

#define X86_CAP_FMT "%s"

#define x86_cap_flag(flag) x86_cap_flags[flag]

#else

#define X86_CAP_FMT "%d:%d"

#define x86_cap_flag(flag) ((flag) >> 5), ((flag) & 31)

#endif



/*

 * In order to save room, we index into this array by doing

arch/x86/kernel/cpu/Makefile

+4 −1
Original line number Diff line number Diff line
@@ -13,11 +13,12 @@ nostackp := $(call cc-option, -fno-stack-protector) 
CFLAGS_common.o		:= $(nostackp)



obj-y			:= intel_cacheinfo.o scattered.o topology.o

obj-y			+= capflags.o powerflags.o common.o

obj-y			+= common.o

obj-y			+= rdrand.o

obj-y			+= match.o



obj-$(CONFIG_PROC_FS)	+= proc.o

obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o



obj-$(CONFIG_X86_32)	+= bugs.o

obj-$(CONFIG_X86_64)	+= bugs_64.o
@@ -50,6 +51,7 @@ obj-$(CONFIG_X86_LOCAL_APIC) += perfctr-watchdog.o perf_event_amd_ibs.o 


obj-$(CONFIG_HYPERVISOR_GUEST)		+= vmware.o hypervisor.o mshyperv.o



ifdef CONFIG_X86_FEATURE_NAMES

quiet_cmd_mkcapflags = MKCAP   $@

      cmd_mkcapflags = $(CONFIG_SHELL) $(srctree)/$(src)/mkcapflags.sh $< $@
@@ -58,3 +60,4 @@ cpufeature = $(src)/../../include/asm/cpufeature.h 
targets += capflags.c

$(obj)/capflags.c: $(cpufeature) $(src)/mkcapflags.sh FORCE

	$(call if_changed,mkcapflags)

endif