Re: [PATCH 2/2] x86: Support compiling out human-friendly processor feature names

[H. Peter Anvin]

Also, for the numeric message at least please show it in word:bit format.

On February 22, 2014 11:09:30 AM PST, Josh Triplett <josh@xxxxxxxxxxxxxxxx> wrote:
>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: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
>---
> arch/x86/Kconfig                  | 12 +++++++
> arch/x86/boot/Makefile            |  5 ++-
>arch/x86/boot/cpu.c               | 68
>+++++++++++++++++++++++----------------
> arch/x86/include/asm/cpufeature.h | 13 ++++++++
> arch/x86/kernel/cpu/Makefile      |  5 ++-
> arch/x86/kernel/cpu/common.c      |  4 +--
> 6 files changed, 76 insertions(+), 31 deletions(-)
>
>diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>index 0af5250..4dfdbdc 100644
>--- a/arch/x86/Kconfig
>+++ b/arch/x86/Kconfig
>@@ -127,6 +127,7 @@ config X86
> 	select HAVE_DEBUG_STACKOVERFLOW
> 	select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
> 	select HAVE_CC_STACKPROTECTOR
>+	select X86_FEATURE_NAMES if PROC_FS
> 
> config INSTRUCTION_DECODER
> 	def_bool y
>@@ -304,6 +305,17 @@ config SMP
> 
> 	  If you don't know what to do here, say N.
> 
>+config X86_FEATURE_NAMES
>+	bool "Processor feature human-readable names"
>+	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
>diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
>index 878df7e..ca6f7ed 100644
>--- a/arch/x86/boot/Makefile
>+++ b/arch/x86/boot/Makefile
>@@ -35,7 +35,7 @@ setup-y		+= video-vesa.o
> setup-y		+= video-bios.o
> 
> targets		+= $(setup-y)
>-hostprogs-y	:= mkcpustr tools/build
>+hostprogs-y	:= tools/build
> 
> HOST_EXTRACFLAGS += -I$(srctree)/tools/include \
> 		    -include include/generated/autoconf.h \
>@@ -43,11 +43,14 @@ HOST_EXTRACFLAGS += -I$(srctree)/tools/include \
> 
> $(obj)/cpu.o: $(obj)/cpustr.h
> 
>+ifdef CONFIG_X86_FEATURE_NAMES
>+hostprogs-y += mkcpustr
> quiet_cmd_cpustr = CPUSTR  $@
>       cmd_cpustr = $(obj)/mkcpustr > $@
> targets		+= cpustr.h
> $(obj)/cpustr.h: $(obj)/mkcpustr FORCE
> 	$(call if_changed,cpustr)
>+endif
> 
>#
>---------------------------------------------------------------------------
> 
>diff --git a/arch/x86/boot/cpu.c b/arch/x86/boot/cpu.c
>index 6ec6bb6..29207f6 100644
>--- a/arch/x86/boot/cpu.c
>+++ b/arch/x86/boot/cpu.c
>@@ -16,7 +16,9 @@
>  */
> 
> #include "boot.h"
>+#ifdef CONFIG_X86_FEATURE_NAMES
> #include "cpustr.h"
>+#endif
> 
> static char *cpu_name(int level)
> {
>@@ -32,11 +34,48 @@ static char *cpu_name(int level)
> 	}
> }
> 
>+static void show_cap_strs(u32 *err_flags)
>+{
>+	int i, j;
>+#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)) {
>+				/* Skip to the next string */
>+				msg_strs += 2;
>+				while (*msg_strs++)
>+					;
>+			}
>+			if (e & 1) {
>+				if (msg_strs[0] == i &&
>+				    msg_strs[1] == j &&
>+				    msg_strs[2])
>+					printf("%s ", msg_strs+2);
>+				else
>+					printf("%d:%d ", i, j);
>+			}
>+			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;
>-	const unsigned char *msg_strs;
> 
> 	check_cpu(&cpu_level, &req_level, &err_flags);
> 
>@@ -49,34 +88,9 @@ int validate_cpu(void)
> 	}
> 
> 	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;
>-
>-		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)) {
>-					/* Skip to the next string */
>-					msg_strs += 2;
>-					while (*msg_strs++)
>-						;
>-				}
>-				if (e & 1) {
>-					if (msg_strs[0] == i &&
>-					    msg_strs[1] == j &&
>-					    msg_strs[2])
>-						printf("%s ", msg_strs+2);
>-					else
>-						printf("%d:%d ", i, j);
>-				}
>-				e >>= 1;
>-			}
>-		}
>+		show_cap_strs(err_flags);
> 		putchar('\n');
> 		return -1;
> 	} else {
>diff --git a/arch/x86/include/asm/cpufeature.h
>b/arch/x86/include/asm/cpufeature.h
>index e099f95..af6d7d5 100644
>--- a/arch/x86/include/asm/cpufeature.h
>+++ b/arch/x86/include/asm/cpufeature.h
>@@ -237,8 +237,21 @@
> #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"
>+static inline const char *x86_cap_flag(u32 flag)
>+{
>+	return x86_cap_flags[flag];
>+}
>+#else
>+#define X86_CAP_FMT "%x"
>+static inline u32 x86_cap_flag(u32 flag)
>+{
>+	return flag;
>+}
>+#endif
> 
> #define test_cpu_cap(c, bit)						\
> 	 test_bit(bit, (unsigned long *)((c)->x86_capability))
>diff --git a/arch/x86/kernel/cpu/Makefile
>b/arch/x86/kernel/cpu/Makefile
>index 64038d8..77dcab2 100644
>--- a/arch/x86/kernel/cpu/Makefile
>+++ b/arch/x86/kernel/cpu/Makefile
>@@ -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
>diff --git a/arch/x86/kernel/cpu/common.c
>b/arch/x86/kernel/cpu/common.c
>index 8e28bf2..3991a81 100644
>--- a/arch/x86/kernel/cpu/common.c
>+++ b/arch/x86/kernel/cpu/common.c
>@@ -336,8 +336,8 @@ static void filter_cpuid_features(struct
>cpuinfo_x86 *c, bool warn)
> 			continue;
> 
> 		printk(KERN_WARNING
>-		       "CPU: CPU feature %s disabled, no CPUID level 0x%x\n",
>-				x86_cap_flags[df->feature], df->level);
>+		       "CPU: CPU feature " X86_CAP_FMT " disabled, no CPUID level
>0x%x\n",
>+				x86_cap_flag(df->feature), df->level);
> 	}
> }
> 

-- 
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