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Commit 67bad2fd authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Greg Kroah-Hartman
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cpu: add generic support for CPU feature based module autoloading 



This patch adds support for advertising optional CPU features over udev
using the modalias, and for declaring compatibility with/dependency upon
such a feature in a module.

The mapping between feature numbers and actual features should be provided
by the architecture in a file called <asm/cpufeature.h> which exports the
following functions/macros:
- cpu_feature(FEAT), a preprocessor macro that maps token FEAT to a
  numeric index;
- bool cpu_have_feature(n), returning whether this CPU has support for
  feature #n;
- MAX_CPU_FEATURES, an upper bound for 'n' in the previous function.

The feature can then be enabled by setting CONFIG_GENERIC_CPU_AUTOPROBE
for the architecture.

For instance, a module that registers its module init function using

  module_cpu_feature_match(FEAT_X, module_init_function)

will be probed automatically when the CPU's support for the 'FEAT_X'
feature is advertised over udev, and will only allow the module to be
loaded by hand if the 'FEAT_X' feature is supported.

Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 91219a3b

drivers/base/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -185,6 +185,14 @@ config GENERIC_CPU_DEVICES 
	bool

	default n



config HAVE_CPU_AUTOPROBE

	def_bool ARCH_HAS_CPU_AUTOPROBE



config GENERIC_CPU_AUTOPROBE

	bool

	depends on !ARCH_HAS_CPU_AUTOPROBE

	select HAVE_CPU_AUTOPROBE



config SOC_BUS

	bool

drivers/base/cpu.c

+45 −5
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <linux/percpu.h>

#include <linux/acpi.h>

#include <linux/of.h>

#include <linux/cpufeature.h>



#include "base.h"
@@ -286,6 +287,45 @@ static void cpu_device_release(struct device *dev) 
	 */

}



#ifdef CONFIG_HAVE_CPU_AUTOPROBE

#ifdef CONFIG_GENERIC_CPU_AUTOPROBE

static ssize_t print_cpu_modalias(struct device *dev,

				  struct device_attribute *attr,

				  char *buf)

{

	ssize_t n;

	u32 i;



	n = sprintf(buf, "cpu:type:" CPU_FEATURE_TYPEFMT ":feature:",

		    CPU_FEATURE_TYPEVAL);



	for (i = 0; i < MAX_CPU_FEATURES; i++)

		if (cpu_have_feature(i)) {

			if (PAGE_SIZE < n + sizeof(",XXXX\n")) {

				WARN(1, "CPU features overflow page\n");

				break;

			}

			n += sprintf(&buf[n], ",%04X", i);

		}

	buf[n++] = '\n';

	return n;

}

#else

#define print_cpu_modalias	arch_print_cpu_modalias

#endif



static int cpu_uevent(struct device *dev, struct kobj_uevent_env *env)

{

	char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);

	if (buf) {

		print_cpu_modalias(NULL, NULL, buf);

		add_uevent_var(env, "MODALIAS=%s", buf);

		kfree(buf);

	}

	return 0;

}

#endif



/*

 * register_cpu - Setup a sysfs device for a CPU.

 * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
@@ -306,8 +346,8 @@ int register_cpu(struct cpu *cpu, int num) 
	cpu->dev.offline_disabled = !cpu->hotpluggable;

	cpu->dev.offline = !cpu_online(num);

	cpu->dev.of_node = of_get_cpu_node(num, NULL);

#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE

	cpu->dev.bus->uevent = arch_cpu_uevent;

#ifdef CONFIG_HAVE_CPU_AUTOPROBE

	cpu->dev.bus->uevent = cpu_uevent;

#endif

	cpu->dev.groups = common_cpu_attr_groups;

	if (cpu->hotpluggable)
@@ -330,8 +370,8 @@ struct device *get_cpu_device(unsigned cpu) 
}

EXPORT_SYMBOL_GPL(get_cpu_device);



#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE

static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);

#ifdef CONFIG_HAVE_CPU_AUTOPROBE

static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);

#endif



static struct attribute *cpu_root_attrs[] = {
@@ -344,7 +384,7 @@ static struct attribute *cpu_root_attrs[] = { 
	&cpu_attrs[2].attr.attr,

	&dev_attr_kernel_max.attr,

	&dev_attr_offline.attr,

#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE

#ifdef CONFIG_HAVE_CPU_AUTOPROBE

	&dev_attr_modalias.attr,

#endif

	NULL

include/linux/cpufeature.h

0 → 100644
+60 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */



#ifndef __LINUX_CPUFEATURE_H

#define __LINUX_CPUFEATURE_H



#ifdef CONFIG_GENERIC_CPU_AUTOPROBE



#include <linux/mod_devicetable.h>

#include <asm/cpufeature.h>



/*

 * Macros imported from <asm/cpufeature.h>:

 * - cpu_feature(x)		ordinal value of feature called 'x'

 * - cpu_have_feature(u32 n)	whether feature #n is available

 * - MAX_CPU_FEATURES		upper bound for feature ordinal values

 * Optional:

 * - CPU_FEATURE_TYPEFMT	format string fragment for printing the cpu type

 * - CPU_FEATURE_TYPEVAL	set of values matching the format string above

 */



#ifndef CPU_FEATURE_TYPEFMT

#define CPU_FEATURE_TYPEFMT	"%s"

#endif



#ifndef CPU_FEATURE_TYPEVAL

#define CPU_FEATURE_TYPEVAL	ELF_PLATFORM

#endif



/*

 * Use module_cpu_feature_match(feature, module_init_function) to

 * declare that

 * a) the module shall be probed upon discovery of CPU feature 'feature'

 *    (typically at boot time using udev)

 * b) the module must not be loaded if CPU feature 'feature' is not present

 *    (not even by manual insmod).

 *

 * For a list of legal values for 'feature', please consult the file

 * 'asm/cpufeature.h' of your favorite architecture.

 */

#define module_cpu_feature_match(x, __init)			\

static struct cpu_feature const cpu_feature_match_ ## x[] =	\

	{ { .feature = cpu_feature(x) }, { } };			\

MODULE_DEVICE_TABLE(cpu, cpu_feature_match_ ## x);		\

								\

static int cpu_feature_match_ ## x ## _init(void)		\

{								\

	if (!cpu_have_feature(cpu_feature(x)))			\

		return -ENODEV;					\

	return __init();					\

}								\

module_init(cpu_feature_match_ ## x ## _init)



#endif

#endif

include/linux/mod_devicetable.h

+9 −0
Original line number Diff line number Diff line
@@ -564,6 +564,15 @@ struct x86_cpu_id { 
#define X86_MODEL_ANY  0

#define X86_FEATURE_ANY 0	/* Same as FPU, you can't test for that */



/*

 * Generic table type for matching CPU features.

 * @feature:	the bit number of the feature (0 - 65535)

 */



struct cpu_feature {

	__u16	feature;

};



#define IPACK_ANY_FORMAT 0xff

#define IPACK_ANY_ID (~0)

struct ipack_device_id {

scripts/mod/devicetable-offsets.c

+3 −0
Original line number Diff line number Diff line
@@ -174,6 +174,9 @@ int main(void) 
	DEVID_FIELD(x86_cpu_id, model);

	DEVID_FIELD(x86_cpu_id, vendor);



	DEVID(cpu_feature);

	DEVID_FIELD(cpu_feature, feature);



	DEVID(mei_cl_device_id);

	DEVID_FIELD(mei_cl_device_id, name);