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: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ard Biesheuvel 2014-02-08 13:34:09 +01:00 committed by Greg Kroah-Hartman
parent 91219a3b20
commit 67bad2fdb7
6 changed files with 135 additions and 5 deletions

View File

@ -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

View File

@ -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

View File

@ -0,0 +1,60 @@
/*
* 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

View File

@ -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 {

View File

@ -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);

View File

@ -1135,6 +1135,16 @@ static int do_x86cpu_entry(const char *filename, void *symval,
}
ADD_TO_DEVTABLE("x86cpu", x86_cpu_id, do_x86cpu_entry);
/* LOOKS like cpu:type:*:feature:*FEAT* */
static int do_cpu_entry(const char *filename, void *symval, char *alias)
{
DEF_FIELD(symval, cpu_feature, feature);
sprintf(alias, "cpu:type:*:feature:*%04X*", feature);
return 1;
}
ADD_TO_DEVTABLE("cpu", cpu_feature, do_cpu_entry);
/* Looks like: mei:S */
static int do_mei_entry(const char *filename, void *symval,
char *alias)