Re: [PATCH v2 6/7] powerpc/secvar: Extend sysfs to include config vars

Michael Ellerman
2023-01-06T04:15:55Z

Russell Currey <ruscur@russell.cc> writes:
> The forthcoming pseries consumer of the secvar API wants to expose a
> number of config variables. Allowing secvar implementations to provide
> their own sysfs attributes makes it easy for consumers to expose what
> they need to.
>
> This is not being used by the OPAL secvar implementation at present, and
> the config directory will not be created if no attributes are set.

Would it be slightly cleaner if the attributes were just a member of
secvar_operations?

That would avoid the need for some of the separate handling of the ops
and the attributes.

I know "ops" implies it's only methods, but I think that's not a big
problem. The power_pmu struct does something similar, where it combines
ops and attributes.

cheers

> diff --git a/arch/powerpc/include/asm/secvar.h b/arch/powerpc/include/asm/secvar.h
> index 92d2c051918b..250e7066b6da 100644
> --- a/arch/powerpc/include/asm/secvar.h
> +++ b/arch/powerpc/include/asm/secvar.h
> @@ -10,6 +10,7 @@
>
> #include <linux/types.h>
> #include <linux/errno.h>
> +#include <linux/sysfs.h>
>
> extern const struct secvar_operations *secvar_ops;
>
> @@ -27,10 +28,12 @@ struct secvar_operations {
> #ifdef CONFIG_PPC_SECURE_BOOT
>
> extern void set_secvar_ops(const struct secvar_operations *ops);
> +extern void set_secvar_config_attrs(const struct attribute **attrs);
>
> #else
>
> static inline void set_secvar_ops(const struct secvar_operations *ops) { }
> +static inline void set_secvar_config_attrs(const struct attribute **attrs) { }
>
> #endif
>
> diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
> index aa1daec480e1..ad1e1d72d2ae 100644
> --- a/arch/powerpc/kernel/secvar-sysfs.c
> +++ b/arch/powerpc/kernel/secvar-sysfs.c
> @@ -15,9 +15,17 @@
>
> #define NAME_MAX_SIZE 1024
>
> +const struct attribute **secvar_config_attrs __ro_after_init = NULL;
> +
> static struct kobject *secvar_kobj;
> static struct kset *secvar_kset;
>
> +void set_secvar_config_attrs(const struct attribute **attrs)
> +{
> + WARN_ON_ONCE(secvar_config_attrs);
> + secvar_config_attrs = attrs;
> +}
> +
> static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
> char *buf)
> {
> @@ -134,6 +142,16 @@ static int update_kobj_size(void)
> return 0;
> }
>
> +static int secvar_sysfs_config(struct kobject *kobj)
> +{
> + struct attribute_group config_group = {
> + .name = "config",
> + .attrs = (struct attribute **)secvar_config_attrs,
> + };
> +
> + return sysfs_create_group(kobj, &config_group);
> +}
> +
> static int secvar_sysfs_load(void)
> {
> char *name;
> @@ -196,26 +214,38 @@ static int secvar_sysfs_init(void)
>
> rc = sysfs_create_file(secvar_kobj, &format_attr.attr);
> if (rc) {
> - kobject_put(secvar_kobj);
> - return -ENOMEM;
> + pr_err("secvar: Failed to create format object\n");
> + rc = -ENOMEM;
> + goto err;
> }
>
> secvar_kset = kset_create_and_add("vars", NULL, secvar_kobj);
> if (!secvar_kset) {
> pr_err("secvar: sysfs kobject registration failed.\n");
> - kobject_put(secvar_kobj);
> - return -ENOMEM;
> + rc = -ENOMEM;
> + goto err;
> }
>
> rc = update_kobj_size();
> if (rc) {
> pr_err("Cannot read the size of the attribute\n");
> - return rc;
> + goto err;
> + }
> +
> + if (secvar_config_attrs) {
> + rc = secvar_sysfs_config(secvar_kobj);
> + if (rc) {
> + pr_err("secvar: Failed to create config directory\n");
> + goto err;
> + }
> }
>
> secvar_sysfs_load();
>
> return 0;
> +err:
> + kobject_put(secvar_kobj);
> + return rc;
> }
>
> late_initcall(secvar_sysfs_init);
> --
> 2.38.1