Re: [PATCH v2 6/7] powerpc/secvar: Extend sysfs to include config vars
From: Andrew Donnellan
Date: Thu Jan 05 2023 - 02:28:56 EST
On Fri, 2022-12-30 at 15:20 +1100, Russell Currey wrote:
> 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.
>
> Signed-off-by: Russell Currey <ruscur@xxxxxxxxxx>
Minor comments below, but regardless:
Reviewed-by: Andrew Donnellan <ajd@xxxxxxxxxxxxx>
> ---
> I played around with adding an API call to facilitate a more generic
> key/value interface for config variables and it seemed like
> unnecessary
> complexity. I think this is cleaner. If there was ever a secvar
> interface other than sysfs we'd have to rework it, though.
I concur, this can be dealt with if/when the secvar interface is
exposed by some other means than sysfs.
>
> arch/powerpc/include/asm/secvar.h | 3 +++
> arch/powerpc/kernel/secvar-sysfs.c | 40 ++++++++++++++++++++++++++--
> --
> 2 files changed, 38 insertions(+), 5 deletions(-)
>
> 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,
> + };
I was slightly concerned that you're putting this on the stack, but it
doesn't appear that sysfs_create_group() keeps any references to the
group around after it creates all the files, so I think this is fine.
> +
> + 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");
This file defines pr_fmt, so the secvar: prefix here can go away,
though I notice that is the case for all the existing prints in this
function too.
> + 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");
Same comment as above
> + goto err;
> + }
> }
>
> secvar_sysfs_load();
>
> return 0;
> +err:
> + kobject_put(secvar_kobj);
> + return rc;
> }
>
> late_initcall(secvar_sysfs_init);
--
Andrew Donnellan OzLabs, ADL Canberra
ajd@xxxxxxxxxxxxx IBM Australia Limited