Re: [PATCH v3 05/24] powerpc/secvar: Handle max object size in the consumer

Greg Joyce
2023-01-19T21:26:21Z

On Wed, 2023-01-18 at 17:10 +1100, Andrew Donnellan wrote:
> From: Russell Currey <ruscur@russell.cc>
>
> Currently the max object size is handled in the core secvar code with
> an
> entirely OPAL-specific implementation, so create a new max_size() op
> and
> move the existing implementation into the powernv platform. Should
> be
> no functional change.
>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
>
> ---
>
> v3: Change uint64_t type to u64 (mpe)
> ---
> arch/powerpc/include/asm/secvar.h | 1 +
> arch/powerpc/kernel/secvar-sysfs.c | 17 +++--------------
> arch/powerpc/platforms/powernv/opal-secvar.c | 19
> +++++++++++++++++++
> 3 files changed, 23 insertions(+), 14 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/secvar.h
> b/arch/powerpc/include/asm/secvar.h
> index 8b6475589120..b2cb9bb7c540 100644
> --- a/arch/powerpc/include/asm/secvar.h
> +++ b/arch/powerpc/include/asm/secvar.h
> @@ -20,6 +20,7 @@ struct secvar_operations {
> int (*get_next)(const char *key, u64 *key_len, u64 keybufsize);
> int (*set)(const char *key, u64 key_len, u8 *data, u64
> data_size);
> ssize_t (*format)(char *buf);
> + int (*max_size)(u64 *max_size);
> };
>
> #ifdef CONFIG_PPC_SECURE_BOOT
> diff --git a/arch/powerpc/kernel/secvar-sysfs.c
> b/arch/powerpc/kernel/secvar-sysfs.c
> index d3858eedd72c..031ef37bca99 100644
> --- a/arch/powerpc/kernel/secvar-sysfs.c
> +++ b/arch/powerpc/kernel/secvar-sysfs.c
> @@ -128,27 +128,16 @@ static struct kobj_type secvar_ktype = {
> static int update_kobj_size(void)
> {
>
> - struct device_node *node;
> u64 varsize;
> - int rc = 0;
> + int rc = secvar_ops->max_size(&varsize);
>
> - node = of_find_compatible_node(NULL, NULL, "ibm,secvar-
> backend");
> - if (!of_device_is_available(node)) {
> - rc = -ENODEV;
> - goto out;
> - }
> -
> - rc = of_property_read_u64(node, "max-var-size", &varsize);
> if (rc)
> - goto out;
> + return rc;
>
> data_attr.size = varsize;
> update_attr.size = varsize;
>
> -out:
> - of_node_put(node);
> -
> - return rc;
> + return 0;
> }
>
> static int secvar_sysfs_load(void)
> diff --git a/arch/powerpc/platforms/powernv/opal-secvar.c
> b/arch/powerpc/platforms/powernv/opal-secvar.c
> index 623c6839e66c..c9b9fd3730df 100644
> --- a/arch/powerpc/platforms/powernv/opal-secvar.c
> +++ b/arch/powerpc/platforms/powernv/opal-secvar.c
> @@ -122,11 +122,30 @@ static ssize_t opal_secvar_format(char *buf)
> return rc;
> }
>
> +static int opal_secvar_max_size(u64 *max_size)
> +{
> + int rc;
> + struct device_node *node;
> +
> + node = of_find_compatible_node(NULL, NULL, "ibm,secvar-
> backend");

I assume that node could be NULL and this code relies on
of_device_is_available() and of_node_put() checking for a NULL node
pointer? Would it be safer just to return -ENODEV if node is NULL?

> + if (!of_device_is_available(node)) {
> + rc = -ENODEV;
> + goto out;
> + }
> +
> + rc = of_property_read_u64(node, "max-var-size", max_size);
> +
> +out:
> + of_node_put(node);
> + return rc;
> +}
> +
> static const struct secvar_operations opal_secvar_ops = {
> .get = opal_get_variable,
> .get_next = opal_get_next_variable,
> .set = opal_set_variable,
> .format = opal_secvar_format,
> + .max_size = opal_secvar_max_size,
> };
>
> static int opal_secvar_probe(struct platform_device *pdev)