Re: [PATCH v3 04/24] powerpc/secvar: Handle format string in the consumer

Nicholas Piggin
2023-01-19T01:24:15Z

On Wed Jan 18, 2023 at 4:10 PM AEST, Andrew Donnellan wrote:
> From: Russell Currey <ruscur@russell.cc>
>
> The code that handles the format string in secvar-sysfs.c is entirely
> OPAL specific, so create a new "format" op in secvar_operations to make
> the secvar code more generic. No functional change.
>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
>
> ---
>
> v2: Use sysfs_emit() instead of sprintf() (gregkh)
>
> v3: Enforce format string size limit (ruscur)
> ---
> arch/powerpc/include/asm/secvar.h | 3 +++
> arch/powerpc/kernel/secvar-sysfs.c | 23 ++++--------------
> arch/powerpc/platforms/powernv/opal-secvar.c | 25 ++++++++++++++++++++
> 3 files changed, 33 insertions(+), 18 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/secvar.h b/arch/powerpc/include/asm/secvar.h
> index 07ba36f868a7..8b6475589120 100644
> --- a/arch/powerpc/include/asm/secvar.h
> +++ b/arch/powerpc/include/asm/secvar.h
> @@ -11,12 +11,15 @@
> #include <linux/types.h>
> #include <linux/errno.h>
>
> +#define SECVAR_MAX_FORMAT_LEN 30 // max length of string returned by ->format()
> +
> extern const struct secvar_operations *secvar_ops;
>
> struct secvar_operations {
> int (*get)(const char *key, u64 key_len, u8 *data, u64 *data_size);
> 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);
> };
>
> #ifdef CONFIG_PPC_SECURE_BOOT
> diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
> index 462cacc0ca60..d3858eedd72c 100644
> --- a/arch/powerpc/kernel/secvar-sysfs.c
> +++ b/arch/powerpc/kernel/secvar-sysfs.c
> @@ -21,26 +21,13 @@ static struct kset *secvar_kset;
> static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
> char *buf)
> {
> - ssize_t rc = 0;
> - struct device_node *node;
> - const char *format;
> -
> - node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
> - if (!of_device_is_available(node)) {
> - rc = -ENODEV;
> - goto out;
> - }
> + char tmp[SECVAR_MAX_FORMAT_LEN];
> + ssize_t len = secvar_ops->format(tmp);
>
> - rc = of_property_read_string(node, "format", &format);
> - if (rc)
> - goto out;
> + if (len <= 0)
> + return -EIO;

AFAIKS this does have a functional change, it loses the return value.
Why not return len if it is < 0, and -EIO if len == 0?

Thanks,
Nick