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Date:   Thu, 19 Jan 2023 11:02:36 +1000
Message-Id: <CPVRFKZUFEFE.3IPS9CFR9KPD6@bobo>
Cc:     <sudhakar@linux.ibm.com>, <bgray@linux.ibm.com>,
        <erichte@linux.ibm.com>, <gregkh@linuxfoundation.org>,
        <nayna@linux.ibm.com>, <linux-kernel@vger.kernel.org>,
        <zohar@linux.ibm.com>, <gjoyce@linux.ibm.com>,
        <gcwilson@linux.ibm.com>
Subject: Re: [PATCH v3 04/24] powerpc/secvar: Handle format string in the
 consumer
From:   "Nicholas Piggin" <npiggin@gmail.com>
To:     "Andrew Donnellan" <ajd@linux.ibm.com>,
        <linuxppc-dev@lists.ozlabs.org>, <linux-integrity@vger.kernel.org>
References: <20230118061049.1006141-1-ajd@linux.ibm.com>
 <20230118061049.1006141-5-ajd@linux.ibm.com>
In-Reply-To: <20230118061049.1006141-5-ajd@linux.ibm.com>
Precedence: bulk

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>
> =20
> +#define SECVAR_MAX_FORMAT_LEN	30 // max length of string returned by ->f=
ormat()
> +
>  extern const struct secvar_operations *secvar_ops;
> =20
>  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);

Maybe pass the buf size as an argument here? Which is a bit less error
prone and more flexible than finding the right #define for it.

Thanks,
Nick