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Subject: Re: [PATCH 1/2] sysctl: introduce new proc handler proc_dobool
From:   Thomas Huth <thuth@redhat.com>
To:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Luis Chamberlain <mcgrof@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Iurii Zaikin <yzaikin@google.com>
Cc:     "J. Bruce Fields" <bfields@fieldses.org>,
        Chuck Lever <chuck.lever@oracle.com>,
        linux-s390@vger.kernel.org, Jia He <hejianet@gmail.com>
References: <20210803105937.52052-1-thuth@redhat.com>
 <20210803105937.52052-2-thuth@redhat.com>
Message-ID: <5e359b28-6233-a97e-a30f-0a30fa516833@redhat.com>
Date:   Wed, 18 Aug 2021 11:38:51 +0200
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On 03/08/2021 12.59, Thomas Huth wrote:
> From: Jia He <hejianet@gmail.com>
> 
> This is to let bool variable could be correctly displayed in
> big/little endian sysctl procfs. sizeof(bool) is arch dependent,
> proc_dobool should work in all arches.
> 
> Suggested-by: Pan Xinhui <xinhui@linux.vnet.ibm.com>
> Signed-off-by: Jia He <hejianet@gmail.com>
> [thuth: rebased the patch to the current kernel version]
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   include/linux/sysctl.h |  2 ++
>   kernel/sysctl.c        | 42 ++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 44 insertions(+)
> 
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index d99ca99837de..1fa2b69c6fc3 100644
> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -48,6 +48,8 @@ typedef int proc_handler(struct ctl_table *ctl, int write, void *buffer,
>   		size_t *lenp, loff_t *ppos);
>   
>   int proc_dostring(struct ctl_table *, int, void *, size_t *, loff_t *);
> +int proc_dobool(struct ctl_table *table, int write, void *buffer,
> +		size_t *lenp, loff_t *ppos);
>   int proc_dointvec(struct ctl_table *, int, void *, size_t *, loff_t *);
>   int proc_douintvec(struct ctl_table *, int, void *, size_t *, loff_t *);
>   int proc_dointvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 272f4a272f8c..25e49b4d8049 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -536,6 +536,21 @@ static void proc_put_char(void **buf, size_t *size, char c)
>   	}
>   }
>   
> +static int do_proc_dobool_conv(bool *negp, unsigned long *lvalp,
> +				int *valp,
> +				int write, void *data)
> +{
> +	if (write) {
> +		*(bool *)valp = *lvalp;
> +	} else {
> +		int val = *(bool *)valp;
> +
> +		*lvalp = (unsigned long)val;
> +		*negp = false;
> +	}
> +	return 0;
> +}
> +
>   static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
>   				 int *valp,
>   				 int write, void *data)
> @@ -798,6 +813,26 @@ static int do_proc_douintvec(struct ctl_table *table, int write,
>   				   buffer, lenp, ppos, conv, data);
>   }
>   
> +/**
> + * proc_dobool - read/write a bool
> + * @table: the sysctl table
> + * @write: %TRUE if this is a write to the sysctl file
> + * @buffer: the user buffer
> + * @lenp: the size of the user buffer
> + * @ppos: file position
> + *
> + * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
> + * values from/to the user buffer, treated as an ASCII string.
> + *
> + * Returns 0 on success.
> + */
> +int proc_dobool(struct ctl_table *table, int write, void *buffer,
> +		size_t *lenp, loff_t *ppos)
> +{
> +	return do_proc_dointvec(table, write, buffer, lenp, ppos,
> +				do_proc_dobool_conv, NULL);
> +}
> +
>   /**
>    * proc_dointvec - read a vector of integers
>    * @table: the sysctl table
> @@ -1630,6 +1665,12 @@ int proc_dostring(struct ctl_table *table, int write,
>   	return -ENOSYS;
>   }
>   
> +int proc_dobool(struct ctl_table *table, int write,
> +		void *buffer, size_t *lenp, loff_t *ppos)
> +{
> +	return -ENOSYS;
> +}
> +
>   int proc_dointvec(struct ctl_table *table, int write,
>   		  void *buffer, size_t *lenp, loff_t *ppos)
>   {
> @@ -3425,6 +3466,7 @@ int __init sysctl_init(void)
>    * No sense putting this after each symbol definition, twice,
>    * exception granted :-)
>    */
> +EXPORT_SYMBOL(proc_dobool);
>   EXPORT_SYMBOL(proc_dointvec);
>   EXPORT_SYMBOL(proc_douintvec);
>   EXPORT_SYMBOL(proc_dointvec_jiffies);
> 

Friendly ping!

Luis, Kees, Iurii, could you please have a look and provide an Ack if this 
looks ok to you?

  Thanks,
   Thomas