linux-kernel - Re: [PATCH 1/2] sysctl: introduce new proc handler proc

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Date:   Thu, 16 Sep 2021 07:16:01 +0200
From:   Thomas Huth <thuth@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>
Cc:     "J. Bruce Fields" <bfields@...ldses.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        linux-s390@...r.kernel.org, Jia He <hejianet@...il.com>
Subject: Re: [PATCH 1/2] sysctl: introduce new proc handler proc_dobool

On 18/08/2021 11.38, Thomas Huth wrote:
> On 03/08/2021 12.59, Thomas Huth wrote:
>> From: Jia He <hejianet@...il.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@...ux.vnet.ibm.com>
>> Signed-off-by: Jia He <hejianet@...il.com>
>> [thuth: rebased the patch to the current kernel version]
>> Signed-off-by: Thomas Huth <thuth@...hat.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?

Ping again!

Could anybody please provide an Ack?

Thanks,
  Thomas