linux-kernel - Re: [PATCH] x86/mce: Add compat_ioctl assignment to make it compatible with 32-bit system

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Message-ID: <38398607-c47f-fa3c-9325-5941b4fb7162@windriver.com>
Date:   Sat, 2 May 2020 22:18:19 +0800
From:   He Zhe <zhe.he@...driver.com>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     bp@...en8.de, tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/mce: Add compat_ioctl assignment to make it
 compatible with 32-bit system



On 4/28/20 2:19 AM, Luck, Tony wrote:
> On Thu, Apr 16, 2020 at 04:40:31PM +0800, He Zhe wrote:
>> Can this be considered for the moment?
>>
>> Thanks,
>> Zhe
>>
>> On 3/4/20 2:39 PM, zhe.he@...driver.com wrote:
>>> From: He Zhe <zhe.he@...driver.com>
>>>
>>> 32-bit user-space program would get errors like the following from ioctl
>>> syscall due to missing compat_ioctl.
>>> MCE_GET_RECORD_LEN: Inappropriate ioctl for device
>>>
>>> compat_ptr_ioctl is provided as a generic implementation of .compat_ioctl
>>> file operation to ioctl functions that either ignore the argument or pass
>>> a pointer to a compatible data type.
> I'm not super-familiar with the compat ioctl bits.  But this looks plausible.
>
> All three of the ioctl's for this driver have a "pointer to integer" for the
> "return" value.  And "int" is a compatible type between i386 and x86_64.
>
> I don't have a system setup to build a 32-bit binary to test the theory,
> but I assume that you have built something that tests all three:
>
> 	MCE_GET_RECORD_LEN
> 	MCE_GET_LOG_LEN
> 	MCE_GETCLEAR_FLAGS
>
> So I guess:
>
> Acked-by: Tony Luck <tony.luck@...el.com>

Thanks, and yes, I had tested all three.

Zhe

>
>>> Signed-off-by: He Zhe <zhe.he@...driver.com>
>>> ---
>>>  arch/x86/kernel/cpu/mce/dev-mcelog.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/arch/x86/kernel/cpu/mce/dev-mcelog.c b/arch/x86/kernel/cpu/mce/dev-mcelog.c
>>> index 7c8958d..6c9b91b7 100644
>>> --- a/arch/x86/kernel/cpu/mce/dev-mcelog.c
>>> +++ b/arch/x86/kernel/cpu/mce/dev-mcelog.c
>>> @@ -328,6 +328,7 @@ static const struct file_operations mce_chrdev_ops = {
>>>  	.write			= mce_chrdev_write,
>>>  	.poll			= mce_chrdev_poll,
>>>  	.unlocked_ioctl		= mce_chrdev_ioctl,
>>> +	.compat_ioctl		= compat_ptr_ioctl,
>>>  	.llseek			= no_llseek,
>>>  };
>>>