linux-kernel - Re: [PATCH v4] scsi/ata: Use unsigned int for cmd's type in ioctls in scsi_host

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Date:   Mon, 28 Jan 2019 09:17:37 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Don.Brace@...rochip.com
Cc:     axboe@...nel.dk, aacraid@...rosemi.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, manoj@...ux.ibm.com,
        mrochs@...ux.ibm.com, ukrishn@...ux.ibm.com,
        linuxdrivers@...otech.com, don.brace@...rosemi.com,
        brking@...ibm.com, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        esc.storagedev@...rosemi.com, ndesaulniers@...gle.com,
        bvanassche@....org
Subject: Re: [PATCH v4] scsi/ata: Use unsigned int for cmd's type in ioctls
 in scsi_host_template

On Mon, Jan 28, 2019 at 04:16:34PM +0000, Don.Brace@...rochip.com wrote:
> 
> Clang warns several times in the scsi subsystem (trimmed for brevity):
> 
> drivers/scsi/hpsa.c:6209:7: warning: overflow converting case value to switch condition type (2147762695 to 18446744071562347015) [-Wswitch]
>         case CCISS_GETBUSTYPES:
>              ^
> drivers/scsi/hpsa.c:6208:7: warning: overflow converting case value to switch condition type (2147762694 to 18446744071562347014) [-Wswitch]
>         case CCISS_GETHEARTBEAT:
>              ^
> 
> The root cause is that the _IOC macro can generate really large numbers, which don't find into type 'int', which is used for the cmd paremeter in the ioctls in scsi_host_template. My research into how GCC and Clang are handling this at a low level didn't prove fruitful. However, looking at the rest of the kernel tree, all ioctls use an 'unsigned int' for the cmd parameter, which will fit all of the _IOC values in the scsi/ata subsystems.
> 
> Make that change because none of the ioctls expect to take a negative value, it brings the ioctls inline with the reset of the kernel, and it removes ambiguity, which is never good when dealing with compilers.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/85
> Link: https://github.com/ClangBuiltLinux/linux/issues/154
> Link: https://github.com/ClangBuiltLinux/linux/issues/157
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> Reviewed-by: Bart Van Assche <bvanassche@....org>
> 
>  static void __exit esas2r_exit(void)
> diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c index ff67ef5d5347..28cfd3d01c5a 100644
> --- a/drivers/scsi/hpsa.c
> +++ b/drivers/scsi/hpsa.c
> @@ -251,10 +251,11 @@ static int number_of_controllers;
> 
> Acked-by: Don Brace <don.brace@...rosemi.com>
> 
>  
> diff --git a/drivers/scsi/smartpqi/smartpqi_init.c b/drivers/scsi/smartpqi/smartpqi_init.c
> index f564af8949e8..5d9ccbab7581 100644
> --- a/drivers/scsi/smartpqi/smartpqi_init.c
> +++ b/drivers/scsi/smartpqi/smartpqi_init.c
> @@ -6043,7 +6043,8 @@ static int pqi_passthru_ioctl(struct pqi_ctrl_info *ctrl_info, void __user *arg)
>  	return rc;
>  }
> 
> Acked-by: Don Brace <don.brace@...rosemi.com>
>  
> 

Thank you for the reply and the review, I really appreciate it :)

Nathan