lkml.org 
[lkml]   [2018]   [Oct]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: -Wswitch Clang warnings in drivers/scsi
On Thu, Oct 04, 2018 at 11:34:29AM -0700, Bart Van Assche wrote:
> On Thu, 2018-10-04 at 11:30 -0700, Nathan Chancellor wrote:
> > Hi SCSI folks,
> >
> > In an effort to get the kernel building warning free with Clang, we've
> > come across an interesting occurrence in a few scsi drivers:
> >
> > drivers/scsi/hpsa.c:6533:7: warning: overflow converting case value to switch condition type (2148024833 to 18446744071562609153) [-Wswitch]
> > case CCISS_GETPCIINFO:
> > ^
> > ./include/uapi/linux/cciss_ioctl.h:65:26: note: expanded from macro 'CCISS_GETPCIINFO'
> > #define CCISS_GETPCIINFO _IOR(CCISS_IOC_MAGIC, 1, cciss_pci_info_struct)
> > ^
> > ./include/uapi/asm-generic/ioctl.h:86:28: note: expanded from macro '_IOR'
> > #define _IOR(type,nr,size) _IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(size)))
> > ^
> > ./include/uapi/asm-generic/ioctl.h:70:2: note: expanded from macro '_IOC'
> > (((dir) << _IOC_DIRSHIFT) | \
> > ^
> >
> > I see this warning in drivers/scsi/hpsa.c and drivers/scsi/smartpqi/smartpqi_init.c
> > on an arm64 allyesconfig build and it has also been reported in a couple of files in
> > drivers/scsi/cxlflash.
> >
> > As the warning states, there is an overflow because the switch statement's value is of
> > type int but the switch value is greater than INT_MAX. I did a brief sweep of the tree
> > and it seems that all uses of _IOC in switch statement values either are small enough
> > to fit into size int or the value is of size unsigned int.
> >
> > I am unsure of the implications of using a smaller _IOC value or converting all ioctls
> > to expect a cmd of type unsigned int (especially since that has userspace implications)
> > but I didn't see any negative ioctl commands. Some clarity and insight would be
> > appreciated.
>
> Have you verified how gcc compiles these switch statements? Maybe gcc supports
> switch / case statements on integral types that are larger than an int?
>
> Bart.

Hi Bart,

That is entirely possible, I will do some research. I did build with GCC
to see if there was any warning and there isn't so I'll be curious to
see what is happening at a lower level.

Thanks for the comment!
Nathan

\
 
 \ /
  Last update: 2018-10-04 20:46    [W:0.098 / U:0.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site