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.
