On Thu, 2018-10-04 at 11:30 -0700, Nathan Chancellor wrote: +AD4 Hi SCSI folks, +AD4 +AD4 In an effort to get the kernel building warning free with Clang, we've +AD4 come across an interesting occurrence in a few scsi drivers: +AD4 +AD4 drivers/scsi/hpsa.c:6533:7: warning: overflow converting case value to switch condition type (2148024833 to 18446744071562609153) +AFs--Wswitch+AF0 +AD4 case CCISS+AF8-GETPCIINFO: +AD4 +AF4 +AD4 ./include/uapi/linux/cciss+AF8-ioctl.h:65:26: note: expanded from macro 'CCISS+AF8-GETPCIINFO' +AD4 +ACM-define CCISS+AF8-GETPCIINFO +AF8-IOR(CCISS+AF8-IOC+AF8-MAGIC, 1, cciss+AF8-pci+AF8-info+AF8-struct) +AD4 +AF4 +AD4 ./include/uapi/asm-generic/ioctl.h:86:28: note: expanded from macro '+AF8-IOR' +AD4 +ACM-define +AF8-IOR(type,nr,size) +AF8-IOC(+AF8-IOC+AF8-READ,(type),(nr),(+AF8-IOC+AF8-TYPECHECK(size))) +AD4 +AF4 +AD4 ./include/uapi/asm-generic/ioctl.h:70:2: note: expanded from macro '+AF8-IOC' +AD4 (((dir) +ADwAPA +AF8-IOC+AF8-DIRSHIFT) +AHw +AFw +AD4 +AF4 +AD4 +AD4 I see this warning in drivers/scsi/hpsa.c and drivers/scsi/smartpqi/smartpqi+AF8-init.c +AD4 on an arm64 allyesconfig build and it has also been reported in a couple of files in +AD4 drivers/scsi/cxlflash. +AD4 +AD4 As the warning states, there is an overflow because the switch statement's value is of +AD4 type int but the switch value is greater than INT+AF8-MAX. I did a brief sweep of the tree +AD4 and it seems that all uses of +AF8-IOC in switch statement values either are small enough +AD4 to fit into size int or the value is of size unsigned int. +AD4 +AD4 I am unsure of the implications of using a smaller +AF8-IOC value or converting all ioctls +AD4 to expect a cmd of type unsigned int (especially since that has userspace implications) +AD4 but I didn't see any negative ioctl commands. Some clarity and insight would be +AD4 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.
