On Wed, Feb 24, 2021 at 5:04 AM Arnd Bergmann <arnd@xxxxxxxxxx> wrote: > > On Tue, Feb 23, 2021 at 11:06 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > > > > -#ifdef __CHECKER__ > > -#define _IOC_TYPECHECK(t) (sizeof(t)) > > -#else > > /* provoke compile error for invalid uses of size argument */ > > -extern unsigned int __invalid_size_argument_for_IOC; > > +#undef _IOC_TYPECHECK > > #define _IOC_TYPECHECK(t) \ > > - ((sizeof(t) == sizeof(t[1]) && \ > > - sizeof(t) < (1 << _IOC_SIZEBITS)) ? \ > > - sizeof(t) : __invalid_size_argument_for_IOC) > > -#endif > > + BUILD_BUG_ON_ZERO(sizeof(t) != sizeof(t[1]) || \ > > + sizeof(t) >= (1 << _IOC_SIZEBITS)) > > Using BUILD_BUG_ON_ZERO sounds like a good idea > > > #endif /* _ASM_GENERIC_IOCTL_H */ > > diff --git a/include/uapi/asm-generic/ioctl.h b/include/uapi/asm-generic/ioctl.h > > index a84f4db8a250..d50bd39ec3e3 100644 > > --- a/include/uapi/asm-generic/ioctl.h > > +++ b/include/uapi/asm-generic/ioctl.h > > @@ -72,9 +72,8 @@ > > ((nr) << _IOC_NRSHIFT) | \ > > ((size) << _IOC_SIZESHIFT)) > > > > -#ifndef __KERNEL__ > > -#define _IOC_TYPECHECK(t) (sizeof(t)) > > -#endif > > +#define _IOC_TYPECHECK(t) 0 > > +#define _IOC_SIZE_WITH_TYPECHECK(t) (sizeof(t) + _IOC_TYPECHECK(t)) > > But I think replacing the #ifndef with an #undef in the other file makes it > harder to understand when reading through it and trying to understand > what it would do when this gets included from kernel and user space. > > Arnd My intention is to improve the UAPI/KAPI decoupling to decrease the task of scripts/headers_install.sh Ideally, we could export UAPI headers with almost no modification. It is true that scripts/unifdef can remove #ifndef __KERNEL__ blocks, but having the kernel-space code in UAPI headers does not make sense. Otherwise, our initial motivation "separate them by directory structure" would be lost. So, I believe redefining _IOC_TYPECHECK is the right direction. I can add comments if this is not clear. -- Best Regards Masahiro Yamada
