On Sunday 19 August 2007, Satyam Sharma wrote: > > > On a 32-bit arch "unsigned long" is 32-bit and pointers are 32-bit. > > > > > > On a 64-bit archi "unsigned long" is 64-bit and pointers are 64-bit. > > > > So with 32 bit userspace "unsigned long long" is the type to use > > when talking to a 64-bit kernel; and with pure 64-bit code, it's > > enough to write "unsigned long". > > > > I'm fairly sure that's the root cause of the pain I recall here; > > but I'd have to run experiments again to verify that. > > I suspect the root cause of the pain was that you used "int" or "long" > to talk between kernel and userspace in the first place. You shouldn't, > we have __u32 / __u64 / etc for that.
Nope; the relevant code was always with "__u64". The issue was warning when turning that into a __user pointer. > The reason I ask is that gcc will also complain (understandably so) with > "warning: cast from pointer to integer of different size" i.e. even if > it's a conversion from smaller size to greater size, and not really a > case of truncation. ISTR the warning was the other way around: about "cast from integer to pointer of a different size". The __u64 came from userspace and the kernel pointer was only 32 bits. Not really truncation, but GCC could not know that directly ... ergo the extra non-pointer cast. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
