On Thu, Dec 01, 2011 at 04:44:40PM +0000, Arnd Bergmann wrote: > On Thursday 01 December 2011, Catalin Marinas wrote: > > On Thu, Dec 01, 2011 at 03:42:19PM +0000, Arnd Bergmann wrote: > > > On Thursday 01 December 2011, Catalin Marinas wrote: > > > How do you deal with signed integer arguments passed into SVC or HVC from > > > a caller? If I understand the architecture correctly, the upper > > > halves of the argument register end up zero-padded, while the callee > > > expects sign-extension. > > > > If you treat it as an "int" (32-bit) and function prototype defined > > accordingly, then the generated code only accesses it as a W (rather > > than X) register and the top 32-bit part is ignored (no need for > > sign-extension). If it is defined as a "long" in the 32-bit world, then > > it indeed needs explicit conversion given the different sizes for long > > (for example sys_lseek, the second argument is a 'long' and we do > > explicit sign extension in the wrapper). ... > What about unsigned long and pointer? Can we always rely on the upper > half of the register to be zero-filled when we get an exception from 32 > bit into 64 bit state, or do we also have to zero-extend those? They are also fine, no need for zero-extension. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
