On Thu, Dec 01, 2011 at 04:44:40PM +0000, Arnd Bergmann wrote:

On Thursday 01 December 2011, Catalin Marinas wrote:

quoted

On Thu, Dec 01, 2011 at 03:42:19PM +0000, Arnd Bergmann wrote:

quoted

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