Split out the non-ARM specific portions of SYS_OPEN to a
reusable function. This handles gdb and host file i/o.
Add helpers to validate the length of the filename string.
Prepare for usage by other semihosting by allowing the
filename length parameter to be 0, and calling strlen.
Reviewed-by: Luc Michel <lmichel@kalray.eu>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
5b3f39cb04