[Info-vax] Android development Was Re: OT: Larry Ellison takes retirement as CEO of Oracle

[John Reagan]

On Tuesday, September 23, 2014 1:11:56 PM UTC-4, JF Mezei wrote:
> On 14-09-23 09:43, John Reagan wrote:
> 
> 
> 
> When C compiler compiles my code, does it know that calling SYS$QIO
> requires the addition of special "call" (trap or whatever) instruction
> that it doesn't add when calling a service in another shareable image ?

It doesn't know.

> 
> 
> 
> Are system services (and user written ones) not just a different flavour
> of a shareable image from the compiler and linker's and perhaps image
> actiuvator's points of view ?

SYS$QIO (and all system services) are specially known to the linker/image activator (called the public vectors).  The code you know as SYS$QIO doesn't do much other than trap to some kernel routine after it moves arguments perhaps from the user stack to the kernel stack, etc.

Privilege checks are performed by the services against the process' current privs.  No privs are magically "enabled".  You have them or you don't.