Function validate_rip 

fn validate_rip(rip: u64, address_space: &AddressSpace) -> Result<(), IpcError>

Validate that rip points to an authorized executable page.

Checks:

• Belongs to an executable VMA
• PTE has NX=0
• Not in kernel ring, MigrationFrame, or non-executable zones
• Part of a registered handler or authorized code range