72         let address_space = AddressSpace::current()?;  in brk()  localVariable
73         let mut address_space = address_space.write();  in brk()  localVariable
75         if new_addr < address_space.brk_start || new_addr >= MMArch::USER_END_VADDR {  in brk()
76             return Ok(address_space.brk);  in brk()
78         if new_addr == address_space.brk {  in brk()
79             return Ok(address_space.brk);  in brk()
83             address_space  in brk()
87             return Ok(address_space.sbrk(0).unwrap());  in brk()
94         let address_space = AddressSpace::current()?;  in sbrk()  localVariable
95         let mut address_space = address_space.write();  in sbrk()  localVariable
96         let r = unsafe { address_space.sbrk(incr) };  in sbrk()