Linux process and process boundaries

1. Processes and Threads

2. Development of mobile phone operating system

3. Address space boundaries for processes

4. Security fence at the process boundary: crash non-ductile

5. Secure fencing of process boundaries: global data and service accessibility

Http://www.jikexueyuan.com/course/25.html

---------------------------------

1. Processes and Threads

Executable file: is a file, inactive is a normal file, binary

Process: The running of the executable file, run once.

Threads: CPU (CORE) dispatch units, internal concurrent task scheduling of processes

Concurrency of single-core CPUs: pseudo-concurrency, time-Slice scheduling

Concurrency of multicore CPUs: Real concurrency in physical sense

Resources and Scheduling: a process is the basic allocation unit of a resource, a separate address space, a heap, a stack

Threads: No separate address space, only stand-alone stack, and independent time-slice scheduling

2. Development of mobile phone operating system

Feature Phone era: a single-process multi-tasking (thread) non-intelligent system, a thread is an application. Closed, the application can only be extended by J2ME

Smart phone era: Multi-process multi-tasking intelligent system, open, extensible application

3. Address space boundaries for processes

Physical memory: A fixed piece of memory, as in the bottom

Each process has 0~4g virtual memory (address space), where 3~4g addresses are mapped to the same block of physical memory (this memory is kernel SAPCE)

0~3G (head, stack,..) The physical address of the map is independent, not the same (but not necessarily sequential)

4. Security fence at the process boundary: crash non-ductile

The independent benefits of address space

the crash of a process does not result in the crash of other processes or systems .

Anr:ui block time is too long

Force Close: Process terminated unexpectedly

Kernel Crash or Filesystem Crash then the entire OS Crash, with a widening. Phone blue screen or restart

Much better than Feature phone, Feature phone an application crash the entire system crash

5. Secure fencing of process boundaries: global data and service accessibility

The address space of each application 0~3g is independent,

Other application even if they know the address of the current app, other apps can't read it because the app address maps to different physical memory

Linux process and process boundaries