Editing Porting the kernel

OpenVZ kernel supports x86, x86_64, IA64, power64, and sparc architectures as of now. Below are the quick and dirty information about how to port the  kernel to yet another architecture.

* UBC: need to account any platform specific VMAs created by hand in arch specific code. i.e. if there are calls of <code>insert_vm_struct()</code> this should be accounted with <code>ub_memory_charge()</code>. Didn't find such thing on sparc64.

* If there are user triggerable <code>printk()</code>'s (related to the user, not the system as a whole) better replace them with <code>ve_printk()</code>. Otherwise user can flood (DoS). minor actually.

* Call to functions <code>find_task_by_pid()</code>, <code>for_each_process()</code> and <code>do_each_thread()</code>/<code>while_each_thread()</code> should be replaced with it's counterparts - <code>find_task_by_pid_XXX()</code>, <code>for_each_process_XXX()</code> and <code>do_each_thread_XXX()</code>/<code>while_each_thread_XXX()</code>, where <code>XXX</code> is either <code>all</code> or <code>ve</code>. Here <code>all</code> means that all system processes in the system will be scanned, while <code>ve</code> means that only the [[VE]] accessible from this task (current context - <code>get_exec_env()</code>) will be visible. So you need to decide whether the code in question is about system or user context.

* <code>task->pid</code> should be changed with <code>virt_pid(task)</code> in some places. The rule is simple: user should see only virtual pids, while kernel operate on global pids. e.g. in signals, virtual pid should be delivered to app.

* In interrupt handlers one need to set global host ([[VE0]]) context. i.e. <code>set_exec_env()</code>, <code>set_exec_ub()</code>. i.e. interrupt handlers are running in VE0 context.

* In <code>kernel_thread()</code> one needs to prohibit kernel threads in VE. Mostly security related...

* Extend <code>show_registers()</code> (or <code>show_regs()</code>) to show current VE.

* <code>utsname</code> should be virtualized. This mostly means that <code>system_utsnames</code> should be replaced with <code>ve_utsname</code>. See any arch code for this.

* Some exports will be required. e.g. <code>show_mem()</code> and probably <code>cpu_khz</code>. Easy.

* Everything else are bugfixes.

All these are straightforward and really simple, so it should take a few hours to do.

== External links ==
* [http://forum.openvz.org/index.php?t=msg&goto=3338&&srch=sparc#msg_num_5 Original forum post]

[[Category: Kernel]]
[[Category: Development]]
[[Category: Internals]]