svn commit: r313772 - head/sys/arm64/arm64

[Mark Millard]

> Author: andrew
> Date: Wed Feb 15 14:56:47 2017
> New Revision: 313772
> URL: 
> https://svnweb.freebsd.org/changeset/base/313772
> 
> Log:
>   Load the new sp_el0 with interrupts disabled in fork_trampoline. If an
>   interrupt arrives in fork_trampoline after sp_el0 was written we may then
>   switch to a new thread, enter userland so change this stack pointer, then
>   return to this code with the wrong value. This fixes this case by moving
>   the load of sp_el0 until after interrupts have been disabled.

https://svnweb.freebsd.org/base/stable/11/sys/arm64/arm64/swtch.S?revision=302408&view=markup

shows stable/11 has the same issue.

Is this to be MFC'd at some point?


stable/10 seems to have a different code structure:

https://svnweb.freebsd.org/base/stable/10/sys/amd64/amd64/

does not list swtch.S . So I'm unsure about its status for
fork returning to the child process and its handling of the
stack pointer to be restored.

===
Mark Millard
markmi at dsl-only.net