CVSROOT: /cvs
Module name: src
Changes by: [email protected] 2018/07/23 11:54:04
Modified files:
sys/arch/amd64/amd64: locore.S
sys/arch/amd64/include: asm.h cpufunc.h frameasm.h
Log message:
Do "Return stack refilling", based on the "Return stack underflow" discussion
and its associated appendix at https://support.google.com/faqs/answer/7625886
This should address at least some cases of "SpectreRSB" and earlier
Spectre variants; more commits to follow.
The refilling is done in the enter-kernel-from-userspace and
return-to-userspace-from-kernel paths, making sure to do it before
unblocking interrupts so that a successive interrupt can't get the
CPU to C code without doing this refill. Per the link above, it
also does it immediately after mwait, apparently in case the low-power
CPU states of idle-via-mwait flush the RSB.
ok mlarkin@ deraadt@
