On Thu, Mar 04, 2021 at 04:53:18PM -0800, Jian Cai wrote: > This patch adds CONFIG_HARDEN_SLS_ALL that can be used to turn on > -mharden-sls=all, which mitigates the straight-line speculation > vulnerability, speculative execution of the instruction following some > unconditional jumps. Notice -mharden-sls= has other options as below, > and this config turns on the strongest option. > > all: enable all mitigations against Straight Line Speculation that are > implemented. > none: disable all mitigations against Straight Line Speculation. > retbr: enable the mitigation against Straight Line Speculation for RET and BR > instructions. > blr: enable the mitigation against Straight Line Speculation for BLR > instructions. > > Links: > https://reviews.llvm.org/D93221 > https://reviews.llvm.org/D81404 > https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/downloads/straight-line-speculation > https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/frequently-asked-questions#SLS2 > > Suggested-by: Manoj Gupta <manojgu...@google.com> > Suggested-by: Nick Desaulniers <ndesaulni...@google.com> > Suggested-by: Nathan Chancellor <nat...@kernel.org> > Suggested-by: David Laight <david.lai...@aculab.com> > Suggested-by: Will Deacon <w...@kernel.org>
I'm still reasonably opposed to this patch, so please don't add my "Suggested-by" here as, if I were to suggest anything, it would be not to apply this patch :) I still don't see why SLS is worth a compiler mitigation which will affect all CPUs that run the kernel binary, but Spectre-v1 is not. In other words, the big thing missing from this is a justification as to why SLS is a problem worth working around for general C code. Will
