Re: [PATCH v2 1/4] powerpc/64: Add INTERRUPT_SANITIZE_REGISTERS Kconfig
From: Christophe Leroy <hidden>
Date: 2022-11-07 14:30:16
Le 07/11/2022 à 04:31, Rohan McLure a écrit :
Add Kconfig option for enabling clearing of registers on arrival in an interrupt handler. This reduces the speculation influence of registers on kernel internals. The option will be consumed by 64-bit systems that feature speculation and wish to implement this mitigation. This patch only introduces the Kconfig option, no actual mitigations.
If that has to do with speculation, do we need a new Kconfig option ? Can't we use CONFIG_PPC_BARRIER_NOSPEC for that ?
quoted hunk ↗ jump to hunk
The primary overhead of this mitigation lies in an increased number of registers that must be saved and restored by interrupt handlers on Book3S systems. Enable by default on Book3E systems, which prior to this patch eagerly save and restore register state, meaning that the mitigation when implemented will have minimal overhead. Acked-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Rohan McLure <redacted> --- Resubmitting patches as their own series after v6 partially merged: Link: https://lore.kernel.org/all/166488988686.779920.13794870102696416283.b4-ty@ellerman.id.au/t/ (local) --- arch/powerpc/Kconfig | 9 +++++++++ 1 file changed, 9 insertions(+)diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 2ca5418457ed..9d3d20c6f365 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig@@ -529,6 +529,15 @@ config HOTPLUG_CPU Say N if you are unsure. +config INTERRUPT_SANITIZE_REGISTERS + bool "Clear gprs on interrupt arrival" + depends on PPC64 && ARCH_HAS_SYSCALL_WRAPPER + default PPC_BOOK3E_64 + help + Reduce the influence of user register state on interrupt handlers and + syscalls through clearing user state from registers before handling + the exception. + config PPC_QUEUED_SPINLOCKS bool "Queued spinlocks" if EXPERT depends on SMP