4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Marc Zyngier <marc.zyngier@xxxxxxx> commit 9dd9614f5476687abbff8d4b12cd08ae70d7c2ad upstream. In order to allow userspace to be mitigated on demand, let's introduce a new thread flag that prevents the mitigation from being turned off when exiting to userspace, and doesn't turn it on on entry into the kernel (with the assumption that the mitigation is always enabled in the kernel itself). This will be used by a prctl interface introduced in a later patch. Reviewed-by: Mark Rutland <mark.rutland@xxxxxxx> Acked-by: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/include/asm/thread_info.h | 1 + arch/arm64/kernel/entry.S | 2 ++ 2 files changed, 3 insertions(+) --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -122,6 +122,7 @@ static inline struct thread_info *curren #define TIF_RESTORE_SIGMASK 20 #define TIF_SINGLESTEP 21 #define TIF_32BIT 22 /* 32bit process */ +#define TIF_SSBD 23 /* Wants SSB mitigation */ #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -105,6 +105,8 @@ alternative_cb arm64_enable_wa2_handling alternative_cb_end ldr_this_cpu \tmp2, arm64_ssbd_callback_required, \tmp1 cbz \tmp2, \targ + ldr \tmp2, [tsk, #TI_FLAGS] + tbnz \tmp2, #TIF_SSBD, \targ mov w0, #ARM_SMCCC_ARCH_WORKAROUND_2 mov w1, #\state alternative_cb arm64_update_smccc_conduit
