Commit cf14b896 authored Jul 20, 2018 by Marc Zyngier Committed by Greg Kroah-Hartman Jul 22, 2018

arm64: ssbd: Introduce thread flag to control userspace mitigation



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@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent d8fbc844

arch/arm64/include/asm/thread_info.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -122,6 +122,7 @@ static inline struct thread_info *current_thread_info(void)
		#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)

arch/arm64/kernel/entry.S

+2 −0

Original line number	Diff line number	Diff line
		@@ -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