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Commit 9dd9614f authored by Marc Zyngier's avatar Marc Zyngier Committed by Catalin Marinas
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arm64: ssbd: Introduce thread flag to control userspace mitigation 



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: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 647d0519

arch/arm64/include/asm/thread_info.h

+1 −0
Original line number Diff line number Diff line
@@ -94,6 +94,7 @@ void arch_release_task_struct(struct task_struct *tsk); 
#define TIF_32BIT		22	/* 32bit process */

#define TIF_SVE			23	/* Scalable Vector Extension in use */

#define TIF_SVE_VL_INHERIT	24	/* Inherit sve_vl_onexec across exec */

#define TIF_SSBD		25	/* 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
@@ -147,6 +147,8 @@ alternative_cb arm64_enable_wa2_handling 
alternative_cb_end

	ldr_this_cpu	\tmp2, arm64_ssbd_callback_required, \tmp1

	cbz	\tmp2, \targ

	ldr	\tmp2, [tsk, #TSK_TI_FLAGS]

	tbnz	\tmp2, #TIF_SSBD, \targ

	mov	w0, #ARM_SMCCC_ARCH_WORKAROUND_2

	mov	w1, #\state

alternative_cb	arm64_update_smccc_conduit