Commit d60d65ae authored May 29, 2018 by Marc Zyngier Committed by Isaac J. Manjarres Jun 13, 2018

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.

Change-Id: I9583873ac796489eba615e857cb9f21adcef2179
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>
Git-commit: 9dd9614f5476687abbff8d4b12cd08ae70d7c2ad
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>

parent 9be5bc93

arch/arm64/include/asm/thread_info.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -93,6 +93,7 @@ void arch_setup_new_exec(void);
		#define TIF_SINGLESTEP 21
		#define TIF_32BIT 22 /* 32bit process */
		#define TIF_MM_RELEASED 24
		#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
		@@ -148,6 +148,8 @@ alternative_else_nop_endif
		b.ne \targ
		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
		smc #0