Commit dc802f2b authored by Marc Zyngier's avatar Marc Zyngier Committed by Will Deacon
Browse files

arm64: Rework ARM_ERRATUM_1414080 handling 



The current handling of erratum 1414080 has the side effect that
cntkctl_el1 can get changed for both 32 and 64bit tasks.

This isn't a problem so far, but if we ever need to mitigate another
of these errata on the 64bit side, we'd better keep the messing with
cntkctl_el1 local to 32bit tasks.

For that, make sure that on entering the kernel from a 32bit tasks,
userspace access to cntvct gets enabled, and disabled returning to
userspace, while it never gets changed for 64bit tasks.

Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20200706163802.1836732-5-maz@kernel.org


[will: removed branch instructions per Mark's review comments]
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 4b661d61

arch/arm64/kernel/entry.S

+19 −15
Original line number Diff line number Diff line
@@ -167,6 +167,17 @@ alternative_cb_end 
	stp	x28, x29, [sp, #16 * 14]



	.if	\el == 0

	.if	\regsize == 32

	// If we're returning from a 32-bit task on a system affected by

	// 1418040 then re-enable userspace access to the virtual counter.

#ifdef CONFIG_ARM64_ERRATUM_1418040

alternative_if ARM64_WORKAROUND_1418040

	mrs	x0, cntkctl_el1

	orr	x0, x0, #2	// ARCH_TIMER_USR_VCT_ACCESS_EN

	msr	cntkctl_el1, x0

alternative_else_nop_endif

#endif

	.endif

	clear_gp_regs

	mrs	x21, sp_el0

	ldr_this_cpu	tsk, __entry_task, x20
@@ -320,6 +331,14 @@ alternative_else_nop_endif 
	tst	x22, #PSR_MODE32_BIT		// native task?

	b.eq	3f



#ifdef CONFIG_ARM64_ERRATUM_1418040

alternative_if ARM64_WORKAROUND_1418040

	mrs	x0, cntkctl_el1

	bic	x0, x0, #2			// ARCH_TIMER_USR_VCT_ACCESS_EN

	msr	cntkctl_el1, x0

alternative_else_nop_endif

#endif



#ifdef CONFIG_ARM64_ERRATUM_845719

alternative_if ARM64_WORKAROUND_845719

#ifdef CONFIG_PID_IN_CONTEXTIDR
@@ -331,21 +350,6 @@ alternative_if ARM64_WORKAROUND_845719 
alternative_else_nop_endif

#endif

3:

#ifdef CONFIG_ARM64_ERRATUM_1418040

alternative_if_not ARM64_WORKAROUND_1418040

	b	4f

alternative_else_nop_endif

	/*

	 * if (x22.mode32 == cntkctl_el1.el0vcten)

	 *     cntkctl_el1.el0vcten = ~cntkctl_el1.el0vcten

	 */

	mrs	x1, cntkctl_el1

	eon	x0, x1, x22, lsr #3

	tbz	x0, #1, 4f

	eor	x1, x1, #2	// ARCH_TIMER_USR_VCT_ACCESS_EN

	msr	cntkctl_el1, x1

4:

#endif

	scs_save tsk, x0



	/* No kernel C function calls after this as user keys are set. */

CRA Git | Maintained and supported by SUSTech CRA and CCSE