Commit d0854412 authored by James Morse's avatar James Morse Committed by Will Deacon
Browse files

arm64: suspend: Reconfigure PSTATE after resume from idle 



The suspend/resume path in kernel/sleep.S, as used by cpu-idle, does not
save/restore PSTATE. As a result of this cpufeatures that were detected
and have bits in PSTATE get lost when we resume from idle.

UAO gets set appropriately on the next context switch. PAN will be
re-enabled next time we return from user-space, but on a preemptible
kernel we may run work accessing user space before this point.

Add code to re-enable theses two features in __cpu_suspend_exit().
We re-use uao_thread_switch() passing current.

Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 7209c868

arch/arm64/include/asm/exec.h

+3 −0
Original line number Diff line number Diff line
@@ -18,6 +18,9 @@ 
#ifndef __ASM_EXEC_H

#define __ASM_EXEC_H



#include <linux/sched.h>



extern unsigned long arch_align_stack(unsigned long sp);

void uao_thread_switch(struct task_struct *next);



#endif	/* __ASM_EXEC_H */

arch/arm64/kernel/process.c

+2 −1
Original line number Diff line number Diff line
@@ -49,6 +49,7 @@ 
#include <asm/alternative.h>

#include <asm/compat.h>

#include <asm/cacheflush.h>

#include <asm/exec.h>

#include <asm/fpsimd.h>

#include <asm/mmu_context.h>

#include <asm/processor.h>
@@ -301,7 +302,7 @@ static void tls_thread_switch(struct task_struct *next) 
}



/* Restore the UAO state depending on next's addr_limit */

static void uao_thread_switch(struct task_struct *next)

void uao_thread_switch(struct task_struct *next)

{

	if (IS_ENABLED(CONFIG_ARM64_UAO)) {

		if (task_thread_info(next)->addr_limit == KERNEL_DS)

arch/arm64/kernel/suspend.c

+11 −0
Original line number Diff line number Diff line 
#include <linux/ftrace.h>

#include <linux/percpu.h>

#include <linux/slab.h>

#include <asm/alternative.h>

#include <asm/cacheflush.h>

#include <asm/cpufeature.h>

#include <asm/debug-monitors.h>

#include <asm/exec.h>

#include <asm/pgtable.h>

#include <asm/memory.h>

#include <asm/mmu_context.h>
@@ -49,6 +52,14 @@ void notrace __cpu_suspend_exit(void) 
	 */

	set_my_cpu_offset(per_cpu_offset(cpu));



	/*

	 * PSTATE was not saved over suspend/resume, re-enable any detected

	 * features that might not have been set correctly.

	 */

	asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,

			CONFIG_ARM64_PAN));

	uao_thread_switch(current);



	/*

	 * Restore HW breakpoint registers to sane values

	 * before debug exceptions are possibly reenabled

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