[PATCH 3/3] arm64: suspend: Reconfigure PSTATE after resume from idle
Lorenzo Pieralisi
lorenzo.pieralisi at arm.com
Thu Oct 20 04:27:51 PDT 2016
On Tue, Oct 18, 2016 at 11:27:48AM +0100, James Morse wrote:
> 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: James Morse <james.morse at arm.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
>
> ---
> This patch applies to linux-stable v4.7.8, but with some fuzz...
> but 'git am' rejects it.
>
> asm/exec.h is my best guess at the appropriate header file. Contradictions
> welcome.
uaccess.h ? It is a shame you have to export uao_thread_switch() (see
below for a possible solution) but I agree that prevents useless code
duplication and that this needs fixing.
> arch/arm64/include/asm/exec.h | 3 +++
> arch/arm64/kernel/process.c | 3 ++-
> arch/arm64/kernel/suspend.c | 11 +++++++++++
> 3 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/exec.h b/arch/arm64/include/asm/exec.h
> index db0563c23482..f7865dd9d868 100644
> --- a/arch/arm64/include/asm/exec.h
> +++ b/arch/arm64/include/asm/exec.h
> @@ -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 */
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 27b2f1387df4..4f186c56c5eb 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -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)
> diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
> index ad734142070d..bb0cd787a9d3 100644
> --- a/arch/arm64/kernel/suspend.c
> +++ b/arch/arm64/kernel/suspend.c
> @@ -1,8 +1,11 @@
> #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>
> @@ -50,6 +53,14 @@ 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);
set_fs(get_fs());
would do (?), but that's horrendous to say the least, maybe you can
refactor the code in asm/uaccess.h to achieve the same goal (ie you
factor out the code setting UAO from set_fs() in a separate inline that
you can also reuse in uao_thread_switch() and here).
Other than that:
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> +
> + /*
> * Restore HW breakpoint registers to sane values
> * before debug exceptions are possibly reenabled
> * through local_dbg_restore.
> --
> 2.8.0.rc3
>
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