commit d08544127d9fb4505635e3cb6871fd50a42947bd upstream.
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.
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 this feature in __cpu_suspend_exit().
Signed-off-by: James Morse <james.morse@xxxxxxx>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
[Removed UAO hooks and commit-message references: this feature is not
present in v4.4]
Signed-off-by: James Morse <james.morse@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 4.4.35
---
arch/arm64/kernel/suspend.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index 1095aa483a1c..00c1372bf57b 100644
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -1,7 +1,9 @@
#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/pgtable.h>
#include <asm/memory.h>
@@ -111,6 +113,13 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
/*
+ * 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));
+
+ /*
* Restore HW breakpoint registers to sane values
* before debug exceptions are possibly reenabled
* through local_dbg_restore.
--
2.10.1
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