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: James Morse <james.morse@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/include/asm/exec.h b/arch/arm64/include/asm/exec.h
index db0563c23482d52175bf6c22f733410797122e36..f7865dd9d86854760e69ea71d30452625d6713ec 100644 (file)
--- 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 27b2f1387df40b61b4aa059be5650d329964da6b..4f186c56c5ebfa393141c6495b5a1704b2336fa0 100644 (file)
--- 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 ad734142070dcd143f3a7559ff50a044e93e95ac..bb0cd787a9d31dc4762d3a98257b3e11d8afe6f0 100644 (file)
--- 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>
@@ -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