psci: fix error due to a non zero context id
In the previous psci implementation, the psci_afflvl_power_on_finish()
function would run into an error condition if the value of the context
id parameter in the cpu_on and cpu_suspend psci calls was != 0. The
parameter was being restored as the return value of the affinity level
0 finisher function. A non zero context id would be treated as an
error condition. This would prevent successful wake up of the cpu from
a power down state. Also, the contents of the general purpose
registers were not being cleared upon return to the non-secure world
after a cpu power up. This could potentially allow the non-secure
world to view secure data.
This patch ensures that all general purpose registers are set to ~0
prior to the final eret that drops the execution to the non-secure
world. The context id is used to initialize the general purpose
register x0 prior to re-entry into the non-secure world and is no
longer restored as a function return value. A platform helper
(platform_get_stack()) has been introduced to facilitate this change.
Change-Id: I2454911ffd75705d6aa8609a5d250d9b26fa097c
diff --git a/common/psci/psci_entry.S b/common/psci/psci_entry.S
index 2f39f36..74cdf95 100644
--- a/common/psci/psci_entry.S
+++ b/common/psci/psci_entry.S
@@ -32,6 +32,7 @@
#include <platform.h>
#include <psci.h>
#include <psci_private.h>
+#include <runtime_svc.h>
#include <asm_macros.S>
.globl psci_aff_on_finish_entry
@@ -77,7 +78,6 @@
mov x0, x19
mov x1, #MPIDR_AFFLVL0
blr x22
- mov x21, x0
/* --------------------------------------------
* Give ourselves a stack allocated in Normal
@@ -88,10 +88,13 @@
bl platform_set_stack
/* --------------------------------------------
- * Restore the context id. value
+ * Use the size of the general purpose register
+ * context to restore the register state
+ * stashed by earlier code
* --------------------------------------------
*/
- mov x0, x21
+ sub sp, sp, #SIZEOF_GPREGS
+ exception_exit restore_regs
/* --------------------------------------------
* Jump back to the non-secure world assuming