Use constant stack size with RECLAIM_INIT_CODE
Currently, when RECLAIM_INIT_CODE is set, the
stacks are scaled to ensure that the entirety
of the init section can be reclaimed as stack.
This causes an issue in lib/psci/aarch64/psci_helpers.S,
where the stack size is used for cache operations in
psci_do_pwrdown_cache_maintenance(). If the stacks
are scaled, then the PSCI code may fail to invalidate
some of the stack memory before power down.
Resizing stacks is also not good for stability in general,
since code that works with a small number of cores may
overflow the stack when the number of cores is increased.
Change to make every stack be PLATFORM_STACK_SIZE big,
and allow the total stack to be smaller than the
init section.
Any pages of the init section not reclaimed as
stack will be set to read-only and execute-never,
for security.
Change-Id: I10b3884981006431f2fcbec3864c81d4a8c246e8
Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/plat/arm/common/arm_bl31_setup.c b/plat/arm/common/arm_bl31_setup.c
index fc238b1..81ef6e7 100644
--- a/plat/arm/common/arm_bl31_setup.c
+++ b/plat/arm/common/arm_bl31_setup.c
@@ -47,9 +47,12 @@
#if RECLAIM_INIT_CODE
IMPORT_SYM(unsigned long, __INIT_CODE_START__, BL_INIT_CODE_BASE);
IMPORT_SYM(unsigned long, __INIT_CODE_END__, BL_CODE_END_UNALIGNED);
+IMPORT_SYM(unsigned long, __STACKS_END__, BL_STACKS_END_UNALIGNED);
#define BL_INIT_CODE_END ((BL_CODE_END_UNALIGNED + PAGE_SIZE - 1) & \
~(PAGE_SIZE - 1))
+#define BL_STACKS_END ((BL_STACKS_END_UNALIGNED + PAGE_SIZE - 1) & \
+ ~(PAGE_SIZE - 1))
#define MAP_BL_INIT_CODE MAP_REGION_FLAT( \
BL_INIT_CODE_BASE, \
@@ -291,14 +294,39 @@
#if RECLAIM_INIT_CODE
/*
- * Zero out and make RW memory used to store image boot time code so it can
- * be reclaimed during runtime
+ * Make memory for image boot time code RW to reclaim it as stack for the
+ * secondary cores, or RO where it cannot be reclaimed:
+ *
+ * |-------- INIT SECTION --------|
+ * -----------------------------------------
+ * | CORE 0 | CORE 1 | CORE 2 | EXTRA |
+ * | STACK | STACK | STACK | SPACE |
+ * -----------------------------------------
+ * <-------------------> <------>
+ * MAKE RW AND XN MAKE
+ * FOR STACKS RO AND XN
*/
void arm_free_init_memory(void)
{
- int ret = xlat_change_mem_attributes(BL_INIT_CODE_BASE,
+ int ret = 0;
+
+ if (BL_STACKS_END < BL_INIT_CODE_END) {
+ /* Reclaim some of the init section as stack if possible. */
+ if (BL_INIT_CODE_BASE < BL_STACKS_END) {
+ ret |= xlat_change_mem_attributes(BL_INIT_CODE_BASE,
+ BL_STACKS_END - BL_INIT_CODE_BASE,
+ MT_RW_DATA);
+ }
+ /* Make the rest of the init section read-only. */
+ ret |= xlat_change_mem_attributes(BL_STACKS_END,
+ BL_INIT_CODE_END - BL_STACKS_END,
+ MT_RO_DATA);
+ } else {
+ /* The stacks cover the init section, so reclaim it all. */
+ ret |= xlat_change_mem_attributes(BL_INIT_CODE_BASE,
BL_INIT_CODE_END - BL_INIT_CODE_BASE,
MT_RW_DATA);
+ }
if (ret != 0) {
ERROR("Could not reclaim initialization code");