bl31: Split into two separate memory regions

Some platforms are extremely memory constrained and must split BL31
between multiple non-contiguous areas in SRAM. Allow the NOBITS
sections (.bss, stacks, page tables, and coherent memory) to be placed
in a separate region of RAM from the loaded firmware image.

Because the NOBITS region may be at a lower address than the rest of
BL31, __RW_{START,END}__ and __BL31_{START,END}__ cannot include this
region, or el3_entrypoint_common would attempt to invalidate the dcache
for the entire address space. New symbols __NOBITS_{START,END}__ are
added when SEPARATE_NOBITS_REGION is enabled, and the dcached for the
NOBITS region is invalidated separately.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Change-Id: Idedfec5e4dbee77e94f2fdd356e6ae6f4dc79d37

1 files changed, 2 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 073c2ed3e..42fdb7326 100644
--- a/Makefile
+++ b/Makefile
@@ -736,6 +736,7 @@ $(eval $(call assert_boolean,RAS_EXTENSION))
 $(eval $(call assert_boolean,RESET_TO_BL31))
 $(eval $(call assert_boolean,SAVE_KEYS))
 $(eval $(call assert_boolean,SEPARATE_CODE_AND_RODATA))
+$(eval $(call assert_boolean,SEPARATE_NOBITS_REGION))
 $(eval $(call assert_boolean,SPIN_ON_BL1_EXIT))
 $(eval $(call assert_boolean,SPM_MM))
 $(eval $(call assert_boolean,TRUSTED_BOARD_BOOT))
@@ -800,6 +801,7 @@ $(eval $(call add_define,PSCI_EXTENDED_STATE_ID))
 $(eval $(call add_define,RAS_EXTENSION))
 $(eval $(call add_define,RESET_TO_BL31))
 $(eval $(call add_define,SEPARATE_CODE_AND_RODATA))
+$(eval $(call add_define,SEPARATE_NOBITS_REGION))
 $(eval $(call add_define,RECLAIM_INIT_CODE))
 $(eval $(call add_define,SPD_${SPD}))
 $(eval $(call add_define,SPIN_ON_BL1_EXIT))