core: Allow .bss and .data sections in DRAM

We manually copy other .data from the original section on boot, and
clear DRAM .bss.

This way, a single object file (or archive) can be moved fully to
DRAM.

BRANCH=none
BUG=b:122058243
TEST=With next CL, dram_test works

Change-Id: I1a434bbd8a4135d16b3f49b0d1b75b96506e3e24
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1445652
Reviewed-by: Jett Rink <jettrink@chromium.org>

4 files changed, 46 insertions, 3 deletions

diff --git a/Makefile.rules b/Makefile.rules
index 8ea3c7cac0..7c158ffcad 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -61,9 +61,9 @@ cmd_obj_to_bin ?= $(OBJCOPY) --gap-fill=0xff -O binary $^ $(out)/$*.bin.tmp
 cmd_flat_to_obj = $(CC) -Wl,-T $(out)/firmware_image.lds -nostdlib $(CPPFLAGS) \
                   -Wl,--build-id=none -o $@ $<
 # Allow the .roshared section to overlap other sections (itself)
-cmd_ec_elf_to_flat ?= $(OBJCOPY) --set-section-flags .roshared=share -R .dram \
+cmd_ec_elf_to_flat ?= $(OBJCOPY) --set-section-flags .roshared=share -R .dram* \
 				-O binary $< $@
-cmd_ec_elf_to_flat_dram ?= $(OBJCOPY) -j .dram -O binary $< $@
+cmd_ec_elf_to_flat_dram ?= $(OBJCOPY) -j .dram* -O binary $< $@
 cmd_elf_to_signed ?= $(SIGNER) --key=util/signer/$(3) \
 	--b --input=$< --format=bin --output=$@.signed $(SIGNER_EXTRAS) \
 	&& sudo chown $(shell whoami) $@.signed && mv $@.signed $@
diff --git a/common/main.c b/common/main.c
index 6adea9b049..0a222b23ca 100644
--- a/common/main.c
+++ b/common/main.c
@@ -17,8 +17,9 @@
 #include "flash.h"
 #include "gpio.h"
 #include "hooks.h"
-#include "lpc.h"
 #include "keyboard_scan.h"
+#include "link_defs.h"
+#include "lpc.h"
 #ifdef CONFIG_MPU
 #include "mpu.h"
 #endif
@@ -84,6 +85,14 @@ test_mockable __keep int main(void)
 	system_pre_init();
 	system_common_pre_init();
 
+#ifdef CONFIG_DRAM_BASE
+	/* Now that DRAM is initialized, clear up DRAM .bss, copy .data over. */
+	memset(&__dram_bss_start, 0,
+	       (uintptr_t)(&__dram_bss_end) - (uintptr_t)(&__dram_bss_start));
+	memcpy(&__dram_data_start, &__dram_data_lma_start,
+	       (uintptr_t)(&__dram_data_end) - (uintptr_t)(&__dram_data_start));
+#endif
+
 #if defined(CONFIG_FLASH_PHYSICAL)
 	/*
 	 * Initialize flash and apply write protect if necessary.  Requires
diff --git a/core/cortex-m/ec.lds.S b/core/cortex-m/ec.lds.S
index 06bd83a30d..28c3e691cd 100644
--- a/core/cortex-m/ec.lds.S
+++ b/core/cortex-m/ec.lds.S
@@ -444,7 +444,34 @@ SECTIONS
 #endif /* CONFIG_CHIP_MEMORY_REGIONS */
 
 #ifdef CONFIG_DRAM_BASE
+    /* Allocate space for original copy of .data.dram (see .data_lma above). */
+    .dram.data_lma : {
+        __dram_data_lma_start = .;
+        . += __dram_data_end - __dram_data_start;
+    } > DRAM
+
+    /*
+     * TODO(b:122058243): Both .dram.data and .dram.bss do not actually
+     * need to be in the final image, as we have a second copy of the data
+     * (just above), and dram.bss is zeroed anyway.
+     */
+    .dram.data : AT(ADDR(.dram.data_lma)) {
+        . = ALIGN(4);
+        __dram_data_start = .;
+        *(.dram.data*)
+        __dram_data_end = .;
+    } > DRAM
+
+    .dram.bss : {
+        . = ALIGN(4);
+        __dram_bss_start = .;
+        *(SORT(.dram.bss*))
+        __dram_bss_end = .;
+    } > DRAM
+
+    /* Rest of DRAM sections, e.g. text. */
     .dram : {
+        . = ALIGN(4);
         KEEP(*(SORT(.dram.keep.*)))
         *(SORT(.dram.*))
     } > DRAM
diff --git a/include/link_defs.h b/include/link_defs.h
index 37049a36eb..a9bd0bcf9b 100644
--- a/include/link_defs.h
+++ b/include/link_defs.h
@@ -108,6 +108,13 @@ extern const void *__data_lma_start;
 extern const void *__data_start;
 extern const void *__data_end;
 
+/* DRAM image sections. */
+extern const void *__dram_data_lma_start;
+extern void *__dram_data_start;
+extern void *__dram_data_end;
+extern void *__dram_bss_start;
+extern void *__dram_bss_end;
+
 /* Helper for special chip-specific memory sections */
 #ifdef CONFIG_CHIP_MEMORY_REGIONS
 #define __SECTION(name) __attribute__((section("." STRINGIFY(name) ".50_auto")))