Simplify linker script to remove preprocessing, not check flash sizes

Memory layout is now split into two linker scripts for OTA vs
non-OTA (different starting offsets), remaining functionality in
common.ld.

As discussed in #64, progress towards #38

common.mk

@@ -131,8 +131,12 @@ endif
 GITSHORTREV=\"$(shell cd $(ROOT); git rev-parse --short -q HEAD)\"
 CPPFLAGS += -DGITSHORTREV=$(GITSHORTREV) -DFLASH_SIZE=$(FLASH_SIZE)
 
-# Linker scripts, all found in $(ROOT)/ld
+ifeq ($(OTA),0)
-LINKER_SCRIPTS  = eagle.app.v6.ld eagle.rom.addr.v6.ld
+LINKER_SCRIPTS  = $(ROOT)ld/nonota.ld
+else
+LINKER_SCRIPTS = $(ROOT)ld/ota.ld
+endif
+LINKER_SCRIPTS += $(ROOT)ld/common.ld $(ROOT)ld/rom.ld
 
 ####
 #### no user configurable options below here
@@ -152,19 +156,11 @@ lc = $(subst A,a,$(subst B,b,$(subst C,c,$(subst D,d,$(subst E,e,$(subst F,f,$(s
 # assume the program dir is the directory the top-level makefile was run in
 PROGRAM_DIR := $(dir $(firstword $(MAKEFILE_LIST)))
 
-# linker scripts get run through the C preprocessor
-ifeq ($(OTA),1)
-LD_DIR = $(BUILD_DIR)ld-$(FLASH_SIZE)-ota/
-else
-LD_DIR = $(BUILD_DIR)ld-$(FLASH_SIZE)/
-endif
-LINKER_SCRIPTS_PROCESSED = $(addprefix $(LD_DIR),$(LINKER_SCRIPTS))
-
 # derive various parts of compiler/linker arguments
 SDK_LIB_ARGS  = $(addprefix -l,$(SDK_LIBS))
 LIB_ARGS      = $(addprefix -l,$(LIBS))
 PROGRAM_OUT   = $(BUILD_DIR)$(PROGRAM).out
-LDFLAGS      += $(addprefix -T,$(LINKER_SCRIPTS_PROCESSED))
+LDFLAGS      += $(addprefix -T,$(LINKER_SCRIPTS))
 
 ifeq ($(OTA),0)
 # for non-OTA, we create two different files for uploading into the flash
@@ -335,16 +331,12 @@ $(foreach component,$(COMPONENTS), 					\
 	)								\
 )
 
-## Run linker scripts via C preprocessor to evaluate macros
-$(LD_DIR)%.ld: $(ROOT)ld/%.ld | $(LD_DIR)
-	$(Q) $(CPP) $(CPPFLAGS) -E -C -P $< > $@
-
 # final linking step to produce .elf
-$(PROGRAM_OUT): $(COMPONENT_ARS) $(SDK_PROCESSED_LIBS) $(LINKER_SCRIPTS_PROCESSED)
+$(PROGRAM_OUT): $(COMPONENT_ARS) $(SDK_PROCESSED_LIBS) $(LINKER_SCRIPTS)
 	$(vecho) "LD $@"
 	$(Q) $(LD) $(LDFLAGS) -Wl,--start-group $(COMPONENT_ARS) $(LIB_ARGS) $(SDK_LIB_ARGS) -Wl,--end-group -o $@
 
-$(BUILD_DIR) $(FW_BASE) $(BUILD_DIR)sdklib $(LD_DIR):
+$(BUILD_DIR) $(FW_BASE) $(BUILD_DIR)sdklib:
 	$(Q) mkdir -p $@
 
 $(FW_FILE_1) $(FW_FILE_2): $(PROGRAM_OUT) $(FW_BASE)

ld/common.ld

@@ -1,6 +1,6 @@
-/* This linker script generated from xt-genldscripts.tpp for LSP .
+/*
-
+ * Common (OTA and non-OTA) parts for the esp-open-rtos Linker Script
-   Modified for esp open RTOS, this linker script is no longer the same as the esp_iot_rtos_sdk one.
+ *
  */
 
 /* FreeRTOS memory management functions
@@ -28,43 +28,6 @@ _lock_release_recursive = vPortExitCritical;
 /* SDK compatibility */
 ets_printf = printf;
 
-/* Evaluate FLASH_SIZE to calculate irom size, etc.
-*/
-#ifndef OTA
-
-/* IROM0 section sits after other sections in the "v1" non-OTA bootloader image,
-   so need an 128kB offset to leave room
-*/
-#define IROM0_OFFSET 0x20000
-
-#else /* OTA */
-
-/* For OTA, IROM0 becomes an actual "section" of the bootloader image,
-   so we only need to leave space for the second stage bootloader
-   (0x2000 bytes) and space for the bootloader & section headers (0x10
-   bytes) */
-#define IROM0_OFFSET 0x2010
-
-#if FLASH_SIZE < 16
-#error "OTA support currently requires minimum 16 megabit flash"
-#endif
-
-#endif
-
-/* Full maximum length of IROM section is length of mappable flash (ie up to 1 megabyte),
-   minus anything mapped at start, minus single config SDK WiFi config sector at end
-*/
-#define IROM0_LEN   ((0x20000*MIN(FLASH_SIZE,8)) - IROM0_OFFSET - 0x1000)
-
-/* Linker Script for ld -N */
-MEMORY
-{
-  dport0_0_seg :                      	org = 0x3FF00000, len = 0x10
-  dram0_0_seg :                       	org = 0x3FFE8000, len = 0x14000
-  iram1_0_seg :                       	org = 0x40100000, len = 0x08000
-  irom0_0_seg :                       	org = 0x40200000+IROM0_OFFSET, len = IROM0_LEN
-}
-
 PHDRS
 {
   dport0_0_phdr PT_LOAD;

ld/nonota.ld

@@ -0,0 +1,15 @@
+/* Memory layout for esp-open-rtos when not using OTA
+   (ie ROM bootloader only, no second stage rboot)
+ */
+MEMORY
+{
+  dport0_0_seg :                      	org = 0x3FF00000, len = 0x10
+  dram0_0_seg :                       	org = 0x3FFE8000, len = 0x14000
+  iram1_0_seg :                       	org = 0x40100000, len = 0x08000
+/* irom0 section, mapped from SPI flash
+  - Origin is offset by 0x20000 to leave space for bootloader RAM sections.
+
+  - Length is max 8Mbit of mappable flash, minus start offset
+*/
+  irom0_0_seg :                       	org = 0x40220000, len = (1M - 0x20000)
+}

ld/ota.ld

@@ -0,0 +1,15 @@
+/* Memory layout for esp-open-rtos when using OTA second stage bootloader */
+
+MEMORY
+{
+  dport0_0_seg :                      	org = 0x3FF00000, len = 0x10
+  dram0_0_seg :                       	org = 0x3FFE8000, len = 0x14000
+  iram1_0_seg :                       	org = 0x40100000, len = 0x08000
+/* irom0 section, mapped from SPI flash
+  - Origin is offset by 0x2010 to create spacer for second stage bootloader image,
+    header.
+
+  - Length is max 8Mbit of mappable flash, minus start offset
+*/
+  irom0_0_seg :                       	org = 0x40202010, len = (1M - 0x2010)
+}

ld/rom.ld

@@ -1,3 +1,11 @@
+/* Linker script containing Boot ROM functions for ESP8266
+
+   For more information, see:
+
+   http://esp8266-re.foogod.com/wiki/Boot_ROM
+   https://github.com/jcmvbkbc/esp-elf-rom/
+*/
+
 PROVIDE ( SPI_sector_erase = 0x400040c0 );
 PROVIDE ( SPI_page_program = 0x40004174 );
 PROVIDE ( SPI_read_data = 0x400042ac );
@@ -8,22 +16,22 @@ PROVIDE ( Wait_SPI_Idle = 0x4000448c );
 PROVIDE ( Enable_QMode = 0x400044c0 );
 PROVIDE ( Disable_QMode = 0x40004508 );
 
+/* When using OTA, Cache_Read_Enable is defined in extras/rboot-ota so
+   the ROM Cache_Read_Enable isn't picked up from here. However we
+   also provide access to the ROM function in all cases, via the name
+   rom_Cache_Read_Enable */
 PROVIDE ( rom_Cache_Read_Enable = 0x40004678 );
+PROVIDE ( Cache_Read_Enable = rom_Cache_Read_Enable );
+
 PROVIDE ( Cache_Read_Disable = 0x400047f0 );
 
-#ifndef OTA
-/* If not building an OTA image for boot, can use the default (simple)
-   cache enable function from ROM.
-
-   Otherwise, we need an OTA-aware one (see extras/rboot-ota/rboot-cache.S)
-*/
-Cache_Read_Enable = rom_Cache_Read_Enable;
-#endif
-
 PROVIDE ( lldesc_build_chain = 0x40004f40 );
 PROVIDE ( lldesc_num2link = 0x40005050 );
 PROVIDE ( lldesc_set_owner = 0x4000507c );
 
+/* TODO: Nearly everything below here is probably provided by the
+   libc, so never linked in, and can therefore be removed. */
+
 PROVIDE ( __adddf3 = 0x4000c538 );
 PROVIDE ( __addsf3 = 0x4000c180 );
 PROVIDE ( __divdf3 = 0x4000cb94 );