Sink down the ELF section section symbol start/end extraction from the Makefile into elf2hex.py

Author: kubamracek

Tools/elf2hex.py

@@ -18,11 +18,23 @@
 # file format suitable for flashing onto some embedded devices.
 #
 # Usage:
-#   $ elf2hex.py <input> <output> [--symbol-map <output>]
+#   $ elf2hex.py <input> <output> [--symbol-map <output>] [--relocate-data-segment]
 #
 # Example:
 #   $ elf2hex.py ./blink ./blink.hex --symbol-map ./blink.symbols
 #
+# The --relocate-data-segment option expects to be able to locate symbols with names
+#   - __data_start
+#   - __flash_data_start
+#   - __flash_data_len
+# and then it physically relocates a segment located at __data_start to
+# __flash_data_start, without changing virtual/physical addresses of any ELF
+# headers. This means that the .hex file is not validly mapped until a boot-time
+# reverse relocation step.
+#
+# See the linker script used in a particular demo folder for a detailed
+# explanation of the linking, packing, and runtime relocation scheme.
+#
 
 import argparse
 import json
@@ -36,18 +48,12 @@ def main():
     parser.add_argument('input')
     parser.add_argument('output')
     parser.add_argument('--symbol-map')
-    parser.add_argument('--relocate', action='append')
+    parser.add_argument('--relocate-data-segment', action='store_true')
     args = parser.parse_args()
 
     inf = open(args.input, "rb")
     outf = open(args.output, "wb")
 
-    relocations = {}
-    if args.relocate is not None:
-        for r in args.relocate:
-            (a, b) = r.split(":")
-            relocations[int(a, 16)] = int(b, 16)
-
     def emitrecord(record):
         checksum = 0
         pos = 0
@@ -77,6 +83,30 @@ def emit(vmaddr, data):
             vmaddr += chunklen
 
     elffile = elftools.elf.elffile.ELFFile(inf)
+
+    symbol_map = {}
+    symtab_section = elffile.get_section_by_name(".symtab")
+    for s in symtab_section.iter_symbols():
+        if s.entry.st_info.type not in ["STT_FUNC", "STT_NOTYPE"]:
+            continue
+        if s.name == "":
+            continue
+        symbol_map[s.name] = s.entry.st_value
+
+    if args.symbol_map is not None:
+        pathlib.Path(args.symbol_map).write_text(json.dumps(symbol_map))
+
+    relocations = {}
+    if args.relocate_data_segment:
+        __flash_data_start = symbol_map["__flash_data_start"]
+        __data_start = symbol_map["__data_start"]
+        __flash_data_len = symbol_map["__flash_data_len"]
+        print("Relocation info:")
+        print(f"  __flash_data_start = 0x{__flash_data_start:08x}")
+        print(f"  __data_start       = 0x{__data_start:08x}")
+        print(f"  __flash_data_len   = 0x{__flash_data_len:08x}")
+        relocations = {__data_start: __flash_data_start}
+
     for segment in elffile.iter_segments():
         if segment.header.p_type != "PT_LOAD":
             continue
@@ -101,20 +131,6 @@ def emit(vmaddr, data):
     recordtype = "01"  # EOF
     emitrecord(f"{chunklen:02X}{vmaddr:04X}{recordtype}")
 
-    symbol_map = {}
-    symtab_section = elffile.get_section_by_name(".symtab")
-    for s in symtab_section.iter_symbols():
-        if s.entry.st_info.type not in ["STT_FUNC", "STT_NOTYPE"]:
-            continue
-        if s.entry.st_shndx == "SHN_ABS":
-            continue
-        if s.name == "":
-            continue
-        symbol_map[s.name] = s.entry.st_value
-
-    if args.symbol_map is not None:
-        pathlib.Path(args.symbol_map).write_text(json.dumps(symbol_map))
-
     inf.close()
     outf.close()
 

stm32-lvgl/Makefile

@@ -60,14 +60,8 @@ build:
 		| c++filt | swift demangle > $(BUILDROOT)/Application.disassembly
 
 	@echo "extracting binary..."
-	$(eval FLASH_DATA_START = `$(NM) -p $(BUILDROOT)/Application | grep __flash_data_start | cut -d' ' -f1`)
-	@echo "   FLASH_DATA_START = 0x$(FLASH_DATA_START)"
-	$(eval SRAM_DATA_START = `$(NM) -p $(BUILDROOT)/Application | grep __data_start | cut -d' ' -f1`)
-	@echo "   SRAM_DATA_START = 0x$(SRAM_DATA_START)"
-	$(eval FLASH_DATA_LEN = `$(NM) -p $(BUILDROOT)/Application | grep __flash_data_len | cut -d' ' -f1`)
-	@echo "   FLASH_DATA_LEN = 0x$(FLASH_DATA_LEN)"
 	$(ELF2HEX) \
-		$(BUILDROOT)/Application $(BUILDROOT)/Application.hex --relocate "0x$(SRAM_DATA_START):0x$(FLASH_DATA_START)"
+		$(BUILDROOT)/Application $(BUILDROOT)/Application.hex --relocate
 	ls -al $(BUILDROOT)/Application.hex
 	@echo "\n   *** All done, build succeeded!\n"