[feat] add crc32 for boot2_pre

example/boot2/Makefile

@@ -15,6 +15,7 @@ endif
 # add custom cmake definition
 #cmake_definition+=-Dxxx=sss
 
-LDFLAGS += -T$(EXAMPLE_BASE_DIR)/flash.ld
+LDFLAGS += -T$(EXAMPLE_BASE_DIR)/boot2.ld
+BOOT2_PRE_CRC ?= boot2_pre_crc.bin
 
 include $(SDK_BASE_DIR)/project.build

example/boot2/boot2.ld

@@ -24,6 +24,7 @@ SECTIONS
 {
     .boot2_pre :
     {
+        KEEP(*boot2_pre.*(.text.boot2_pre))
         KEEP(*(.text.boot2_pre))
         _boot2_pre_size = . - ADDR(.boot2_pre);
         ASSERT(_boot2_pre_size <= 252, "Error: .boot2_pre size exceeds 252 bytes!");

example/boot2/boot2_pre.S

@@ -7,15 +7,11 @@
 .section  .text.boot2_pre
 .type  boot2_pre, %function
 boot2_pre:
-    b boot2_copy_self
+    ldr r0, =_stack_top
+    msr msp, r0
+    bl boot2_copy_self
+    bl main
     .word 0x11223344
     .word 0xabcdef58
 
-
-
-boot2_copy_self:
-
-
-    bl main
-
 .size  .boot2_pre, .-boot2_pre

example/boot2/main.c

@@ -1,3 +1,8 @@
+void __attribute__((section(".text.boot2_pre"))) boot2_copy_self(void)
+{
+    return;
+}
+
 int main(void)
 {
     return 0;

project.build

@@ -53,17 +53,25 @@ cmake_definition+= -DEXAMPLE_NAME=$(EXAMPLE_NAME)
 
 FINAL_NAME_PRE := $(EXAMPLE_BASE_DIR)/build/$(EXAMPLE_NAME)
 
+post:build
+ifdef BOOT2_PRE_CRC
+	@$(CROSS_COMPILE)objcopy -O binary --only-section=.boot2_pre $(FINAL_NAME_PRE).elf $(BOOT2_PRE_CRC)
+	@python3 $(SDK_BASE_DIR)/tools/boot2_pre_crc.py $(BOOT2_PRE_CRC)
+	@$(CROSS_COMPILE)objcopy --update-section .boot2_pre=$(BOOT2_PRE_CRC) $(FINAL_NAME_PRE).elf
+	@rm $(BOOT2_PRE_CRC)
+endif
+	@$(CROSS_COMPILE)objcopy -O binary $(FINAL_NAME_PRE).elf $(FINAL_NAME_PRE).bin
+	@$(CROSS_COMPILE)objdump -d -S $(FINAL_NAME_PRE).elf > $(FINAL_NAME_PRE).asm
+	@$(CROSS_COMPILE)nm $(FINAL_NAME_PRE).elf > $(FINAL_NAME_PRE).nm
+	@$(ELF2UF2) $(FINAL_NAME_PRE).elf $(FINAL_NAME_PRE).uf2
+	@size $(FINAL_NAME_PRE).elf
+	@sha256sum $(FINAL_NAME_PRE).bin
+
 build:Makefile
 	$(CMAKE) -S . -B build -G "Unix Makefiles" $(cmake_definition)
 	$(MAKE) -C build -j
-	$(CROSS_COMPILE)objcopy -O binary $(FINAL_NAME_PRE).elf $(FINAL_NAME_PRE).bin
-	$(CROSS_COMPILE)objdump -d -S $(FINAL_NAME_PRE).elf > $(FINAL_NAME_PRE).asm
-	$(CROSS_COMPILE)nm $(FINAL_NAME_PRE).elf > $(FINAL_NAME_PRE).nm
-	$(ELF2UF2) $(FINAL_NAME_PRE).elf $(FINAL_NAME_PRE).uf2
-	size $(FINAL_NAME_PRE).elf
-	sha256sum $(FINAL_NAME_PRE).bin
 
 clean::
 	$(RM) build
 
-.PHONY:build clean
+.PHONY:post build clean

tools/boot2_pre_crc.py

@@ -0,0 +1,55 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+import binascii
+import struct
+import argparse
+
+def calculate_mpeg2_crc32(data):
+    """
+    Calculate MPEG-2 style CRC32 (Polynomial: 0x04C11DB7, Initial: 0xFFFFFFFF)
+    Note: Result is NOT inverted (unlike standard CRC32)
+    """
+    crc = 0xFFFFFFFF
+    for byte in data:
+        crc ^= byte << 24
+        for _ in range(8):
+            if crc & 0x80000000:
+                crc = (crc << 1) ^ 0x04C11DB7
+            else:
+                crc = crc << 1
+        crc &= 0xFFFFFFFF
+    return crc
+
+def process_file(filename):
+    try:
+        with open(filename, 'rb+') as f:
+            # Verify exact 256 bytes size
+            f.seek(0, 2)
+            if f.tell() != 256:
+                raise ValueError(f"File must be exactly 256 bytes (got {f.tell()} bytes)")
+            
+            f.seek(0)
+            data = f.read(252)
+            if len(data) != 252:
+                raise ValueError("Couldn't read 252 bytes from file")
+            
+            crc = calculate_mpeg2_crc32(data)
+            f.seek(252)
+            f.write(struct.pack('<I', crc))
+            
+            print(f"Success: Updated {filename} with CRC32 0x{crc:08X} at offset 252")
+            return True
+            
+    except Exception as e:
+        print(f"Error processing {filename}: {str(e)}")
+        return False
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        description='Calculate MPEG-2 CRC32 for first 252 bytes and write to last 4 bytes of 256-byte file')
+    parser.add_argument('filename', help='Binary file to process (must be 256 bytes)')
+    args = parser.parse_args()
+    
+    if not process_file(args.filename):
+        exit(1)