Reduce binary size

Add pico_minimize_runtime and some other runtime skips

Re-use scratch_y for the workarea, without overwriting the stack

Author: will-v-pi

enc_bootloader/CMakeLists.txt

@@ -39,20 +39,30 @@ if (NOT USE_PRECOMPILED)
     )
 
     # use stack guards, as AES variables are written near the stack
-    target_compile_definitions(enc_bootloader PRIVATE PICO_USE_STACK_GUARDS=1)
+    target_compile_definitions(enc_bootloader PRIVATE
+        PICO_USE_STACK_GUARDS=1
+        PICO_STACK_SIZE=0x200
+        # No heap is used
+        PICO_HEAP_SIZE=0
+        # These inits are not required
+        PICO_RUNTIME_SKIP_INIT_PER_CORE_IRQ_PRIORITIES=1
+        PICO_RUNTIME_SKIP_INIT_BOOTROM_LOCKING_ENABLE=1)
+
+    pico_minimize_runtime(enc_bootloader)
 
     pico_set_binary_type(enc_bootloader no_flash)
     set(USE_USB_DPRAM FALSE)
     # create linker script to run from 0x20070000
     file(READ ${PICO_LINKER_SCRIPT_PATH}/memmap_no_flash.ld LINKER_SCRIPT)
     if (USE_USB_DPRAM)
-        string(REPLACE "RAM(rwx) : ORIGIN =  0x20000000, LENGTH = 512k" "RAM(rwx) : ORIGIN =  0x2007D000, LENGTH = 12k" LINKER_SCRIPT "${LINKER_SCRIPT}")
+        string(REPLACE "RAM(rwx) : ORIGIN =  0x20000000, LENGTH = 512k" "RAM(rwx) : ORIGIN =  0x2007F000, LENGTH = 4k" LINKER_SCRIPT "${LINKER_SCRIPT}")
         target_compile_definitions(enc_bootloader PRIVATE USE_USB_DPRAM=1)
     else()
-        string(REPLACE "RAM(rwx) : ORIGIN =  0x20000000, LENGTH = 512k" "RAM(rwx) : ORIGIN =  0x2007C000, LENGTH = 16k" LINKER_SCRIPT "${LINKER_SCRIPT}")
+        string(REPLACE "RAM(rwx) : ORIGIN =  0x20000000, LENGTH = 512k" "RAM(rwx) : ORIGIN =  0x2007F000, LENGTH = 4k" LINKER_SCRIPT "${LINKER_SCRIPT}")
     endif()
     file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/memmap_enc_bootloader.ld "${LINKER_SCRIPT}")
     pico_set_linker_script(enc_bootloader ${CMAKE_CURRENT_BINARY_DIR}/memmap_enc_bootloader.ld)
+    pico_add_dis_output(enc_bootloader)
 else()
     project(enc_bootloader C CXX ASM)
     message("Using precompiled enc_bootloader.elf")

enc_bootloader/enc_bootloader.c

@@ -21,8 +21,6 @@
 
 #include "config.h"
 
-volatile uint32_t systick_data[18]; // count, R0-R15,RETPSR
-
 extern void remap();
 extern uint32_t gen_rand_sha();
 extern void init_key(uint8_t *key);
@@ -36,7 +34,7 @@ extern uint32_t lut_a_map[1];
 extern uint32_t lut_b_map[1];
 extern uint32_t rstate_sha[4],rstate_lfsr[2];
 
-void resetrng() {
+void __scratch_x("aes") resetrng() {
     uint32_t f0,f1;
     do f0=get_rand_32(); while(f0==0);   // make sure we don't initialise the LFSR to zero
     f1=get_rand_32();
@@ -52,15 +50,15 @@ void resetrng() {
 #endif
 }
 
-static void init_lut_map() {
+static void __scratch_x("aes") init_lut_map() {
     int i;
     for(i=0;i<256;i++) lut_b[i]=gen_rand_sha()&0xff, lut_a[i]^=lut_b[i];
     lut_a_map[0]=0;
     lut_b_map[0]=0;
     remap();
 }
 
-static void init_aes() {
+static void __scratch_x("aes") init_aes() {
     resetrng();
     gen_lut_sbox();
     init_lut_map();
@@ -69,7 +67,8 @@ static void init_aes() {
 #if USE_USB_DPRAM
 uint8_t* workarea = (uint8_t*)USBCTRL_DPRAM_BASE;
 #else
-static __attribute__((aligned(4))) uint8_t workarea[4 * 1024];
+// static __attribute__((aligned(4))) uint8_t workarea[4 * 1024];
+uint8_t* workarea = (uint8_t*)SRAM_SCRATCH_Y_BASE;
 #endif
 
 int main() {
@@ -128,7 +127,7 @@ int main() {
 
     int rc = rom_chain_image(
         workarea,
-        4 * 1024,
+        4 * 1024 - PICO_STACK_SIZE, // Don't use stack in workarea
         data_start_addr,
         data_size
     );
@@ -137,6 +136,4 @@ int main() {
     stdio_init_all();
     printf("Shouldn't return from ROM call %d\n", rc);
 #endif
-
-    reset_usb_boot(0, 0);
 }