Add persist RAM area for passing data across resets; implement booting from a partition specified in the persist RAM area

CMakeLists.txt

@@ -76,6 +76,7 @@ set(COMMON_SOURCES
     defines.h
     main.cpp
     system_stm32f1xx.c
+    persist/persist.c
 )
 
 #
@@ -216,7 +217,11 @@ add_custom_target(greyhash ALL SOURCES greyhash.hex greyhash.bin)
 add_custom_target(flash-greyhash COMMAND st-flash --reset write greyhash.bin ${A_FIRMWARE_APP_BASE} SOURCES greyhash.bin DEPENDS greyhash.bin)
 
 
-add_executable(ab_boot.elf ab_boot/ab_boot.c system_stm32f1xx.c)
+add_executable(ab_boot.elf
+    ab_boot/ab_boot.c
+    system_stm32f1xx.c
+    persist/persist.c
+)
 target_link_options(ab_boot.elf PRIVATE ${COMMON_LINKER_FLAGS} ${AB_BOOT_FIRMWARE_LINKER_FLAGS})
 target_link_libraries(ab_boot.elf stm32_hal)
 target_compile_options(ab_boot.elf PRIVATE )

ab_boot/ab_boot.c

@@ -1,31 +1,51 @@
 #include <stdint.h>
+#include <stdbool.h>
 
 #include "stm32f1xx_hal.h"
 #include "ab_boot.h"
+#include "persist/persist.h"
 
-int main()
-{
-    struct ab_boot_config *config = (struct ab_boot_config *)CONFIG_START;
-
-    uint32_t *bootp;
-    if (config->boot_partition >= FLASH_START &&
-        config->boot_partition < FLASH_END &&
-        (config->boot_partition & 3) == 0)
-    {
-        bootp = (uint32_t *)config->boot_partition;
-    }
-    else
-    {
-        bootp = (uint32_t *)APP_A_START;
-    }
-
-    uint32_t sp = bootp[0];
-    uint32_t entry = bootp[1];
+static inline void __attribute__((noreturn)) boot_image(uint32_t sp, uint32_t entry) {
     asm volatile(
         "   mov sp, %0    \n"
-        "   bx  %1        \n"
+        "   blx  %1       \n"
         "1: b   1b        \n"
         :
         : "r" (sp), "r" (entry)
     );
+    __builtin_unreachable();
+}
+
+static bool is_valid_boot_address(uint32_t *bootp)
+{
+    return (uint32_t)bootp >= FLASH_START &&
+        (uint32_t)bootp < FLASH_END &&
+        ((uint32_t)bootp & 3) == 0;
+}
+
+int main()
+{
+    struct ab_boot_config *flash_config = (struct ab_boot_config *)CONFIG_START;
+    struct ab_boot_config *config = NULL;
+    if (is_persist_valid() &&
+        is_valid_boot_address(persist.ab_boot_config.boot_partition))
+    {
+        // Invalidate persist
+        persist.checksum = 0;
+        config = &persist.ab_boot_config;
+    }
+    else if (is_valid_boot_address(flash_config->boot_partition))
+    {
+        config = flash_config;
+    }
+
+    uint32_t *bootp;
+    if (config)
+        bootp = config->boot_partition;
+    else
+        bootp = (uint32_t *)APP_A_START;
+
+    uint32_t sp = bootp[0];
+    uint32_t entry = bootp[1];
+    boot_image(sp, entry);
 }

ab_boot/ab_boot.h

@@ -17,5 +17,5 @@
 
 struct ab_boot_config
 {
-    uint32_t boot_partition;
+    uint32_t *boot_partition;
 };

ld/STM32F103RCTx_FLASH.ld

@@ -39,7 +39,8 @@ _Min_Stack_Size = 0x400; /* required amount of stack */
 /* Specify the memory areas */
 MEMORY
 {
-RAM (xrw)      : ORIGIN = 0x20000000, LENGTH = 48K
+RAM (xrw)      : ORIGIN = 0x20000000, LENGTH = 47K
+PERSIST (rw)   : ORIGIN = 0x2000BC00, LENGTH =  1K
 FLASH (rx)     : ORIGIN = _App_Base,  LENGTH =  _App_Length
 CONFIG(r)      : ORIGIN = 0x0803f800, LENGTH =  2K
 }
@@ -155,6 +156,14 @@ SECTIONS
   /* Highest address of the user mode stack */
   _estack = ORIGIN(RAM) + LENGTH(RAM);    /* end of RAM area */
 
+  .persist :
+  {
+    . = ALIGN(4);
+    persist = .;
+    . += LENGTH(PERSIST);
+    _epersist = .;
+  } > PERSIST
+
   /* Remove information from the standard libraries */
   /DISCARD/ :
   {

main.cpp

@@ -27,6 +27,8 @@
 #include <cstring>
 
 #include "stm32f1xx_hal.h"
+#include "ab_boot/ab_boot.h"
+#include "persist/persist.h"
 
 #include "defines.h"
 #include "config.h"
@@ -1364,22 +1366,36 @@ void MX_ADC2_Init()
     __HAL_ADC_ENABLE(&hadc2);
 }
 
-#ifdef FEATURE_BUTTON
-void poweroff()
+void shutdown()
 {
-//  if (abs(speed) < 20) {  // wait for the speed to drop, then shut down -> this is commented out for SAFETY reasons
     buzzer.pattern = 0;
     left.enable = false;
-    right.enable = 0;
+    right.enable = false;
 
     for (int i = 0; i < 8; i++) {
         buzzer.freq = (uint8_t)i;
         HAL_Delay(50);
     }
+}
+
+#ifdef FEATURE_BUTTON
+void poweroff()
+{
+    shutdown();
+
     HAL_GPIO_WritePin(OFF_PORT, OFF_PIN, GPIO_PIN_RESET);
     for (int i = 0; i < 5; i++)
         HAL_Delay(1000);
-//  }
+}
+#endif
+
+#ifdef FEATURE_CAN
+void reboot_new_image(uint32_t *bootp)
+{
+    shutdown();
+
+    request_boot_image(bootp);
+    HAL_NVIC_SystemReset();
 }
 #endif
 

persist/persist.c

@@ -0,0 +1,10 @@
+#include <assert.h>
+
+#include "persist.h"
+#include "ab_boot/ab_boot.h"
+
+// keep this in sync with the linker script
+#define PERSIST_SIZE 1024
+
+extern struct persist_data persist;
+static_assert(sizeof(persist) < PERSIST_SIZE);

persist/persist.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "ab_boot/ab_boot.h"
+
+struct persist_data {
+    struct ab_boot_config ab_boot_config;
+    uint32_t checksum;
+};
+
+extern struct persist_data persist;
+
+static inline uint32_t calculate_persist_checksum() {
+    uint32_t checksum = 0;
+    uint32_t *pd = (uint32_t *)&persist;
+    for (int i = 0; i < (sizeof(persist) - 4) / 4; i++) {
+        checksum += pd[i];
+        checksum = (checksum >> 3) | (checksum << 29);
+    }
+
+    checksum = ~checksum;
+
+    return checksum;
+}
+
+static inline void update_persist_checksum() {
+    persist.checksum = calculate_persist_checksum();
+}
+
+static inline bool is_persist_valid() {
+    return calculate_persist_checksum() == persist.checksum;
+}
+
+static inline void request_boot_image(uint32_t *bootp) {
+    persist.ab_boot_config.boot_partition = bootp;
+    update_persist_checksum();
+}