arch: arm: core: fix vector table relocate write to flash

Some SOCs (e.g. STM32F0) can map the flash to address 0 and
the flash base address at the same time. Prevent writing to
duplicate flash address which stops the SOC.

Allow Cortex M SOCs to create their own vector table relocation
function.

Provide a relocation function for STM32F0x SOCs.

Fixes #3923

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

arch/arm/core/cortex_m/prep_c.c

@@ -27,7 +27,7 @@
 #ifdef CONFIG_ARMV6_M
 
 #define VECTOR_ADDRESS 0
-static inline void relocate_vector_table(void)
+void __weak relocate_vector_table(void)
 {
 #if defined(CONFIG_XIP) && (CONFIG_FLASH_BASE_ADDRESS != 0) || \
     !defined(CONFIG_XIP) && (CONFIG_SRAM_BASE_ADDRESS != 0)

arch/arm/soc/st_stm32/stm32f0/soc.c

@@ -15,6 +15,39 @@
 #include <soc.h>
 #include <arch/cpu.h>
 #include <cortex_m/exc.h>
+#include <linker/linker-defs.h>
+#include <string.h>
+
+
+/**
+ * @brief Relocate vector table to SRAM.
+ *
+ * On Cortex-M0 platforms, the Vector Base address cannot be changed.
+ *
+ * A Zephyr image that is run from the mcuboot bootloader must relocate the
+ * vector table to SRAM to be able to replace the vectors pointing to the
+ * bootloader.
+ *
+ * A zephyr image that is a bootloader does not have to relocate the
+ * vector table.
+ *
+ * Replaces the default function from prep_c.c.
+ *
+ * @note Zephyr applications that will not be loaded by a bootloader should
+ *       pretend to be a bootloader if the SRAM vector table is not needed.
+ */
+void relocate_vector_table(void)
+{
+#ifndef CONFIG_IS_BOOTLOADER
+	extern char _ram_vector_start[];
+
+	size_t vector_size = (size_t)_vector_end - (size_t)_vector_start;
+
+	memcpy(_ram_vector_start, _vector_start, vector_size);
+	LL_SYSCFG_SetRemapMemory(LL_SYSCFG_REMAP_SRAM);
+#endif
+}
+
 
 /**
  * @brief This function configures the source of stm32cube time base.

include/arch/arm/cortex_m/scripts/linker.ld

@@ -181,6 +181,16 @@ SECTIONS
 
     GROUP_START(RAMABLE_REGION)
 
+#if defined(CONFIG_SOC_SERIES_STM32F0X) && !defined(CONFIG_IS_BOOTLOADER)
+    /* Must be first in ramable region */
+	SECTION_PROLOGUE(.st_stm32f0x_vt,(NOLOAD),)
+	{
+        _ram_vector_start = .;
+        . += _vector_end - _vector_start;
+        _ram_vector_end = .;
+	} GROUP_DATA_LINK_IN(RAMABLE_REGION, RAMABLE_REGION)
+#endif
+
 #ifdef CONFIG_APPLICATION_MEMORY
 	SECTION_DATA_PROLOGUE(_APP_DATA_SECTION_NAME, (OPTIONAL),)
 	{