bootloader: self lock at the end of execution

Disables read and execute on memory containing NSIB
right before jumping to application.

Signed-off-by: Mateusz Michalek <[email protected]>

subsys/bootloader/Kconfig

@@ -103,6 +103,12 @@ config SB_CLEANUP_RAM
 	help
 	  Sets contents of memory to 0 before jumping to application.
 
+config SB_DISABLE_SELF_R_X
+	bool "Disable read and execution on self NVM"
+	depends on SOC_NRF54L15_CPUAPP && !FPROTECT_ALLOW_COMBINED_REGIONS
+	help
+	  Sets RRAMC's BOOTCONF region protection before jumping to application.
+
 endif # IS_SECURE_BOOTLOADER
 
 config IS_BOOTLOADER_IMG

subsys/bootloader/bl_boot/bl_boot.c

@@ -19,6 +19,54 @@
 #include <hal/nrf_gpio.h>
 #endif
 
+/* Disabling R_X has to be done while running from RAM for obvious reasons.
+ * Moreover as a last step before jumping to application it must work even after
+ * RAW has been cleared, therefore we are using custom RAM function relocator.
+ * Size of the relocated are isn't known but it doesn't matter as long as it contains at least
+ * entire aforementioned function.
+ */
+#define FUNCTION_BUFFER_LEN 128
+#define RRAMC_REGION_TO_LOCK_ADDR 0x5004b56c
+#define RRAMC_REGION_TO_LOCK_ADDR_H (RRAMC_REGION_TO_LOCK_ADDR >> 16)
+#define RRAMC_REGION_TO_LOCK_ADDR_L (RRAMC_REGION_TO_LOCK_ADDR & 0x0000fffful)
+typedef void (*ram_fn_ptr)(uint32_t);
+uint8_t ram_exec_buf[FUNCTION_BUFFER_LEN];
+
+static void bootconf_disable_r_x_and_jump(uint32_t vector)
+{
+	__asm__ volatile (
+		"   MOV r5, %0\n"
+		"   MOV r1, %1\n"
+		"   MOVT r1, %2\n"
+		"   LDR r0, [r1]\n"
+		/* Size of the region should be set at this point
+		 * by provisioning through BOOTCONF. If not set it according partition size.
+		 */
+		"   RORS r4, r0, #16\n"
+		"   CBNZ r4, clear_rwx\n"
+		"   MOVT r0, %3\n"
+		"clear_rwx:\n"
+		"   BFC r0, #0, #3\n"
+		"   STR r0, [r1]\n"
+		"   DSB\n"
+		"   BX r5\n"
+		:
+		: "r" (vector), "i" (RRAMC_REGION_TO_LOCK_ADDR_L),
+		  "i" (RRAMC_REGION_TO_LOCK_ADDR_H), "i" (CONFIG_PM_PARTITION_SIZE_B0_IMAGE / 1024)
+		: "r0", "r1", "r2", "r4", "r5", "memory"
+	);
+}
+
+static ram_fn_ptr relocate_bootconf_disable_r_x_and_jump(void)
+{
+	uint32_t *adjusted_addr =
+		(uint32_t *)((uint32_t)bootconf_disable_r_x_and_jump & 0xfffffffeul);
+	memcpy(ram_exec_buf, adjusted_addr, FUNCTION_BUFFER_LEN);
+	ram_fn_ptr call_ptr = (ram_fn_ptr)((uint32_t)ram_exec_buf | 0x00000001ul);
+	return call_ptr;
+}
+
+
 #ifdef CONFIG_UART_NRFX_UARTE
 static void uninit_used_uarte(NRF_UARTE_Type *p_reg)
 {
@@ -174,13 +222,18 @@ void bl_boot(const struct fw_info *fw_info)
 		"   b   clear\n"
 		"out:\n"
 		"   dsb\n"
+#ifndef CONFIG_SB_DISABLE_SELF_R_X
 		/* Jump to reset vector of an app */
 		"   bx r0\n"
+#endif
 		:
 		: "r" (vector_table[1]), "i" (CONFIG_SRAM_BASE_ADDRESS),
 		  "i" (CONFIG_SRAM_SIZE * 1024), "i" (0)
 		: "r0", "r1", "r2", "r3", "memory"
 	);
+#elif defined(CONFIG_SB_DISABLE_SELF_R_X)
+
+	relocate_bootconf_disable_r_x_and_jump()(vector_table[1]);
 #else
 	/* Call reset handler. */
 	((void (*)(void))vector_table[1])();